WO2021244136A1 - Refinement method for nitromethane - Google Patents

Refinement method for nitromethane Download PDF

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Publication number
WO2021244136A1
WO2021244136A1 PCT/CN2021/086228 CN2021086228W WO2021244136A1 WO 2021244136 A1 WO2021244136 A1 WO 2021244136A1 CN 2021086228 W CN2021086228 W CN 2021086228W WO 2021244136 A1 WO2021244136 A1 WO 2021244136A1
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nitromethane
rectification
crude
membrane
permeate
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PCT/CN2021/086228
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French (fr)
Chinese (zh)
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田童
丁红林
黄进虎
时嘉鸿
曹帅
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湖北远大富驰医药化工股份有限公司
湖北富博化工有限责任公司
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Publication of WO2021244136A1 publication Critical patent/WO2021244136A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
    • C07C201/06—Preparation of nitro compounds
    • C07C201/16—Separation; Purification; Stabilisation; Use of additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
    • B01D17/02—Separation of non-miscible liquids
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C205/00—Compounds containing nitro groups bound to a carbon skeleton
    • C07C205/01—Compounds containing nitro groups bound to a carbon skeleton having nitro groups bound to acyclic carbon atoms
    • C07C205/02—Compounds containing nitro groups bound to a carbon skeleton having nitro groups bound to acyclic carbon atoms of a saturated carbon skeleton
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency

Definitions

  • the invention relates to the field of chemical engineering. Specifically, the present invention relates to a method for refining nitromethane and the use of a hydrophilic, oleophobic or lipophilic or hydrophobic organic polymer modified membrane in the purification of nitromethane.
  • Nitromethane is a colorless oily liquid, soluble in ethanol, ether and dimethylformamide, and partially soluble in water. It can be used to make explosives, rocket fuel, pesticides, medicines, dyes, pesticides and gasoline additives, etc. As an organic solvent.
  • the main process used in domestic production of nitromethane is the use of dimethyl sulfate substitution method (even if the substitution reaction of dimethyl sulfate and sodium nitrite solution) is used to synthesize nitromethane.
  • dimethyl sulfate substitution method even if the substitution reaction of dimethyl sulfate and sodium nitrite solution
  • heating is distilled for solid-liquid distillation.
  • the fraction obtained by separation and distillation is a mixture of nitromethane, moisture and methanol.
  • the preliminary separation of this mixture is usually based on the immiscibility of nitromethane and water, and the relative density of nitromethane (1.14) is slightly higher than that of water.
  • the separation of nitromethane and water phase is achieved by means of natural sedimentation.
  • the natural sedimentation separation method has the disadvantages of time-consuming, low efficiency, and occupying a large amount of separation storage equipment and space; in addition, the separation method also has the difficulty to completely avoid the two-phase separation because the two-phase boundary is not accurately grasped, so As a result, the water phase is also partially mixed into the crude nitromethane, resulting in a decrease in the purity of the crude nitromethane and an increase in moisture content.
  • the crude nitromethane separated by natural sedimentation after distillation cannot meet the quality requirements and needs further purification.
  • distillation is usually carried out in a rectification tower.
  • the vapor drawn from the top of the tower is condensed, and a part of the condensate is returned to the rectification tower from the top of the tower as reflux, and the remaining distillate is the top product.
  • impurities such as moisture and methanol in nitromethane
  • nitromethane forms an azeotropic system with water and methanol. Therefore, it is difficult to efficiently separate impurities such as water, methanol and nitromethane from the nitromethane by simply relying on the repeated rectification and reflux of the conventional distillation tower, resulting in the entire distillation process Is inefficient.
  • azeotropic systems ordinary distillation methods cannot be effectively separated. It is usually necessary to combine special distillation methods such as extractive distillation.
  • extractive distillation By adding a solvent to the separated system, the relative volatility of the separated components Improve and then separate.
  • this type of method has the disadvantages of introducing impurity solvents, causing pollution, and requiring multi-tower operation, complicated process operation, high energy consumption and cost. Therefore, avoiding the use of processes that require the introduction and recovery of reagents can significantly reduce the complexity of the process and save the investment in production costs.
  • the present invention proposes a method for refining nitromethane, which can quickly and efficiently remove nitromethane.
  • Impurities such as moisture in crude methane can quickly break the emulsification of rectified fractions and realize effective oil-water separation, thereby greatly reducing the number of rectification refluxes, improving the purity of nitromethane products, shortening rectification time, and reducing rectification energy consumption ,
  • the operation is simple and fast, suitable for large-scale, continuous and standardized production, and has a wide range of application prospects.
  • the present invention provides a method for refining nitromethane, which includes the following steps:
  • the present invention also provides a method for refining nitromethane, which includes the following steps:
  • steps (1) and (2) Filter the liquid fraction of the rectification liquid through a lipophilic hydrophobic membrane that can separate the nitromethane and the water phase, collect the rectification permeate, and return the collected rectification permeate to step (1).
  • the operations of steps (1) and (2) are repeated at least one more time to obtain a refined product of nitromethane.
  • the present invention also provides a method for refining nitromethane, which includes the following steps:
  • the rectification permeate is collected to obtain a refined nitromethane product.
  • the crude nitromethane is derived from the reaction of dimethyl sulfate and sodium nitrite, followed by distillation, the distilled product is subjected to sedimentation and stratification, and the lower distilled liquid fraction is separated;
  • Step (1) in the method for refining nitromethane includes the following steps:
  • the pre-refined product is subjected to rectification, and the gas phase fraction is collected for condensation treatment to obtain the rectified liquid phase fraction.
  • step A When the nitromethane content in the crude nitromethane product is greater than the moisture content, step A is:
  • the crude nitromethane is filtered through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and the distillation permeate is collected to obtain the pre-refined product.
  • step A When the moisture content in the crude nitromethane is greater than or equal to the nitromethane content, step A is:
  • the crude nitromethane is pre-filtered with a hydrophilic and oleophobic membrane to collect the distillation retentate; then the distillation retentate is filtered with a lipophilic and hydrophobic membrane to collect the distillation permeate to obtain the pre-refined product.
  • the present invention also provides a method for refining nitromethane, which includes the following steps:
  • the use includes the following steps:
  • the nitromethane pre-refined product is refined in a non-rectification manner to obtain a refined nitromethane product.
  • the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is selected from any one or two or more of polyetherimide, polyetheramide, polyimide, polyamide, polyethersulfone, and polyetheretherketone
  • the modified film is preferably a polyetherimide modified film.
  • the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is a flat membrane fixed on a hollow support.
  • the invention also provides a use of a hydrophilic, oleophobic or lipophilic and hydrophobic organic polymer modified membrane in the purification of nitromethane.
  • the lipophilic hydrophobic membrane is placed at the separation position of the liquid fraction after condensation, breaking the traditional inherent rectification system, that is, relying only on refluxing the condensed liquid phase Into the rectification tower, the required purity of nitromethane is obtained through repeated rectification and reflux.
  • the introduction of the rectification system of "lipophilic hydrophobic membrane filtration-rectification reflux" succeeded in achieving the removal of water from the membrane. Realize the effective removal of water in the entire batch of nitromethane materials.
  • crude nitromethane refers to the nitromethane product that does not meet the relevant quality standards (such as HG/T2021-2008 industrial nitromethane), including, for example, the product after the reaction of dimethyl sulfate and sodium nitrite The product and the distilled product obtained by distillation of the product undergo sedimentation and stratification, and the distilled liquid fraction separated from the lower layer.
  • relevant quality standards such as HG/T2021-2008 industrial nitromethane
  • the present invention provides a method for refining nitromethane, which includes the following steps:
  • the inventors discovered the fraction distribution characteristics of the nitromethane rectification process, that is, the moisture fraction from the initial stage of the nitromethane rectification process is locally enriched and content. Relatively high, the use of local water "excess" in the nitromethane rectification process, the introduction of lipophilic hydrophobic membrane to the separation of the condensed liquid phase fraction, the nitromethane and the water phase are quickly separated.
  • This method breaks the traditional inherent rectification system, that is, it no longer only relies on refluxing the condensed liquid phase into the rectification tower to obtain the required nitromethane purity through repeated rectification and refluxing, and cannot rely on one-time membrane filtration to achieve complete moisture The problem of effective separation is well solved.
  • an azeotropic system such as nitromethane-water-methanol is formed in the rectification tower, which causes the problem of distillation "azeotrope", resulting in low rectification efficiency.
  • the lipophilic and hydrophobic membrane can quickly destroy the emulsification phenomenon of the rectification liquid fraction and realize the effective removal of impurities, especially moisture and methanol.
  • the lipophilic hydrophobic membrane is filtered, a large amount of impurities are intercepted, and the purity of the obtained rectification permeate or the nitromethane distillate refluxed into the rectification tower is significantly improved, which can fundamentally solve the traditional rectification process
  • the rectification permeate obtained in the distillation column or the nitromethane flowing back into the rectification tower still contains water that exceeds its saturated solubility, which makes the nitromethane-water-methanol and other components of the azeotropic system in the rectification tower
  • the moisture and methanol content rapidly decreased, and the gas phase content of nitromethane increased, which changed the original phase equilibrium state, quickly and efficiently broke the formation of the azeotropic system in the rectification tower, and finally eliminated the need for repeated rectification reflux circulation of nitromethane.
  • the quality standard involved in this application is the relevant quality standard that the product needs to meet, such as HG/T2021-2008 industrial nitromethane.
  • the lipophilic hydrophobic membrane is placed at the separation position of the liquid phase fraction after condensation, and separation can be achieved only by gravity, without additional energy consumption and pressurization, simple modification method, and low input cost.
  • the lipophilic and hydrophobic membrane separation liquid phase fraction is in a normal temperature environment, the membrane loss is small, and it does not need to be replaced frequently, which is convenient for industrial application.
  • the lipophilic hydrophobic membrane is used to separate the liquid phase fraction. Compared with the gas phase fraction, the energy consumption is low and the efficiency is high. If the gas phase fraction is separated, whether it is separated by steam permeation inside or outside the rectification column, it is necessary Heating the material to a gas phase state and vacuuming it requires additional energy consumption, low efficiency, and a large amount of membrane input. Moreover, the membrane is prone to wear and tear in a high-temperature environment and needs to be replaced frequently, which is not conducive to continuous production, and it is inconvenient to modify existing equipment.
  • the present invention can solve the traditional distillation process due to the formation of an azeotropic system of nitromethane-water and methanol.
  • the technical problem of high-efficiency separation of methane The application of the lipophilic and hydrophobic membrane can effectively and quickly separate the water in the liquid fraction formed by these "azeotropes" (in these initial fractions, the water content is relative to the solubility of water in nitromethane). It is greatly supersaturated, and these fractions have emulsification phenomenon), thereby effectively reducing the moisture content of the nitromethane flowing back into the rectification tower due to incomplete separation in the traditional rectification process.
  • the use of lipophilic and hydrophobic membrane filtration to filter the liquid phase fraction helps to reduce the energy consumption of the refining treatment, shorten the refining time, and improve the efficiency. At the same time, it reduces the use safety risk of refining equipment, especially distillation equipment. Because the small amount of impurities contained in the crude nitromethane product is not stable at higher temperatures (about 125°C), long-term high-temperature heating will not only cause the system to become more viscous, reduce the product distillation rate, but also significantly increase its combustion and explosion. risk.
  • lipophilic and hydrophobic membranes greatly shortens or even halves the distillation time, which significantly reduces the risk of explosion.
  • the rectification residue is a viscous nitrogen-containing organic matter, which is difficult to biochemically treat.
  • the above-mentioned lipophilic and hydrophobic membrane treatment increases the distilling rate of nitromethane, reduces the amount of distillation residue produced, reduces the amount of distillation residue handled, and reduces the pressure on safety and environmental protection.
  • the lipophilic hydrophobic membrane is used to filter the rectified liquid fraction, which can quickly and efficiently separate the nitromethane oil phase, remove most of the impurities such as water and methanol, and overcome the use of traditional natural sedimentation and stratification methods.
  • Long time, low efficiency, and high moisture content in the obtained refined nitromethane products which improve the purity of refined nitromethane products, reduce energy consumption, and are simple and fast to operate, suitable for large-scale, continuous, and standardized production. Wide application prospects.
  • the present invention also provides a method for refining nitromethane, which includes the following steps:
  • steps (1) and (2) Filter the liquid fraction of the rectification liquid through a lipophilic hydrophobic membrane that can separate the nitromethane and the water phase, collect the rectification permeate, and return the collected rectification permeate to step (1).
  • the operations of steps (1) and (2) are repeated at least one more time to obtain a refined product of nitromethane.
  • the rectification permeate filtered by the lipophilic and hydrophobic membrane can be further rectified to further improve the purity of the refined product. Specifically, when the content of moisture and/or other impurities in the rectification permeate does not meet certain quality requirements, the collected rectification permeate is returned to step (1) to continue rectification, and step (1) is repeated And (2) until the quality requirements are met, and finally a refined nitromethane product is obtained; when the content of moisture and/or other impurities in the rectification permeate meets the quality requirements, the rectification permeate is collected, Obtain nitromethane refined products. Therefore, after single or multiple fractions are condensed and filtered, the moisture content of the entire fraction can be effectively reduced until the index requirements are met, the rectification is stopped, and the rectification permeate is collected to obtain the final refined nitromethane product.
