A kind of method for preparing dichloroacetic acid by selective dechlorination of trichloroacetic acid

A technology of trichloroacetic acid and dichloroacetic acid, applied in the preparation of carboxylate, chemical instruments and methods, preparation of organic compounds, etc., can solve the problems of low product purity, long process flow, large amount of waste water, etc., and achieve hydrogen The effect of uniform concentration, favorable selectivity and low equipment cost

Active Publication Date: 2020-07-21
XIAN CATALYST NEW MATERIALS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Dichloroacetic acid and trichloroacetic acid can be separated by crystallization according to the difference in melting point, but the product purity is not high
[0003] Chinese patent CN1129210A discloses a method for producing dichloroacetic acid. The mother liquor of chloroacetic acid is subjected to secondary distillation, water, acetic acid and monochloroacetic acid are separated, thiourea is added, and after chemical reaction, filtration, acidification, extraction, distillation and other operations, The obtained dichloroacetic acid has a purity of more than 95%, but the whole technological process is long, the cost is high, and the amount of waste water is large

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] 1. Catalyst loading

[0023] Fill the catalyst diluted with coal-based activated carbon in the fixed-bed catalytic reactor, according to the catalyst dilution ratio, the mass fraction of the catalyst in each section of A, B, and C is successively 30%, 60% and 100%, wherein the catalyst contains Pt The loading of Pd is 0.5%, the loading of Pd is 0.3%, the loading of Ag is 0.2%, the loading of Mg is 0.1%, the loading of Al is 0.4%, and the rest is coal-based activated carbon. The reaction tube internals and connecting pipes of the fixed bed catalytic reactor are made of carbon steel lining enamel.

[0024] 2. Pretreatment

[0025] The air in the reactor is replaced by nitrogen gas from the air inlet on the top and side of the fixed-bed catalytic reactor for 2 hours, then the nitrogen is switched to pure hydrogen, and the temperature in the fixed-bed catalytic reactor is raised to 200°C at a rate of 1°C / min. Hold for 3 hours to activate and pretreat the catalyst, then co...

Embodiment 2

[0029] 1. Catalyst loading

[0030] Fill the catalyst diluted with coal-based activated carbon in the fixed-bed catalytic reactor, according to the catalyst dilution ratio, the mass fraction of the catalyst in each section of A, B, and C is successively 40%, 60% and 90%, wherein the Pt in the catalyst The loading of Pd is 0.9%, the loading of Pd is 0.1%, the loading of Ag is 0.1%, the loading of Mg is 0.2%, the loading of Al is 0.1%, and the rest is coal-based activated carbon. The reaction tube internals and connecting pipes of the fixed bed catalytic reactor are made of carbon steel lining enamel.

[0031] 2. Pretreatment

[0032] The air in the reactor is replaced by nitrogen gas from the air inlet on the top and side of the fixed-bed catalytic reactor for 2 hours, then the nitrogen is switched to pure hydrogen, and the temperature in the fixed-bed catalytic reactor is raised to 200°C at a rate of 1°C / min. Hold for 3 hours to activate and pretreat the catalyst, then lower...

Embodiment 3

[0036] 1. Catalyst loading

[0037] Fill the catalyst diluted with coal-based activated carbon in the fixed-bed catalytic reactor, according to the catalyst dilution ratio, the mass fraction of the catalyst in each section of A, B, and C is successively 30%, 70% and 100%, wherein the catalyst contains Pt The loading of Pd is 0.3%, the loading of Pd is 0.4%, the loading of Ag is 0.2%, the loading of Mg is 0.1%, the loading of Al is 0.3%, and the rest is coal-based activated carbon. The reaction tube internals and connecting pipes of the fixed bed catalytic reactor are made of carbon steel lining enamel.

[0038] 2. Pretreatment

[0039] The air in the reactor is replaced by nitrogen gas from the air inlet on the top and side of the fixed-bed catalytic reactor for 2 hours, then the nitrogen is switched to pure hydrogen, and the temperature in the fixed-bed catalytic reactor is raised to 200°C at a rate of 1°C / min. Hold for 3 hours to activate and pretreat the catalyst, then lowe...

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Abstract

The invention discloses a method for preparing dichloroacetic acid by selective dechlorination of trichloroacetic acid. The method adopts a fixed fixed-bed catalytic reactor, and can convert trichloroacetic acid into dichloroacetic acid. The conversion rate is greater than 99.5%, and the selectivity is greater than 98%, the rest is monochloroacetic acid and acetic acid. The catalyst is a noble metal catalyst supported by coal-based activated carbon. The trichloroacetic acid solution and hydrogen are preheated to the reaction temperature, enter from the top of the reactor, contact the catalyst from top to bottom, and undergo hydrodechlorination reaction. Gas port, during the reaction process, hydrogen is continuously replenished to keep the hydrogen concentration in the reaction at 10% to 40%. The liquid and gas phase products are all discharged from the bottom of the reactor. After condensation and gas-liquid separation, the liquid phase products are then distilled High-purity dichloroacetic acid products can be obtained.

Description

technical field [0001] The invention belongs to the technical field of selective catalytic hydrogenation process, in particular to a method for preparing dichloroacetic acid by selective catalytic hydrogenation dechlorination. Background technique [0002] Dichloroacetic acid is an important chemical intermediate, which has many applications in the fields of medicine, pesticides and active fuels. It can be used to prepare dichloroacetic acid salt, glyoxylic acid and dichloroacetyl chloride, etc., or to prepare cellulose Derivatives of plasticizers. The preparation methods of dichloroacetic acid include: chloroacetic acid mother liquor distillation method, iodine-catalyzed acetic acid rechlorination method and chloral method. Wherein the purity of dichloroacetic acid prepared by the first two methods is relatively low, no more than 90%, and high-purity dichloroacetic acid can be obtained by cyaniding, dechlorinating and rehydrolyzing chloral, but the process is complicated a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C51/377C07C53/16
CPCC07C51/377C07C53/16
Inventor 林涛万克柔程杰张炳亮张力陈丹张之翔曾永康曾利辉高武
Owner XIAN CATALYST NEW MATERIALS CO LTD
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