阅读说明：本技术 维生素b6中间体生产尾气的回收方法 (Vitamin B6Recovery method of intermediate production tail gas ) 是由 徐勇智 党登峰 俞诚 章根宝 于 2019-03-13 设计创作，主要内容包括：本发明涉及维生素B<Sub>6</Sub>合成领域,公开了一种维生素B<Sub>6</Sub>中间体生产尾气的回收方法,包括：(1)用溶剂吸收维生素B<Sub>6</Sub>中间体生产尾气中的4-甲基-5-烷氧基噁唑,得到吸收液；(2)将所述吸收液与酸性盐水接触,再将所得体系进行静置和分离,得到油层和水层；(3)将步骤(2)所得油层进行至少一次洗涤并分离出水层；(4)将步骤(2)和步骤(3)得到的水层进行碱化；(5)将步骤(4)得到的混合物进行蒸馏,得到4-甲基-5-烷氧基噁唑。本发明提供的方法实现了对维生素B6中间体生产尾气中4-甲基-5-烷氧基噁唑的高效回收,该方法简便易行,适于工业化生产。(The present invention relates to vitamin B 6 The field of synthesis and discloses vitamin B 6 The recovery method of the tail gas in the production of the intermediate comprises the following steps: (1) absorbing vitamin B with solvent 6 4-methyl-5-alkoxy oxazole in tail gas generated in the production of the intermediate is used for obtaining absorption liquid; (2) contacting the absorption liquid with acidic saline water, and standing and separating the obtained system to obtain an oil layer and a water layer; (3) washing the oil layer obtained in the step (2) at least once and separating a water outlet layer; (4) alkalizing the water layers obtained in the step (2) and the step (3); (5) and (4) distilling the mixture obtained in the step (4) to obtain the 4-methyl-5-alkoxy oxazole. The method provided by the invention realizes the high-efficiency recovery of the 4-methyl-5-alkoxy oxazole in the tail gas in the production of the vitamin B6 intermediate, is simple and feasible, and is suitable for industrial production.)

1. Vitamin B₆A method for recovering tail gas from intermediate production, the method comprising:

(1) absorbing vitamin B with solvent₆4-methyl-5-alkoxy oxazole in tail gas generated in the production of the intermediate is used for obtaining absorption liquid containing 4-methyl-5-alkoxy oxazole;

(2) contacting the absorption liquid with acidic saline water at the temperature of between 15 ℃ below zero and 0 ℃ to convert 4-methyl-5-alkoxy oxazole into 4-methyl-5-alkoxy oxazole salt, and standing and separating the obtained system to obtain an oil layer and a water layer;

(3) washing the oil layer obtained in the step (2) at least once and separating a water outlet layer;

(4) alkalizing the water layers obtained in the step (2) and the step (3) to convert the 4-methyl-5-alkoxy oxazole salt into 4-methyl-5-alkoxy oxazole;

(5) and (4) distilling the mixture obtained in the step (4) to obtain the 4-methyl-5-alkoxy oxazole.

2. The recovery process according to claim 1, wherein the alkoxy group in the 4-methyl-5-alkoxyoxazole is selected from C₁～C₄Alkoxy group of (2).

3. The recovery method according to claim 1, wherein the vitamin B₆The tail gas of the intermediate production contains 1-5 wt% of 4-methyl-5-alkoxy oxazole, 25-40 wt% of carbon dioxide and 50-70 wt% of water.

4. The recovery method according to claim 1, wherein, in the step (1), the solvent is selected from C₁₀～C₁₂At least one of an alkane of (a), tetralin, decalin, 4, 7-dihydro-2-alkyl-1, 3-dioxepin, and 2-alkyl-1, 3-dioxepan;

preferably, the 4, 7-dihydro-2-alkyl-1, 3The alkyl group in the dioxin is C₁～C₄Alkyl groups of (a);

preferably, the alkyl group in the 2-alkyl-1, 3-dioxepane is C₁～C₄Alkyl group of (1).

