CN109096062B - Method for purifying polymethoxy dimethyl ether - Google Patents
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Abstract
Aiming at solving the problem that the long-term continuous production and operation are difficult to realize due to the existence of formaldehyde in the process of purifying polymethoxy dimethyl ether by a rectification method, the technical scheme comprising the following steps is adopted: firstly, removing methylal in a first separation tower to obtain a first tower bottom liquid from a reaction equilibrium mixture obtained by a reaction synthesis unit; the first tower bottom liquid enters a purifying kettle and contacts with the chemical treatment liquid to obtain the liquid containing PODE2～8Purifying the feed liquid; the purified feed liquid enters a second rectifying tower, a second fraction containing PODE2, methanol and water is separated from the top, and a second tower bottom liquid is obtained at the tower bottom; the second fraction enters a third rectifying tower, and a third fraction containing methanol and water is separated from the top of the third rectifying tower to obtain a third tower bottom liquid, namely a high-purity PODE2 product; the second tower bottom liquid enters a fourth rectifying tower, and a fourth rectifying tower product fraction is separated from the tower top of the fourth rectifying tower; the product fraction of the fourth rectifying tower is PODE3～4Or PODE3～5。
Description
Technical Field
The invention relates to a method for purifying polyoxymethylene dimethyl ethers, in particular to a method for preparing high-purity PODE (polyoxymethylene dimethyl ether) from a polyoxymethylene-containing polyoxymethylene dimethyl ether reaction mixture obtained in a reaction taking polyoxymethylene as a raw material3～4Products or PODE3～5A method of producing the product.
Background
With the rapid increase of energy consumption in modern society, the petroleum resources are increasingly tense, the environmental pressure is also increased, and the development of new clean diesel fuel is urgently needed. The oxygen-containing compound is used as the diesel additive, and no additional device or engine structure change is needed, so that the method is a convenient and effective measure and becomes a new idea for development of the petroleum industry.
Polyoxymethylene dimethyl ethers (PODE) are oxygen-containing compounds of the general formula CH3O(CH2O)nCH3Wherein n is an integer ≧ 1 (generally, the value is less than 10, and for PODE of different n, hereinafter, PODEN is expressed). Polymethoxy dimethyl ether, especially polymer with n ═ 3-5, not only has suitable melting point and boiling pointMeanwhile, the diesel oil has higher oxygen content (47-49%) and cetane number (78-100), which is beneficial to improving the combustion condition of diesel oil in an engine, improving the heat efficiency and reducing the pollutant emission; thus, PODE3～5The diesel fuel additive is an ideal component with great application prospect, can be used for partially replacing diesel oil, and improves the combustion efficiency of the diesel oil.
In recent years, the production of PODE has attracted much attention, and a large number of patents have been reported. In the process for synthesizing PODE from formaldehyde and methanol, water is inevitable as a reaction product, which is also a fatal disadvantage of the synthetic route. The reason is that under acidic conditions, the presence of water easily causes the polyoxymethylene dimethyl ethers to hydrolyze to form hemiacetal, and the hemiacetal is difficult to remove from the polyoxymethylene dimethyl ethers, so that the separation and purification of the polyoxymethylene dimethyl ethers are more complicated.
The method for controlling water content from the source is to prepare polymethoxy dimethyl ether by taking methylal and trioxymethylene or cheap paraformaldehyde as raw materials, however, most patent reports pay attention to the selection of a raw material route and a catalyst, and no deep research report is made on the subsequent separation and purification. US2449269 and US5746785 describe the synthesis of polyoxymethylene dimethyl ethers from methylal and paraformaldehyde (or concentrated formaldehyde solution) in the presence of sulfuric acid and formic acid. European patent EP1070755A1 discloses a process for preparing polymethoxy dimethyl ether by reacting methylal with paraformaldehyde in the presence of trifluorosulfonic acid, the conversion of methylal being 54%, PODE being2～5The yield of (b) was 51.2%. CN103664549A and CN103880614A adopt paraformaldehyde as raw materials and solid super acid as a catalyst to synthesize polymethoxy dimethyl ether, the product of which contains unreacted raw materials of methylal and paraformaldehyde, and the composition of a reaction mixture contains 8.3 percent of unreacted paraformaldehyde besides methylal and polymethoxy dimethyl ether.
