CN113214145B - Vitamin B6 production method - Google Patents

Vitamin B6 production method Download PDF

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CN113214145B
CN113214145B CN202110382414.5A CN202110382414A CN113214145B CN 113214145 B CN113214145 B CN 113214145B CN 202110382414 A CN202110382414 A CN 202110382414A CN 113214145 B CN113214145 B CN 113214145B
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ester acyl
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CN113214145A (en
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柳道晗
杨家友
王海
肖谦
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Anhui Taige Vitamin Industrial Co ltd
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07DHETEROCYCLIC COMPOUNDS
    • C07D213/00Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/62Oxygen or sulfur atoms
    • C07D213/63One oxygen atom
    • C07D213/65One oxygen atom attached in position 3 or 5
    • C07D213/66One oxygen atom attached in position 3 or 5 having in position 3 an oxygen atom and in each of the positions 4 and 5 a carbon atom bound to an oxygen, sulphur, or nitrogen atom, e.g. pyridoxal
    • C07D213/672-Methyl-3-hydroxy-4,5-bis(hydroxy-methyl)pyridine, i.e. pyridoxine

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention belongs to the technical field of vitamin production, and particularly discloses a production method of vitamin B6. The production method comprises the steps of distilling and purifying an ester acyl crude product obtained by ester acylation reaction to obtain an ester acyl pure product and a distillation residue containing a byproduct of 2,2' -oxalylamino dipropionic acid ethyl ester; then hydrolyzing the distillation residue containing the by-product ethyl 2,2' -oxalylamino dipropionate; performing ester acylation reaction on the hydrolysate to prepare an ester acyl substance, and purifying the reaction product to obtain an ester acyl substance pure product; the obtained pure product of the ester acyl is used for cyclization reaction. The invention provides a production method of vitamin B6, which improves the yield of an ester acylation reaction step and solves the problem of black tar substances in the production process by separating and utilizing a byproduct of 2,2' -oxalylamino dipropionic acid ethyl ester.

Description

Vitamin B6 production method
Technical Field
The invention relates to the technical field of vitamin production, in particular to a production method of vitamin B6.
Background
Vitamin B6 (Vitamin B6), also known as pyridoxine, pyridoxine or pyridoxamine, is an important water-soluble Vitamin, an indispensable Vitamin for humans and animals, and can participate in various metabolic reactions. The vitamin B6 is mainly used for feed additives, food additives, medicines, cosmetics and the like.
The current process for synthesizing vitamin B6 is an ethoxy oxazole process, which is mature and stable, but has the disadvantage of lower overall yield. The first step in the synthesis of vitamin B6 is the esterification reaction, which is carried out synchronously with the acylation reaction, and the main product is an ester acyl compound, and various byproducts are produced at the same time. During the reaction, alanine, oxalic acid, ethanol and diethyl oxalate are dissolved and added into benzene for reflux water diversion reaction, wherein the diethyl oxalate participates in the reaction and is one of the products, and the reaction is balanced in theory. The general reaction formula is as follows:
The reaction comprises three dehydration reactions: the carboxyl group of alanine and ethanol are dehydrated to form ester, the amino group of alanine and carboxylic acid on one side of oxalic acid are dehydrated to form amide, and the carboxyl group on the other side of oxalic acid and ethanol are dehydrated to form ester. However, in the reaction process, the carboxyl on the other side of oxalic acid inevitably reacts with amino, namely side reaction occurs, and the reaction formula is as follows:
The side reaction produces ethyl 2,2' -oxalylamino dipropionate as the main side product of the ester acylation reaction. The proportion of the byproducts in the product is influenced by factors such as reaction temperature, time, proportion and the like, and the production of the byproducts can be reduced by controlling proper reaction conditions, but the proportion of the byproducts in the industrial process optimized for many years still reaches more than 8 percent, namely the quantity of the byproducts is more than 8 percent of the target product, which is the main factor influencing the yield of the step. In production, in order to reduce the production of the by-product, it is generally required to greatly increase the amount of oxalic acid or diethyl oxalate, which reduces the economic efficiency.
