CN-121974796-A - Method for preparing chloroacetic acid by hydrogenation reduction of dichloroacetic acid

CN121974796ACN 121974796 ACN121974796 ACN 121974796ACN-121974796-A

Abstract

The invention belongs to the technical field of acyclic compounds, and in particular relates to a method for preparing chloroacetic acid by reducing dichloroacetic acid through hydrogenation, which comprises the following steps that A1, a chloridizing solution containing dichloroacetic acid is added into a raw material storage tank, and then mixed and heated with hydrogen to obtain a mixed material; A2, conveying the mixed material into a hydrogenation reactor loaded with a composite metal modified catalyst for reaction to obtain chloroacetic acid solution and mixed gas, and conveying the mixed gas into a stripping tower for condensation by a condenser to obtain hydrogen chloride gas and condensate, and conveying the condensate into the hydrogenation reactor again for recycling. The method takes the byproduct generated by the chlorination reaction in the chloroacetic acid production process, namely the chlorinated solution, as the reaction raw material, can effectively reduce the dichloroacetic acid and the trichloroacetic acid in the chlorinated solution into the chloroacetic acid, and can not influence other substances in the chlorinated solution.

Inventors

MA ZHENG
ZHAI JINGJING
ZHANG MENG
LI PING
JIA HAIPENG
GUO MENGLI
CHEN XIANGYUN
ZHANG JIAYU
LI GUODONG
YAN BIN

Assignees

山东民基新材料科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260408

Claims (10)

1. A method for preparing chloroacetic acid by hydrogenation reduction of dichloroacetic acid, which is characterized by comprising the following steps: A1, adding a chloridizing solution containing dichloroacetic acid into a raw material storage tank (3), and then mixing and heating with hydrogen to obtain a mixed material; a2, conveying the mixed material into a hydrogenation reactor (1) loaded with a composite metal modified catalyst for reaction to obtain chloroacetic acid solution and mixed gas; A3, conveying the mixed gas to a stripping tower (4), condensing the mixed gas by a condenser (5) to obtain hydrogen chloride gas and condensate, and conveying the condensate to a hydrogenation reactor (1) again for recycling.
2. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 1, wherein a heater (2) is connected to the top of the hydrogenation reactor (1), a raw material storage tank (3) is connected to the heater (2), a hydrogen pipeline (8) is arranged between the heater (2) and the raw material storage tank (3), a stripping tower (4) is connected to the top of the hydrogenation reactor (1), a condenser (5) is connected to the top of the inner side of the stripping tower (4), a central feed pipe (10) and a plurality of packed beds (9) are arranged inside the hydrogenation reactor (1), the plurality of packed beds (9) are arranged outside the central feed pipe (10), a stirring plate (11) is arranged between the plurality of packed beds (9) and the central feed pipe (10), the central feed pipe (10) is connected with the heater (2), a plurality of through holes are formed in the central feed pipe (10), and a motor is connected to the bottom of the stirring plate (11).
3. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 2, wherein the upper part of the hydrogenation reactor (1) is connected with the middle part of the stripping tower (4), and the bottom of the stripping tower (4) is connected with the top of the hydrogenation reactor (1).
4. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 2, wherein a chloroacetic acid pipeline (6) is arranged at the bottom of the hydrogenation reactor (1), and a hydrogen chloride pipeline (7) is arranged at the top of the stripping tower (4).
5. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 2, wherein the packed beds (9) are of columnar structures as a whole, a plurality of the packed beds (9) are arranged at intervals, the packed beds (9) are filled with metal modified catalysts, the filling density of the composite metal modified catalysts in the packed beds (9) is 0.2-0.6kg/L, and the filling height is 2-3m.
6. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 1, wherein the composition of the chloridizing solution in the step A1 comprises dichloroacetic acid, acetic acid, water, trichloroacetic acid and chloroacetic acid, wherein the mass ratio of the dichloroacetic acid in the chloridizing solution is 60-70%, the mass ratio of the trichloroacetic acid is 2-3%, the mass ratio of hydrogen to the chloridizing solution is 1:55-65, the heating temperature is 140-160 ℃, and the heating time is 10-20min.
7. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 1, wherein the preparation method of the composite metal modified catalyst in the step A2 is as follows: a1, adding ferric salt and nickel salt into water, mixing to obtain a mixed salt solution, adding cerium oxide nano particles into the mixed salt solution, then adding alkali liquor for coprecipitation, filtering, drying and roasting to obtain composite matrix nano particles; and a2, dissolving palladium salt in water to obtain palladium salt solution, dispersing the composite matrix nano particles in absolute ethyl alcohol to obtain dispersion liquid, dripping aluminum isopropoxide ethanol solution and palladium salt solution into the dispersion liquid under the stirring condition, regulating pH, precipitating and placing, centrifuging, washing, drying and roasting to obtain the composite metal modified catalyst.
8. The method for preparing chloroacetic acid by hydrogenation reduction of dichloroacetic acid according to claim 7, wherein in the step a1, the ferric salt is ferric nitrate or ferric chloride, the nickel salt is nickel nitrate or nickel sulfate, the mass ratio of the ferric salt to the nickel salt to water is 1:1.26-1.5:10-12, the mass ratio of cerium oxide nano particles to the ferric salt is 1:0.3-0.5, the alkali solution is sodium hydroxide solution, the concentration of the sodium hydroxide solution is 25-40 wt%, the pH of coprecipitation is 8-10, the coprecipitation temperature is 35-45 ℃, the coprecipitation time is 2.5-3h, the drying temperature is 50-60 ℃, the drying time is 0.5-1h, the roasting temperature is 130-150 ℃ and the roasting time is 40-50min.
9. The method for preparing chloroacetic acid by hydrogenation reduction of dichloroacetic acid according to claim 7, wherein in the step a2, palladium salt is palladium nitrate, the mass ratio of palladium salt to water is 0.035-0.05:1, the pH is adjusted to 8.5-9.5 by using sodium hydroxide solution, the concentration of sodium hydroxide solution is 25-40 wt%, the mass ratio of composite matrix nano particles to absolute ethyl alcohol is 1:8-10, the concentration of aluminum isopropoxide ethyl alcohol solution is 65-70 wt%, the mass ratio of aluminum isopropoxide ethyl alcohol solution to palladium salt solution is 1:0.02-0.1, the mass ratio of composite matrix nano particles to aluminum isopropoxide ethyl alcohol solution is 1:2-2.4, the precipitation placement temperature is normal temperature, the precipitation placement time is 10-14h, the washing is carried out by adopting deionized water for 2-3 times, the drying temperature is 60-70 ℃, the drying time is 15-30min, the roasting time is 130-150 ℃ and the roasting time is 40-50min.
10. The method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid according to claim 1, wherein the reaction temperature in the step A2 is 150-170 ℃, the reaction time is 50-70min, the conveying speed in the step A3 is 0.2-0.5m 3 /s, and the condensing temperature is 30-50 ℃.

