CN114276216B - Method for removing aldehyde impurities in 1, 3-propylene glycol - Google Patents
Method for removing aldehyde impurities in 1, 3-propylene glycol Download PDFInfo
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Abstract
The invention provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps: mixing the 1, 3-propylene glycol reaction liquid with hydrazine, heating to react, adding alkali to react continuously to obtain a reduction product, separating the reduction product, decoking the obtained reaction kettle material, and decompressing and rectifying the decoked Jiao Liufen to obtain the 1, 3-propylene glycol product. According to the method, according to the characteristics of aldehyde groups, hydrazine and alkali are used for reducing the aldehyde groups into alkyl groups, so that aldehyde impurities in reaction liquid are removed in a large amount, the total aldehyde content is obviously reduced, the boiling point of corresponding impurities can be obviously reduced by converting the aldehyde groups into the alkyl groups, the purification difficulty of 1, 3-propylene glycol is reduced, and a high-purity product is obtained; in the method, the 1, 3-propylene glycol can be used as a solvent without introducing new substances, so that the influence on the quality of the product is reduced; the method has the advantages of simple operation procedure, simple and convenient operation, reduced equipment investment and easy industrialized implementation.
Description
Technical Field
The invention belongs to the technical field of chemical separation, and relates to a method for removing aldehyde impurities in 1, 3-propanediol.
Background
1, 3-propanediol is used as an important organic chemical raw material for producing unsaturated polyester, plasticizer, surfactant, emulsifier and demulsifier, for example, as raw material for producing polyester polyol, initiator for producing polyether polyol and chain extender for producing polyurethane, etc., and can be widely used in engineering plastics, clothing fabric, paint, cosmetics, pharmacy, etc., especially as main raw material for producing poly (1, 3-propanediol terephthalate) (PTT); the PTT fiber is a novel polyester fiber with excellent performance, combines the characteristics of softness of nylon, fluffiness of acrylic fibers, dirt resistance of terylene, inherent elasticity, normal-temperature dyeing and the like, integrates the excellent performance of various fibers, and becomes one of the most popular novel polymer materials at present.
The raw materials for PTT synthesis are terephthalic acid and 1, 3-propylene glycol, and the quality of the 1, 3-propylene glycol product has a great influence on the characteristics of PTT fiber, for example, the purity of the product can influence the intrinsic viscosity of the product, and the aldehyde content and chromaticity of the product can influence the appearance of PTT; therefore, the research on synthesizing the high-purity 1, 3-propanediol is one of the current hot spots, and mainly comprises two major types, namely a chemical method and a biological method, wherein the chemical method comprises an ethylene oxide carbonylation method and an acrolein hydration hydrogenation method, wherein the acrolein hydration hydrogenation method has the characteristics of low technical difficulty, mild process conditions, high atom utilization rate and the like, and is one of the current industrialized routes, but in the method, acrolein and an intermediate product 3-hydroxy propanal are unstable and are extremely easy to generate polycondensation reaction, so that aldehyde byproducts are generated, more byproducts are generated after hydrogenation, the components of a reaction system are complex, and aldehyde impurities are important factors affecting the quality of PTT fibers, so that the removal of the aldehyde impurities is a key step in the process of purifying the 1, 3-propanediol.
CN 110790636a discloses a refining method for removing trace aldehyde groups in 1, 3-propylene glycol, which comprises the steps of adding sulfonic acid ionic liquid into 1, 3-propylene glycol dehydration concentrate containing trace aldehyde group impurities, carrying out aldehyde removal reaction by catalyzing aldehyde groups through the ionic liquid, and obtaining a product with low aldehyde content and high purity of 1, 3-propylene glycol through vacuum rectification; although the method can obviously reduce the content of aldehyde impurities, the ionic liquid has higher cost, complicated preparation process and lower product yield, and is not suitable for mass preparation.
CN 112979420a discloses a process for purifying 1, 3-propanediol, which comprises the steps of: the preparation method comprises the steps of adjusting and reacting a raw material containing 1, 3-propylene glycol through pH, wherein the raw material contains aldehyde organic matters to obtain a reaction product; the reaction product is subjected to first rectification and second reduced pressure rectification to obtain crude 1, 3-propanediol; and (3) adsorbing the crude 1, 3-propanediol by resin and performing third rectification to obtain the 1, 3-propanediol. The method utilizes the characteristic of aldehyde substances, adds reactants to convert the aldehyde substances into macromolecular substances, but side reactions can also occur, and the yield of the product is lower although the aldehyde content can be reduced, and resin adsorption operation is also needed, so that the operation is complex and the cost is higher.
In summary, for removing aldehyde impurities in the 1, 3-propanediol reaction solution, a proper process and operation are required to be selected, so that the yield of the 1, 3-propanediol product is improved while the aldehyde impurities are sufficiently removed, the operation is simplified, and the cost is reduced.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention aims to provide a method for removing aldehyde impurities in 1, 3-propylene glycol, which adopts a yellow crotyl reaction, utilizes hydrazine and alkali to reduce aldehyde groups into alkyl groups, so that the aldehyde impurities in reaction liquid are removed in a large amount, the total aldehyde content is obviously reduced, and meanwhile, the boiling point of corresponding impurities can be obviously reduced by converting the aldehyde groups into the alkyl groups, thereby being beneficial to separation and purification of the 1, 3-propylene glycol and further preparing a high-purity 1, 3-propylene glycol product; the method has the advantages of simple operation procedure, mild condition, lower cost and easy industrialized implementation.
To achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps:
(1) Mixing the 1, 3-propylene glycol reaction solution with hydrazine, heating to react, adding alkali to continue to react to obtain a reduction product, and separating the reduction product to obtain a reaction kettle material;
(2) Decoking the reaction kettle material obtained in the step (1) to obtain decoked Jiao Liufen;
(3) And (3) carrying out reduced pressure rectification on the removed Jiao Liufen obtained in the step (2) to obtain a 1, 3-propylene glycol product.
According to the invention, separation and purification are carried out on the synthesized 1, 3-propanediol, wherein removal of aldehyde impurities is a key step, according to the characteristics of aldehyde groups, a yellow crotyl reaction is adopted to react the aldehyde groups with hydrazine to generate hydrazones, the hydrazones are destroyed to form alkyl groups, the aldehyde groups are reduced to the alkyl groups, so that a large amount of aldehyde impurities in reaction liquid are removed, the total aldehyde content is obviously reduced, the boiling point of the converted product is obviously reduced compared with that of original aldehyde impurities and 1, 3-propanediol, the purification difficulty of the 1, 3-propanediol is reduced, the reduced product is directly separated out through synchronous rectification in the reaction process, and then the high-purity 1, 3-propanediol product can be obtained through the purification steps of decoking and reduced pressure rectification;
according to the characteristics of the yellow cron reaction, alcohols are also required to be used as solvents, and the 1, 3-propanediol can be used as the solvents without introducing new substances, so that the influence on the product quality is reduced, and the treatment cost is reduced; the method has the advantages of simple operation procedure, simple and convenient operation, reduced equipment investment and easy industrialized implementation.
The following technical scheme is a preferred technical scheme of the invention, but is not a limitation of the technical scheme provided by the invention, and the technical purpose and beneficial effects of the invention can be better achieved and realized through the following technical scheme.
As a preferable technical scheme of the invention, the 1, 3-propanediol reaction liquid in the step (1) is obtained by an acrolein hydration hydrogenation process.
Preferably, the composition of the 1, 3-propanediol reaction liquid in the step (1) comprises 1, 3-propanediol, 3-hydroxypropanal, 3-hydroxymethyl tetrahydropyran, 1, 3-dioxane-2-ethanol, 5, 6-dihydropyran-3-formaldehyde, 4-hetero-oxo-heptanediol and water.
Preferably, the composition of the 1, 3-propanediol reaction solution in step (1) comprises, in terms of mass concentration, 95.0wt% or less of 1, 3-propanediol, for example 95.0wt%, 94.0wt%, 93.0wt%, 92.0wt%, 91.0wt% or 90.0wt% or the like, 0.1wt% or less of 3-hydroxypropionaldehyde, for example 0.1wt%, 0.05wt%, 0.01wt% or 0.005wt% or the like, 0.1wt% or less of 3-hydroxymethyltetrahydropyran, for example 0.1wt%, 0.05wt%, 0.01wt% or 0.005wt% or the like, 0.1wt% or less of 1, 3-dioxane-2-ethanol, such as 0.1wt%, 0.05wt%, 0.01wt% or 0.005wt% etc., 5, 6-dihydropyran-3-carbaldehyde.ltoreq.0.1 wt%, such as 0.1wt%, 0.05wt%, 0.01wt% or 0.005wt% etc., 4-hetero-oxo-heptanediol.ltoreq.0.1 wt%, such as 0.1wt%, 0.05wt% or 0.005wt% etc., 4-hetero-oxo-heptanediol.ltoreq.5.0 wt%, such as 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt% or 7.0wt% etc., water.ltoreq.0.2 wt%, such as 0.2wt%, 0.19wt%, 0.18wt%, 0.16wt% or 0.15wt% etc.; wherein the total aldehyde concentration is less than or equal to 1000ppm, such as 1000ppm, 800ppm, 600ppm, 500ppm, 400ppm, 200ppm, 100ppm, etc., but is not limited to the recited values, and other non-recited values within the respective ranges are equally applicable.
In the invention, the reaction liquid of the 1, 3-propylene glycol obtained by the acrolein hydration hydrogenation process contains various aldehyde byproducts, and the aldehyde byproducts can obviously influence the product performance, so that the total aldehyde content of the reaction liquid can be generally defined to reflect the purity of the product, and the total aldehyde content is measured by taking formaldehyde as a reference; according to the mass concentration of each component in the invention, the water content is very low, which indicates that the reaction liquid has been subjected to concentration treatment.
According to the composition in the 1, 3-propanediol reaction liquid, aldehyde substances 3-hydroxy propionaldehyde, 5, 6-dihydropyran-3-formaldehyde and 4-hetero-oxo-heptanediol are subjected to aldehyde reduction reaction to correspondingly generate n-propanol, 3-methyl-5, 6-dihydropyran and n-propyl ether, and compared with corresponding aldehydes, the respective boiling points are obviously reduced, so that separation of reduction products is facilitated.
As a preferred technical scheme of the invention, the hydrazine in the step (1) is added in the form of a hydrazine hydrate solution.
Preferably, the concentration of the hydrazine hydrate solution is 50 to 85wt%, such as 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the hydrazine hydrate solution is present in an amount of 0.01 to 1.0wt%, for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.25wt%, 0.5wt%, 0.75wt%, or 1.0wt%, based on the mass of the 1, 3-propanediol reaction solution, but the hydrazine hydrate solution is not limited to the above-mentioned values, and other non-mentioned values are equally applicable, preferably 0.1 to 0.3wt%.
Preferably, step (1) is carried out by adding hydrazine and then heating to 90 to 120 ℃, for example, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, or the like, but not limited to the values listed, and other non-listed values in the range are equally applicable, and the reaction is carried out by reacting aldehyde impurities with hydrazine to generate hydrazone, and the reaction time is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or the like, but not limited to the values listed, and other non-listed values in the range are equally applicable.