  • the nitrate Methane After being filtered by the lipophilic hydrophobic membrane, a large amount of water, methanol and other impurities are intercepted, and the purity of the nitromethane distillate that is refluxed into the rectification tower is significantly improved. In this way, after fewer refluxes and a shorter reflux time, the nitrate Methane can meet the quality standard, improve the efficiency of the entire rectification process, shorten the time-consuming process, and greatly reduce energy consumption, so as to realize the energy-saving and high-efficiency of the nitromethane rectification process.
  • the present invention also provides a method for refining nitromethane, which includes the following steps:
  • the rectification permeate is collected to obtain a refined nitromethane product.
  • the crude nitromethane is derived from the reaction of dimethyl sulfate and sodium nitrite, followed by distillation, the distilled product is subjected to sedimentation and stratification, and the lower distilled liquid fraction is separated;
  • Step (1) in the method for refining nitromethane includes the following steps:
  • the pre-refined product is subjected to rectification, and the gas phase fraction is collected for condensation treatment to obtain the rectified liquid phase fraction.
  • nitromethane separation by lipophilic and hydrophobic membranes not only shows excellent effects in the distillation process, but also can be applied to the distillation process to pre-refine the crude nitromethane.
  • the pre-refined nitromethane can be pre-refined. It removes most of the impurities such as water and methanol, and overcomes the shortcomings of long time and low efficiency that exist in the traditional natural sedimentation and stratification method.
  • the crude nitromethane obtained by condensation after the distillation treatment is filtered by a lipophilic hydrophobic membrane or a hydrophilic oleophobic membrane, which can quickly and efficiently remove most of the impurities such as water and methanol, which is conducive to the purification and purification of the nitromethane pre-refined products. Reduce the subsequent distillation load and improve the purity of nitromethane products.
  • a lipophilic hydrophobic membrane or a hydrophilic oleophobic membrane is used to filter the crude nitromethane, thereby quickly and efficiently separating the nitromethane oil phase, and the obtained nitromethane pre-refined product has a low water content.
  • step A when the content of nitromethane in the crude nitromethane is greater than the moisture content, step A is:
  • the crude nitromethane is filtered through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and the distillation permeate is collected to obtain a pre-refined product.
  • the oil phase nitromethane and the water phase contact the surface of the lipophilic and hydrophobic membrane, the oil phase nitromethane spreads and penetrates quickly on the membrane surface.
  • the water phase is trapped on the membrane and cannot permeate because it cannot wet the membrane surface.
  • the nitromethane is separated from the water phase.
  • step A is: first pre-filter the crude nitromethane with a hydrophilic and oleophobic membrane, and collect the distillation retentate; then use lipophilic and hydrophobic The membrane filters the distillation retentate and collects the distillation permeate to obtain the pre-refined product.
  • the oleophilic hydrophobic membrane that can make the nitromethane flow out through the membrane is selected for further filtration to collect the permeate. Therefore, in order to better remove impurities such as moisture and achieve the purpose of purification.
  • the pore size of the hydrophilic oleophobic membrane or the oleophilic hydrophobic membrane of the present invention is suitable for separating the oil phase nitromethane and the water phase. If the pore size is too small, the filtration rate will be slow and it is easy to cause pore blockage; If the pore size is too large, it is easy for the retentate to pass through, resulting in more retentate remaining in the permeate. In some embodiments, the pore size is preferably 0.1-3 ⁇ m.
  • the crude nitromethane is obtained by reacting dimethyl sulfate and sodium nitrite.
  • the present invention does not strictly limit the components of the crude nitromethane, as long as the crude nitromethane contains water can be applied to the refining method of the present invention, and the method for obtaining the crude nitromethane is not strictly limited. It can be the crude nitromethane obtained by the reaction synthesis method of dimethyl sulfate and sodium nitrite, methane gas phase nitration method and other production methods, which can be selected according to the actual situation.
  • the present invention also provides a method for refining nitromethane, which includes the following steps:
  • nitromethane content in the crude nitromethane is greater than the moisture content, filter the crude nitromethane through a lipophilic hydrophobic membrane, and collect the distillation permeate to obtain a nitromethane pre-refined product;
  • the use includes the following steps:
  • Distill in advance to remove system salt The distilled product obtained by distillation is condensed by a condenser and converted into a distilled liquid fraction, that is, crude nitromethane.
  • Membrane separation is used to filter the crude nitromethane, so that the nitromethane oil phase can be separated quickly and efficiently, and most of the water, methanol and other impurities are removed.
  • Distillation method processes the nitromethane pre-refined products to facilitate further refining and improve the purity and yield of refined products.
  • the moisture content is measured by Karl Fischer moisture determination method.
  • the temperature of the gas phase fraction is close to the boiling point temperature of nitromethane, it indicates that the moisture content in the nitromethane permeate is low.
  • the temperature of the gas phase fraction it can be Estimate the moisture content in the nitromethane permeate.
  • the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is selected from the group consisting of polyetherimide, polyetheramide, polyimide, polyamide, polyethersulfone, and polyetheretherketone Any one or two or more modified films of the above, preferably a polyetherimide modified film.
  • hydrophilic oleophobic membrane or oleophilic hydrophobic membrane can quickly and efficiently separate the nitromethane phase, and the filtration process can be separated under the action of gravity without additional energy consumption and pressure, which is convenient for implementation.
  • the modification modes of the present invention are reactive grafting, chemical crosslinking, surface modification, and the like.
  • hydrophobic modification or hydrophilic modification is carried out in the modification process, and the modifier for hydrophobic modification is trichloromethyl silane, fluorinated alkyl silane, dimethyl siloxane, butyl acrylate, methyl Any one or more of n-butyl acrylate, methyl methpropionate, octadecylamine, and polytetrafluoroethylene;
  • the modifier for hydrophilic modification is acrylamide, acrylic acid, polyethyleneimine, and Malay Any one or more of the acid glycosides.
  • the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is a flat membrane fixed on a hollow support.
  • the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane can be made into various desired shapes according to production needs, thereby facilitating filtration.
  • the invention also provides a use of a hydrophilic, oleophobic or lipophilic and hydrophobic organic polymer modified membrane in the purification of nitromethane.
  • the organic polymer modified membrane is suitable for the separation of the aqueous phase of crude nitromethane products containing water and nitromethane.
  • the organic polymer modified membrane can quickly destroy the emulsification phenomenon of the rectification liquid fraction composed of nitromethane-water-methanol, and realize the effective removal of impurities such as moisture and methanol. It is more meaningful to use this in the rectification process.
  • the membrane quickly and efficiently separates the moisture in the initial fraction, which can greatly reduce the number of reflux of rectification, shorten the time of rectification, thereby reduce the load of rectification, reduce the energy consumption of rectification, and improve the purity of nitromethane products.
  • the modification methods of the above-mentioned organic polymer modified film include reactive grafting, chemical cross-linking, surface modification and the like.
  • hydrophobic modification or hydrophilic modification is carried out in the modification process, and the modifier for hydrophobic modification is trichloromethyl silane, fluorinated alkyl silane, dimethyl siloxane, butyl acrylate, methyl Any one or more of n-butyl acrylate, methyl methpropionate, octadecylamine, and polytetrafluoroethylene;
  • the modifier for hydrophilic modification is acrylamide, acrylic acid, polyethyleneimine, and Malay Any one or more of the acid glycosides.
  • nitromethane was produced according to the following method.
  • the nitromethane is synthesized by the reaction of dimethyl sulfate and sodium nitrite aqueous solution, and the reaction system is emulsified and contains a large amount of sodium sulfate solid.
  • the crude nitromethane is subjected to atmospheric distillation, the vapor phase obtained by distillation is condensed into a liquid fraction by the second condenser, and the liquid fraction flows into the membrane (B) filter part connected to the second condenser, and is filtered by the membrane (B) module.
  • the obtained distillation permeate flows out and is collected to obtain a pre-refined nitromethane product.
  • the membrane (B) used in the filter component of the membrane (B) is an organosilane-modified polyetherimide membrane with an average pore diameter of 1.5 ⁇ m.
  • the nitromethane content in the nitromethane pre-refined product was 95.1%, the moisture content was 2.2%, and the rest were methanol and other impurities.
  • the steering valve Based on the measured moisture content (the actual production is judged based on the closeness of the tower top temperature to the boiling point of nitromethane at 101.2°C), when the moisture content is greater than or equal to 0.6%, the steering valve is controlled to make the nitromethane permeate enter the return pipe and enter the rectification again. Circulating rectification in the tower; when the water content is less than 0.6%, the steering valve is controlled to make the nitromethane permeate enter the collection tank, and the rectification is completed after 16 hours of rectification to obtain a refined product.
  • the nitromethane content in the refined product was 99.7%, and the moisture content was 0.2%.
  • the nitromethane content is measured by the GC method, and the moisture content is measured by the Karl Fischer Moisture Analyzer. The following methods for determining the nitromethane content and moisture content are the same.
  • the crude nitromethane product is subjected to atmospheric distillation, the vapor phase obtained from the distillation is condensed into a liquid fraction through the second condenser, and the liquid fraction is placed in a storage tank for 3 hours.
  • the crude nitromethane in the lower layer is collected and placed in the storage tank. Leave it to stand for 20 hours in the liquid tank to collect the lower nitromethane pre-refined product.
  • the nitromethane content in the nitromethane pre-refined product was 92%, the moisture content was 5.7%, and the rest were methanol and other impurities.
  • the nitromethane content in the refined product was 99.3%, and the moisture content was 0.33%.
  • Example 1 From the pre-refining steps of Example 1 and Comparative Example 1, it can be seen that the nitromethane content of the lipophilic hydrophobic membrane in Example 1 is 95.1% and the moisture content is 2.2%, while the conventional lipophilic hydrophobic membrane is not used in Comparative Example 1.
  • the nitromethane content of the method is 92%, and the moisture content is 5.7%.
  • the nitromethane content of Example 1 is increased through the lipophilic hydrophobic membrane filtration, and the moisture content is reduced, that is, the crude nitromethane after distillation passes through the membrane After separation, pre-refining and filtration, the technical effects of increasing the content of nitromethane, reducing the moisture content, and shortening the natural sedimentation time can be effectively achieved.
  • Example 1 overcomes the time taken by the traditional natural sedimentation and stratification method (for example, Comparative Example 1 is stratified by two sedimentation, a total of about 23 hours), low efficiency, and moisture in the obtained nitromethane pre-refined product High content (such as 5.7% of Comparative Example 1) and other defects.
  • Using membrane separation and filtration to filter liquid fractions can significantly reduce the subsequent refining processing load and shorten the time required for the entire refining process of nitromethane.
  • the natural sedimentation stratification method requires a long time to stand to effectively separate the nitromethane and the water phase, and the water content of the separated nitromethane is still high. Refining takes a short time, and the water content of nitromethane after pre-refining is low.
  • the reflux rectification time in the rectification tower in Example 1 is significantly shorter than the reflux rectification time in the rectification tower in Comparative Example 1, which can effectively reduce the risk of explosion of the rectification system caused by long-term "high temperature” heating, and Product purity is also more advantageous.
  • nitromethane was produced according to the following method.
  • the distilled crude nitromethane without membrane separation and filtration (where the nitromethane content is 92%, the moisture content is 5.7%, and the rest are other impurities) are added to the rectification tower for rectification treatment, which is time-consuming 22 hours, the rest of the process is the same as the refining process in Example 1.
  • the nitromethane content in the refined product is 99.56%, and the moisture content is 0.22%.
  • nitromethane was produced according to the following method.
  • the pre-refining method is the same as in Example 1, wherein the membrane (B) is a dimethylsiloxane modified polyetheramide membrane with an average pore diameter of 1.5 ⁇ m.
  • the nitromethane content in the nitromethane pre-refined product was 94.9%, the moisture content was 2.7%, and the rest were methanol and other impurities.
  • the membrane (A) is a dimethylsiloxane modified polyetheramide membrane with an average pore diameter of 1.5 ⁇ m.
  • the nitromethane content in the refined product was 99.68% and the moisture content was 0.2% after testing.
  • nitromethane was produced according to the following method.
  • the pre-refining method is the same as in Example 1, wherein the membrane (B) is a methyl methacrylate modified polyamide membrane with an average pore diameter of 1.5 ⁇ m.
  • the nitromethane content in the nitromethane pre-refined product is 95%, the moisture content is 2.5%, and the rest are methanol and other impurities.
  • the purification method is the same as in Example 1, wherein the membrane (A) is an organosilane-modified polyetherimide membrane with an average pore diameter of 1.5 ⁇ m. After 18 hours of rectification, the content of nitromethane in the refined product is 99.6%, moisture content is 0.21%.
  • the difference is that the average pore size of membrane (A) and membrane (B) is 0.1 ⁇ m.
  • Example 2 Same as Example 1, the difference is that the average pore size of membrane (A) and membrane (B) is 3 ⁇ m.
  • the crude nitromethane is subjected to atmospheric distillation, and the vapor phase obtained by the distillation is condensed into a liquid phase through the second condenser.
  • the content of nitromethane was 71.2%, the moisture content was 17.5%, and the rest were methanol and other impurities.
  • the nitromethane filtered by the membrane has high purity, low water content, short distillation time and high efficiency.
  • Modified organic polymer membrane filtration can quickly and efficiently remove impurities such as moisture in crude nitromethane and pre-refined products, reduce the number of rectification reflux times and rectification reflux time, and improve the purity and yield of nitromethane products. Reduce energy consumption of rectification.