5. The recovery method according to any one of claims 1 to 4, wherein the step (1) is carried out in a spray absorber, and the vitamin B is₆Tail gas generated in the production of the intermediate enters the spray absorption tower from the bottom of the tower and is in countercurrent contact with the sprayed solvent, and the tail gas after absorption treatment is discharged from the top of the spray absorption tower;

preferably, the solvent absorbs so that the content of the 4-methyl-5-alkoxy oxazole in the obtained absorption liquid is 1-10 wt%;

more preferably, the absorption time is 3-10 days, and the amount of the solvent is equivalent to the amount of the vitamin B treated per day₆The mass of the 4-methyl-5-alkoxy oxazole in the tail gas of the intermediate production is 10-100 times that of the 4-methyl-5-alkoxy oxazole.

6. The recovery method according to claim 1, wherein in the step (2), the acidic brine is prepared by adding an inorganic salt to an aqueous acid solution; and wherein the acid is selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, sulfamic acid and p-toluenesulfonic acid; the inorganic salt is at least one selected from potassium chloride, sodium chloride, lithium chloride, calcium chloride, magnesium chloride, sodium sulfate, potassium sulfate and magnesium sulfate;

preferably, the concentration of acid in the acidic brine is 1-20 wt%;

preferably, the concentration of the salt in the acidic brine is 5-30 wt%.

7. The recovery method according to claim 1, wherein in the step (2), the ratio of the number of moles of the 4-methyl-5-alkoxyoxazole in the absorption liquid to the equivalent weight of the acid in the acidic brine is 1: 1.05 to 1.5; the contact is carried out under the condition of stirring, and the stirring time is 20-60 min.

8. The recovery method according to claim 1, wherein in the step (4), the alkalifying is performed using a base selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, and lithium hydroxide;

preferably, the amount of the base is such that the pH of the mixture obtained is 8 to 9.

9. The recycling method according to claim 1 or 8, wherein in the step (4), the alkalization temperature is-10 ℃ to 0 ℃, the alkalization is carried out under stirring condition, and the stirring time is 20-60 min.

10. The recovery method according to claim 1, wherein, in the step (5), the distillation comprises the steps of:

s1: distilling the mixture at normal pressure, and separating a water layer from a distillate to obtain a crude product of the 4-methyl-5-alkoxy oxazole;

s2: carrying out reduced pressure distillation on the 4-methyl-5-alkoxy oxazole crude product to remove low-boiling-point substances to obtain 4-methyl-5-alkoxy oxazole; the temperature of the reduced pressure distillation is 40-100 ℃, and the operation pressure is-0.08 MPa to-0.1 MPa.

Technical Field

The present invention relates to vitamin B₆The field of synthesis, in particular to vitamin B₆A method for recovering 4-methyl-5-alkoxy oxazole from tail gas in the production of intermediates.

Background

Vitamin B₆Is a water-soluble vitamin, and has wide application in medicine, food, feed and other fieldsUse is provided. At present, the synthesis process (namely, the oxazole method) using 4-methyl-5-alkoxy oxazole and 4, 7-dihydro-1, 3-dioxepin as raw materials is vitamin B₆General method for industrial production. In the preparation process, the yield of the key intermediate 4-methyl-5-alkoxy oxazole (the structure is shown as formula I) has important significance for reducing the production cost:

wherein R is C₁～C₄Alkyl group of (1).

In the production, the 4-methyl-5-alkoxy oxazole can be applied to the subsequent production after distillation, separation and purification. Although the boiling point is higher, part of uncondensed material vapor enters a tail gas system in the distillation process due to the actions of solvent azeotropy, entrainment and the like. The oxazole compound has foul smell and low solubility in water, and the conventional water spraying measure is adopted in production, so that the absorption effect is poor, the cost is increased, and the environmental pollution is caused. When the 4-methyl-5-alkoxy oxazole is absorbed by a high boiling point solvent, the obtained absorption liquid is difficult to obtain a high-purity reclaimed material by a conventional distillation or rectification method due to the high boiling point of the 4-methyl-5-alkoxy oxazole, so that the absorption liquid is difficult to recycle for production.

