阅读说明：本技术 一种精馏制备乳酸乙酯的工艺方法 (Process method for preparing ethyl lactate by rectification ) 是由 吴兵 顾松 黄埔 刘亚生 于 2020-12-16 设计创作，主要内容包括：本发明适用乳酸乙酯生产技术领域,提供了一种精馏制备乳酸乙酯的工艺方法,包括以下步骤：将丙交酯和乙醇加入到装有强酸型阳离子交换树脂催化剂的催化精馏塔内,催化酯化反应生成的乙酸乙酯与水形成共沸物从催化精馏塔的顶部馏出后经过分相器,得到粗酯；将得到的粗酯采至精制塔中,精制塔底部采出成品乳酸乙酯,顶部物料返回催化精馏塔。通过丙交酯和乙醇在催化精馏塔内进行催化反应生成乳酸乙酯。通过反应精馏作用,有效地降低粗酯中乙醇的含量,精制塔可得到纯度≥99.95％的乳酸乙酯。(The invention is suitable for the technical field of ethyl lactate production, and provides a process method for preparing ethyl lactate by rectification, which comprises the following steps: adding lactide and ethanol into a catalytic rectifying tower filled with a strong acid type cation exchange resin catalyst, forming an azeotrope by ethyl acetate and water generated by catalytic esterification reaction, distilling the azeotrope from the top of the catalytic rectifying tower, and passing the azeotrope through a phase separator to obtain crude ester; and (3) extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower. The lactide and the ethanol are subjected to catalytic reaction in a catalytic rectifying tower to generate the ethyl lactate. The content of ethanol in the crude ester is effectively reduced through the reaction rectification, and ethyl lactate with the purity of more than or equal to 99.95 percent can be obtained by a refining tower.)

1. A process method for preparing ethyl lactate by rectification is characterized by comprising the following steps:

1) adding lactide and ethanol into a catalytic rectifying tower filled with a strong acid type cation exchange resin catalyst, forming an azeotrope by ethyl acetate and water generated by catalytic esterification reaction, distilling the azeotrope from the top of the catalytic rectifying tower, and passing the azeotrope through a phase separator to obtain crude ester;

2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

2. The process for preparing ethyl lactate by rectification according to claim 1, wherein the lactide is selected from one or more of L lactide, D lactide or meso-lactide.

3. The rectification process for preparing ethyl lactate according to claim 1, wherein the ethanol is absolute ethanol.

4. The process for preparing ethyl lactate by rectification according to claim 3, wherein the lactide is added from the upper part of the catalytic rectification section of the catalytic rectification tower, the ethanol is added from the tower bottom, and after an azeotrope formed by the lactic acid and the water is obtained from the catalytic rectification section, the lactide enters a phase separator after being separated from the rectification section, so that the crude ester and the water phase are respectively obtained.

5. The rectification process for preparing ethyl lactate as claimed in claim 1, wherein the catalyst is a lewis acid or a tin salt.

6. The rectification process for preparing ethyl lactate according to claim 2, wherein the reaction temperature is 82-100 ℃ and the reaction time is 3-10 h.

7. The rectification process for preparing ethyl lactate according to claim 1, wherein the molar ratio of lactide to ethanol is 3: (2-10).

8. The process for preparing ethyl lactate by rectification according to claim 1, wherein the catalytic rectification tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Technical Field

The invention belongs to the technical field of ethyl lactate production, and particularly relates to a process method for preparing ethyl lactate by rectification.

Background

The molecular formula of the ethyl lactate is C5H10O3, the melting point is-126 ℃, the boiling point is 154 ℃, and the ethyl lactate can be mutually dissolved with water and is an important chemical raw material. As the solvent has the advantages of no toxicity, good solubility, difficult volatilization, biodegradability and the like, the solvent can be used as a green solvent with great development value to replace the traditional toxic solvents used in the industry at present, such as halogenated solvents, ethers solvents, chlorofluorocarbons solvents, such as cleaning oil field pipelines, preparing various high-grade paints and the like; ethyl lactate is also an edible flavor with wine aroma, is used for preparing various wines and edible essences, and can also be used as a flavoring agent in the feed industry; in addition, it is used as a lubricant for tablet compression, a pharmaceutical intermediate, etc. in the pharmaceutical industry; ethyl lactate has wide industrial applications.

The synthesis industry of ethyl lactate generally adopts an intermittent esterification method, lactic acid and ethanol are subjected to esterification reaction under the action of a concentrated sulfuric acid catalyst, then benzene or toluene is used as a water-carrying agent, water generated in a reaction system is removed, so that balance is moved forward, a crude product of ethyl lactate is obtained, and a food-grade product is obtained through intermittent reduced pressure distillation. The process has the problems that the produced ethyl lactate is often limited in use as a green solvent due to the fact that benzene or toluene as a water-carrying agent is toxic, and the concentrated sulfuric acid can promote the lactic acid to generate side reactions such as intermolecular and intramolecular dehydration reaction, condensation reaction, cyclization reaction and the like, so that the ethyl lactate product is poor in color and luster, low in yield and not beneficial to large-scale industrial popularization.