Description

Method for preparing chloroacetic acid by hydrogenation reduction of dichloroacetic acid Technical Field The invention belongs to the technical field of acyclic compounds, and particularly relates to a method for preparing chloroacetic acid by reducing dichloroacetic acid through hydrogenation. Background Chloroacetic acid is an important chemical raw material and is widely used in the fields of dyes, medicines, pesticides, synthetic resins and other organic synthesis. In the chloroacetic acid production process, side reactions can occur in the chlorination reaction process to generate dichloroacetic acid, and common methods for converting dichloroacetic acid into chloroacetic acid include a catalytic hydrodechlorination method and a chemical reduction method, wherein the catalytic hydrodechlorination method is the most direct, most effective and most industrial application prospect. The chemical reduction method has relatively simple operation and does not need high-pressure equipment, but can generate a large amount of zinc-containing waste residues and wastewater, has serious environmental pollution, troublesome post-treatment and poor economy, and is not suitable for large-scale production. The catalytic hydrogenation dechlorination method is that dichloroacetic acid can be reduced into chloroacetic acid by hydrogenation in the presence of a catalyst, and palladium carbon is generally used as the catalyst in the production of chloroacetic acid at present. Chinese patent CN107413333a discloses a method for preparing modified hydrodechlorination catalyst and producing high purity chloroacetic acid. The catalyst comprises the following components, by mass, 0.5-2.0% of metal active component simple substance, 1.0-4.0% of metal auxiliary simple substance and the balance of carrier, wherein the metal active component simple substance is selected from one or more of palladium, platinum and nickel. The metal auxiliary simple substance is selected from one or more of rhenium, zirconium, ruthenium, cadmium, barium and vanadium, and the carrier is selected from one or more of active carbon, alumina, titanium dioxide and aluminum fluoride. The catalyst prepared by the patent has poor removal rate of the dichloroacetic acid and poor hydrogenation effect. Chinese patent CN106488903a discloses a process for purifying a feed comprising monochloroacetic acid and dichloroacetic acid, wherein the feed is subjected to a catalytic hydrodechlorination step by contacting the feed under hydrodechlorination conditions with a source of hydrogen in the presence of a solid heterogeneous hydrogenation catalyst comprising a supported group VIII noble metal to convert dichloroacetic acid to monochloroacetic acid, wherein the reaction is carried out in the presence of a catalyst enhancer comprising a salt of a metal selected from group VIII, group VIB, group VIIB and group IIB non-noble metals. The patent takes active carbon supported palladium as a catalyst, and ferrous chloride is only used as an enhancer for hydrogenation reaction, so that the catalytic effect is poor. Disclosure of Invention According to the defects in the prior art, the technical problem to be solved by the invention is to provide a method for preparing chloroacetic acid by hydrogenating and reducing dichloroacetic acid, wherein the dichloroacetic acid is converted into chloroacetic acid by adopting a composite metal modified catalyst in the process, so that the high-efficiency conversion of chloroacetic acid is realized. The technical scheme adopted for solving the technical problems is as follows: the method for preparing chloroacetic acid by hydrogenation reduction of dichloroacetic acid comprises the following steps: A1, adding a chloridizing solution containing dichloroacetic acid into a raw material storage tank, and then mixing and heating with hydrogen to obtain a mixed material; a2, conveying the mixed material into a hydrogenation reactor loaded with a composite metal modified catalyst for reaction to obtain chloroacetic acid solution and mixed gas; and A3, conveying the mixed gas to a stripping tower, condensing the mixed gas by a condenser to obtain hydrogen chloride gas and condensate, and conveying the condensate to a hydrogenation reactor again for recycling. Wherein: The hydrogenation reactor is characterized in that the top of the hydrogenation reactor is connected with a heater, the heater is connected with a raw material storage tank, a hydrogen pipeline is arranged between the heater and the raw material storage tank, the top of the hydrogenation reactor is connected with a stripping tower, the top of the inner side of the stripping tower is connected with a condenser, a central feeding pipe and a plurality of packed beds are arranged in the hydrogenation reactor, the packed beds are arranged outside the central feeding pipe, a stirring plate is arranged between the packed beds and the central feeding pipe, the central feeding pipe is connecte