Disclosure of Invention

The present invention is to overcome the above problems of the prior art and to provide a novel vitamin B₆A method for recovering tail gas in the production of an intermediate.

The inventor of the invention finds in research that 4-methyl-5-alkoxy oxazole can react with an aqueous solution of inorganic acid or organic acid salt (acidic salt water, pH below 3) to form a water-soluble salt, but the salt is unstable at room temperature (4-methyl-5-alkoxy oxazole salt is easy to destroy in acidic solution); while below 0 ℃, the 4-methyl-5-alkoxy oxazole salt can have better stability. The inventor further finds that the 4-methyl-5-alkoxy oxazole in the tail gas is absorbed by a high boiling point solvent, then the acid saline is added to extract the absorption liquid at the temperature of below 0 ℃, the generated 4-methyl-5-alkoxy oxazole salt is transferred to a water layer, and the water layer is alkalized, distilled and the like, so that the target intermediate 4-methyl-5-alkoxy oxazole can be efficiently recovered and separated. The present invention has been made based on the above findings.

In order to achieve the above object, the present invention provides a vitamin B₆A method for recovering tail gas from intermediate production, the method comprising:

(1) absorbing vitamin B with solvent₆4-methyl-5-alkoxy oxazole in tail gas generated in the production of the intermediate is used for obtaining absorption liquid containing 4-methyl-5-alkoxy oxazole;

(2) contacting the absorption liquid with acidic saline water at the temperature of between 15 ℃ below zero and 0 ℃ to convert 4-methyl-5-alkoxy oxazole into 4-methyl-5-alkoxy oxazole salt, and standing and separating the obtained system to obtain an oil layer and a water layer;

(3) washing the oil layer obtained in the step (2) at least once and separating a water outlet layer;

(4) alkalizing the water layers obtained in the step (2) and the step (3) to convert the 4-methyl-5-alkoxy oxazole salt into 4-methyl-5-alkoxy oxazole;

(5) and (4) distilling the mixture obtained in the step (4) to obtain the 4-methyl-5-alkoxy oxazole.

The method provided by the invention realizes the generation of vitamin B by an oxazole method₆The method is simple and easy to implement, and is suitable for industrial production. As can be seen from the following examples, the yield of 4-methyl-5-alkoxy oxazole is more than 40%, and the purity is more than or equal to 98%, and the oxazole can be reused as vitamin B₆The production of (1).

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides vitamin B₆A method for recovering tail gas from intermediate production, the method comprising:

(1) absorbing vitamin B with solvent₆4-methyl-5-alkoxy oxazole in tail gas generated in the production of the intermediate is used for obtaining absorption liquid containing 4-methyl-5-alkoxy oxazole;

(2) contacting the absorption liquid with acidic saline water at the temperature of between 15 ℃ below zero and 0 ℃ to convert 4-methyl-5-alkoxy oxazole into 4-methyl-5-alkoxy oxazole salt, and standing and separating the obtained system to obtain an oil layer and a water layer;

(3) washing the oil layer obtained in the step (2) at least once and separating a water outlet layer;

(4) alkalizing the water layers obtained in the step (2) and the step (3) to convert the 4-methyl-5-alkoxy oxazole salt into 4-methyl-5-alkoxy oxazole;

(5) and (4) distilling the mixture obtained in the step (4) to obtain the 4-methyl-5-alkoxy oxazole.

In the present invention, the vitamin B₆Tail gas from intermediate production (hereinafter also referred to as "vitamin B₆Production off-gas ") refers to vitamin B₆In the production process, uncondensed tail gas generated in the decarboxylation of 4-methyl-5-alkoxy-2-oxazole carboxylic acid and the subsequent distillation for preparing 4-methyl-5-alkoxy oxazole generally contains 1-5 wt% of 4-methyl-5-alkoxy oxazole, 25-40 wt% of carbon dioxide and 50-70 wt% of water. In addition, the process off-gas may optionally contain a small amount of air.