  • the organosilane-modified polyetherimide lipophilic hydrophobic membrane with an average pore size of 0.1 ⁇ m can effectively separate nitromethane from the water phase, but under the same pore size conditions, molecular sieve membranes and ceramic membranes separated by the principle of molecular pore size cannot Effectively separate the water phase and the nitromethane phase, resulting in a higher water content in the nitromethane phase after membrane filtration, and low nitromethane purity.

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Abstract

Provided in the present invention is a refinement method for nitromethane. The refinement method comprises the following steps: (1) rectifying a nitromethane crude product, and collecting a gas phase fraction for condensation, thus producing a rectified liquid-phase fraction; (2) filtering the rectified liquid-phase fraction via a lipophilic and hydrophobic membrane capable of separating nitromethane from an aqueous phase, collecting a rectification permeate, and producing a nitromethane refined product. The refinement method for nitromethane of the present invention allows quick and highly efficient removal of impurities such as water in the nitromethane crude product, reduces the number of instances of rectification and the time for rectification reflux, increases the purity and yield of the nitromethane product, reduces the energy consumption of rectification, is simple and convenient to operate, and has broad application prospects.

Description

一种硝基甲烷的精制方法Method for refining nitromethane 技术领域Technical field
本发明涉及化工领域。具体地，本发明涉及一种硝基甲烷的精制方法以及亲水疏油或亲油疏水的有机聚合物改性膜在硝基甲烷纯化作用中的用途。The invention relates to the field of chemical engineering. Specifically, the present invention relates to a method for refining nitromethane and the use of a hydrophilic, oleophobic or lipophilic or hydrophobic organic polymer modified membrane in the purification of nitromethane.
背景技术Background technique
硝基甲烷为无色油状液体，溶于乙醇、***和二甲基甲酰胺，部分溶于水，可用于制作***、火箭燃料、农药、医药、染料、杀虫剂和汽油添加剂等，也可作为有机溶剂。Nitromethane is a colorless oily liquid, soluble in ethanol, ether and dimethylformamide, and partially soluble in water. It can be used to make explosives, rocket fuel, pesticides, medicines, dyes, pesticides and gasoline additives, etc. As an organic solvent.
目前，国内硝基甲烷生产主要采用的工艺为利用硫酸二甲酯取代法(即使硫酸二甲酯与亚硝酸钠溶液发生取代反应)进行硝基甲烷的合成，合成反应完毕后加热蒸馏进行固液分离，蒸馏所得馏分即为硝基甲烷、水分及甲醇等所形成的混合物。对此混合物的初步分离，通常是利用硝基甲烷与水不互溶，并且硝基甲烷的相对密度(1.14)比水略高的特性，依靠自然沉降的方式而实现硝基甲烷与水相的分层分离，所得硝基甲烷相即为硝基甲烷粗品。但是，该自然沉降分离方式存在耗时长、效率低、占用大量分离存储设备及空间等缺点；此外，该分离方式还存在难以完全避免在两相分离时由于两相分界线不好准确把握，从而导致水相也被部分混入硝基甲烷粗品中，致使硝基甲烷粗品的纯度降低，水分含量增加。蒸馏后自然沉降方式分离所得硝基甲烷粗品尚不能满足质量要求，需要进一步纯化。At present, the main process used in domestic production of nitromethane is the use of dimethyl sulfate substitution method (even if the substitution reaction of dimethyl sulfate and sodium nitrite solution) is used to synthesize nitromethane. After the synthesis reaction is completed, heating is distilled for solid-liquid distillation. The fraction obtained by separation and distillation is a mixture of nitromethane, moisture and methanol. The preliminary separation of this mixture is usually based on the immiscibility of nitromethane and water, and the relative density of nitromethane (1.14) is slightly higher than that of water. The separation of nitromethane and water phase is achieved by means of natural sedimentation. The layers are separated, and the obtained nitromethane phase is the crude nitromethane. However, the natural sedimentation separation method has the disadvantages of time-consuming, low efficiency, and occupying a large amount of separation storage equipment and space; in addition, the separation method also has the difficulty to completely avoid the two-phase separation because the two-phase boundary is not accurately grasped, so As a result, the water phase is also partially mixed into the crude nitromethane, resulting in a decrease in the purity of the crude nitromethane and an increase in moisture content. The crude nitromethane separated by natural sedimentation after distillation cannot meet the quality requirements and needs further purification.
目前工业上普遍采用传统的精馏方法对硝基甲烷进行精制纯化。精馏通常在精馏塔中进行，从塔顶引出的蒸气经冷凝，一部分凝液作为回流液从塔顶返回精馏塔，其余馏出液即为塔顶产品。为了将硝基甲烷中的水分及甲醇等杂质较为彻底地予以去除，就需要反复进行精馏回流，这必然导致高能耗以及由于长时间“高温”加热而出现的燃爆风险。At present, traditional distillation methods are widely used in industry to refine and purify nitromethane. Distillation is usually carried out in a rectification tower. The vapor drawn from the top of the tower is condensed, and a part of the condensate is returned to the rectification tower from the top of the tower as reflux, and the remaining distillate is the top product. In order to more thoroughly remove impurities such as moisture and methanol in nitromethane, it is necessary to perform rectification and reflux repeatedly, which will inevitably lead to high energy consumption and the risk of explosion due to long-term "high temperature" heating.
此外，硝基甲烷与水及甲醇等会形成共沸体系，故单纯依靠常规精馏塔反复精馏回流很难使其中的水及甲醇等杂质与硝基甲烷实现高效分离，致使整个精馏过程的效率低下。对于共沸体系，通过普通精馏方法不能使其得到有效的 分离，通常需要结合萃取精馏等特殊精馏方法，通过向被分离体系中加入溶剂，使被分离组分之间的相对挥发度提高进而分离。然而这类方法存在着引入杂质溶剂，造成污染，且需要多塔操作，存在工艺操作复杂、能耗成本高等缺点。因此，避免采用需要引入并回收试剂的工艺，可以明显减少流程复杂程度，节约生产成本的投入。In addition, nitromethane forms an azeotropic system with water and methanol. Therefore, it is difficult to efficiently separate impurities such as water, methanol and nitromethane from the nitromethane by simply relying on the repeated rectification and reflux of the conventional distillation tower, resulting in the entire distillation process Is inefficient. For azeotropic systems, ordinary distillation methods cannot be effectively separated. It is usually necessary to combine special distillation methods such as extractive distillation. By adding a solvent to the separated system, the relative volatility of the separated components Improve and then separate. However, this type of method has the disadvantages of introducing impurity solvents, causing pollution, and requiring multi-tower operation, complicated process operation, high energy consumption and cost. Therefore, avoiding the use of processes that require the introduction and recovery of reagents can significantly reduce the complexity of the process and save the investment in production costs.
发明内容Summary of the invention
为了解决上述传统硝基甲烷纯化技术中存在的分离效率不佳、效果不好的困扰，本发明提出了硝基甲烷的精制方法，利用该硝基甲烷的精制方法可以快速、高效地除去硝基甲烷粗品中的水分等杂质，快速破除精馏馏分的乳化现象，实现油-水有效分离，从而大幅减少精馏回流次数，提高硝基甲烷产品的纯度，缩短精馏时间，降低精馏能耗，并且操作简便、快捷，适于实现规模化、连续化、标准化生产，具有广泛的应用前景。In order to solve the problems of poor separation efficiency and poor effect in the above-mentioned traditional nitromethane purification technology, the present invention proposes a method for refining nitromethane, which can quickly and efficiently remove nitromethane. Impurities such as moisture in crude methane can quickly break the emulsification of rectified fractions and realize effective oil-water separation, thereby greatly reducing the number of rectification refluxes, improving the purity of nitromethane products, shortening rectification time, and reducing rectification energy consumption , And the operation is simple and fast, suitable for large-scale, continuous and standardized production, and has a wide range of application prospects.
本发明提供一种硝基甲烷的精制方法，包括以下步骤：The present invention provides a method for refining nitromethane, which includes the following steps:
(1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
(2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，得到硝基甲烷精制成品。(2) Filter the rectified liquid fraction through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and collect the rectification permeate to obtain a refined nitromethane product.
本发明还提供一种硝基甲烷的精制方法，包括以下步骤：The present invention also provides a method for refining nitromethane, which includes the following steps:
(1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
(2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，将收集的所述精馏透过液返回到步骤(1)中，再重复至少一次步骤(1)和(2)的操作，得到硝基甲烷精制成品。(2) Filter the liquid fraction of the rectification liquid through a lipophilic hydrophobic membrane that can separate the nitromethane and the water phase, collect the rectification permeate, and return the collected rectification permeate to step (1). In ), the operations of steps (1) and (2) are repeated at least one more time to obtain a refined product of nitromethane.
本发明还提供一种硝基甲烷的精制方法，包括以下步骤：The present invention also provides a method for refining nitromethane, which includes the following steps:
(1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
(2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，监测其中水分和/或其他杂质的含量，(2) Filter the rectification liquid fraction through a lipophilic hydrophobic membrane that can separate nitromethane and water, collect the rectification permeate, and monitor the content of water and/or other impurities in it,
当所述精馏透过液中水分和/或其他杂质的含量不满足质量要求时，将所述精馏透过液返回到步骤(1)中继续精馏；When the content of moisture and/or other impurities in the rectification permeate does not meet the quality requirements, return the rectification permeate to step (1) to continue rectification;
当所述精馏透过液中水分和/或其他杂质的含量满足质量要求时，收集精馏透过液，得到硝基甲烷精制成品。When the content of moisture and/or other impurities in the rectification permeate meets the quality requirements, the rectification permeate is collected to obtain a refined nitromethane product.
根据本发明所述的硝基甲烷的精制方法，According to the refining method of nitromethane according to the present invention,
所述硝基甲烷粗品来源于将由硫酸二甲酯与亚硝酸钠反应后进行蒸馏处理，馏出产物进行沉降分层，分离出下层的蒸馏液相馏分；The crude nitromethane is derived from the reaction of dimethyl sulfate and sodium nitrite, followed by distillation, the distilled product is subjected to sedimentation and stratification, and the lower distilled liquid fraction is separated;
所述的硝基甲烷的精制方法中的步骤(1)包括如下步骤：Step (1) in the method for refining nitromethane includes the following steps:
A、将所述硝基甲烷粗品经能将硝基甲烷和水相分离的亲油疏水膜或亲水疏油膜过滤，得到预精制产物；A. Filter the crude nitromethane through a lipophilic hydrophobic membrane or a hydrophilic and oleophobic membrane that can separate the nitromethane from the water phase to obtain a pre-refined product;
B、将所述预精制产物进行精馏，收集气相馏分进行冷凝处理，得到精馏液相馏分。B. The pre-refined product is subjected to rectification, and the gas phase fraction is collected for condensation treatment to obtain the rectified liquid phase fraction.
根据本发明所述的硝基甲烷的精制方法，According to the refining method of nitromethane according to the present invention,
当所述硝基甲烷粗品中硝基甲烷含量大于水分含量时，步骤A为：When the nitromethane content in the crude nitromethane product is greater than the moisture content, step A is:
将所述硝基甲烷粗品经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集蒸馏透过液，得到所述预精制产物。The crude nitromethane is filtered through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and the distillation permeate is collected to obtain the pre-refined product.
根据本发明所述的硝基甲烷的精制方法，According to the refining method of nitromethane according to the present invention,
当所述硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，步骤A为：When the moisture content in the crude nitromethane is greater than or equal to the nitromethane content, step A is:
先用亲水疏油膜将所述硝基甲烷粗品进行预过滤，收集蒸馏截留液；再用亲油疏水膜将所述蒸馏截留液进行过滤，收集蒸馏透过液，得到所述预精制产物。The crude nitromethane is pre-filtered with a hydrophilic and oleophobic membrane to collect the distillation retentate; then the distillation retentate is filtered with a lipophilic and hydrophobic membrane to collect the distillation permeate to obtain the pre-refined product.
本发明还提供一种硝基甲烷的精制方法，包括以下步骤：The present invention also provides a method for refining nitromethane, which includes the following steps:
(1)将由硫酸二甲酯与亚硝酸钠反应后得到的产物进行蒸馏处理，所得馏出产物进行沉降分层，分离出下层的蒸馏液相馏分即为硝基甲烷粗品；(1) The product obtained after the reaction of dimethyl sulfate and sodium nitrite is subjected to distillation treatment, and the obtained distillate product is subjected to sedimentation and stratification, and the distilled liquid fraction in the lower layer is separated to be the crude nitromethane;
(2)检测所述硝基甲烷粗品中硝基甲烷含量：(2) Detect the content of nitromethane in the crude nitromethane:
当所述硝基甲烷粗品中硝基甲烷含量大于水分含量时，将所述硝基甲烷粗品经亲油疏水膜过滤，收集蒸馏透过液得到硝基甲烷预精制产物；When the nitromethane content in the crude nitromethane is greater than the moisture content, filtering the crude nitromethane through a lipophilic hydrophobic membrane, and collecting the distillation permeate to obtain the nitromethane pre-refined product;
当所述硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，使用包括以下步骤：When the moisture content in the crude nitromethane is greater than or equal to the nitromethane content, the use includes the following steps:
先用亲水疏油膜进行预过滤，收集蒸馏截留液；Pre-filter with hydrophilic and oleophobic membrane to collect distillation retentate;
再用亲油疏水膜将所述蒸馏截留液进行过滤，再收集蒸馏透过液得到硝基甲烷预精制产物；Then use a lipophilic hydrophobic membrane to filter the distillation retentate, and then collect the distillation permeate to obtain a nitromethane pre-refined product;
(3)将所述硝基甲烷预精制产物进行非精馏方式精制，得到硝基甲烷精 制成品。(3) The nitromethane pre-refined product is refined in a non-rectification manner to obtain a refined nitromethane product.