In the preparation method of polymethoxy dimethyl ether, not only products, unreacted raw materials, formaldehyde (or paraformaldehyde) dissolved in a system, and even by-product methanol and the like exist in a reaction mixture, and the reaction mixture needs to be separated and purified to obtain pure PODE for adding diesel oil.The preparation processes of polymethoxy dimethyl ether introduced in CN101048357A and CN102786397A adopt multi-stage series rectification towers to prepare PODE3～4Unreacted formaldehyde (or trioxymethylene) with PODE as the target product2The distillate is directly recycled to the reaction unit as a recycled material after rectification, so that the separation of formaldehyde (or trioxymethylene) is avoided. However, PODE2Having good solubility properties, is a potentially good solvent, and must involve the separation of formaldehyde when this fraction needs to be separated off separately or is not suitable for direct return to the synthesis unit.
Our long-term study of the separation by distillation of the reaction mixture obtained by reacting methylal with paraformaldehyde found that PODE was isolated2During the rectification process, formaldehyde is easy to gather into white solids on a condenser and is accumulated along with the operation of the device, so that the blockage of a return pipe and a discharge pipe causes the shutdown maintenance, and the long-term continuous production operation is difficult. Chinese patent CN103333060B discloses a method for refining and purifying polymethoxy dialkyl ether, which adds 40-50 wt% sodium hydroxide aqueous solution into the equilibrium product of the reaction for condensation and reflux to achieve the purpose of eliminating the formaldehyde reaction. However, the method needs 2 hours of condensation and reflux, and has long treatment time, which is not beneficial to the scale-up of production.
Therefore, the separation problem of formaldehyde is a technical bottleneck influencing the continuous and stable operation of the polymethoxy dimethyl ether separation process.
Disclosure of Invention
The invention aims to solve the technical problem of formaldehyde separation in the purification process of rectifying to purify the polymethoxy dimethyl ether, and provides a method for refining the polymethoxy dimethyl ether, which simply and rapidly eliminates the influence of formaldehyde, has low cost and is beneficial to long-term continuous operation of production.
In order to solve the technical problem of formaldehyde separation, the technical scheme of the invention is as follows: a process for purifying polymethoxy dimethyl ether comprising:
(a) firstly, removing methylal fraction in a first separation tower to obtain a reaction equilibrium mixture obtained by a reaction synthesis unit to obtain first tower bottom liquid;
(b) the first tower bottom liquid enters a purifying kettle and contacts with the chemical treatment liquid added into the purifying kettle, and the chemical treatment waste liquid is discharged from the bottom of the purifying kettle to obtain the product containing PODE2～8Purifying the feed liquid;
(c) the purified feed liquid enters a second rectifying tower, and a second fraction containing PODE2, methanol and water is separated from the top of the second rectifying tower to obtain a second tower bottom liquid;
(d) the second fraction enters a third rectifying tower, and a third fraction containing methanol and water is separated from the top of the third rectifying tower to obtain a third tower bottom liquid;
(e) the second tower bottom liquid enters a fourth rectifying tower, and a fourth rectifying tower product fraction is separated from the tower top of the fourth rectifying tower;
the chemical treatment fluid comprises an aqueous dispersion selected from the group consisting of alkaline compounds; the third tower bottom liquid is a high-purity PODE2 product; the product fraction of the fourth rectifying tower is PODE3～4Or PODE3～5。
Under the condition that the technical scheme is disclosed, a person skilled in the art can reasonably adjust the process conditions such as the operating pressure and the tower top temperature of the fourth rectifying tower according to the market demand condition, and select the product fraction of the fourth rectifying tower as PODE3～4Or PODE3～5。
In the above technical solution, the alkaline compound is preferably selected from metal hydroxides or metal sulfites, and the metal is more preferably an alkali metal or an alkaline earth metal.