The byproduct not only can reduce the yield of the step of the ester acylation reaction, but also more importantly, as the product of the first step cannot be purified in the current industrial production process, namely, the crude product of the ester acyl product obtained after the solvent is recovered after the reaction of the first step is ended directly enters the step of the cyclization reaction, the byproduct also enters the step of the cyclization reaction, and the byproduct also affects the next step of the cyclization reaction. In particular, on the one hand, under severely cyclized dehydration conditions, the by-product can further polymerize into complex tar-like substances, forming solid hazardous waste, causing pipeline blockage, and being unfavorable for process operation; on the other hand, the by-product also consumes the dehydration reagents phosphorus oxychloride and triethylamine, so that the raw material unit consumption is increased; in addition, a large amount of black tar substances are dissolved in the wastewater generated in the production, so that adverse effects are brought to wastewater treatment, the wastewater treatment cost is high, and the black tar substances are one of main pollution sources in the vitamin B6 synthesis process.
Based on the above problems in the current vitamin B6 production, there is a need for further optimization and improvement of the vitamin B6 production process.
Disclosure of Invention
In order to solve the problems, the invention provides a production method of vitamin B6, which improves the yield of the ester acylation reaction step and solves the problem of black tar substances in the production process by separating and utilizing the byproduct of 2,2' -oxalylamino dipropionic acid ethyl ester.
Specifically, the invention provides a production method of vitamin B6, which comprises the following steps:
(1) Distilling and purifying the crude product of the ester acyl obtained by the ester acylation reaction to obtain a pure product of the ester acyl and a distillation residue containing a byproduct of 2,2' -oxalylamino dipropionic acid ethyl ester;
(2) Hydrolyzing the distillation residue containing by-product ethyl 2,2' -oxalamido dipropionate;
(3) And (3) performing ester acylation reaction on the hydrolysate obtained in the step (2) to prepare an ester acyl product, and purifying the reaction product to obtain the ester acyl pure product.
As a preferred embodiment of the invention, the distillation residue containing the by-product 2,2' -oxalylamino dipropionic acid ethyl ester in the step (1) is treated for 1-3 times by sequentially repeating the step (2) and the step (3) to obtain the pure product of the ester acyl. By repeating the treatment of the distillation residue containing the by-product ethyl 2,2' -oxalylamino dipropionate several times, the by-product can be fully utilized, and the yield of the ester acyl compound can be improved. The residue of distillation purification after repeated use is treated as waste. Because the byproducts of the first-step ester acylation reaction are complex, and besides the main byproduct of the 2,2' -oxalylamino dipropionate, other impurities which are difficult to hydrolyze are also included, after multiple uses, the impurities are accumulated continuously, the use value is reduced, and the method is generally not suitable for recycling after three uses, namely, the method can be used as solid waste treatment.
As a preferred embodiment of the invention, the reaction product is firstly separated to obtain crude ester acyl product, and the crude ester acyl product is distilled and purified to obtain pure ester acyl product.
As a preferred embodiment of the invention, the pure product of the ester acyl compound is used for preparing vitamin B6 through cyclization.
As a preferred embodiment of the present invention, the hydrolysis reaction is catalyzed by an acid, which is an organic acid and/or an inorganic acid.
As a preferred embodiment of the present invention, the acid used in the hydrolysis catalysis of the present invention is oxalic acid.
As a preferred embodiment of the invention, diethyl oxalate is also added during the hydrolysis reaction.
As a preferred embodiment of the present invention, the diethyl oxalate is recovered from the reactant of the ester acylation reaction.
As a preferred embodiment of the invention, the pure product of the ester acyl is obtained by collecting the fraction with the temperature of 106-110 ℃ at the top of the column during the distillation and purification.
The recovered pure ester acyl product is used for the next cyclization reaction to prepare vitamin B6.
The invention also provides a vitamin B6 product prepared by the production method.
It has been found that, during the synthesis of vitamin B6, the by-product 2,2' -oxalylamino dipropionate produced by the first step of ester acylation reaction is mainly formed by dehydration polycondensation of oxalic acid, alanine and ethanol, so that the by-product impurities can be decomposed by hydrolysis, oxalic acid, alanine and ethanol are mainly produced by hydrolysis, and the hydrolysis products can be reused as raw materials for the ester acylation reaction to prepare ester acyl compounds, thereby utilizing the ester acyl compounds and improving the yield of the ester acyl compounds.