根据本发明所述的硝基甲烷的精制方法，其特征在于，The method for refining nitromethane according to the present invention is characterized in that:
所述亲水疏油膜或亲油疏水膜选自包含聚醚酰亚胺、聚醚酰胺、聚酰亚胺、聚酰胺、聚醚砜、聚醚醚酮中的任意一种或两种以上的改性膜，优选为聚醚酰亚胺改性膜。The hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is selected from any one or two or more of polyetherimide, polyetheramide, polyimide, polyamide, polyethersulfone, and polyetheretherketone The modified film is preferably a polyetherimide modified film.
根据本发明所述硝基甲烷的精制方法，其特征在于，The method for purifying nitromethane according to the present invention is characterized in that:
所述亲水疏油膜或亲油疏水膜为固定于中空支撑物的平板膜。The hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is a flat membrane fixed on a hollow support.
本发明还提供一种亲水疏油或亲油疏水的有机聚合物改性膜在硝基甲烷纯化作用中的用途。The invention also provides a use of a hydrophilic, oleophobic or lipophilic and hydrophobic organic polymer modified membrane in the purification of nitromethane.
有益效果Beneficial effect
(1)利用精馏过程中初始馏分水分的富集现象，将亲油疏水膜置于冷凝过后对液相馏分的分离位置，打破了传统固有的精馏体系，即仅仅依靠将冷凝液相回流进入精馏塔中通过反复精馏回流的方式得到需要的硝基甲烷纯度。将硝基甲烷纯化技术领域未使用的膜技术与现有的精馏体系结合，引进“亲油疏水膜过滤-精馏回流”的精馏体系，最终成功实现水分的膜去除，“以点带面”地实现整批硝基甲烷物料中水分的有效去除。(1) Taking advantage of the concentration of moisture in the initial fraction in the rectification process, the lipophilic hydrophobic membrane is placed at the separation position of the liquid fraction after condensation, breaking the traditional inherent rectification system, that is, relying only on refluxing the condensed liquid phase Into the rectification tower, the required purity of nitromethane is obtained through repeated rectification and reflux. Combining the unused membrane technology in the field of nitromethane purification technology with the existing rectification system, the introduction of the rectification system of "lipophilic hydrophobic membrane filtration-rectification reflux", and finally succeeded in achieving the removal of water from the membrane. Realize the effective removal of water in the entire batch of nitromethane materials.
(2)利用亲油疏水膜的引入，成功解决了精馏过程中初始多元馏分的“破乳”(此所谓乳化现象更多地侧重于“微观”层面，宏观上肉眼并不易观察到明显的乳化现象)问题，从而实现了精馏回流连续性与馏分质量的一致性(稳定性)的统一，快速地分离出整个精馏塔内所含的水分，进而破除精馏过程的共沸问题。(2) The introduction of lipophilic and hydrophobic membranes successfully solved the "demulsification" of the initial multi-component fractions in the rectification process (the so-called emulsification phenomenon focuses more on the "micro" level, which is not easy to be observed by the naked eye on the macro level. Emulsification phenomenon) problem, so as to realize the unity of rectification reflux continuity and the consistency (stability) of distillate quality, quickly separate the water contained in the entire rectification tower, and then eliminate the azeotropic problem in the rectification process.
(3)由于精馏效率的大幅提升，物料因长时间加热而变性的几率也得到了降低，故产品馏出率即精馏收率也会有所提高，所产生的精馏残液也会有所降低。精馏残液是高氮有机物，极难处理，故膜的引入也极大减轻了环保压力。(3) Due to the substantial increase in rectification efficiency, the probability of denaturation of materials due to long-term heating has also been reduced, so the product distillation rate, that is, the rectification yield will also increase, and the resulting rectification residue will also be Reduced. The distillation residue is high-nitrogen organic matter, which is extremely difficult to handle, so the introduction of the membrane greatly reduces the pressure on environmental protection.
(4)实现了对精馏过程的液相回流液进行膜过滤分离，降低生产投入成本的同时，极大地提高了精馏回流效率，解决了硝基甲烷精馏高沸残留量大的问题，极大地降低了精馏能耗。(4) Membrane filtration and separation of the liquid phase reflux liquid of the rectification process is realized, while reducing the production input cost, it greatly improves the efficiency of the rectification reflux, and solves the problem of high boiling residue of nitromethane rectification. Greatly reduce the energy consumption of rectification.
本发明的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。The additional aspects and advantages of the present invention will be partially given in the following description, and some will become obvious from the following description, or be understood through the practice of the present invention.
具体实施方式detailed description
除非另有定义，本发明中所使用的所有科学和技术术语具有与本发明涉及技术领域的技术人员通常理解的相同的含义。Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by those skilled in the technical field related to the present invention.
本发明中，“硝基甲烷粗品”是指未满足相关质量标准(如HG/T2021-2008工业用硝基甲烷)的硝基甲烷产品，例如包括由硫酸二甲酯与亚硝酸钠反应后的产物以及该产物进行蒸馏所得馏出产物进行沉降分层，下层分离出的蒸馏液相馏分。In the present invention, "crude nitromethane" refers to the nitromethane product that does not meet the relevant quality standards (such as HG/T2021-2008 industrial nitromethane), including, for example, the product after the reaction of dimethyl sulfate and sodium nitrite The product and the distilled product obtained by distillation of the product undergo sedimentation and stratification, and the distilled liquid fraction separated from the lower layer.
下面将结合本发明实施例，对本发明的技术方案进行清楚、完整地描述，显然，所描述的实施例仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
本发明提供一种硝基甲烷的精制方法，包括以下步骤：The present invention provides a method for refining nitromethane, which includes the following steps:
(1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
(2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，得到硝基甲烷精制成品。(2) Filter the rectified liquid fraction through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and collect the rectification permeate to obtain a refined nitromethane product.
传统的精馏分离是将从塔顶出来的含有甲醇、水及硝基甲烷的多元体系经冷凝后进行静置，以期实现水分和硝基甲烷的分层分离，分出的水层排出精馏体系外，硝基甲烷层回流至精馏塔内继续精馏。但是，此时的馏分存在乳化现象，使原本与水不互溶的硝基甲烷，在此状态下混合到一起。因此，仅仅依靠静置自然沉降分层的方法效率低，需要耗费很长的时间。而实际生产过程为了保证回流的连续性以及馏出产品质量的稳定性，尚来不及等待其充分分层就需要将下层液(硝基甲烷相)回流进入精馏塔内，这就导致大量水分又随硝基甲烷回到了精馏釜内的物料中。Traditional distillation separation is to condense the multi-component system containing methanol, water and nitromethane from the top of the tower and then stand still, in order to achieve the layered separation of water and nitromethane, and the separated water layer is discharged for rectification Outside the system, the nitromethane layer is refluxed to the distillation tower to continue distillation. However, the distillate at this time has an emulsification phenomenon, so that the nitromethane, which is originally immiscible with water, is mixed together in this state. Therefore, the method of relying solely on the natural settlement and stratification is inefficient and takes a long time. In the actual production process, in order to ensure the continuity of the reflux and the stability of the quality of the distilled product, it is necessary to reflux the lower liquid (nitromethane phase) into the rectification tower before it has time to wait for its full stratification, which leads to a large amount of moisture. With the nitromethane returned to the material in the rectification kettle.
为了解决硝基甲烷纯化效率低下的技术问题，发明人发现了硝基甲烷精馏过程的馏分分布特性，即，硝基甲烷精馏过程中初始阶段所出的水分馏分得到了局部富集、含量相对较高，利用硝基甲烷精馏过程中局部水分“过量”，引入亲油疏水膜到冷凝过后的液相馏分的分离，将硝基甲烷和水相快速分离。该方法打破了传统固有的精馏体系，即不再仅仅依靠将冷凝液相回流进入精馏塔通过反复精馏回流的方式得到需要的硝基甲烷纯度，将不能依靠一次性膜过滤实现水分完全有效分离的难题予以很好地解决。In order to solve the technical problem of low purification efficiency of nitromethane, the inventors discovered the fraction distribution characteristics of the nitromethane rectification process, that is, the moisture fraction from the initial stage of the nitromethane rectification process is locally enriched and content. Relatively high, the use of local water "excess" in the nitromethane rectification process, the introduction of lipophilic hydrophobic membrane to the separation of the condensed liquid phase fraction, the nitromethane and the water phase are quickly separated. This method breaks the traditional inherent rectification system, that is, it no longer only relies on refluxing the condensed liquid phase into the rectification tower to obtain the required nitromethane purity through repeated rectification and refluxing, and cannot rely on one-time membrane filtration to achieve complete moisture The problem of effective separation is well solved.
传统的硝基甲烷精馏方法，在精馏塔内会形成硝基甲烷-水-甲醇等共沸体系，从而产生精馏“共沸”问题，导致精馏效率低下。本发明中，采用亲油疏水膜可以快速破坏精馏液相馏分的乳化现象，实现杂质，特别是水分、甲醇的有效去除。经过亲油疏水膜过滤后大量的杂质被截留，得到的精馏透过液或回流进入精馏塔内的硝基甲烷馏出液的纯度显著提高，这样就能从根本上解决传统精馏过程中得到的精馏透过液或回流入精馏塔内的硝基甲烷依然夹带有超过其饱和溶解度的水分问题，使得精馏塔内的硝基甲烷-水-甲醇等共沸体系构成要素的水分及甲醇含量迅速降低，硝基甲烷气相含量升高，改变了原有相平衡状态，快速高效地破除了精馏塔内共沸体系的形成，最终使硝基甲烷无需反复进行精馏回流循环，无需回流或只需回流较短时间、较少次数，即可达到质量标准，提高了整个精馏过程的效率、缩短耗时，极大降低了能耗，从而实现了硝基甲烷精馏过程的节能高效。In the traditional nitromethane rectification method, an azeotropic system such as nitromethane-water-methanol is formed in the rectification tower, which causes the problem of distillation "azeotrope", resulting in low rectification efficiency. In the present invention, the lipophilic and hydrophobic membrane can quickly destroy the emulsification phenomenon of the rectification liquid fraction and realize the effective removal of impurities, especially moisture and methanol. After the lipophilic hydrophobic membrane is filtered, a large amount of impurities are intercepted, and the purity of the obtained rectification permeate or the nitromethane distillate refluxed into the rectification tower is significantly improved, which can fundamentally solve the traditional rectification process The rectification permeate obtained in the distillation column or the nitromethane flowing back into the rectification tower still contains water that exceeds its saturated solubility, which makes the nitromethane-water-methanol and other components of the azeotropic system in the rectification tower The moisture and methanol content rapidly decreased, and the gas phase content of nitromethane increased, which changed the original phase equilibrium state, quickly and efficiently broke the formation of the azeotropic system in the rectification tower, and finally eliminated the need for repeated rectification reflux circulation of nitromethane. , No need to reflux or only need to reflux for a short time and fewer times to reach the quality standard, which improves the efficiency of the entire distillation process, shortens time-consuming, and greatly reduces energy consumption, thereby realizing the nitromethane distillation process Energy saving and high efficiency.
本申请所涉及到的质量标准为产品所需满足的相关质量标准，例如HG/T2021-2008工业用硝基甲烷。The quality standard involved in this application is the relevant quality standard that the product needs to meet, such as HG/T2021-2008 industrial nitromethane.
优选地，将亲油疏水膜置于冷凝过后对液相馏分的分离位置，仅依靠重力作用即可实现分离，无需额外耗能加压，改造方式简单，投入成本低。而且亲油疏水膜分离液相馏分处于常温环境，膜耗损小，不用经常更换，便于工业应用。Preferably, the lipophilic hydrophobic membrane is placed at the separation position of the liquid phase fraction after condensation, and separation can be achieved only by gravity, without additional energy consumption and pressurization, simple modification method, and low input cost. Moreover, the lipophilic and hydrophobic membrane separation liquid phase fraction is in a normal temperature environment, the membrane loss is small, and it does not need to be replaced frequently, which is convenient for industrial application.
采用亲油疏水膜对液相馏分进行分离，相较于气相馏分，能耗低，效率高，如果对气相馏分进行分离，无论是精馏塔内还是精馏塔外通过蒸汽渗透分离，都需将物料加热到气相状态，并抽真空，需要额外更多能耗，效率低，膜投入量大。而且膜在高温环境下易于损耗，需要经常更换，不利于生产持续进行，对现有设备的改造也不便。The lipophilic hydrophobic membrane is used to separate the liquid phase fraction. Compared with the gas phase fraction, the energy consumption is low and the efficiency is high. If the gas phase fraction is separated, whether it is separated by steam permeation inside or outside the rectification column, it is necessary Heating the material to a gas phase state and vacuuming it requires additional energy consumption, low efficiency, and a large amount of membrane input. Moreover, the membrane is prone to wear and tear in a high-temperature environment and needs to be replaced frequently, which is not conducive to continuous production, and it is inconvenient to modify existing equipment.