As a preferred embodiment of the present invention, the base in step (1) comprises any one or a combination of at least two of an alkali metal hydroxide, a rare earth metal hydroxide or a solid super base, and typical but non-limiting examples of such combinations are: a combination of an alkali metal hydroxide and a rare earth metal hydroxide, a combination of a rare earth metal hydroxide and a solid super alkali, a combination of an alkali metal hydroxide, a rare earth metal hydroxide and a solid super alkali, and the like.
In the present invention, the alkali metal hydroxide includes sodium hydroxide, potassium hydroxide, etc., the rare earth metal hydroxide includes lanthanum hydroxide, ytterbium hydroxide, etc., and the solid super base includes K 2 O/γ-Al 2 O 3 、Na-Na 2 CO 3 /γ-Al 2 O 3 Etc.
Preferably, the amount of the base added in the step (1) is 0.01 to 1wt%, for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.25wt%, 0.5wt%, 0.75wt%, or 1.0wt%, etc., based on the mass of the 1, 3-propanediol reaction solution, but the amount is not limited to the above-mentioned values, and other non-mentioned values in the above-mentioned value range are applicable, preferably 0.1 to 0.3wt%.
Preferably, the reaction after adding the alkali in the step (1) is that hydrazone is decomposed to generate alkyl under the action of the alkali, the reaction temperature is 90-180 ℃, such as 90 ℃, 95 ℃, 100 ℃, 110 ℃, 120 ℃, 150 ℃ or 180 ℃, and the like, the reaction temperature is not fixed, and the temperature gradually rises along with the reaction, but does not exceed 180 ℃; the reaction time is 1 to 10 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 8 hours, or 10 hours, etc., but is not limited to the exemplified values, and other non-exemplified values within the range are applicable, and preferably 2 to 5 hours.
As a preferable technical scheme of the invention, the reaction in the step (1) is carried out in a reaction rectifying device.
Preferably, the reaction of step (1) is carried out with a rectification process also taking place to separate the reduced product from the 1, 3-propanediol.
Preferably, the theoretical plate number of the reactive distillation apparatus is not more than 10, for example, 10, 9, 8, 7, 6 or 5, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable; the reflux ratio is not more than 3, for example, 3, 2.5, 2, 1.5, 1, or the like, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the reactor temperature of the reactive distillation apparatus is not more than 180 ℃, for example 180 ℃, 178 ℃, 175 ℃, 172 ℃, 170 ℃, 165 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
As a preferred embodiment of the present invention, the decoking in step (2) is performed in a decoking tower.
Preferably, the theoretical plate number of the coke-removing tower is not more than 20, such as 20, 17, 15, 12, 10, 8 or 5, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable; the reflux ratio is not more than 3, for example, 3, 2.5, 2, 1.5, 1, or the like, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the operating absolute pressure of the coke removal column is no greater than 5kPa, such as 5kPa, 4kPa, 3kPa, 2kPa, 1kPa or 0.5kPa, etc., but is not limited to the listed values and other non-listed values within this range of values are equally applicable; the overhead operating temperature is 90 to 135 ℃, for example 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, or 135 ℃, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the mass proportion of the decoking Jiao Liufen extracted from the top of the decoking tower is 90-95 wt%, such as 90wt%, 91wt%, 92wt%, 93wt%, 94wt% or 95wt%, etc., but is not limited to the recited values, and other non-recited values within the range of the values are equally applicable.
As a preferable technical scheme of the invention, the reduced pressure rectification in the step (3) is performed in a rectifying tower.
Preferably, the theoretical plate number of the rectifying column is not more than 30, for example, 30, 28, 25, 22, 20 or 15, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable; the reflux ratio is not more than 5, for example, 5, 4, 3, 2.5, 2, or 1, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the pressure reduction distillation is operated at an absolute pressure of no greater than 5kPa, such as 5kPa, 4kPa, 3kPa, 2kPa, 1kPa or 0.5kPa, etc., but is not limited to the listed values, and other non-listed values within this range of values are equally applicable.
As a preferable technical scheme of the invention, in the step (3), the front fraction and the main fraction are sequentially extracted from the top of the rectifying tower during the vacuum rectification.
The overhead temperature at the time of drawing the front-end fraction is preferably 90 to 134 ℃, for example 90 ℃, 100 ℃, 110 ℃, 120 ℃, 125 ℃, 130 ℃, 134 ℃ or the like, but is not limited to the values recited, and other values not recited in the range are equally applicable.
Preferably, the front-end fraction comprises 1 to 10wt% of the feed except Jiao Liufen, for example 1wt%, 2wt%, 3wt%, 5wt%, 6wt%, 8wt%, or 10wt%, etc., but is not limited to the recited values, as other non-recited values within this range are equally applicable.
Preferably, the overhead temperature at the time of taking out the main fraction is 92 to 135 ℃, for example 92 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 120 ℃, 130 ℃, 135 ℃, or the like, but is not limited to the values recited, and other values not recited in the range are equally applicable.
Preferably, the main fraction comprises 85 to 95wt% of the feed except Jiao Liufen, such as 85wt%, 86wt%, 88wt%, 90wt%, 92wt% or 95wt%, etc., but is not limited to the recited values, as other non-recited values within this range are equally applicable.
As a preferred embodiment of the invention, the operations of the method are carried out in a protective atmosphere, the pressure of the operations of the steps being provided by the protective atmosphere.
Preferably, the protective atmosphere comprises nitrogen and/or an inert gas.
In the invention, the protective atmosphere is adopted because oxidation reaction can occur under the air condition, so that the heavy components and tar content of the tower kettle are increased, and the product yield is reduced.