In the above-mentioned embodiment, the basic compound preferably includes Ca (OH)2、KOH、NaOH、Mg(OH)2、Na2SO3And K2SO3At least one compound of (a).
In the above-mentioned embodiment, the basic compound preferably includes Ca (OH)2、KOH、NaOH、Mg(OH)2、Na2SO3And K2SO3At least two compounds of (1).
As one of the most preferred embodiments, where the alkaline compound comprises both a metal hydroxide and a metal sulfite, we have surprisingly found that the metal hydroxideImprovement of PODE by compound and metal sulfite3～4And/or PODE3～5The purity and purity of the PODE2 fraction have a synergistic effect. By way of non-limiting example, such as but not limited to Ca (OH)2With Na2SO3NaOH and Na2SO3KOH and K2SO3. The mass ratio of the metal hydroxide to the metal sulfite is more preferably 0.1 to 10, for example, but not limited to, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and the like, and still more preferably 0.5 to 8.
As a second preferred technical scheme, the alkaline compound comprises a first metal hydroxide and a second metal hydroxide, wherein the first metal hydroxide is preferably NaOH, and the second metal hydroxide is preferably KOH or Ca (OH)2When the first metal hydroxide and the second hydroxide are increasing PODE3～4And/or PODE3～5The purity and purity of the PODE2 fraction have a synergistic effect. By way of non-limiting example, such as but not limited to, combinations of first and second metal hydroxides are NaOH and KOH, NaOH and Ca (OH)2And so on. The mass ratio of the first metal hydroxide to the second hydroxide is more preferably 0.1 to 10, for example, but not limited to, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and the like, and still more preferably 0.5 to 8.
In the above technical solution, the reaction synthesis unit in step (a) preferably uses a compound containing formaldehyde or solid formaldehyde (trioxymethylene or paraformaldehyde) as a starting material, and most preferably polyformaldehyde.
In the above technical solution, the reaction equilibrium mixture in step (a) preferably comprises methylal, formaldehyde, methanol, water and PODE2～8The most preferable formaldehyde content is 0.1 to 6%, and the water content is preferably 0.1 to 5%.
In the above technical solution, the first separation column in step (a) is preferably an atmospheric distillation column, a vacuum distillation column or a flash distillation column.
The above techniquesIn the method, the first column bottoms preferably comprises PODE2-8And formaldehyde.
In the above technical solution, the mass percentage of water in the chemical treatment liquid in the step (b) is preferably 30 to 70%, and more preferably 40 to 60%.
In the above technical solution, the amount of the chemical treatment liquid in the step (b) is preferably 5-20% of the first tower bottoms.
In the above technical solutions, those skilled in the art understand that the purification tank in step (b) is a liquid-liquid mixing device, and those commonly used in the art can be selected, for example, but not limited to, the device can be a stirred tank, a counter-current contact tower, an extraction tower, and the like.
In the above technical scheme, the working pressure of the purification kettle in the step (b) is not particularly limited, but is preferably normal pressure, and the operating temperature of the purification kettle is preferably 30-90 ℃; the residence time of the materials in the purification kettle is preferably 5-60 min, and more preferably 10-30 min.
In the above technical solution, the second distillation column in the step (c) is preferably an atmospheric column.
In the above technical solution, the second bottom liquid in step (c) preferably contains PODE3～8The mixture of (1), wherein the content of PODE2 is not more than 0.5%.
In the technical scheme, the operating pressure of the third rectifying tower in the step (d) is 0.1-0.5 MPa, the tower top temperature is 70-130 ℃, the reflux ratio is 1-10, and the optimal reflux ratio is 2-6.