本发明由于引入亲油疏水膜，能解决传统的精馏过程中，由于硝基甲烷-水及甲醇等会形成共沸体系而导致的单纯依靠精馏方法并不能使水及甲醇等杂质与硝基甲烷实现高效分离的技术问题。该亲油疏水膜的应用能有效、快速地分离这些“共沸物”所形成的液相馏分中的水分(在这些初始馏分中，水分的含量相对于水在硝基甲烷中的溶解度而言是大大过饱和的，且这些馏分存在乳化现象)，从而有效降低相较传统精馏过程中由于分离不彻底而随硝基甲烷回流入精馏塔内的水分含量。如此便显著减少了反复回流的次数，大幅提升了精馏效率，缩短了精馏时间进而极大降低了精馏能耗。采用亲油疏水膜过滤方 式过滤液相馏分有助于降低精制处理的能耗，缩短精制时间，提高效率。同时，降低了精制设备尤其是精馏设备的使用安全风险。由于硝基甲烷粗产品中所含少量杂质在较高温度下(125℃左右)稳定性不足，长时间高温加热既会导致体系越发粘稠、降低产品馏出率，也会显著提升其燃爆风险。亲油疏水膜的使用大幅缩短甚至是减半精馏时间，显著降低了这一燃爆风险。此外，精馏残液为粘稠状含氮有机物，生化处理困难。经上述亲油疏水膜处理提升了硝基甲烷馏出率、降低了精馏残液产生量，减轻了精馏残液的处理量，更减轻了安全环保压力。Due to the introduction of the lipophilic and hydrophobic membrane, the present invention can solve the traditional distillation process due to the formation of an azeotropic system of nitromethane-water and methanol. The technical problem of high-efficiency separation of methane. The application of the lipophilic and hydrophobic membrane can effectively and quickly separate the water in the liquid fraction formed by these "azeotropes" (in these initial fractions, the water content is relative to the solubility of water in nitromethane). It is greatly supersaturated, and these fractions have emulsification phenomenon), thereby effectively reducing the moisture content of the nitromethane flowing back into the rectification tower due to incomplete separation in the traditional rectification process. In this way, the number of repeated reflux is significantly reduced, the rectification efficiency is greatly improved, the rectification time is shortened, and the rectification energy consumption is greatly reduced. The use of lipophilic and hydrophobic membrane filtration to filter the liquid phase fraction helps to reduce the energy consumption of the refining treatment, shorten the refining time, and improve the efficiency. At the same time, it reduces the use safety risk of refining equipment, especially distillation equipment. Because the small amount of impurities contained in the crude nitromethane product is not stable at higher temperatures (about 125°C), long-term high-temperature heating will not only cause the system to become more viscous, reduce the product distillation rate, but also significantly increase its combustion and explosion. risk. The use of lipophilic and hydrophobic membranes greatly shortens or even halves the distillation time, which significantly reduces the risk of explosion. In addition, the rectification residue is a viscous nitrogen-containing organic matter, which is difficult to biochemically treat. The above-mentioned lipophilic and hydrophobic membrane treatment increases the distilling rate of nitromethane, reduces the amount of distillation residue produced, reduces the amount of distillation residue handled, and reduces the pressure on safety and environmental protection.
采用亲油疏水膜对精馏液相馏分进行过滤，能够快速、高效分离出硝基甲烷油相，除去大部分的水、甲醇等杂质，克服了采用传统的自然沉降分层方式所存在的用时长、效率低、所得硝基甲烷精制成品中水分含量高等缺陷，提高了硝基甲烷精制成品的纯度，降低能耗，并且操作简便、快捷，适于实现规模化、连续化、标准化生产，具有广泛的应用前景。The lipophilic hydrophobic membrane is used to filter the rectified liquid fraction, which can quickly and efficiently separate the nitromethane oil phase, remove most of the impurities such as water and methanol, and overcome the use of traditional natural sedimentation and stratification methods. Long time, low efficiency, and high moisture content in the obtained refined nitromethane products, which improve the purity of refined nitromethane products, reduce energy consumption, and are simple and fast to operate, suitable for large-scale, continuous, and standardized production. Wide application prospects.
本发明还提供一种硝基甲烷的精制方法，包括以下步骤：The present invention also provides a method for refining nitromethane, which includes the following steps:
(1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
(2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，将收集的所述精馏透过液返回到步骤(1)中，再重复至少一次步骤(1)和(2)的操作，得到硝基甲烷精制成品。(2) Filter the liquid fraction of the rectification liquid through a lipophilic hydrophobic membrane that can separate the nitromethane and the water phase, collect the rectification permeate, and return the collected rectification permeate to step (1). In ), the operations of steps (1) and (2) are repeated at least one more time to obtain a refined product of nitromethane.
经亲油疏水膜过滤的精馏透过液可以再进行精馏，以便于进一步提高精制成品的纯度。具体地，当精馏透过液中水分和/或其他杂质的含量不符合某些质量要求时，则将收集的精馏透过液返回到步骤(1)继续精馏，重复步骤(1)和(2)的操作，直至满足该质量要求，最终得到硝基甲烷精制成品；当所述精馏透过液中水分和/或他杂质的含量满足质量要求时，收集精馏透过液，得到硝基甲烷精制成品。由此，经过单次或多次馏分的冷凝和过滤，可以有效地降低整体馏分的水分含量直至满足指标要求，停止精馏，收集精馏透过液，得到最终的硝基甲烷精制成品。The rectification permeate filtered by the lipophilic and hydrophobic membrane can be further rectified to further improve the purity of the refined product. Specifically, when the content of moisture and/or other impurities in the rectification permeate does not meet certain quality requirements, the collected rectification permeate is returned to step (1) to continue rectification, and step (1) is repeated And (2) until the quality requirements are met, and finally a refined nitromethane product is obtained; when the content of moisture and/or other impurities in the rectification permeate meets the quality requirements, the rectification permeate is collected, Obtain nitromethane refined products. Therefore, after single or multiple fractions are condensed and filtered, the moisture content of the entire fraction can be effectively reduced until the index requirements are met, the rectification is stopped, and the rectification permeate is collected to obtain the final refined nitromethane product.
经过亲油疏水膜过滤后大量的水分、甲醇等杂质被截留，回流进入精馏塔内的硝基甲烷馏出液的纯度显著提高，这样经过较少次数的回流，较短的回流时间，硝基甲烷即可达到质量标准，提高了整个精馏过程的效率、缩短耗时，极大降低了能耗，从而实现硝基甲烷精馏过程的节能高效。After being filtered by the lipophilic hydrophobic membrane, a large amount of water, methanol and other impurities are intercepted, and the purity of the nitromethane distillate that is refluxed into the rectification tower is significantly improved. In this way, after fewer refluxes and a shorter reflux time, the nitrate Methane can meet the quality standard, improve the efficiency of the entire rectification process, shorten the time-consuming process, and greatly reduce energy consumption, so as to realize the energy-saving and high-efficiency of the nitromethane rectification process.
本发明还提供一种硝基甲烷的精制方法，包括以下步骤：The present invention also provides a method for refining nitromethane, which includes the following steps:
(1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
(2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，监测其中水分和/或其他杂质的含量，(2) Filter the rectification liquid fraction through a lipophilic hydrophobic membrane that can separate nitromethane and water, collect the rectification permeate, and monitor the content of water and/or other impurities in it,
当所述精馏透过液中水分和/或其他杂质的含量不满足质量要求时，将所述精馏透过液返回到步骤(1)中继续精馏；When the content of moisture and/or other impurities in the rectification permeate does not meet the quality requirements, return the rectification permeate to step (1) to continue rectification;
当所述精馏透过液中水分和/或其他杂质的含量满足质量要求时，收集精馏透过液，得到硝基甲烷精制成品。When the content of moisture and/or other impurities in the rectification permeate meets the quality requirements, the rectification permeate is collected to obtain a refined nitromethane product.
所述硝基甲烷粗品来源于将由硫酸二甲酯与亚硝酸钠反应后进行蒸馏处理，馏出产物进行沉降分层，分离出下层的蒸馏液相馏分；The crude nitromethane is derived from the reaction of dimethyl sulfate and sodium nitrite, followed by distillation, the distilled product is subjected to sedimentation and stratification, and the lower distilled liquid fraction is separated;
所述的硝基甲烷的精制方法中的步骤(1)包括如下步骤：Step (1) in the method for refining nitromethane includes the following steps:
A、将所述硝基甲烷粗品经能将硝基甲烷和水相分离的亲油疏水膜或亲水疏油膜过滤，得到预精制产物；A. Filter the crude nitromethane through a lipophilic hydrophobic membrane or a hydrophilic and oleophobic membrane that can separate the nitromethane from the water phase to obtain a pre-refined product;
B、将所述预精制产物进行精馏，收集气相馏分进行冷凝处理，得到精馏液相馏分。B. The pre-refined product is subjected to rectification, and the gas phase fraction is collected for condensation treatment to obtain the rectified liquid phase fraction.
采用亲油疏水膜分离硝基甲烷除了在精馏过程中表现出优异的效果，还可以前置应用到蒸馏过程后对硝基甲烷粗品进行预精制，经过预精制的硝基甲烷预精制产物能除去大部分的水、甲醇等杂质，克服了采用传统的自然沉降分层方式所存在的用时长、效率低的缺点。The separation of nitromethane by lipophilic and hydrophobic membranes not only shows excellent effects in the distillation process, but also can be applied to the distillation process to pre-refine the crude nitromethane. The pre-refined nitromethane can be pre-refined. It removes most of the impurities such as water and methanol, and overcomes the shortcomings of long time and low efficiency that exist in the traditional natural sedimentation and stratification method.
对蒸馏处理后冷凝得到的硝基甲烷粗品采用亲油疏水膜或亲水疏油膜过滤，可以快速、高效地除去大部分的水、甲醇等杂质，有利于硝基甲烷预精制产物的精制提纯，减少后续的精馏负荷，提高硝基甲烷产品的纯度。采用亲油疏水膜或亲水疏油膜对硝基甲烷粗品进行过滤，从而快速、高效分离出硝基甲烷油相，所得硝基甲烷预精制产物中水分含量较低。The crude nitromethane obtained by condensation after the distillation treatment is filtered by a lipophilic hydrophobic membrane or a hydrophilic oleophobic membrane, which can quickly and efficiently remove most of the impurities such as water and methanol, which is conducive to the purification and purification of the nitromethane pre-refined products. Reduce the subsequent distillation load and improve the purity of nitromethane products. A lipophilic hydrophobic membrane or a hydrophilic oleophobic membrane is used to filter the crude nitromethane, thereby quickly and efficiently separating the nitromethane oil phase, and the obtained nitromethane pre-refined product has a low water content.
根据本发明所述的精制方法，当所述硝基甲烷粗品中硝基甲烷含量大于水分含量时，步骤A为：According to the refining method of the present invention, when the content of nitromethane in the crude nitromethane is greater than the moisture content, step A is:
将所述硝基甲烷粗品经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集蒸馏透过液，得到预精制产物。The crude nitromethane is filtered through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and the distillation permeate is collected to obtain a pre-refined product.
当油相硝基甲烷和水相接触亲油疏水膜表面时，油相硝基甲烷迅速在膜表面铺展并渗透，水相因不能润湿膜表面，而截留在膜上无法渗透下去，从而使 硝基甲烷和水相分离。When the oil phase nitromethane and the water phase contact the surface of the lipophilic and hydrophobic membrane, the oil phase nitromethane spreads and penetrates quickly on the membrane surface. The water phase is trapped on the membrane and cannot permeate because it cannot wet the membrane surface. The nitromethane is separated from the water phase.
根据本发明所述的硝基甲烷的精制方法，According to the refining method of nitromethane according to the present invention,
当所述硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，步骤A为：先用亲水疏油膜将所述硝基甲烷粗品进行预过滤，收集蒸馏截留液；再用亲油疏水膜将所述蒸馏截留液进行过滤，收集蒸馏透过液，得到所述预精制产物。When the moisture content in the crude nitromethane is greater than or equal to the content of nitromethane, step A is: first pre-filter the crude nitromethane with a hydrophilic and oleophobic membrane, and collect the distillation retentate; then use lipophilic and hydrophobic The membrane filters the distillation retentate and collects the distillation permeate to obtain the pre-refined product.
根据硝基甲烷粗品中硝基甲烷含量与水含量之间的关系选择膜类型，当硝基甲烷含量大于水分含量时，选择能够使硝基甲烷透过膜流出的亲油疏水膜，水相将大部分被截留，收集硝基甲烷透过液，从而实现分离；当硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，先选择能够使水相透过膜流出，硝基甲烷将大部分被截留的亲水疏油膜，收集硝基甲烷截留液，初步分离出硝基甲烷后，再选择能够使硝基甲烷透过膜流出的亲油疏水膜进一步过滤，收集透过液。由此，以便于更好地除去水分等杂质，实现纯化目的。Select the membrane type according to the relationship between the nitromethane content and the water content in the crude nitromethane. When the nitromethane content is greater than the water content, select the lipophilic hydrophobic membrane that can make the nitromethane flow out through the membrane, and the water phase will Most of them are intercepted, and the nitromethane permeate is collected to achieve separation; when the moisture content of the crude nitromethane is greater than or equal to the content of nitromethane, the first choice is to allow the water phase to flow out through the membrane, and the nitromethane will be larger. Part of the intercepted hydrophilic and oleophobic membrane collects the nitromethane retentate. After the nitromethane is initially separated, the oleophilic hydrophobic membrane that can make the nitromethane flow out through the membrane is selected for further filtration to collect the permeate. Therefore, in order to better remove impurities such as moisture and achieve the purpose of purification.
