CN1031563C

CN1031563C - Process for producing chloracetic acid

Info

Publication number: CN1031563C
Application number: CN 92105796
Authority: CN
Inventors: 何正�
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-07-10
Filing date: 1992-07-10
Publication date: 1996-04-17
Anticipated expiration: 2007-07-10
Also published as: CN1070183A

Abstract

The present invention discloses a technology for producing chloracetic acid, which uses acetic acid as a raw material and prepares the chloracetic acid by a chloridizing method under the existence of sulfur as a contact agent. The technology comprises the working procedures of adding the acetic acid and the sulfur in a reaction kettle, heating the reaction kettle, chlorinating by introducing chlorine, crystallizing crystals in the kettle, separating the chloroacetic acid, etc., and is the improvement of the existing chloroacetic acid producing technology. The chloroacetic acid yield of each ton of acetic acid can be increased from 1.2 tons of the prior art to 1.4 tons. The purity and the stability of the chloroacetic acid can be increased by adding a nitrogen washing technology. By the technology, the income of a chemical plant which consumes 40 to 60 tons of acetic acid per month can be increased by 40 to 60 thousand yuan per month.

Description

Chloroacetic acid production process

The invention relates to a chloroacetic acid production process.

Chloroacetic acid is also called monochloroacetic acid or monochloroacetic acid, and its chemical molecular formula is CLCH₂COOH, a widely used organic chemical raw material, is prepared by chlorination of acetic acid as a raw material in the presence of a contact agent, namely sulfur, and has the following reaction equation: the preparation method comprises the following steps of feeding acetic acid and sulfur into a reaction kettle, heating the reaction kettle, introducing chlorine for chlorination, crystallizing in a crystallizationkettle, separating chloroacetic acid and the like, and the specific operation is as follows: adding acetic acid into a reaction kettle, adding sulfur with the amount (weight) of 3 percent of acetic acid, heating the reaction kettle to 98 +/-2 ℃, introducing chlorine for chlorination, wherein the introduction amount of chlorine at the initial stage is 20-25kg/h, the introduction amount of chlorine at the middle stage is 35-40kg/h, the introduction amount of chlorine at the later stage is 20-25kg/h, condensing and refluxing low-boiling-point substance acetyl chloride gas in a reaction kettle condenser by using tap water, stopping introducing chlorine when the mass ratio in the reaction kettle reaches 1.35/80 ℃, indicating that the reaction in the reaction kettle reaches the end point, introducing the substances in the reaction kettle into a crystallization kettle, adding a proper amount of chloroacetic acid crystallization mother liquor, slowly cooling and crystallizing under stirring, and separating crystals from the mother liquor to obtain chloroacetic acid crystals. In the reaction kettle, chlorine does not directly react with acetic acid to prepare chloroacetic acid, but firstly reacts with a contact agent, namely sulfur to prepare sulfur monochloride, and the reaction equation is as follows:

reacting sulfur monochloride with acetic acid to prepare acetyl chloride, wherein the reaction equation is as follows:

acetyl chloride reacts with chlorine to prepare chloroacetyl chloride, and the reaction equation is as follows:

reacting chloroacetyl chloride with acetic acid to prepare chloroacetic acid, wherein the reaction equation is as follows:

since there is also a reaction between chlorine and chloroacetyl chloride in the reaction, the reaction equation is:

the reaction product-dichloroacetyl chloride reacts with acetic acid, and the reaction equation is as follows:

in such side reactions, the chloroacetyl chloride obtained in the reaction cannot be converted to chloroacetic acid in its entirety. In the existing production process of chloroacetic acid, acetyl chloride gas which is a reaction product with low boiling point is condensed and refluxed by using tap water with higher temperature in a condenser of a reaction kettle, the condensation and reflux effects are poor, the acetyl chloride is lost much, the ineffective consumption of raw materials is large, a large amount of acetyl chloride is lost, the number of chlorine molecules participating in the side reaction with chloroacetyl chloride is relatively increased, the side reaction is enhanced, and the yield of the product is also reduced.

The present invention aims to overcome the defects of the prior art and provide an improved chloroacetic acid production process to improve the yield of the product.

The purpose of the invention is realized as follows: an improved chloroacetic acid production process, taking acetic acid as raw material, chloridizing to prepare chloroacetic acid in the presence of contact agent-sulfur, comprising the procedures of feeding acetic acid and sulfur into a reaction kettle, heating the reaction kettle, introducing chlorine for chlorination, crystallizing in a crystallization kettle, separating chloroacetic acid and the like, wherein the specific improved operation is as follows: heating the reaction kettle to 70 ℃, then starting introducing chlorine for chlorination, using frozen salt water with the temperature below-15 ℃ in a condenser of the reaction kettle to enable generated acetyl chloride gas to be condensed and refluxed well, reducing the loss of acetyl chloride with low boiling point, inhibiting the reaction of chloroacetyl chloride and chlorine, the reaction of dichloroacetyl chloride and acetic acid, reducing the ineffective loss of raw materials, gradually raising the temperature in the reaction kettle along with the progress of the reaction to finally reach 98 +/-2 ℃, closing the frozen salt water when the mass ratio in the reaction kettle reaches 1.21-1.24/80 ℃, distilling the gas and low-boiling point substances in the reaction kettle, wherein the distilled substances comprise sulfur monochloride, acetyl chloride and chloroacetyl chloride, and further distilling the substances in the reaction kettle through a short-cut distillation tube (a distillation tube which does not pass through the condenser of the reaction kettle) arranged on the reaction kettle when the mass ratio in the reaction kettle reaches 1.32/80 ℃, when the mass ratio in the reaction kettle reaches 1.35/80 ℃, indicating that the reaction is finished, stopping introducing chlorine gas to finish the acetic acid chlorination process.