As a preferred technical solution of the present invention, the method comprises the steps of:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, the composition of the 1, 3-propylene glycol reaction liquid comprises less than or equal to 95.0wt% of 1, 3-hydroxy propanal less than or equal to 0.1wt%, 3-hydroxymethyl tetrahydropyran less than or equal to 0.1wt% of 1, 3-dioxane-2-ethanol less than or equal to 0.1wt%,5, 6-dihydropyran-3-formaldehyde less than or equal to 0.1wt%, 4-hetero-oxo heptanediol more than or equal to 5.0wt% and water less than or equal to 0.2wt%, wherein the total aldehyde concentration is less than or equal to 1000ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 50-85 wt%, the added amount of the hydrazine hydrate solution accounts for 0.01-1.0 wt% of the mass ratio of the 1, 3-propanediol reaction solution, the temperature is raised to 90-120 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 1-5 h;
then adding alkali to continue the reaction, wherein the alkali comprises any one or a combination of at least two of alkali metal hydroxide, rare earth metal hydroxide and solid super alkali, the addition amount of the alkali accounts for 0.01-1wt% of the 1, 3-propanediol reaction liquid, the reaction after adding the alkali is that hydrazone is decomposed into corresponding functional groups under the action of the alkali to obtain alkyl, the reaction temperature is 90-180 ℃, and the reaction time is 2-5 hours, so as to obtain a reduction product; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is not more than 10, the reflux ratio is not more than 3, and the temperature of the tower kettle is not more than 180 ℃;
(2) Decoking the reaction kettle material obtained in the step (1), wherein the decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is not more than 20, the reflux ratio is not more than 3, the operation absolute pressure of the decoking tower is not more than 5kPa, the tower top operation temperature is 90-135 ℃, the decoking Jiao Liufen is obtained, and the decoking Jiao Liufen extracted from the tower top accounts for 90-95 wt% of the entering reaction kettle material;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is not more than 30, the reflux ratio is not more than 5, and the operation absolute pressure of the reduced pressure rectification is not more than 5kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 90-134 ℃ when the front cut is extracted, the mass proportion of the main cut is 1-10 wt% except Jiao Liufen, the operation temperature of the top of the rectifying tower is 92-135 ℃ when the main cut is extracted, the mass proportion of the main cut is 85-95 wt% except Jiao Liufen, and the main cut is the required 1, 3-propylene glycol product.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the method, according to the characteristics of aldehyde groups, a yellow crotyl reaction is adopted, and hydrazine and alkali are used for reducing the aldehyde groups into alkyl groups, so that a large amount of aldehyde impurities in reaction liquid are removed, and the total aldehyde content is obviously reduced;
(2) The method can obviously reduce the boiling point of corresponding impurities by converting aldehyde groups into alkyl groups, thereby reducing the purification difficulty of 1, 3-propanediol, directly separating reduction products by synchronous rectification in the reaction process, and obtaining the 1, 3-propanediol with the purity of more than 99.97wt% and the total aldehyde content of less than 5.0ppm by the purification steps of decoking and reduced pressure rectification;
(3) In the method, the 1, 3-propylene glycol can be used as a solvent without introducing new substances, so that the influence on the quality of the product is reduced, and the treatment cost is reduced;
(4) The method has the advantages of simple operation procedure, simple and convenient operation, reduced equipment investment and easy industrialized implementation.
Detailed Description
For better illustrating the present invention, the technical scheme of the present invention is convenient to understand, and the present invention is further described in detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
The invention provides a method for removing aldehyde impurities in 1, 3-propanediol, which comprises the following steps:
(1) Mixing the 1, 3-propylene glycol reaction solution with hydrazine, heating to react, adding alkali to continue to react to obtain a reduction product, and separating the reduction product to obtain a reaction kettle material;
(2) Decoking the reaction kettle material obtained in the step (1) to obtain decoked Jiao Liufen;
(3) And (3) carrying out reduced pressure rectification on the removed Jiao Liufen obtained in the step (2) to obtain a 1, 3-propylene glycol product.
The following are exemplary but non-limiting examples of the invention:
example 1:
the embodiment provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, and the composition of the 1, 3-propylene glycol reaction liquid comprises, by mass, 94.3% of 1, 3-propylene glycol, 0.08% of 3-hydroxypropanal, 0.05% of 3-hydroxymethyl tetrahydropyran, 0.04% of 1, 3-dioxane-2-ethanol, 0.03% of 5, 6-dihydropyran-3-formaldehyde, 0.01% of 4-hetero-oxo-heptanediol, 5.4% of 4-hetero-oxo-heptanediol and 0.09% of water, wherein the total aldehyde concentration is 450.8ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 85wt%, the adding amount of the hydrazine hydrate solution accounts for 0.18wt% of the mass of the 1, 3-propanediol reaction solution, the temperature is raised to 100 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 3 hours;
then adding sodium hydroxide for continuous reaction, wherein the adding amount of the sodium hydroxide accounts for 0.19 weight percent of the mass ratio of the 1, 3-propanediol reaction solution, and the reaction after adding the sodium hydroxide is that hydrazone is decomposed into corresponding functional groups to generate alkyl under the action of the hydrazone, the reaction temperature is 90 ℃, and the reaction time is 5 hours, so that a reduction product is obtained; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is 10, the reflux ratio is 1, and the temperature of the tower kettle is increased to 180 ℃ to finish;
(2) Decoking the reaction kettle material obtained in the step (1), wherein the decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is 20, the reflux ratio is 3, the operation absolute pressure of the decoking tower is 1kPa, the tower top operation temperature is 100-105 ℃, the decoking Jiao Liufen is obtained, and the mass ratio of Jiao Liufen extracted from the tower top to the entering reaction kettle material is 94.33wt%;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is 30, the reflux ratio is 5, and the operation absolute pressure of the reduced pressure rectification is 1kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 100-103 ℃ when the front cut is extracted, the mass proportion of the main cut divided by Jiao Liufen is 7.30wt%, the operation temperature of the top of the rectifying tower is 103-104 ℃ when the main cut is extracted, the mass proportion of the main cut divided by Jiao Liufen is 88.92wt%, and the main cut is the required 1, 3-propylene glycol product.