需要说明的是，优选地，本发明的亲水疏油膜或亲油疏水膜的孔径适于分离油相硝基甲烷和水相，若孔径过小，过滤速度慢，且容易造成孔堵塞；若孔径过大，容易使截留物透过，导致透过液中仍残留较多截留物。在一些实施例中，孔径优选为0.1-3μm。It should be noted that, preferably, the pore size of the hydrophilic oleophobic membrane or the oleophilic hydrophobic membrane of the present invention is suitable for separating the oil phase nitromethane and the water phase. If the pore size is too small, the filtration rate will be slow and it is easy to cause pore blockage; If the pore size is too large, it is easy for the retentate to pass through, resulting in more retentate remaining in the permeate. In some embodiments, the pore size is preferably 0.1-3 μm.
根据本发明所述的精制方法，所述硝基甲烷粗品是通过硫酸二甲酯和亚硝酸钠反应所得。需要说明的是，本发明对于硝基甲烷粗品的组分不作严格限定，只要是含有水的硝基甲烷粗品均可适用于本发明的精制方法，对于硝基甲烷粗品的获得方式也不作严格限定，可以为硫酸二甲酯与亚硝酸钠反应合成法、甲烷气相硝化法等生产方法得到的硝基甲烷粗品，具体可以根据实际情况选择。According to the refining method of the present invention, the crude nitromethane is obtained by reacting dimethyl sulfate and sodium nitrite. It should be noted that the present invention does not strictly limit the components of the crude nitromethane, as long as the crude nitromethane contains water can be applied to the refining method of the present invention, and the method for obtaining the crude nitromethane is not strictly limited. It can be the crude nitromethane obtained by the reaction synthesis method of dimethyl sulfate and sodium nitrite, methane gas phase nitration method and other production methods, which can be selected according to the actual situation.
本发明还提供一种硝基甲烷的精制方法，包括以下步骤：The present invention also provides a method for refining nitromethane, which includes the following steps:
(1)将由硫酸二甲酯与亚硝酸钠反应后得到的产物进行蒸馏处理，所得馏出产物进行沉降分层，分离出下层的蒸馏液相馏分即为硝基甲烷粗品；(1) The product obtained after the reaction of dimethyl sulfate and sodium nitrite is subjected to distillation treatment, and the obtained distillate product is subjected to sedimentation and stratification, and the distilled liquid fraction in the lower layer is separated to be the crude nitromethane;
(2)检测所述硝基甲烷粗品中硝基甲烷含量：(2) Detect the content of nitromethane in the crude nitromethane:
当所述硝基甲烷粗品中硝基甲烷含量大于水分含量时，将所述硝基甲烷粗品经亲油疏水膜过滤，收集蒸馏透过液得到硝基甲烷预精制产物；When the nitromethane content in the crude nitromethane is greater than the moisture content, filter the crude nitromethane through a lipophilic hydrophobic membrane, and collect the distillation permeate to obtain a nitromethane pre-refined product;
当所述硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，使用包括以下步骤：When the moisture content in the crude nitromethane is greater than or equal to the nitromethane content, the use includes the following steps:
先用亲水疏油膜进行预过滤，收集蒸馏截留液；Pre-filter with hydrophilic and oleophobic membrane to collect distillation retentate;
再用亲油疏水膜将所述蒸馏截留液进行过滤，再收集蒸馏透过液得到硝基 甲烷预精制产物；Then use a lipophilic hydrophobic membrane to filter the distillation retentate, and then collect the distillation permeate to obtain a nitromethane pre-refined product;
(3)将所述硝基甲烷预精制产物进行非精馏方式精制，得到硝基甲烷精制成品。(3) Refining the nitromethane pre-refined product in a non-rectification manner to obtain a refined nitromethane product.
预先进行蒸馏，以除去体系盐分。经蒸馏处理所得蒸馏产物经冷凝器冷凝后转化为蒸馏液相馏分，即硝基甲烷粗品。采用膜分离对硝基甲烷粗品进行过滤，从而能够快速、高效分离出硝基甲烷油相，除去大部分的水、甲醇等杂质，所得硝基甲烷预精制产物中水分含量较低，采用非精馏方式对硝基甲烷预精制产物进行处理，以便于进一步精制，提高精制成品的纯度和得率。Distill in advance to remove system salt. The distilled product obtained by distillation is condensed by a condenser and converted into a distilled liquid fraction, that is, crude nitromethane. Membrane separation is used to filter the crude nitromethane, so that the nitromethane oil phase can be separated quickly and efficiently, and most of the water, methanol and other impurities are removed. Distillation method processes the nitromethane pre-refined products to facilitate further refining and improve the purity and yield of refined products.
通常水分含量是通过卡尔费休水分测定法进行测定的。在生产实际过程中由于硝基甲烷的沸点为101.2℃，气相馏分的温度接近硝基甲烷的沸点温度，则表明硝基甲烷透过液中水分含量较低，通过对气相馏分的温度检测，可以估算出硝基甲烷透过液中水分含量。Usually the moisture content is measured by Karl Fischer moisture determination method. In the actual production process, since the boiling point of nitromethane is 101.2°C and the temperature of the gas phase fraction is close to the boiling point temperature of nitromethane, it indicates that the moisture content in the nitromethane permeate is low. By detecting the temperature of the gas phase fraction, it can be Estimate the moisture content in the nitromethane permeate.
根据本发明所述的精制方法，所述亲水疏油膜或亲油疏水膜选自包含聚醚酰亚胺、聚醚酰胺、聚酰亚胺、聚酰胺、聚醚砜、聚醚醚酮中的任意一种或两种以上的改性膜，优选聚醚酰亚胺改性膜。According to the refining method of the present invention, the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is selected from the group consisting of polyetherimide, polyetheramide, polyimide, polyamide, polyethersulfone, and polyetheretherketone Any one or two or more modified films of the above, preferably a polyetherimide modified film.
发明人发现，采用上述亲水疏油膜或亲油疏水膜可以快速、高效地分离出硝基甲烷相，并且，过滤过程在重力作用下即可实现分离，无需额外耗能加压，方便实施。The inventor found that the above-mentioned hydrophilic oleophobic membrane or oleophilic hydrophobic membrane can quickly and efficiently separate the nitromethane phase, and the filtration process can be separated under the action of gravity without additional energy consumption and pressure, which is convenient for implementation.
需要说明的是，本发明的改性方式为反应性接枝、化学交联、表面改性等。优选地，改性过程中进行疏水改性或亲水改性，疏水改性的改性剂为三氯甲基硅烷、氟化烷基硅烷、二甲基硅氧烷、丙烯酸丁酯、甲基丙烯酸正丁酯、甲基丙酸甲酯、十八胺、聚四氟乙烯中的任意一种或几种；亲水改性的改性剂为丙烯酰胺、丙烯酸、聚乙烯亚胺、马来酸苷中的任意一种或几种。It should be noted that the modification modes of the present invention are reactive grafting, chemical crosslinking, surface modification, and the like. Preferably, hydrophobic modification or hydrophilic modification is carried out in the modification process, and the modifier for hydrophobic modification is trichloromethyl silane, fluorinated alkyl silane, dimethyl siloxane, butyl acrylate, methyl Any one or more of n-butyl acrylate, methyl methpropionate, octadecylamine, and polytetrafluoroethylene; the modifier for hydrophilic modification is acrylamide, acrylic acid, polyethyleneimine, and Malay Any one or more of the acid glycosides.
根据本发明所述的精制方法，所述亲水疏油膜或亲油疏水膜为固定于中空支撑物的平板膜。此外，根据生产需要可以将亲水疏油膜或亲油疏水膜制成各种需要的形状，由此，以便于实现过滤。According to the refining method of the present invention, the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is a flat membrane fixed on a hollow support. In addition, the hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane can be made into various desired shapes according to production needs, thereby facilitating filtration.
本发明还提供一种亲水疏油或亲油疏水的有机聚合物改性膜在硝基甲烷纯化作用中的用途。The invention also provides a use of a hydrophilic, oleophobic or lipophilic and hydrophobic organic polymer modified membrane in the purification of nitromethane.
有机聚合物改性膜适用于含有水的硝基甲烷粗产品的水相和硝基甲烷分离。有机聚合物改性膜可以快速破坏硝基甲烷-水-甲醇等构成的精馏液相馏分 的乳化现象，实现水分、甲醇等杂质的有效去除，更为有意义的是在精馏过程利用该膜对初始馏分中的水分进行快速、高效地分离，可大幅减少精馏回流次数，缩短精馏时间进而减少精馏负荷，降低精馏能耗，提高硝基甲烷产品的纯度。克服了传统精馏过程中由于共沸体系的长时间存在，从而需要反复精馏回流的缺陷，显著提高了精馏效率，缩短了精馏时间，装置简便，操作快捷，适于实现规模化、连续化、标准化生产，具有广泛的应用前景。The organic polymer modified membrane is suitable for the separation of the aqueous phase of crude nitromethane products containing water and nitromethane. The organic polymer modified membrane can quickly destroy the emulsification phenomenon of the rectification liquid fraction composed of nitromethane-water-methanol, and realize the effective removal of impurities such as moisture and methanol. It is more meaningful to use this in the rectification process. The membrane quickly and efficiently separates the moisture in the initial fraction, which can greatly reduce the number of reflux of rectification, shorten the time of rectification, thereby reduce the load of rectification, reduce the energy consumption of rectification, and improve the purity of nitromethane products. It overcomes the defect that the azeotropic system exists for a long time in the traditional rectification process, which requires repeated rectification and reflux, significantly improves the rectification efficiency, shortens the rectification time, the device is simple, the operation is quick, and it is suitable for realizing large-scale, Continuous and standardized production has broad application prospects.
上述有机聚合物改性膜的改性方式为反应性接枝、化学交联、表面改性等。优选地，改性过程中进行疏水改性或亲水改性，疏水改性的改性剂为三氯甲基硅烷、氟化烷基硅烷、二甲基硅氧烷、丙烯酸丁酯、甲基丙烯酸正丁酯、甲基丙酸甲酯、十八胺、聚四氟乙烯中的任意一种或几种；亲水改性的改性剂为丙烯酰胺、丙烯酸、聚乙烯亚胺、马来酸苷中的任意一种或几种。The modification methods of the above-mentioned organic polymer modified film include reactive grafting, chemical cross-linking, surface modification and the like. Preferably, hydrophobic modification or hydrophilic modification is carried out in the modification process, and the modifier for hydrophobic modification is trichloromethyl silane, fluorinated alkyl silane, dimethyl siloxane, butyl acrylate, methyl Any one or more of n-butyl acrylate, methyl methpropionate, octadecylamine, and polytetrafluoroethylene; the modifier for hydrophilic modification is acrylamide, acrylic acid, polyethyleneimine, and Malay Any one or more of the acid glycosides.
下面将结合实施例对本发明的方案进行解释。本领域技术人员将会理解，下面的实施例仅用于说明本发明，而不应视为限定本发明的范围。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的产品。The solution of the present invention will be explained below in conjunction with examples. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the examples, the procedures shall be carried out in accordance with the techniques or conditions described in the literature in the field or in accordance with the product specification. Those reagents or instruments that do not indicate the manufacturer are all commercially available products.
实施例1Example 1
在该实施例中，按照下列方法生产硝基甲烷。In this example, nitromethane was produced according to the following method.
1、制备硝基甲烷粗品1. Preparation of crude nitromethane
采用硫酸二甲酯和亚硝酸钠水溶液反应合成硝基甲烷，反应体系呈乳化状并含大量硫酸钠固体。The nitromethane is synthesized by the reaction of dimethyl sulfate and sodium nitrite aqueous solution, and the reaction system is emulsified and contains a large amount of sodium sulfate solid.
2、预精制2. Pre-refined
将硝基甲烷粗品进行常压蒸馏，蒸馏所得气相经第二冷凝器冷凝为液相馏分，液相馏分流入与第二冷凝器相连的膜(B)过滤部件，经膜(B)组件过滤，所得蒸馏透过液流出并收集，得到硝基甲烷预精制产物。其中，膜(B)过滤部件采用的膜(B)为平均孔径1.5μm的有机硅烷改性的聚醚酰亚胺膜。The crude nitromethane is subjected to atmospheric distillation, the vapor phase obtained by distillation is condensed into a liquid fraction by the second condenser, and the liquid fraction flows into the membrane (B) filter part connected to the second condenser, and is filtered by the membrane (B) module. The obtained distillation permeate flows out and is collected to obtain a pre-refined nitromethane product. Among them, the membrane (B) used in the filter component of the membrane (B) is an organosilane-modified polyetherimide membrane with an average pore diameter of 1.5 μm.
经检测，该硝基甲烷预精制产物中硝基甲烷含量为95.1％，水分含量为2.2％，其余为甲醇等其它杂质。After testing, the nitromethane content in the nitromethane pre-refined product was 95.1%, the moisture content was 2.2%, and the rest were methanol and other impurities.