In the above technical solution, the third column bottoms of step (d) contains PODE2The content is preferably 98-99.9%.
In the above technical solution, the product fraction PODE in the step (e)3～4Or PODE3～5The purity is preferably 98-99.9%.
Unless otherwise specified,% referred to in the present invention means weight percent or weight percent content.
We have surprisingly found that this process is based on rectification, after separation of the methylal, by reaction with a mixture of dimethyl ethers containing dimethyl ethersThe alkaline substances with catalytic action are contacted, the formaldehyde can be removed by utilizing the waste heat of the first rectifying tower, the operation is simple, the efficiency is higher, the influence of the formaldehyde on the rectifying process is greatly reduced, the rectifying efficiency is improved, the contact time is short, and the reaction is thoroughly beneficial to enlarging production. PODE in product fraction obtained by the process3～4/PODE3～5The purity reaches more than 98 percent, and PODE with the purity of more than 98 percent is obtained at the same time2The product can ensure the smooth separation and continuous rectification of the paraformaldehyde.
Drawings
FIG. 1 is a process flow diagram of an embodiment of the present invention.
Obtaining a reaction equilibrium mixture 1 of polymethoxy dimethyl ether in a reaction synthesis unit, firstly passing through a first rectifying tower 2, distilling out a first fraction 5 containing methanol and unreacted methylal from the top of the tower, allowing a first tower bottom liquid 4 to enter a purifying kettle 6 through a heat-insulating pipeline to contact with a chemical treatment liquid 5, separating out a chemical treatment waste liquid 7 to obtain a purified material liquid 8, entering a second rectifying tower 9, collecting a fraction 10 containing PODE2, methanol and water from the top, and obtaining a second tower bottom liquid 11 containing PODE 3-8 from the bottom of the tower; the second fraction 10 enters a third rectifying tower 12, and a third fraction 13 containing methanol and water is separated from the top of the tower to obtain a third tower bottom liquid 14; the second tower bottom liquid 11 enters a fourth rectifying tower 15, and high-purity PODE is separated from the tower top3～4Or PODE3～5Product fraction 16. The first fraction 3 and the fourth bottom liquid 17 can be used as circulating materials to return to the synthesis unit to participate in the synthesis reaction. The third bottoms 14 may be returned to the synthesis unit as recycle or withdrawn as high purity PODE2 product.
Detailed Description
[ example 1 ]
The method comprises the steps of taking paraformaldehyde and methylal as raw materials, carrying out catalytic reaction to obtain a reaction mixture, and carrying out atmospheric distillation in a first distillation tower to remove a first fraction to obtain a first tower bottom liquid with the temperature of 105 ℃. The first tower bottom liquid enters a purifying kettle to contact and react with the chemical treatment liquid; the chemical treatment liquid is a 40% alkaline water solution prepared by a solid mixture of NaOH and KOH and water in a mass ratio of 1: 1; the amount of the first tower bottom liquid is 10 percent. Medicine for treating rheumatismThe reaction temperature of the reaction kettle is 90 ℃, the stirring reaction time is 20min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, wherein the temperature of the tower bottom is 155 ℃, and extracting a second fraction containing PODE2, methanol and water from the top. And the second fraction enters a third rectifying tower, is rectified under the conditions that the operating pressure is 0.2MPa, the reflux ratio is 6 and the tower top temperature is 92.5 ℃, and light components are separated from the tower top to obtain a third tower bottom liquid, namely a PODE2 product. The second tower bottom liquid enters a fourth rectifying tower, and high-purity PODE is separated from the tower top3～4Or PODE3～5And (3) product fractions. And the first fraction and the fourth tower bottom liquid are returned to the synthesis unit as circulating materials to participate in the reaction. The contents were analyzed by gas chromatography and the results are shown in Table 1.