In the embodiment, through the treatment of the step (1), the reduced products of propanol, 3-methyl-5, 6-dihydropyran and n-propyl ether can be separated, the mass concentration of the total aldehyde in the reaction kettle material is 24.7ppm, the mass concentration of the 1, 3-propanediol product in the main fraction obtained in the step (3) is 99.99wt%, and the total aldehyde content is only 2.5ppm, so that the index requirement of the polymerization grade 1, 3-propanediol for fibers can be met.
Example 2:
the embodiment provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, and the composition of the 1, 3-propylene glycol reaction liquid comprises, by mass, 94.3% of 1, 3-propylene glycol, 0.08% of 3-hydroxypropanal, 0.05% of 3-hydroxymethyl tetrahydropyran, 0.04% of 1, 3-dioxane-2-ethanol, 0.03% of 5, 6-dihydropyran-3-formaldehyde, 0.01% of 4-hetero-oxo-heptanediol, 5.4% of 4-hetero-oxo-heptanediol and 0.09% of water, wherein the total aldehyde concentration is 450.8ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 85wt%, the adding amount of the hydrazine hydrate solution accounts for 0.15wt% of the mass of the 1, 3-propanediol reaction solution, the temperature is raised to 95 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 4 hours;
then adding potassium hydroxide for continuous reaction, wherein the adding amount of the potassium hydroxide accounts for 0.16 weight percent of the 1, 3-propanediol reaction solution, the reaction after adding the potassium hydroxide is that hydrazone is decomposed into corresponding functional groups to generate alkyl under the action of the hydrazone, the reaction temperature is 100 ℃, and the reaction time is 3 hours, so that a reduction product is obtained; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is 8, the reflux ratio is 2, and the temperature of the tower kettle is increased to 180 ℃ to finish;
(2) Decoking the reaction kettle material obtained in the step (1), wherein the decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is 18, the reflux ratio is 2, the operation absolute pressure of the decoking tower is 3kPa, the operation temperature of the tower top is 120-125 ℃, the decoking Jiao Liufen is obtained, and the mass ratio of Jiao Liufen extracted from the tower top to the entering reaction kettle material is 93.11wt%;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is 25, the reflux ratio is 4, and the operation absolute pressure of the reduced pressure rectification is 3kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 120-123 ℃ when the front cut is extracted, the mass proportion of the main cut divided by Jiao Liufen is 9.36wt%, the operation temperature of the top of the rectifying tower is 123-124 ℃ when the main cut is extracted, the mass proportion of the main cut divided by Jiao Liufen is 86.00wt%, and the main cut is the required 1, 3-propylene glycol product.
In the embodiment, through the treatment of the step (1), the reduced products of propanol, 3-methyl-5, 6-dihydropyran and n-propyl ether can be separated, the mass concentration of the total aldehyde in the reaction kettle material is 38.4ppm, the mass concentration of the 1, 3-propanediol product in the main fraction obtained in the step (3) is 99.98wt%, and the total aldehyde content is only 4.8ppm, so that the index requirement of the polymerization grade 1, 3-propanediol for fibers can be met.
Example 3:
the embodiment provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, and the composition of the 1, 3-propylene glycol reaction liquid comprises, by mass, 94.3% of 1, 3-propylene glycol, 0.08% of 3-hydroxypropanal, 0.05% of 3-hydroxymethyl tetrahydropyran, 0.04% of 1, 3-dioxane-2-ethanol, 0.03% of 5, 6-dihydropyran-3-formaldehyde, 0.01% of 4-hetero-oxo-heptanediol, 5.4% of 4-hetero-oxo-heptanediol and 0.09% of water, wherein the total aldehyde concentration is 450.8ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 85wt%, the adding amount of the hydrazine hydrate solution accounts for 0.3wt% of the mass of the 1, 3-propanediol reaction solution, the temperature is raised to 90 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 5 hours;
then adding potassium hydroxide for continuous reaction, wherein the adding amount of the potassium hydroxide accounts for 0.3 weight percent of the 1, 3-propanediol reaction solution, the reaction after adding the potassium hydroxide is that hydrazone is decomposed into corresponding functional groups to generate alkyl under the action of the hydrazone, the reaction temperature is 110 ℃, and the reaction time is 2 hours, so that a reduction product is obtained; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is 9, the reflux ratio is 3, and the temperature of the tower kettle is increased to 180 ℃ to finish;
(2) Decoking the reaction kettle material obtained in the step (1), wherein decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is 15, the reflux ratio is 2.5, the operation absolute pressure of the decoking tower is 0.5kPa, the tower top operation temperature is 90-94 ℃, the decoking Jiao Liufen is obtained, and the decoking Jiao Liufen extracted from the tower top accounts for 94.36wt% of the entering reaction kettle material;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is 20, the reflux ratio is 4.5, and the operation absolute pressure of the reduced pressure rectification is 0.5kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 90-93 ℃ when the front cut is extracted, the mass proportion of the main cut is 5.32wt% except Jiao Liufen, the operation temperature of the top of the rectifying tower is 93-94 ℃ when the main cut is extracted, the mass proportion of the main cut is 93.15wt% except Jiao Liufen, and the main cut is the required 1, 3-propylene glycol product.