In the invention, the alkoxy in the 4-methyl-5-alkoxy oxazole is C₁～C₄Alkoxy group of (2). C₁～C₄Examples of the alkoxy group of (b) are a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group and the like. For example, the 4-methyl-5-alkoxyoxazole is 4-methyl-5-ethoxyoxazole.

In the present invention, step (1) is to absorb 4-methyl-5-ethoxyoxazole from the production off-gas by a solvent. The solvent is not particularly limited in the present invention, and may be any high boiling point solvent capable of achieving the above object. The high boiling point solvent means that the boiling point of the solvent is higher than 150 ℃.

Preferably, the solvent may be selected from C₁₀～C₁₂At least one of alkane, tetralin, decalin, 4, 7-dihydro-2-alkyl-1, 3-dioxepin, 2-alkyl-1, 3-dioxepane. Wherein, the C₁₀～C₁₂Non-limiting examples of alkanes of (a) include decane, undecane, dodecane; the alkyl groups of the 4, 7-dihydro-2-alkyl-1, 3-dioxepin and 2-alkyl-1, 3-dioxepan can be respectively selected from C₁～C₄Alkyl group of (1). C₁～C₄Examples of the alkyl group in (b) include methyl, ethyl, n-propyl, isopropyl, n-butyl and the like.

Preferably, the solvent is selected from at least one of dodecane, tetralin, decalin, and 4, 7-dihydro-2-propyl-1, 3-dioxepin (i.e., 2-n-propyl-4, 7-dihydro-1, 3-dioxepin).

In the step (1), the absorption is carried out in a spray absorption tower which is well known in the art, the production tail gas enters the spray absorption tower from the bottom of the spray absorption tower and is in countercurrent contact with the sprayed solvent, and the tail gas after absorption treatment is discharged from the top of the spray absorption tower. And (3) returning the oil phase obtained by treating the absorption liquid in the step (2) to the spray absorption tower for recycling. The amount of the solvent used in the present invention is not particularly limited, and may be selected according to the absorption time, and it is preferable to stop the absorption when the concentration of 4-methyl-5-alkoxyoxazole in the absorption liquid is increased to be kept almost constant (for example, increased to 1 to 10 wt%). The absorption can be carried out at a temperature of 0 to 40 ℃.

According to one embodiment, the solvent is absorbed so that the content of 4-methyl-5-alkoxy oxazole in the obtained absorption liquid is 1-10 wt%, the absorption time is 3-10 days, and the amount of the solvent is equivalent to the amount of the vitamin B treated every day₆The mass of the 4-methyl-5-alkoxy oxazole in the tail gas of the intermediate production is 10-100 times that of the 4-methyl-5-alkoxy oxazole.

In the present invention, in the step (2), the 4-methyl-5-alkoxyoxazole in the absorption liquid reacts with the acidic brine under low temperature conditions to form a water-soluble salt and stabilize the salt. The contact is preferably carried out under the condition of stirring, and the stirring time is 20-60 min. The structure of the water-soluble salt is shown as a formula II:

in the formula II, R is C₁～C₄H-B is an acid.

In the present invention, the acidic brine means a brine having a pH of not more than 3 and capable of reacting with 4-methyl-5-alkoxyoxazole to produce 4-methyl-5-alkoxyoxazole salt.

According to one embodiment, the acidic brine is prepared by adding an inorganic salt to an aqueous acid solution, wherein the acid is selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, sulfamic acid and p-toluenesulfonic acid; the inorganic salt is at least one selected from potassium chloride, sodium chloride, lithium chloride, calcium chloride, magnesium chloride, sodium sulfate, potassium sulfate and magnesium sulfate.

Preferably, the concentration of the acid in the acidic brine is 1-20 wt%.

Preferably, the concentration of the salt in the acidic brine is 5-30 wt%.