Based on the above, the invention improves on the existing vitamin B6 production process. Specifically, the following is described.
The existing production method is that after the first step of ester acylation reaction is finished, solvent, excessive diethyl oxalate and the like are recovered to obtain crude ester acyl product, and the crude ester acyl product is directly subjected to the second step of cyclization reaction. This process has disadvantages as described in the background art since the by-product of the first step of ester acylation, ethyl 2,2' -oxalylamino dipropionate, also enters the cyclization step.
The improvement of the application is that: after obtaining the crude ester acyl product, distilling and purifying the crude ester acyl product to obtain a pure ester acyl product, wherein the pure ester acyl product does not contain a byproduct of 2,2' -oxalylamino dipropionic acid ethyl ester; the remainder of the distillation is a mixture containing ethyl 2,2' -oxalamido dipropionate as a byproduct; and then hydrolyzing distillation residues containing by-product 2,2' -oxalylamino dipropionic acid ethyl ester, wherein the by-product is hydrolyzed to mainly generate oxalic acid, alanine and ethanol, then the hydrolysis products are used as raw materials to prepare an ester acyl product, the ester acyl product is treated to obtain a crude ester acyl product, and the crude ester acyl product is distilled and purified to obtain a pure ester acyl product. The pure ester acyl product enters the next cyclization reaction.
In actual production, the product of the hydrolysis of the distillation residue containing the by-product ethyl 2,2' -oxalylamino dipropionate can be returned to the existing ester acylation reaction step for use. The preferred method is to treat it separately, because although hydrolyzed, the hydrolysis product has other difficult-to-hydrolyze impurities which can adversely affect the reaction by mixing into the existing normal ester acylation reaction. The independent treatment means that the hydrolyzed product is mixed with benzene, ethanol and the like, and then the mixture is subjected to an ester acylation reaction to prepare an ester acyl substance, and the reaction product is purified to obtain an ester acyl substance pure product.
The hydrolysis reaction is generally catalyzed by strong acid or base, and the alkali or acid is finally neutralized by the strong acid or base, so that byproduct salt is generated, which is unfavorable for subsequent purification. According to the invention, oxalic acid is used as a hydrolysis catalyst, and can provide enough acidic conditions to enable hydrolysis reaction to be carried out smoothly; oxalic acid is one of the raw materials for the acylation reaction of the ester, and oxalic acid is also generated after the hydrolysis of byproducts, so that the acidity of a reaction system can be further enhanced, and the reaction is promoted. Therefore, oxalic acid is selected as a catalyst, so that the hydrolysis of the byproduct can be effectively catalyzed, and the problem of introducing impurities does not exist.
In the first step of the ester acylation reaction, diethyl oxalate is theoretically balanced before and after the reaction, but in actual operation, the amount of diethyl oxalate gradually increases, so that the excess diethyl oxalate needs to be separated and hydrolyzed for reuse in general. The main component of the hydrolysis liquid of the diethyl oxalate is oxalic acid, which can be just used for hydrolyzing the byproducts of the invention, thereby saving the consumption of oxalic acid and fully utilizing the excessive diethyl oxalate. In actual operation, diethyl oxalate is not required to be hydrolyzed to obtain oxalic acid, and then the by-product of the invention is hydrolyzed, but diethyl oxalate can be directly added into a mixture containing the by-product for use, and the purpose can be achieved by hydrolysis.
According to the invention, through improving the existing vitamin B6 preparation process, the main byproduct ethyl 2,2' -oxalylamino dipropionate accounting for more than 8% of the ester acyl product is hydrolyzed and reused, and after improvement, the yield of the ester acylation reaction can be remarkably improved.
Because the byproducts of the first step are effectively separated, and the pure product of the ester acyl is used for the cyclization reaction, the purity of the cyclization raw material ester acyl is improved, the auxiliary raw materials required during the cyclization reaction are also greatly reduced, and the raw material cost is reduced.