Comparative example 1
The method comprises the steps of taking paraformaldehyde and methylal as raw materials, carrying out catalytic reaction to obtain a reaction mixture, and carrying out atmospheric distillation in a first distillation tower to remove a first fraction to obtain a first tower bottom liquid with the temperature of 105 ℃. The first tower bottom liquid directly enters a second rectifying tower without a purifying kettle and is directly rectified; as a result, it was found that: after about 2 hours, a large amount of white solids are adhered to the wall of the condensing pipe in the condenser at the top of the rectifying tower, the condensate at the top of the rectifying tower is turbid, continuous rectification cannot be carried out continuously, and the rectifying tower is stopped.
[ example 2 ]
The method comprises the steps of taking paraformaldehyde and methylal as raw materials, carrying out catalytic reaction to obtain a reaction mixture, and carrying out atmospheric distillation in a first distillation tower to remove a first fraction to obtain a first tower bottom liquid with the temperature of 105 ℃. The first tower bottom liquid enters a purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is 40% NaOH aqueous solution, and the dosage of the chemical treatment liquid is 10% of that of the first tower bottom liquid. The reaction temperature of the purification kettle is 90 ℃, the stirring reaction time is 20min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, and rectifying under normal pressure, wherein white solids are separated out from the top of the second rectifying tower after about 4 hours. The composition analysis found that the formaldehyde content in the purified feed was relatively high, and the results are shown in Table 1 c.
[ example 3 ]
The method comprises the steps of taking paraformaldehyde and methylal as raw materials, carrying out catalytic reaction to obtain a reaction mixture, and carrying out atmospheric distillation in a first distillation tower to remove a first fraction to obtain a first tower bottom liquid with the temperature of 105 ℃. The first tower bottom liquid enters a purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is KOH aqueous solution with the concentration of 40 percent, and the dosage of the chemical treatment liquid is 10 percent of the first tower bottom liquid. The reaction temperature of the purification kettle is 90 ℃, the stirring reaction time is 20min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, and rectifying under normal pressure, wherein white solids are separated out from the top of the second rectifying tower after about 3 hours. The composition analysis found that the formaldehyde content in the purified feed was relatively high, and the results are shown in Table 1 c.
[ example 4 ]
The method comprises the steps of taking paraformaldehyde and methylal as raw materials, carrying out catalytic reaction to obtain a reaction mixture, and carrying out atmospheric distillation in a first distillation tower to remove a first fraction to obtain a first tower bottom liquid with the temperature of 105 ℃. The first tower bottom liquid enters a purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is Ca (OH) with the mass ratio of 2:12And Na2SO330% alkaline water mixed solution prepared by the solid mixture and water; the amount of the first tower bottom liquid is 5 percent. The reaction temperature of the purification kettle is 80 ℃, the stirring reaction time is 30min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, wherein the temperature of the tower bottom is 155 ℃, and extracting a second fraction containing PODE2, methanol and water from the top. And the second fraction enters a third rectifying tower, is rectified under the conditions that the operating pressure is 0.1MPa, the reflux ratio is 10 and the tower top temperature is 73 ℃, and light components are separated from the tower top to obtain a third tower bottom liquid, namely a PODE2 product. The second tower bottom liquid enters a fourth rectifying tower, and high-purity PODE is separated from the tower top3～4Or PODE3～5And (3) product fractions. And the first fraction and the fourth tower bottom liquid are returned to the synthesis unit as circulating materials to participate in the reaction. The contents were analyzed by gas chromatography and the results are shown in Table 2.
[ example 5 ]
Obtained in the same manner as in example 4The first tower bottom liquid enters the purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is Ca (OH)2A 30% suspension prepared with water; the amount of the first tower bottom liquid is 5 percent. The reaction temperature of the purification kettle is 80 ℃, the stirring reaction time is 30min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, and finding that white solids are separated out from the top of the second rectifying tower in the rectifying process. The composition analysis found that the formaldehyde content in the purified feed was relatively high, and the results are shown in Table 1 c.