In the step (2), the dosage of the acidic saline can be determined according to the amount of the 4-methyl-5-alkoxy oxazole in the absorption liquid. In the present invention, it is preferable that the number of moles of the 4-methyl-5-alkoxyoxazole in the absorbent liquid is equal to the acid equivalent (H) in the acidic saline⁺Mole number of (b) is 1: 1.05 to 1.5.

According to the invention, the purpose of step (3) is to extract the soluble salts formed in step (2) into the aqueous phase, obtaining an oil layer and an aqueous layer containing said soluble salts. Typically, the washing is such that the content of 4-methyl-5-alkoxyoxazole in the resulting oil layer is less than 0.1 wt%. The washing may be carried out one or more times, for example, once, twice, three times, four times, etc., depending on the actual situation. The aqueous layer obtained in each washing may be subjected to the subsequent alkalization and distillation treatment, respectively, or the aqueous layer obtained in each washing may be mixed and subjected to the subsequent alkalization and distillation treatment. The specific operation conditions of the washing are not particularly limited, each washing can be usually carried out under the stirring condition of 0 ℃, and the stirring time is 10-50 min. The mass ratio of the water for each washing to the oil layer dosage obtained in the step (2) can be 0.05-0.5: 1.

In the present invention, the basification of step (4) is capable of converting the 4-methyl-5-alkoxy oxazole salt to 4-methyl-5-alkoxy oxazole. The alkalifying may be performed using a base selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, and lithium hydroxide. The alkali can be applied in the form of an aqueous solution, and the concentration of the alkali in the aqueous solution can be 1-20 wt%, preferably 2-10 wt%. The amount of the alkali can be determined according to the pH of a system, and is generally determined so that the pH of the mixture is 7.5-10, preferably 8-9. The alkalization is carried out at low temperature, for example below 0 ℃, preferably at a temperature of-10 ℃ to 0 ℃.

According to the present invention, in the step (5), the distillation is aimed at removing water and other low boiling substances from the mixture to obtain 4-methyl-5-alkoxyoxazole with high purity. According to a preferred embodiment, the distillation comprises the following steps:

s1: distilling the mixture at normal pressure, and separating a water layer from a distillate to obtain a crude product of the 4-methyl-5-alkoxy oxazole;

s2: and carrying out reduced pressure distillation on the 4-methyl-5-alkoxy oxazole crude product to remove low-boiling-point substances to obtain 4-methyl-5-alkoxy oxazole.

The purpose of the atmospheric distillation is to remove water from the mixture and recover the crude 4-methyl-5-alkoxyoxazole with a distillation overhead temperature of about 100 ℃.

The purpose of the reduced pressure distillation is to further remove low-boiling-point substances in the crude product and recover and obtain the high-purity 4-methyl-5-alkoxy oxazole. The conditions of the reduced pressure distillation may include: the temperature is 40-100 ℃, and the operation pressure is-0.08 MPa to-0.1 MPa.

By adopting the recovery method of the invention, the recovery of vitamin B is improved₆In tail gas of intermediate productionThe yield of the 4-methyl-5-alkoxy oxazole is reduced, and the production of vitamin B is reduced₆The cost of (a). For the recycling production of the intermediate 4-methyl-5-alkoxy oxazole in the field, the content of the 4-methyl-5-alkoxy oxazole is generally required to be not less than 98 percent, and the recycled 4-methyl-5-alkoxy oxazole meets the recycling requirement.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples,

vitamin B₆The content of 4-methyl-5-ethoxy oxazole in the production tail gas is 2 wt%, the content of carbon dioxide is 30 wt%, and the balance is water; the absorption process is carried out in a spray absorption tower, and vitamin B entering the spray absorption tower every day₆The total amount of 4-methyl-5-alkoxy oxazole in the production tail gas is 20 kg.

The content of 4-methyl-5-ethoxy oxazole in the absorption liquid is measured by gas chromatography;

the content of the recovered 4-methyl-5-ethoxyoxazole was measured by gas chromatography.

The following examples 1-6 are illustrative of vitamin B of the present invention₆A method for recovering tail gas in the production of an intermediate.