And because of the separation and utilization of byproducts, tar-like substances are not generated during the cyclization reaction, namely solid dangerous wastes are not generated any more, the solid waste amount is reduced by 75% as a whole, meanwhile, black tar substances are not contained in the wastewater, and the wastewater treatment cost is reduced.
The invention not only greatly improves the yield of the step of the ester acylation reaction, but also greatly reduces the organic matters in the wastewater, eliminates tar asphalt-like solid waste and reduces the unit consumption of raw materials for vitamin B6 production. The vitamin B6 produced by the process has remarkable economic benefit and environmental protection benefit.
Detailed Description
The technical scheme of the invention is described in detail through specific examples.
The production method of vitamin B6 provided by the invention comprises the following steps:
in the original process, after the ester acylation reaction is finished, removing the solvent in the reaction system, and recovering the redundant diethyl oxalate to obtain the crude ester acyl product.
Putting the separated crude product of the ester acyl into a distillation system, and evaporating the target intermediate ester acyl under reduced pressure to obtain a pure product of the ester acyl; the remainder gives a black substance mainly containing ethyl 2,2' -oxalylamino dipropionate, which is liquid at high temperature and solidifies after cooling.
Adding water, oxalic acid and excessive diethyl oxalate recovered in the original process into a bottle, stirring, heating and dissolving, and slowly adding the black material into the bottle at high temperature. And refluxing after the addition is finished for hydrolysis reaction for more than 20 hours, and continuously evaporating ethanol generated by hydrolysis in the reaction process.
After the hydrolysis reaction is finished, evaporating excessive water, adding ethanol to dissolve the water until the water is clear, then adding benzene and ethanol, heating and refluxing the mixture, and carrying out ester acylation reaction, and separating the water for 60 to 72 hours. And then recovering benzene, ethanol and diethyl oxalate from the reaction product to obtain a crude ester acyl product, and purifying the crude ester acyl product by distillation to obtain a pure ester acyl product with higher purity and secondary byproduct impurities. The secondary byproduct impurities can be hydrolyzed and reused again according to the method, and the secondary byproduct impurities are treated as solid waste after repeated for 1 to 3 times.
The pure product of the ester acyl is used for cyclization reaction.
Specifically, the present invention provides the following examples to explain the above technical scheme in detail.
Example 1
The embodiment provides a production method of vitamin B6, which is based on the existing technology, and comprises the following steps: and (3) purifying the crude product of the ester acyl obtained by the normal ester acylation reaction, separating out a byproduct of ethyl 2,2' -oxalylamino dipropionate, and carrying out hydrolysis and recycling treatment on the byproduct. The method comprises the following specific steps:
(1) 3000g of crude ester acyl product (gas phase purity of about 89-92%) of benzene, ethanol and diethyl oxalate is recovered after the ester acylation reaction is finished, the crude ester acyl product is put into a distillation flask, reduced pressure is carried out to 10-100 pa by an oil pump, the distillation flask is slowly heated and rectified, about 180g of front fraction before 106 ℃ is respectively collected according to different temperatures of the top of the distillation flask (the front fraction is applied to the next batch of normal ester acylation reaction), and about 2580g of normal fraction (pure ester acyl product with purity of more than 98%) between 106 and 110 ℃ is respectively collected. The residual high boiling point of about 240g in the bottle is Wen Daochu when the bottle is still high, and the bottle is cooled and solidified and then divided into small blocks for standby;
(2) Taking a reaction bottle, pouring 600mL of water into the reaction bottle, weighing 240g of oxalic acid, pouring and stirring to dissolve, pouring 240mL of recovered diethyl oxalate, pouring 240g of solidified high-boiling point obtained in the step (1), heating to reflux, carrying out reflux hydrolysis reaction for 20 hours at the temperature of about 98-102 ℃, and extracting ethanol generated by the reaction according to the temperature of the tower top, wherein the temperature of the tower top is about 80 ℃. After the reaction is finished, a circulating water pump is used for decompressing and steaming water after the temperature is slightly reduced, until the reaction bottle is solid;
(3) Adding 720mL of ethanol with the mass concentration of 95% into a reaction bottle, heating to dissolve solid in the bottle, adding 240mL of benzene after dissolving, heating to reflux, and carrying out the ester acylation reaction for about 60 hours until the reaction is finished without water separation. Benzene and ethanol mixture was recovered by atmospheric distillation, diethyl oxalate was recovered by vacuum recovery with a recirculating water pump, and finally the front cut and about 240g of n-boiling ester acyl compound (pure ester acyl compound, purity 98%) were distilled off in the distillation mode of step (1). About 96g of secondary high boiling remained in the bottle.