In the embodiment, through the treatment of the step (1), the reduced products of propanol, 3-methyl-5, 6-dihydropyran and n-propyl ether can be separated, the mass concentration of the total aldehyde in the reaction kettle material is 3.5ppm, the mass concentration of the 1, 3-propanediol product in the main fraction obtained in the step (3) is 99.99wt%, and the total aldehyde content is only 0.7ppm, so that the index requirement of the polymerization grade 1, 3-propanediol for fibers can be met.
Example 4:
the embodiment provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, and the composition of the 1, 3-propylene glycol reaction liquid comprises 93.8wt% of 1, 3-propylene glycol, 0.1wt% of 3-hydroxy-propionaldehyde, 0.06wt% of 3-hydroxymethyl-tetrahydropyran, 0.05wt% of 1, 3-dioxane-2-ethanol, 0.05wt% of 5, 6-dihydropyran-3-formaldehyde, 0.03wt% of 4-hetero-oxo-heptanediol, 5.75wt% of 4-hetero-oxo-heptanediol and 0.16wt% of water according to mass concentration, wherein the total aldehyde concentration is 667.8ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 75wt%, the adding amount of the hydrazine hydrate solution accounts for 0.5wt% of the mass of the 1, 3-propanediol reaction solution, the temperature is raised to 110 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 2 hours;
then adding solid super strong base K 2 O/γ-Al 2 O 3 Continuing the reaction, wherein the adding amount of the catalyst accounts for 0.5 weight percent of the mass ratio of the 1, 3-propanediol reaction solution, and the reaction after adding the solid super alkali is that hydrazone is decomposed into corresponding functional groups to generate alkyl under the action of the hydrazone, the reaction temperature is 95 ℃, and the reaction time is 4 hours, so that a reduction product is obtained; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is 10, the reflux ratio is 2, and the temperature of the tower kettle is increased to 170 ℃ to finish;
(2) Decoking the reaction kettle material obtained in the step (1), wherein the decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is 20, the reflux ratio is 3, the operation absolute pressure of the decoking tower is 5kPa, the tower top operation temperature is 131-135 ℃, the decoking Jiao Liufen is obtained, and the mass ratio of Jiao Liufen extracted from the tower top to the entering reaction kettle material is 93.2wt%;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is 30, the reflux ratio is 3, and the operation absolute pressure of the reduced pressure rectification is 5kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 131-134 ℃ when the front cut is extracted, the mass proportion of the material fed except Jiao Liufen is 6.10wt%, the operation temperature of the top of the rectifying tower is 134-135 ℃ when the main cut is extracted, the mass proportion of the material fed except Jiao Liufen is 92.05wt%, and the main cut is the required 1, 3-propylene glycol product.
In the embodiment, through the treatment of the step (1), the reduced products of propanol, 3-methyl-5, 6-dihydropyran and n-propyl ether can be separated, the mass concentration of the total aldehyde in the reaction kettle material is 6.2ppm, the mass concentration of the 1, 3-propanediol product in the main fraction obtained in the step (3) is 99.99wt%, and the total aldehyde content is only 0.9ppm, so that the index requirement of the polymerization grade 1, 3-propanediol for fibers can be met.
Example 5:
the embodiment provides a method for removing aldehyde impurities in 1, 3-propylene glycol, which comprises the following steps:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, and the composition of the 1, 3-propylene glycol reaction liquid comprises 94.5wt% of 1, 3-propylene glycol, 0.05wt% of 3-hydroxy-propionaldehyde, 0.04wt% of 3-hydroxymethyl-tetrahydropyran, 0.03wt% of 1, 3-dioxane-2-ethanol, 0.03wt% of 5, 6-dihydropyran-3-formaldehyde, 0.02wt% of 4-hetero-oxo-heptanediol, 5.15wt% of 4-hetero-oxo-heptanediol and 0.18wt% of water according to mass concentration, wherein the total aldehyde concentration is 375.4ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 50wt%, the adding amount of the hydrazine hydrate solution accounts for 1.0wt% of the mass ratio of the 1, 3-propanediol reaction solution, the temperature is raised to 120 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 1h;
then adding lanthanum hydroxide for continuous reaction, wherein the adding amount of the lanthanum hydroxide accounts for 0.6wt% of the mass ratio of the 1, 3-propanediol reaction solution, and the reaction after adding the lanthanum hydroxide is that hydrazone is decomposed into corresponding functional groups to generate alkyl under the action of the hydrazone, the reaction temperature is 120 ℃, and the reaction time is 2 hours, so that a reduction product is obtained; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is 10, the reflux ratio is 2.5, and the temperature of the tower kettle is increased to 175 ℃ to finish;
(2) Decoking the reaction kettle material obtained in the step (1), wherein the decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is 20, the reflux ratio is 3, the operation absolute pressure of the decoking tower is 2kPa, the tower top operation temperature is 112-116 ℃, the decoking Jiao Liufen is obtained, and the mass ratio of Jiao Liufen extracted from the tower top to the entering reaction kettle material is 93.58wt%;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is 28, the reflux ratio is 1, and the operation absolute pressure of the reduced pressure rectification is 2kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 112-115 ℃ when the front cut is extracted, the mass proportion of the main cut divided by Jiao Liufen is 4.32wt%, the operation temperature of the top of the rectifying tower is 115-116 ℃ when the main cut is extracted, the mass proportion of the main cut divided by Jiao Liufen is 92.15wt%, and the main cut is the required 1, 3-propylene glycol product.
In the embodiment, through the treatment of the step (1), the reduced products of propanol, 3-methyl-5, 6-dihydropyran and n-propyl ether can be separated, the mass concentration of the total aldehyde in the reaction kettle material is 3.15ppm, the mass concentration of the 1, 3-propanediol product in the main fraction obtained in the step (3) is 99.99wt%, and the total aldehyde content is only 0.5ppm, so that the index requirement of the polymerization grade 1, 3-propanediol for fibers can be met.