[ example 6 ]
Obtaining a first tower bottom liquid in the same way as the example 4, and enabling the first tower bottom liquid to enter a purifying kettle to react with the chemical treatment liquid; the chemical treatment solution is 30% Na2SO3An aqueous solution; the amount of the first tower bottom liquid is 5 percent. The reaction temperature of the purification kettle is 80 ℃, the stirring reaction time is 30min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, and finding that white solids are separated out from the top of the second rectifying tower in the rectifying process. The composition analysis found that the formaldehyde content in the purified feed was relatively high, and the results are shown in Table 1 c.
[ example 7 ]
Obtaining a first tower bottom liquid in the same way as the example 1, and enabling the first tower bottom liquid to enter a purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is 50% alkaline water solution prepared by solid mixture of NaOH and Ca (OH)2 and water in a mass ratio of 4: 1; the amount of the first tower bottom liquid is 15 percent. The reaction temperature of the purification kettle is 70 ℃, the stirring reaction time is 10min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, wherein the temperature of the tower bottom is 155 ℃, and extracting a second fraction containing PODE2, methanol and water from the top. And the second fraction enters a third rectifying tower, is rectified under the conditions that the operating pressure is 0.4MPa, the reflux ratio is 3 and the tower top temperature is 114.8 ℃, and light components are separated from the tower top to obtain a third tower bottom liquid, namely a PODE2 product. The second tower bottom liquid enters a fourth rectifying tower, and high-purity PODE is separated from the tower top3～4Or PODE3～5And (3) product fractions. And the first fraction and the fourth tower bottom liquid are returned to the synthesis unit as circulating materials to participate in the reaction. The contents were analyzed by gas chromatography and the results are shown in Table 3.
[ example 8 ]
Obtaining a first tower bottom liquid in the same way as the example 1, and enabling the first tower bottom liquid to enter a purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is NaOH and Na with the mass ratio of 6:12SO360% alkali water solution prepared by the solid mixture and water; the dosage of the first tower bottom liquid is 20 percent of the first tower bottom liquid. The reaction temperature of the purification kettle is 60 ℃, the stirring reaction time is 40min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, wherein the temperature of the tower bottom is 155 ℃, and extracting a second fraction containing PODE2, methanol and water from the top. And the second fraction enters a third rectifying tower, is rectified under the conditions that the operating pressure is 0.3MPa, the reflux ratio is 4 and the tower top temperature is 105 ℃, and light components are separated from the tower top to obtain a third tower bottom liquid, namely a PODE2 product. The second tower bottom liquid enters a fourth rectifying tower, and high-purity PODE is separated from the tower top3～4Or PODE3～5And (3) product fractions. And the first fraction and the fourth tower bottom liquid are returned to the synthesis unit as circulating materials to participate in the reaction. The contents were analyzed by gas chromatography and the results are shown in Table 4.
[ example 9 ]
Obtaining a first tower bottom liquid in the same way as the example 1, and enabling the first tower bottom liquid to enter a purifying kettle to react with the chemical treatment liquid; the chemical treatment liquid is KOH and K with the mass ratio of 8:12SO3A 50% aqueous alkali solution prepared from the solid mixture and water; the amount of the first tower bottom liquid is 8 percent. The reaction temperature of the purification kettle is 40 ℃, the stirring reaction time is 60min, and then chemical treatment liquid is separated to obtain the product containing PODE2-5The purified feed liquid of (1). And (3) feeding the purified feed liquid into a second rectifying tower, rectifying under normal pressure, wherein the temperature of the tower bottom is 155 ℃, and extracting a second fraction containing PODE2, methanol and water from the top. The second fraction enters a third rectifying tower, is rectified under the conditions that the operating pressure is 0.5MPa, the reflux ratio is 2.1 and the tower top temperature is 123 ℃, and light components are separated from the tower top to obtain the first fractionThe three-tower bottom liquid is PODE2 product. The second tower bottom liquid enters a fourth rectifying tower, and high-purity PODE is separated from the tower top3～4Or PODE3～5And (3) product fractions. And the first fraction and the fourth tower bottom liquid are returned to the synthesis unit as circulating materials to participate in the reaction. The contents were analyzed by gas chromatography and the results are shown in Table 5.