3、精制3. Refined
将2.2吨所得硝基甲烷预精制产物加入到精馏塔内进行精馏处理，产生的塔顶气相馏分经第一冷凝器冷凝为液相馏分，流入膜(A)过滤部件，经过滤 所得精馏透过液经透过液出口流出，膜(A)过滤部件采用的膜(A)为平均孔径1.5μm的有机硅烷改性的聚醚酰亚胺膜。Add 2.2 tons of the obtained nitromethane pre-refined product to the rectification tower for rectification. The gas phase fraction at the top of the tower is condensed into the liquid phase fraction by the first condenser, and flows into the membrane (A) filter part, and the refined fraction is filtered. The distilled permeate flows out through the permeate outlet, and the membrane (A) used in the membrane (A) filter part is an organosilane-modified polyetherimide membrane with an average pore diameter of 1.5 μm.
基于测定的水分含量(实际生产根据塔顶温度与硝基甲烷沸点101.2℃接近程度判断)，当含水量大于等于0.6％时，控制转向阀使硝基甲烷透过液进入回流管道重新进入精馏塔中循环精馏；当含水量小于0.6％，控制转向阀使硝基甲烷透过液进入收集槽中，精馏16小时后精馏完毕，得到精制成品。Based on the measured moisture content (the actual production is judged based on the closeness of the tower top temperature to the boiling point of nitromethane at 101.2°C), when the moisture content is greater than or equal to 0.6%, the steering valve is controlled to make the nitromethane permeate enter the return pipe and enter the rectification again. Circulating rectification in the tower; when the water content is less than 0.6%, the steering valve is controlled to make the nitromethane permeate enter the collection tank, and the rectification is completed after 16 hours of rectification to obtain a refined product.
经检测，该精制成品中硝基甲烷含量为99.7％，水分含量为0.2％。After testing, the nitromethane content in the refined product was 99.7%, and the moisture content was 0.2%.
其中，in,
硝基甲烷含量通过GC法测定，水分含量通过卡尔费休水分测定仪测定，以下测定硝基甲烷含量和水分含量的方法相同。The nitromethane content is measured by the GC method, and the moisture content is measured by the Karl Fischer Moisture Analyzer. The following methods for determining the nitromethane content and moisture content are the same.
对比例1Comparative example 1
1、制备硝基甲烷粗品1. Preparation of crude nitromethane
同实施例1。The same as in Example 1.
2、预精制2. Pre-refined
将硝基甲烷粗产品进行常压蒸馏，蒸馏所得气相经第二冷凝管冷凝为液相馏分，液相馏分置于储液槽中静置3小时，收集下层硝基甲烷粗品，再置于储液槽中静置20小时，收集下层硝基甲烷预精制产品。The crude nitromethane product is subjected to atmospheric distillation, the vapor phase obtained from the distillation is condensed into a liquid fraction through the second condenser, and the liquid fraction is placed in a storage tank for 3 hours. The crude nitromethane in the lower layer is collected and placed in the storage tank. Leave it to stand for 20 hours in the liquid tank to collect the lower nitromethane pre-refined product.
经检测，该硝基甲烷预精制品中硝基甲烷含量为92％，水分含量为5.7％，其余为甲醇等其它杂质。After testing, the nitromethane content in the nitromethane pre-refined product was 92%, the moisture content was 5.7%, and the rest were methanol and other impurities.
3、精制3. Refined
将2.2吨所述硝基甲烷粗品加入到精馏塔中进行精馏处理(此精馏设备与实施例1所用精馏塔相同，不含膜(A)过滤部件100)，产生的塔顶气相经冷凝器冷凝为液相馏分，液体馏分流向中间回流调节槽中静置约10分钟(此处流体实际是连续流动的)，上层水相连续排出，下层硝基甲烷相连续回流至精馏塔内，直至此回流调节槽不再有水相分出。Add 2.2 tons of the crude nitromethane to the rectification tower for rectification treatment (this rectification equipment is the same as the rectification tower used in Example 1, without membrane (A) filter component 100), and the gas phase at the top of the tower is generated The liquid fraction is condensed into the liquid fraction by the condenser, and the liquid fraction flows to the middle reflux adjustment tank and stands for about 10 minutes (the fluid here is actually continuous flow), the upper water phase is continuously discharged, and the lower nitromethane phase is continuously refluxed to the rectification tower Inside, until this reflux regulating tank no longer has the water phase to separate.
根据塔顶温度，调节回流比继续精馏，收集合格馏分即为所需成品。整个精馏过程31小时方精馏完毕。According to the temperature at the top of the tower, adjust the reflux ratio to continue rectification, and collect qualified fractions to obtain the desired finished product. The entire distillation process is completed in 31 hours.
经检测，该精制成品中硝基甲烷含量为99.3％，水分含量0.33％。After testing, the nitromethane content in the refined product was 99.3%, and the moisture content was 0.33%.
从实施例1和对比例1预精制步骤可以看出，实施例1采用亲油疏水膜的硝基甲烷含量为95.1％，水分含量为2.2％，而对比例1未采用亲油疏水膜的传统方式的硝基甲烷含量为92％，水分含量为5.7％，实施例1经过亲油疏水 膜过滤硝基甲烷含量有所增加，水分含量有所降低，也即经过蒸馏的硝基甲烷粗品经过膜分离预精制过滤后能有效取得增加硝基甲烷含量、降低水分含量、缩短自然沉降时间的技术效果。同时，实施例1克服了采用传统的自然沉降分层方式所存在的用时长(如对比例1经两次沉降分层，共约23小时)、效率低、所得硝基甲烷预精制产物中水分含量高(如对比例1的5.7％)等缺陷。采用膜分离过滤方式过滤液相馏分能显著降低后续精制处理负荷，缩短硝基甲烷整个精制过程所需时间。From the pre-refining steps of Example 1 and Comparative Example 1, it can be seen that the nitromethane content of the lipophilic hydrophobic membrane in Example 1 is 95.1% and the moisture content is 2.2%, while the conventional lipophilic hydrophobic membrane is not used in Comparative Example 1. The nitromethane content of the method is 92%, and the moisture content is 5.7%. The nitromethane content of Example 1 is increased through the lipophilic hydrophobic membrane filtration, and the moisture content is reduced, that is, the crude nitromethane after distillation passes through the membrane After separation, pre-refining and filtration, the technical effects of increasing the content of nitromethane, reducing the moisture content, and shortening the natural sedimentation time can be effectively achieved. At the same time, Example 1 overcomes the time taken by the traditional natural sedimentation and stratification method (for example, Comparative Example 1 is stratified by two sedimentation, a total of about 23 hours), low efficiency, and moisture in the obtained nitromethane pre-refined product High content (such as 5.7% of Comparative Example 1) and other defects. Using membrane separation and filtration to filter liquid fractions can significantly reduce the subsequent refining processing load and shorten the time required for the entire refining process of nitromethane.
通过精制步骤可以看出，采用自然沉降分层方式，需要长时间静置才能够有效地分离硝基甲烷和水相，且分离出的硝基甲烷中水含量仍很高，而采用膜过滤预精制，耗时短，预精制后硝基甲烷的含水量低。实施例1中精馏塔中回流精馏的时间明显少于对比例1精馏塔中回流精馏时间，能有效降低由于长时间“高温”加热所带来的精馏体系燃爆风险，且产品纯度亦更有优势。It can be seen from the refining step that the natural sedimentation stratification method requires a long time to stand to effectively separate the nitromethane and the water phase, and the water content of the separated nitromethane is still high. Refining takes a short time, and the water content of nitromethane after pre-refining is low. The reflux rectification time in the rectification tower in Example 1 is significantly shorter than the reflux rectification time in the rectification tower in Comparative Example 1, which can effectively reduce the risk of explosion of the rectification system caused by long-term "high temperature" heating, and Product purity is also more advantageous.
实施例2Example 2
在该实施例中，按照下列方法生产硝基甲烷。In this example, nitromethane was produced according to the following method.
1、制备硝基甲烷粗品1. Preparation of crude nitromethane
同实施例1。The same as in Example 1.
2、预精制2. Pre-refined
同对比例1。Same as Comparative Example 1.
3、精制3. Refined
将没有经过膜分离过滤的蒸馏后的硝基甲烷粗品(其中硝基甲烷含量为92％，水分含量为5.7％，其余为其它杂质)加入到精馏塔中进行精馏处理，精馏耗时22小时，其余过程同实施例1中的精制过程。The distilled crude nitromethane without membrane separation and filtration (where the nitromethane content is 92%, the moisture content is 5.7%, and the rest are other impurities) are added to the rectification tower for rectification treatment, which is time-consuming 22 hours, the rest of the process is the same as the refining process in Example 1.
经检测，该精制成品中硝基甲烷含量为99.56％，水分含量为0.22％。After testing, the nitromethane content in the refined product is 99.56%, and the moisture content is 0.22%.
实施例3Example 3
在该实施例中，按照下列方法生产硝基甲烷。In this example, nitromethane was produced according to the following method.
1、制备硝基甲烷粗品1. Preparation of crude nitromethane
同实施例1。The same as in Example 1.
2、预精制2. Pre-refined
预精制方法同实施例1，其中，膜(B)为平均孔径1.5μm的二甲基硅氧烷改性的聚醚酰胺膜。The pre-refining method is the same as in Example 1, wherein the membrane (B) is a dimethylsiloxane modified polyetheramide membrane with an average pore diameter of 1.5 μm.
经检测，该硝基甲烷预精制产物中硝基甲烷含量为94.9％，水分含量为2.7％，其余为甲醇等其它杂质。After testing, the nitromethane content in the nitromethane pre-refined product was 94.9%, the moisture content was 2.7%, and the rest were methanol and other impurities.
3、精制3. Refined
将2.2吨所得硝基甲烷预精制产物加入到精馏塔内进行精馏纯化，产生的塔顶气相馏分经第一冷凝器冷凝为液相，流入膜(A)过滤部件。其中，膜(A)为平均孔径1.5μm的二甲基硅氧烷改性的聚醚酰胺膜。The 2.2 tons of obtained nitromethane pre-refined product is added to the rectification tower for rectification and purification, and the gas phase fraction at the top of the tower is condensed into the liquid phase by the first condenser, and flows into the membrane (A) filter part. Among them, the membrane (A) is a dimethylsiloxane modified polyetheramide membrane with an average pore diameter of 1.5 μm.
基于水分等杂质含量的判定(实际生产时根据塔顶温度进行预判)，当含水量大于0.6％时，控制初液阀门开启、终液阀门关闭，硝基甲烷透过液回流至精馏塔中循环精馏；当含水量小于0.6％，控制初液阀门关闭、终液阀门开启，硝基甲烷透过液为终产品，进入收集槽中得到精制成品。Based on the judgment of impurity content such as moisture (pre-judgment according to the tower top temperature in actual production), when the water content is greater than 0.6%, control the initial liquid valve to open, the final liquid valve to close, and the nitromethane permeate to return to the rectification tower Middle-cycle distillation; when the water content is less than 0.6%, control the initial liquid valve to close and the final liquid valve to open, and the nitromethane permeate is the final product, which enters the collection tank to obtain a refined product.
经过19小时精馏完毕，经检测，该精制成品中硝基甲烷含量为99.68％，水分含量为0.2％。After 19 hours of rectification, the nitromethane content in the refined product was 99.68% and the moisture content was 0.2% after testing.
实施例4Example 4
在该实施例中，按照下列方法生产硝基甲烷。In this example, nitromethane was produced according to the following method.
1、制备硝基甲烷粗品1. Preparation of crude nitromethane
同实施例1。The same as in Example 1.
2、预精制2. Pre-refined
预精制方法同实施例1，其中，膜(B)为平均孔径1.5μm的甲基丙酸甲酯改性的聚酰胺膜。The pre-refining method is the same as in Example 1, wherein the membrane (B) is a methyl methacrylate modified polyamide membrane with an average pore diameter of 1.5 μm.
经检测，该硝基甲烷预精制产物中硝基甲烷含量为95％，水分含量为2.5％，其余为甲醇等其它杂质。After testing, the nitromethane content in the nitromethane pre-refined product is 95%, the moisture content is 2.5%, and the rest are methanol and other impurities.
3、精制3. Refined
精制方法同实施例1，其中，膜(A)为平均孔径1.5μm的有机硅烷改性的聚醚酰亚胺膜，经18小时精馏完毕，经检测，该精制成品中硝基甲烷含量为99.6％，水分含量为0.21％。The purification method is the same as in Example 1, wherein the membrane (A) is an organosilane-modified polyetherimide membrane with an average pore diameter of 1.5μm. After 18 hours of rectification, the content of nitromethane in the refined product is 99.6%, moisture content is 0.21%.
实施例5Example 5
同实施例1，区别在于，膜(A)和膜(B)的平均孔径为0.1μm。Same as Example 1, the difference is that the average pore size of membrane (A) and membrane (B) is 0.1 μm.
实施例6Example 6
同实施例1，区别在于，膜(A)和膜(B)的平均孔径为3μm。Same as Example 1, the difference is that the average pore size of membrane (A) and membrane (B) is 3 μm.
对比例2Comparative example 2
制备硝基甲烷粗品和预精制步骤同实施例1，区别在于，膜(B)采用分 子筛膜，结果如表1所示。The steps for preparing crude nitromethane and pre-refining are the same as in Example 1, except that the membrane (B) uses a molecular sieve membrane. The results are shown in Table 1.