Example 6:
this example provides a process for removing aldehyde impurities from 1, 3-propanediol, the process being distinguished only by the fact that, with reference to the process in example 1: in the step (1), the hydrazine hydrate solution and the sodium hydroxide are added simultaneously, and the reaction time is the sum of the two reaction times.
In this example, since the hydrazine hydrate solution and sodium hydroxide are added simultaneously, the conversion reaction of the aldehyde group proceeds with the conversion of the subsequent alkyl group being affected by insufficient reaction of the aldehyde impurities, so that the total aldehyde mass concentration in the reaction vessel is 60.4ppm, the mass concentration of the 1, 3-propanediol product in the main fraction obtained in step (3) is 99.97wt%, and the total aldehyde content is 9.82ppm.
Comparative example 1:
this comparative example provides a process for removing aldehyde impurities from 1, 3-propanediol, which process is distinguished only by the fact that it is referred to the process in example 1: the operation of step (1) is not included.
In the comparative example, as aldehyde reduction reaction is not carried out, aldehyde impurities in the reaction liquid can only be removed through decoking and reduced pressure rectification, and the removal of the aldehyde impurities is limited, and the total aldehyde content in the obtained 1, 3-propanediol product is still 58.8ppm; and because the difference of boiling points of aldehyde impurities and 1, 3-propanediol is smaller, the loss of 1, 3-propanediol is larger while the aldehyde is removed, and the yield of 1, 3-propanediol is only 75.5 percent, which is obviously reduced compared with the embodiment 1.
According to the method, according to the characteristics of aldehyde groups, the yellow crotyl reaction is adopted, and hydrazine and alkali are used for reducing the aldehyde groups into alkyl groups, so that a large amount of aldehyde impurities in the reaction solution are removed, and the total aldehyde content is obviously reduced; the method can obviously reduce the boiling point of corresponding impurities by converting aldehyde groups into alkyl groups, thereby reducing the purification difficulty of 1, 3-propanediol, directly separating reduction products by synchronous rectification in the reaction process, and obtaining the 1, 3-propanediol with the purity of more than 99.97wt% and the total aldehyde content of less than 5.0ppm by the purification steps of decoking and reduced pressure rectification; in the method, the 1, 3-propylene glycol can be used as a solvent without introducing new substances, so that the influence on the quality of the product is reduced, and the treatment cost is reduced; the method has the advantages of simple operation procedure, simple and convenient operation, reduced equipment investment and easy industrialized implementation.
The present invention is described in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e., it does not mean that the present invention must be practiced depending on the above detailed methods. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitutions for the method of the present invention, addition of auxiliary steps, selection of specific modes, etc., are within the scope of the present invention and the scope of the disclosure.
Claims (26)
1. A method for removing aldehyde impurities from 1, 3-propanediol, comprising the steps of:
(1) Mixing 1, 3-propylene glycol reaction liquid and hydrazine, heating to 90-120 ℃ for reaction, wherein the composition of the 1, 3-propylene glycol reaction liquid comprises 1, 3-propylene glycol, 3-hydroxy-propionaldehyde, 3-hydroxymethyl tetrahydropyran, 1, 3-dioxane-2-ethanol, 5, 6-dihydropyran-3-formaldehyde, 4-hetero-oxo-heptanediol and water, wherein the total aldehyde concentration is less than or equal to 1000ppm, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, the reaction time is 1-5 h, then alkali is added for continuous reaction, the alkali is selected from any one or a combination of at least two of alkali metal hydroxide, rare earth metal hydroxide and solid super alkali, the reaction after the alkali is added is that the hydrazone is decomposed to generate alkyl under the action of the alkali, the reaction temperature is 90-180 ℃ and the reaction time is 1-10 h, so as to obtain a reduction product, when the reaction is carried out, the rectification process is carried out, the reduction product and the 1, 3-propanediol are separated, so that the reduction product is separated is obtained;
(2) Decoking the reaction kettle material obtained in the step (1) to obtain decoked Jiao Liufen;
(3) Performing vacuum distillation on the removed Jiao Liufen obtained in the step (2), wherein during the vacuum distillation, the top of a distillation tower sequentially extracts a front fraction and a main fraction, and the main fraction is a 1, 3-propylene glycol product;
in the method, each operation is carried out in a protective atmosphere, and the pressure of each operation is provided by the protective atmosphere.
2. The method of claim 1, wherein the 1, 3-propanediol reaction solution in step (1) is obtained from acrolein by a hydrohydrogenation process.
3. The method according to claim 1, wherein the composition of the 1, 3-propanediol reaction solution in the step (1) comprises, in mass concentration, not more than 95.0 wt.% of 1, 3-propanediol, not more than 0.1 wt.% of 3-hydroxypropanal, not more than 0.1 wt.% of 3-hydroxymethyltetrahydropyran, not more than 0.1 wt.% of 1, 3-dioxane-2-ethanol, not more than 0.1 wt.% of 5, 6-dihydropyran-3-formaldehyde, not more than 0.1 wt.% of 4-heteroarylheptanal, not more than 5.0 wt.% of 4-heteroarylheptanediol, and not more than 0.2 wt.% of water.
4. The method of claim 1, wherein the hydrazine of step (1) is added as a hydrazine hydrate solution.
5. The method according to claim 4, wherein the concentration of the hydrazine hydrate solution is 50 to 85wt%.
6. The method according to claim 5, wherein the hydrazine hydrate solution accounts for 0.1-1.0 wt% of the 1, 3-propanediol reaction solution.
7. The method according to claim 6, wherein the hydrazine hydrate solution accounts for 0.1 to 0.3wt% of the 1, 3-propanediol reaction solution.