TABLE 1
TABLE 1c
TABLE 2
TABLE 3
TABLE 4
TABLE 5
Claims (10)
1. A process for purifying polymethoxy dimethyl ether comprising:
(a) firstly, removing a methylal fraction (3) in a first separation tower (2) to obtain a first tower bottom liquid (4) from a reaction equilibrium mixture (1) obtained in a reaction synthesis unit;
(b) first of allThe tower bottom liquid enters a purifying kettle (6) to contact with chemical treatment liquid (5) added into the purifying kettle, and the chemical treatment waste liquid (7) is separated to obtain the product containing PODE2～8The purified feed liquid (8);
(c) feeding the purified feed liquid (8) into a second rectifying tower (9), and separating a second fraction (10) containing PODE2, methanol and water from the top to obtain a second tower bottom liquid (11);
(d) the second fraction (10) enters a third rectifying tower (12), a third fraction (13) containing methanol and water is separated from the top of the third rectifying tower (12), and a third tower bottom liquid (14) is obtained;
(e) the second tower bottom liquid (11) enters a fourth rectifying tower (15), and a fourth rectifying tower product fraction (16) is separated from the tower top of the fourth rectifying tower;
the chemical treatment liquid (5) comprises an aqueous dispersion selected from basic compounds; the basic compound comprises Ca (OH)2、KOH、NaOH、Mg(OH)2、Na2SO3And K2SO3At least two compounds of (a); the third tower bottom liquid (14) is a high-purity PODE2 product; the product fraction (16) of the fourth rectifying tower is PODE3～4Or PODE3～5。
2. The method for purifying polymethoxy dimethyl ether according to claim 1, wherein the first separation column of the step (a) is an atmospheric distillation column, a vacuum distillation column or a flash distillation column.
3. The method of claim 1, wherein the first column bottoms comprises methanol, water, PODE2-8And formaldehyde.
4. The method for purifying polymethoxy dimethyl ether according to claim 3, wherein the chemical treatment liquid in the step (b) contains water in an amount of 30 to 70% by mass.
5. The method for purifying polymethoxy dimethyl ether according to claim 1, wherein the amount of the chemical treatment liquid in the step (b) is 5 to 20% of the first bottom liquid.
6. The method for purifying polymethoxy dimethyl ether according to claim 1, wherein the purifying vessel in step (b) is a stirred vessel or a countercurrent contact tower, and the operating temperature is 30-90 ℃.
7. The method for purifying polymethoxy dimethyl ether according to claim 1, wherein the second rectifying tower of the step (c) is an atmospheric tower.
8. The method of claim 1, wherein the third distillation column in step (d) is operated at a pressure of 0.1-0.5 MPa, a temperature at the top of the column of 70-130 ℃, and a reflux ratio of 1-10.
9. The process according to claim 1, wherein PODE is present in the third bottom liquid of step (d)2The content is 98-99.9%.
10. Process according to claim 1, characterized in that the product fraction PODE of step (e) is3～4Or PODE3～5The purity is 98-99.9%.
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| FR3094178B1 (en) * | 2019-03-28 | 2021-05-14 | Arkema France | AQUEOUS COMPOSITION BASED ON POLYOXYMETHYLENES DIALKYL ETHERS (POM) AND ITS USE FOR THE CONSERVATION AND / OR BIRTH OF THE HUMAN OR ANIMAL BODY |
| CN110031569A (en) * | 2019-05-17 | 2019-07-19 | 四川省产品质量监督检验检测院 | A kind of separation and measuring method of polymethoxy dimethyl ether |
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