对比例3Comparative example 3
制备硝基甲烷粗品和预精制步骤同实施例1，区别在于，膜(B)采用陶瓷膜，结果如表1所示。The steps of preparing crude nitromethane and pre-refining are the same as in Example 1, except that the membrane (B) uses a ceramic membrane, and the results are shown in Table 1.
对比例4Comparative example 4
1、制备硝基甲烷粗品1. Preparation of crude nitromethane
同实施例1。The same as in Example 1.
2、预精制2. Pre-refined
将硝基甲烷粗品进行常压蒸馏，蒸馏所得气相经第二冷凝管冷凝为液相。The crude nitromethane is subjected to atmospheric distillation, and the vapor phase obtained by the distillation is condensed into a liquid phase through the second condenser.
经检测，硝基甲烷含量为71.2％，水分含量为17.5％，其余为甲醇等其它杂质。After testing, the content of nitromethane was 71.2%, the moisture content was 17.5%, and the rest were methanol and other impurities.
结果表明，有机硅烷改性的聚醚酰亚胺膜在硝基甲烷纯化破乳作用中效果最好，经过该膜过滤的硝基甲烷纯度高，含水量低，精馏时间短，效率高。经过改性有机聚合物膜过滤能快速、高效地除去硝基甲烷粗品及预精制产物中的水分等杂质，减少精馏回流次数及精馏回流时间，提高硝基甲烷产品的纯度及得率，降低精馏能耗。The results show that the organosilane modified polyetherimide membrane has the best effect in the purification and demulsification of nitromethane. The nitromethane filtered by the membrane has high purity, low water content, short distillation time and high efficiency. Modified organic polymer membrane filtration can quickly and efficiently remove impurities such as moisture in crude nitromethane and pre-refined products, reduce the number of rectification reflux times and rectification reflux time, and improve the purity and yield of nitromethane products. Reduce energy consumption of rectification.
平均孔径为0.1μm的有机硅烷改性的聚醚酰亚胺亲油疏水膜能使硝基甲烷和水相有效分离，但是同样孔径条件下，利用分子孔径大小原理分离的分子筛膜和陶瓷膜无法有效地分离水相和硝基甲烷相，导致经膜过滤后的硝基甲烷相中水含量较高，硝基甲烷纯度低。The organosilane-modified polyetherimide lipophilic hydrophobic membrane with an average pore size of 0.1μm can effectively separate nitromethane from the water phase, but under the same pore size conditions, molecular sieve membranes and ceramic membranes separated by the principle of molecular pore size cannot Effectively separate the water phase and the nitromethane phase, resulting in a higher water content in the nitromethane phase after membrane filtration, and low nitromethane purity.
尽管上面已经示出和描述了本发明的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本发明的限制，本领域的普通技术人员在本发明的范围内可以对上述实施例进行变化、修改、替换和变型。Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can comment on the above-mentioned embodiments within the scope of the present invention. The embodiment undergoes changes, modifications, substitutions, and modifications.
表1硝基甲烷预精制和精制结果Table 1 Pre-refining and refining results of nitromethane
Figure PCTCN2021086228-appb-000001
Figure PCTCN2021086228-appb-000001

Claims (10)

  1. 一种硝基甲烷的精制方法，其特征在于，包括以下步骤：A method for refining nitromethane, which is characterized in that it comprises the following steps:
    (1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
    (2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，得到硝基甲烷精制成品。(2) Filter the rectified liquid fraction through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and collect the rectification permeate to obtain a refined nitromethane product.
  2. 一种硝基甲烷的精制方法，其特征在于，包括以下步骤：A method for refining nitromethane, which is characterized in that it comprises the following steps:
    (1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
    (2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，将收集的所述精馏透过液返回到步骤(1)中，再重复至少一次步骤(1)和(2)的操作，得到硝基甲烷精制成品。(2) Filter the liquid fraction of the rectification liquid through a lipophilic hydrophobic membrane that can separate the nitromethane and the water phase, collect the rectification permeate, and return the collected rectification permeate to step (1). In ), the operations of steps (1) and (2) are repeated at least one more time to obtain a refined product of nitromethane.
  3. 一种硝基甲烷的精制方法，其特征在于，包括以下步骤：A method for refining nitromethane, which is characterized in that it comprises the following steps:
    (1)将硝基甲烷粗品进行精馏，收集气相馏分进行冷凝处理，由此得到精馏液相馏分；(1) The crude nitromethane is rectified, and the gas phase fraction is collected for condensation treatment, thereby obtaining the rectified liquid phase fraction;
    (2)将所述精馏液相馏分经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集精馏透过液，监测其中水分和/或其他杂质的含量，(2) Filter the rectification liquid fraction through a lipophilic hydrophobic membrane that can separate nitromethane and water, collect the rectification permeate, and monitor the content of water and/or other impurities in it,
    当所述精馏透过液中水分和/或其他杂质的含量不满足质量要求时，将所述精馏透过液返回到步骤(1)中继续精馏；When the content of moisture and/or other impurities in the rectification permeate does not meet the quality requirements, return the rectification permeate to step (1) to continue rectification;
    当所述精馏透过液中水分和/或其他杂质的含量满足质量要求时，收集精馏透过液，得到硝基甲烷精制成品。When the content of moisture and/or other impurities in the rectification permeate meets the quality requirements, the rectification permeate is collected to obtain a refined nitromethane product.
  4. 根据权利要求1-3任一项所述的硝基甲烷的精制方法，其特征在于，The method for refining nitromethane according to any one of claims 1 to 3, characterized in that:
    所述硝基甲烷粗品来源于将由硫酸二甲酯与亚硝酸钠反应后进行蒸馏处理，馏出产物进行沉降分层，分离出下层的蒸馏液相馏分；The crude nitromethane is derived from the reaction of dimethyl sulfate and sodium nitrite, followed by distillation, the distilled product is subjected to sedimentation and stratification, and the lower distilled liquid fraction is separated;
    所述的硝基甲烷的精制方法中的步骤(1)包括如下步骤：Step (1) in the method for refining nitromethane includes the following steps:
    A、将所述硝基甲烷粗品经能将硝基甲烷和水相分离的亲油疏水膜或亲水疏油膜过滤，得到预精制产物；A. Filter the crude nitromethane through a lipophilic hydrophobic membrane or a hydrophilic and oleophobic membrane that can separate the nitromethane from the water phase to obtain a pre-refined product;
    B、将所述预精制产物进行精馏，收集气相馏分进行冷凝处理，得到精馏液相馏分。B. The pre-refined product is subjected to rectification, and the gas phase fraction is collected for condensation treatment to obtain the rectified liquid phase fraction.
  5. 根据权利要求4所述的硝基甲烷的精制方法，其特征在于，The method for refining nitromethane according to claim 4, wherein:
    当所述硝基甲烷粗品中硝基甲烷含量大于水分含量时，步骤A为：When the nitromethane content in the crude nitromethane product is greater than the moisture content, step A is:
    将所述硝基甲烷粗品经能将硝基甲烷和水相分离的亲油疏水膜过滤，收集蒸馏透过液，得到所述预精制产物。The crude nitromethane is filtered through a lipophilic hydrophobic membrane capable of separating the nitromethane and the water phase, and the distillation permeate is collected to obtain the pre-refined product.
  6. 根据权利要求4所述的硝基甲烷的精制方法，其特征在于，The method for refining nitromethane according to claim 4, wherein:
    当所述硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，步骤A为：When the moisture content in the crude nitromethane is greater than or equal to the nitromethane content, step A is:
    先用亲水疏油膜将所述硝基甲烷粗品进行预过滤，收集蒸馏截留液；再用亲油疏水膜将所述蒸馏截留液进行过滤，收集蒸馏透过液，得到所述预精制产物。The crude nitromethane is pre-filtered with a hydrophilic and oleophobic membrane to collect the distillation retentate; then the distillation retentate is filtered with a lipophilic and hydrophobic membrane to collect the distillation permeate to obtain the pre-refined product.
  7. 一种硝基甲烷的精制方法，其特征在于，包括以下步骤：A method for refining nitromethane, which is characterized in that it comprises the following steps:
    (1)将由硫酸二甲酯与亚硝酸钠反应后得到的产物进行蒸馏处理，所得馏出产物进行沉降分层，分离出下层的蒸馏液相馏分即为硝基甲烷粗品；(1) The product obtained after the reaction of dimethyl sulfate and sodium nitrite is subjected to distillation treatment, and the obtained distillate product is subjected to sedimentation and stratification, and the distilled liquid fraction in the lower layer is separated to be the crude nitromethane;
    (2)检测所述硝基甲烷粗品中硝基甲烷含量：(2) Detect the content of nitromethane in the crude nitromethane:
    当所述硝基甲烷粗品中硝基甲烷含量大于水分含量时，将所述硝基甲烷粗品经亲油疏水膜过滤，收集蒸馏透过液得到硝基甲烷预精制产物；When the nitromethane content in the crude nitromethane is greater than the moisture content, filtering the crude nitromethane through a lipophilic hydrophobic membrane, and collecting the distillation permeate to obtain the nitromethane pre-refined product;
    当所述硝基甲烷粗品中水分含量大于或等于硝基甲烷含量时，使用包括以下步骤：When the moisture content in the crude nitromethane is greater than or equal to the nitromethane content, the use includes the following steps:
    先用亲水疏油膜进行预过滤，收集蒸馏截留液；Pre-filter with hydrophilic and oleophobic membrane to collect distillation retentate;
    再用亲油疏水膜将所述蒸馏截留液进行过滤，再收集蒸馏透过液得到硝基甲烷预精制产物；Then use a lipophilic hydrophobic membrane to filter the distillation retentate, and then collect the distillation permeate to obtain a nitromethane pre-refined product;
    (3)将所述硝基甲烷预精制产物进行非精馏方式精制，得到硝基甲烷精制成品。(3) Refining the nitromethane pre-refined product in a non-rectification manner to obtain a refined nitromethane product.
  8. 根据权利要求1-7任一项所述的硝基甲烷的精制方法，其特征在于，The method for refining nitromethane according to any one of claims 1-7, wherein:
    所述亲水疏油膜或亲油疏水膜选自包含聚醚酰亚胺、聚醚酰胺、聚酰亚胺、聚酰胺、聚醚砜、聚醚醚酮中的任意一种或两种以上的改性膜，优选为聚醚酰亚胺改性膜。The hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is selected from any one or two or more of polyetherimide, polyetheramide, polyimide, polyamide, polyethersulfone, and polyetheretherketone The modified film is preferably a polyetherimide modified film.
  9. 根据权利要求1-7任一项所述硝基甲烷的精制方法，其特征在于，The method for refining nitromethane according to any one of claims 1-7, wherein:
    所述亲水疏油膜或亲油疏水膜为固定于中空支撑物的平板膜。The hydrophilic and oleophobic membrane or the lipophilic and hydrophobic membrane is a flat membrane fixed on a hollow support.
  10. 一种亲水疏油或亲油疏水的有机聚合物改性膜在硝基甲烷纯化作用中的用途。The use of a hydrophilic, oleophobic or oleophobic or hydrophobic organic polymer modified membrane in the purification of nitromethane.
PCT/CN2021/086228 2020-06-02 2021-04-09 Refinement method for nitromethane WO2021244136A1 (en)

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US3211630A (en) * 1964-05-28 1965-10-12 Commercial Solvents Corp Process for purification of nitromethane
US3480516A (en) * 1968-08-26 1969-11-25 Commercial Solvents Corp Separation of nitroalkanes and alkanes by codistilling with methanol
CN103553924A (en) * 2013-10-21 2014-02-05 石家庄铁道大学 Method for synthesizing nitromethane
CN105237404A (en) * 2015-09-17 2016-01-13 湖北远大富驰医药化工股份有限公司 Recovery method for water-phase nitromethane
CN106278901A (en) * 2016-08-16 2017-01-04 湖北远大富驰医药化工股份有限公司 A kind of new method of nitromethane purification
CN109053454A (en) * 2018-07-25 2018-12-21 湖北远大富驰医药化工股份有限公司 A kind of preparation method of nitromethane and the application of poly- (4-vinylpyridine)
CN111019127A (en) * 2019-12-24 2020-04-17 中海油天津化工研究设计院有限公司 Modified hyperbranched polyamidoamine polymer and preparation method thereof

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3211630A (en) * 1964-05-28 1965-10-12 Commercial Solvents Corp Process for purification of nitromethane
US3480516A (en) * 1968-08-26 1969-11-25 Commercial Solvents Corp Separation of nitroalkanes and alkanes by codistilling with methanol
CN103553924A (en) * 2013-10-21 2014-02-05 石家庄铁道大学 Method for synthesizing nitromethane
CN105237404A (en) * 2015-09-17 2016-01-13 湖北远大富驰医药化工股份有限公司 Recovery method for water-phase nitromethane
CN106278901A (en) * 2016-08-16 2017-01-04 湖北远大富驰医药化工股份有限公司 A kind of new method of nitromethane purification
CN109053454A (en) * 2018-07-25 2018-12-21 湖北远大富驰医药化工股份有限公司 A kind of preparation method of nitromethane and the application of poly- (4-vinylpyridine)
CN111019127A (en) * 2019-12-24 2020-04-17 中海油天津化工研究设计院有限公司 Modified hyperbranched polyamidoamine polymer and preparation method thereof

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