In order to improve the quality and purity of chloroacetic acid products, nitrogen gas can be introduced for flushing after the acetic acid chlorination process is finished so as to take away residual chlorine gas, hydrogen chloride gas and acetyl chloride gas in the reaction kettle.

The chloroacetic acid production process provided by the invention has high product yield, can improve the chloroacetic acid yield of each ton of acetic acid from the existing 1, 2 tons to 1.4 tons, ensures that the monthly income of a chemical plant consuming 40-60 tons of acetic acid is increased by 4-6ten thousand yuan, and has stable product quality and high purity.

The present invention will be further described in detail with reference to the following examples:

installing a freezer to obtain frozen brine below-15 ℃, pumping the frozen brine into a condenser, and then: 1. respectively filling acetic acid into a 1 st reaction kettle and a 2 nd reaction kettle, and respectively adding sulfur with the amount of about 1 percent of the acetic acid into the two reaction kettles. 2. The reaction kettle was heated to 70 ℃. 3. Introducing chlorine into a first reaction kettle 1 for chlorination, introducing unreacted chlorine into a second reaction kettle 2 after passing through a first reaction kettle condenser for use in the next reaction, wherein the chlorine introduction amount in the initial stage is controlled to be 20-2kg/h, the chlorine introduction amount in the middle stage is controlled to be 35-40kg/h, the chlorine introduction amount in the later stage is controlled to be 20-25kg/h, the temperature in the first reaction kettle 1 is gradually increased along with the reaction, the temperature finally reaches 98 +/-2 ℃, the temperature in the second reaction kettle 2 is kept unchanged at about 70 ℃, after the substance specific gravity in the first reaction kettle 1 reaches 1.21-1.24/80 ℃, the frozen brine in the first reaction kettle condenser is closed, so that the gas and low-boiling-point distillate (the substances comprise monosulfuric chloride, acetyl chloride and chloroacetyl chloride) in the first reaction kettle are distilled out, after the substance specific gravity in the first reaction kettle 1 reaches 1.32/80 ℃, the substances in the reaction kettle 2 are further distilled through a short-cut distillation pipe (a distillation pipe which does not pass through a reaction kettle condenser) arranged on the reaction kettle 2, when the specific gravity of the substances in the reaction kettle 1 reaches 1.35/80 ℃, the reaction in the reaction kettle 1 reaches the end point, and the chlorine gas can be stopped from being introduced into the reaction kettle 1. 4. And (3) introducing nitrogen into the reaction kettle 1 to flush for 10-20 minutes so as to take away residual chlorine, hydrogen chloride gas and acetyl chloride gas in the reaction kettle. 5. Introducing the substances in the reaction kettle 1 into a crystallization kettle, adding a proper amount of chloroacetic acid crystallization mother liquor, and slowly cooling and crystallizing chloroacetic acid under stirring. 6. And (3) separating chloroacetic acid crystals from mother liquor to finish the work of preparing chloroacetic acid by chlorination of acetic acid in the reaction kettle 1, wherein the yield of chloroacetic acid in each ton of acetic acid can reach 1.4 tons.

Claims

1. A kind of chloroacetic acid production technology, take acetic acid as raw materials, chloridize and prepare chloroacetic acid under the condition that the contact agent-sulphur exists, it includes feeding into the reactor-acetic acid and sulphur, the reactor is heated, introduce chlorine chloridize, crystallization, chloroacetic acid separation process in the crystallization kettle, characterized by that: the chlorine is introduced for chlorination when the temperature of the reaction kettle reaches 70 ℃, the acetyl chloride gas which is a low-boiling-point substance generated by the reaction is condensed and refluxed by using frozen brine with the temperature of below 15 ℃ below zero in a condenser of the reaction kettle, the temperature in the reaction kettle is gradually increased along with the reaction and finally reaches 98 +/-2 ℃, when the substance ratio in the reaction kettle reaches 1.21-1.24/80 ℃, the frozen brine is closed, the gas and the low-boiling-point substance generated by the reaction are distilled, the distilled substance comprises sulfur monochloride, acetyl chloride and chloroacetyl chloride, when the substance ratio in the reaction kettle reaches 1.32/80 ℃, the substance in the reaction kettle is further distilled through a shortcut distillation pipe arranged on the reaction kettle, when the substance ratio in the reaction kettle reaches 1.35/80 ℃, the reaction is ended, the chlorine introduction is stopped, and the acetic acid chlorination process is ended.

2. The chloroacetic acid production process of claim 1, characterized in that: when the specific weight of the substances in the reaction kettle reaches 1.35/80 ℃, stopping introducing chlorine, introducing nitrogen for flushing, and then introducing the substances in the reaction kettle into a crystallization kettle for crystallization.

3. The chloroacetic acid production process of claim 2, characterized in that: the nitrogen flushing time is 10-20 minutes.

4. The chloroacetic acid production process of claim 1, characterized in that: the amount (weight) of the contact agent-sulfur added into the reaction kettle is about 1 percent of that of the acetic acid added into the reaction kettle.