Disclosure of Invention

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a process method for preparing ethyl lactate by rectification, aiming at solving the problems of poor color and luster and low yield of the existing ethyl lactate product.

The embodiment of the invention is realized in such a way that the process method for preparing ethyl lactate by rectification comprises the following steps:

1) adding lactide and ethanol into a catalytic rectifying tower filled with a strong acid type cation exchange resin catalyst, forming an azeotrope by ethyl acetate and water generated by catalytic esterification reaction, distilling the azeotrope from the top of the catalytic rectifying tower, and passing the azeotrope through a phase separator to obtain crude ester;

2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

As a further scheme of the invention: the lactide is selected from one or more of L lactide, D lactide or meso lactide.

As a further scheme of the invention: the ethanol is absolute ethanol.

As a further scheme of the invention: the lactide is added from the upper part of a catalytic rectifying section of a catalytic rectifying tower, the ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to respectively obtain crude ester and a water phase.

As a further scheme of the invention: the catalyst is Lewis acid or tin salt.

As a further scheme of the invention: the reaction temperature is 82-100 ℃, and the reaction time is 3-10 h.

As a further scheme of the invention: the molar ratio of lactide to ethanol is 3: (2-10).

As a further scheme of the invention: the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

The invention generates ethyl lactate by the catalytic reaction of lactide and ethanol in a catalytic rectifying tower. The content of ethanol in the crude ester is effectively reduced through the reaction rectification, and ethyl lactate with the purity of more than or equal to 99.95 percent can be obtained by a refining tower. The method reduces the alcohol content in the crude ester to the maximum extent, reduces the circulation of the ethanol in a system, and saves energy consumption; the raw material lactide used in the invention has no optical rotation requirement, can be L lactide, D lactide, racemic lactide or a mixture of a plurality of lactides, has wide application range, and can particularly reuse the racemic lactide which is not beneficial to producing high-quality polylactic acid to produce ethyl lactate, thereby realizing the comprehensive utilization of the raw material, also achieving the maximization of economic benefit and having quite high economic price.

Detailed Description

The technical effects of the process for preparing ethyl lactate by rectification and the oat obtained by the process are further described below with reference to specific examples, but the specific implementation methods mentioned in the examples are only illustrative and explanatory of the technical scheme of the present invention, and do not limit the implementation scope of the present invention, and all modifications and substitutions based on the above principles should be within the protection scope of the present invention.

Example 1

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding the L lactide and ethanol into a catalytic rectifying tower filled with Lewis acid, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

Specifically, the reaction temperature is 82 ℃, and the reaction time is 3 hours.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 2.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Example 2

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding the D lactide and ethanol into a catalytic rectifying tower filled with tin salt, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

The reaction temperature is 100 ℃, and the reaction time is 10 h.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 10.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Example 3

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding meso lactide and ethanol into a catalytic rectifying tower filled with Lewis acid, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

Specifically, the reaction temperature is 85 ℃, and the reaction time is 5 hours.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 4.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Example 4

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding the L lactide and ethanol into a catalytic rectifying tower filled with Lewis acid, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

Specifically, the reaction temperature is 90 ℃, and the reaction time is 7 h.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 6.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Example 5

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding the L lactide and ethanol into a catalytic rectifying tower filled with Lewis acid, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

Specifically, the reaction temperature is 92 ℃, and the reaction time is 7 h.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 8.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Example 6

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding the D lactide and ethanol into a catalytic rectifying tower filled with tin salt, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

Specifically, the reaction temperature is 95 ℃, and the reaction time is 8 h.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 8.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

Example 7

A process method for preparing ethyl lactate by rectification comprises the following steps: 1) adding meso lactide and ethanol into a catalytic rectifying tower filled with tin salt, and distilling off an azeotrope formed by ethyl acetate and water generated by catalytic esterification from the top of the catalytic rectifying tower through a phase separator to obtain crude ester; 2) and extracting the obtained crude ester into a refining tower, extracting a finished product ethyl lactate from the bottom of the refining tower, and returning the top material to the catalytic rectification tower.

Specifically, the ethanol is absolute ethanol.

Specifically, the reaction temperature is 97 ℃, and the reaction time is 3-9 h.

Further, lactide is added from the upper part of a catalytic rectifying section of the catalytic rectifying tower, ethanol is added from a tower kettle, an azeotrope formed by lactic acid and water is obtained from the catalytic rectifying section, and after separation is carried out in the rectifying section, the lactide enters a phase separator to obtain crude ester and a water phase respectively.

Specifically, the molar ratio of lactide to ethanol is 3: 9.

specifically, the catalytic distillation tower is a packed tower, and the used packing is stainless steel random packing or regular packing.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.