8. The method according to claim 1, wherein the alkali in the step (1) is added in an amount of 0.1 to 1wt% based on the mass of the 1, 3-propanediol reaction solution.
9. The method according to claim 8, wherein the alkali in the step (1) is added in an amount of 0.1 to 0.3wt% based on the mass of the 1, 3-propanediol reaction solution.
10. The process of claim 1, wherein the reaction time after the addition of the base in step (1) is 2 to 5 hours.
11. The method of claim 1, wherein the reaction of step (1) is performed in a reactive distillation apparatus.
12. The process of claim 11 wherein the theoretical plate number of the reactive distillation apparatus is no greater than 10 and the reflux ratio is no greater than 3.
13. The method of claim 11, wherein the reactor temperature of the reactive distillation apparatus does not exceed 180 ℃.
14. The method of claim 1, wherein the decoking of step (2) is performed in a decoking tower.
15. The method of claim 14, wherein the theoretical plate number of the decoking tower is no greater than 20 and the reflux ratio is no greater than 3.
16. The method of claim 14 wherein the operating absolute pressure of the decoking column is no greater than 5kPa and the overhead operating temperature is between 90 ℃ and 135 ℃.
17. The method of claim 14, wherein the decoking tower overhead withdrawn decoking Jiao Liufen comprises 90 to 95wt% of the incoming reaction vessel material.
18. The method according to claim 1, wherein the reduced pressure rectification of step (3) is performed in a rectification column.
19. The method of claim 18, wherein the theoretical plate number of the rectifying column is not more than 30 and the reflux ratio is not more than 5.
20. The method of claim 18, wherein the vacuum distillation is operated at an absolute pressure of no greater than 5kPa.
21. The process of claim 1 wherein the overhead operating temperature at which the pre-cut fraction is withdrawn in step (3) is from 90 to 134 ℃.
22. The process according to claim 1, wherein the front-end fraction comprises from 1 to 10% by weight of the feed divided by Jiao Liufen.
23. The process of claim 1 wherein the overhead operating temperature at which step (3) is carried out to produce the main fraction is from 92 to 135 ℃.
24. The method according to claim 1, wherein the main fraction accounts for 85-95 wt% of the feed except Jiao Liufen.
25. The method of claim 1, wherein the protective atmosphere comprises nitrogen and/or an inert gas.
26. The method according to claim 1, characterized in that it comprises the steps of:
(1) Mixing 1, 3-propylene glycol reaction liquid with hydrazine, and then heating to react, wherein the 1, 3-propylene glycol reaction liquid is obtained by an acrolein hydration hydrogenation process, the composition of the 1, 3-propylene glycol reaction liquid comprises less than or equal to 95.0wt% of 1, 3-hydroxy propanal less than or equal to 0.1wt%, 3-hydroxymethyl tetrahydropyran less than or equal to 0.1wt% of 1, 3-dioxane-2-ethanol less than or equal to 0.1wt%,5, 6-dihydropyran-3-formaldehyde less than or equal to 0.1wt%, 4-hetero-oxo heptanediol more than or equal to 5.0wt% and water less than or equal to 0.2wt%, wherein the total aldehyde concentration is less than or equal to 1000ppm; the hydrazine is added in the form of hydrazine hydrate solution, the concentration of the hydrazine hydrate solution is 50-85 wt%, the adding amount of the hydrazine hydrate solution accounts for 0.1-1.0 wt% of the mass ratio of the 1, 3-propanediol reaction solution, the temperature is raised to 90-120 ℃ for reaction, the reaction is that aldehyde impurities react with the hydrazine to generate hydrazone, and the reaction time is 1-5 h;
then adding alkali to continue the reaction, wherein the alkali is selected from any one or a combination of at least two of alkali metal hydroxide, rare earth metal hydroxide and solid super alkali, the addition amount of the alkali accounts for 0.1-1wt% of the 1, 3-propanediol reaction liquid, the reaction after adding the alkali is that hydrazone is decomposed into corresponding functional groups to generate alkyl under the action of the alkali, the reaction temperature is 90-180 ℃, and the reaction time is 2-5 h, so that a reduction product is obtained; the reaction is carried out in a reaction rectifying device, and a rectifying process is carried out while the reaction is carried out, so that a reduction product and 1, 3-propylene glycol are separated to obtain a reaction kettle material; the theoretical plate number of the reaction rectifying device is not more than 10, the reflux ratio is not more than 3, and the temperature of the tower kettle is not more than 180 ℃;
(2) Decoking the reaction kettle material obtained in the step (1), wherein the decoking is performed in a decoking tower, the theoretical plate number of the decoking tower is not more than 20, the reflux ratio is not more than 3, the operation absolute pressure of the decoking tower is not more than 5kPa, the tower top operation temperature is 90-135 ℃, the decoking Jiao Liufen is obtained, and the decoking Jiao Liufen extracted from the tower top accounts for 90-95 wt% of the entering reaction kettle material;
(3) Performing reduced pressure rectification on the removal Jiao Liufen obtained in the step (2), wherein the reduced pressure rectification is performed in a rectifying tower, the theoretical plate number of the rectifying tower is not more than 30, the reflux ratio is not more than 5, and the operation absolute pressure of the reduced pressure rectification is not more than 5kPa; the top of the rectifying tower sequentially extracts a front cut and a main cut, the operation temperature of the top of the rectifying tower is 90-134 ℃ when the front cut is extracted, the mass proportion of the main cut is 1-10 wt% except Jiao Liufen, the operation temperature of the top of the rectifying tower is 92-135 ℃ when the main cut is extracted, the mass proportion of the main cut is 85-95 wt% except Jiao Liufen, and the main cut is the required 1, 3-propylene glycol product.
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