The secondary high boiling point can be reused, namely, the secondary high boiling point can be hydrolyzed again, and then the ester acylation reaction is carried out to prepare the ester acyl compound.
In this example, the second high boiling point was hydrolyzed, and then, the ester acylation reaction was carried out to prepare an ester acyl compound, and 90g of an n-boiling ester acyl compound (pure ester acyl compound, purity 98%) was obtained by distillation, and 60g of a third high boiling point was obtained.
Through experiments, the three times of high-boiling impurities are more, and the produced ester acyl compound is little for reuse. Four times high boiling is unsuitable for reuse, in terms of solid waste disposal.
Through the above experiments, 2910g of pure ester acyl (purity 98%) was obtained. Raw 3000g of crude ester acyl product contains 2700g of ester acyl product with purity of 90%. The polymer separated in this example was hydrolyzed to obtain about 200g of an ester acyl compound, thereby improving the yield of the ester acyl compound.
Because the pure product does not contain an impurity polymer, the amount of phosphorus oxychloride and triethylamine required by the next cyclization reaction is reduced, and the wastewater almost contains no tar and is easy to treat.
By adopting the method of the embodiment, although 60g of high-boiling solid waste is produced, the tar of about 240g is reduced in the next cyclization reaction, namely, the waste is reduced by 75%, so that the economic benefit and the environmental benefit are considerable.
While the invention has been described in detail in the foregoing general description, embodiments and experiments, it will be apparent to those skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.

Claims (9)

1. A process for producing an ester acyl compound comprising the steps of:
(1) Distilling and purifying the crude product of the ester acyl obtained by the ester acylation reaction to obtain a pure product of the ester acyl and a distillation residue containing a byproduct of 2,2' -oxalylamino dipropionic acid ethyl ester;
the structure of the ester acyl is shown as a formula I, and the structure of the 2,2' -oxalylamino dipropionate is shown as a formula II:
(2) Hydrolyzing the distillation residue containing by-product ethyl 2,2' -oxalamido dipropionate;
(3) And (3) performing ester acylation reaction on the hydrolysate obtained in the step (2) to prepare an ester acyl product, and purifying the reaction product to obtain the ester acyl pure product.
2. The production method according to claim 1, wherein the distillation residue containing the by-product ethyl 2,2' -oxalylamino dipropionate in the step (1) is treated 1 to3 times by repeating the step (2) and the step (3) to obtain the pure product of the ester acyl.
3. The production method according to claim 1 or 2, wherein the reaction product is separated into crude ester acyl product, and the crude ester acyl product is distilled and purified to obtain pure ester acyl product.
4. The method of claim 1, wherein the pure ester acyl product is used for the cyclization of vitamin B6.
5. The method according to claim 1, wherein the hydrolysis reaction is catalyzed by an acid, which is an organic acid and/or an inorganic acid.
6. The method of claim 5, wherein the acid is oxalic acid.
7. The method according to claim 5 or 6, wherein diethyl oxalate is further added during the hydrolysis reaction.
8. The method according to claim 7, wherein the diethyl oxalate is recovered from the reactants of the ester acylation reaction.
9. The method according to claim 1, wherein the purified product of the ester acyl is obtained by collecting a fraction having a temperature of 106 to 110 ℃ at the top of the column.
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CN116332783A (en) * 2021-12-23 2023-06-27 杭州鑫富科技有限公司 A kind of continuous preparation method of N-ethoxy oxalylalanine ethyl ester
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CN102311360B (en) * 2011-07-11 2014-03-26 湖北惠生药业有限公司 Method for preparing N-ethoxy oxalyl alanine ethyl ester

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