CN102001930B - Method for purifying chloroacetic acid by catalytic hydrogenolysis in chloroacetic acid production and application thereof - Google Patents

Abstract

A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid and its application. The method comprises that in a catalytic reactor lined with polytetrafluoroethylene or zirconium material, the Group VIII noble metal is installed as a hydrogenolysis catalyst bed; Flow through the fixed bed layer, make the hydrogen-nitrogen mixed gas and the liquid phase flow into the bed layer; make all or most of the polychloroacetic acid in the chlorinated liquid undergo hydrogenolysis reaction; the material is discharged from the reactor, and the gas-liquid separation; the chlorine The liquid phase is crystallized and washed to obtain the monochloroacetic acid product; the gas phase is condensed, absorbed, and separated to recover hydrogen, hydrogen chloride, and acetic acid. It can improve the removal effect, treatment efficiency and product purity of dichloroacetic acid and trichloroacetic acid, reduce the catalyst deactivation trend and activity decline rate, shorten the reaction time, reduce hydrogen consumption, improve the utilization rate of raw materials and the yield of products, Further improve economic benefits.

Description

Method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid and its application

technical field

The invention belongs to the technical field of monochloroacetic acid production technology, and more specifically relates to the improvement and innovation of the method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid and its application.

Background technique

Chloroacetic acid is an important organic fine chemical raw material, widely used in pesticides, medicines, dyes, oilfield chemicals, paper chemicals, textile auxiliaries, surfactants, electroplating, spices, flavors and other fields. Its largest use is the production of carboxymethyl cellulose, followed by the production of thioglycolic acid. With the advancement and development of technology, new application fields of chloroacetic acid have been gradually developed, and the prospect is very broad. In recent years, the world's total consumption of chloroacetic acid has exceeded 800,000 t/a, and China's consumption has also exceeded 400,000 t/a. The synthesis method of chloroacetic acid has always been the focus of people's research and development. There have been new synthesis methods such as vinyl chloride and chlorohydrin oxidation, chloroacetyl chloride and trichloroethylene hydrolysis, ketene chlorination, and acetic acid catalytic chlorination. However, there are only two industrial production methods: trichlorethylene hydrolysis and acetic acid catalytic chlorination.

The trichlorethylene hydrolysis method uses concentrated sulfuric acid as a catalyst to carry out water addition and hydrolysis reactions at the same time. The trichlorethylene hydrolysis method has been developed due to its simpler process and higher product purity. This process has been used to build industrial production plants in Europe, but it has been eliminated in recent years due to expensive raw materials. The acetic acid catalytic chlorination method is under the action of catalysts (such as iodine, phosphorus, sulfur or sulfur and phosphorus halides and acetic anhydride, etc.), at 95-140 ° C, glacial acetic acid and chlorine gas in one or several series reactors The chlorination reaction in the process generates monochloroacetic acid, and a small amount of dichloroacetic acid or even trichloroacetic acid is produced as a by-product. Due to the existence of by-products, the reaction product must be purified by crystallization to obtain high-purity chloroacetic acid products.

The sulfur method is widely used in China to catalyze the chlorination of acetic acid. That is, in the presence of sulfur, acetic acid reacts directly with chlorine gas to form chloroacetic acid. However, acetic anhydride is commonly used to catalyze the chlorination of acetic acid in foreign countries. Regardless of the sulfur method or the acetic anhydride method, except for the start-up stage, the actual catalyst in the reaction process is acetyl chloride, and both sulfur and acetic anhydride are generators of acetyl chloride. Acetic anhydride is also different from sulfur as a catalyst. The amount of acetyl chloride produced by acetic anhydride as a catalyst is certain and is disposable. It can be used as a reaction raw material and can also neutralize the moisture brought in in the reaction system. Therefore, the dosage is larger. Sulfur is used as a catalyst to circulate continuously in the reaction process, and the consumption is small, but the consumption of chlorine gas is large, and at the same time, SOx waste gas is generated. Although the price and dosage of sulfur are lower than those of acetic anhydride, the consumption of acetic acid and chlorine gas in the sulfur method is higher than that of the acetic anhydride method, and the quality of the by-product hydrochloric acid in the acetic anhydride method can reach the level of synthetic hydrochloric acid, while the by-product hydrochloric acid in the sulfur method contains Sulfur cannot be used in many industries. Compared with the sulfur method, the acetic anhydride method has lower production consumption and less "three wastes" pollution. The mass fraction of chloroacetic acid in the intermediate product chlorination solution reaches 93%-95%, the generation amount of by-product dichloroacetic acid is greatly reduced (3%-5%), and the product quality is high and stable. Therefore, from the perspective of comprehensive output, the advantages of the acetic anhydride method are obvious, and this has not considered the weakness of the products produced by the sulfur method in terms of quality and the capital investment in environmental protection. With the increase in the demand for chloroacetic acid and the improvement of the quality requirements of downstream products for chloroacetic acid, large-scale (above 10,000 tons) and continuous process chloroacetic acid has room for development in China.

No matter which production method is adopted, by-products such as dichloroacetic acid and trichloroacetic acid will inevitably be produced in the production process of chloroacetic acid, which is determined by the reaction mechanism. In the initial stage of chlorination, the reaction proceeds rapidly, so the generated chloroacetyl chloride can be quickly converted into chloroacetic acid; in the later stage of the reaction, the content of acetic acid decreases and the content of chloroacetic acid increases, resulting in excess chloroacetyl chloride. After the enolization reaction of the excess chloroacetyl chloride, the chlorination continues to generate dichloroacetyl chloride, which in turn generates dichloroacetic acid. However, since the source of chloroacetyl chloride cannot be single, it is impossible to determine whether the generation of dichloroacetic acid is carried out by a parallel reaction mechanism or a series reaction mechanism, or two reaction mechanisms coexist, so there is no control of polychlorinated substances. Generate efficient methods. Therefore, how to extract monochloroacetic acid with higher purity from the reaction mixture as simply as possible and with high income has become the focus of further reducing costs, improving quality and reducing pollution for various manufacturers.

Due to the difference in production process and national conditions, the conversion or removal process of dichloroacetic acid in chlorinated liquid is quite different at home and abroad. In China, after most of the chloroacetic acid is crystallized from the chlorinated liquid, the main methods for the treatment of the chloroacetic acid crystallization mother liquor are as follows: esterification with methanol to form methyl chloroacetate, methyl dichloroacetate and mixed esters, which may be the most important in my country. Common disposal routes for chloroacetic acid mother liquors. After the mother liquor is esterified, it is neutralized, washed with water, dried and dehydrated, and the mixed ester can be sold as an intermediate product, or separated by vacuum distillation to obtain methyl chloroacetate and methyl dichloroacetate. The main shortcoming of this method is that a. the trichloro impurity cannot be completely removed, so that the methyl trichloroacetate is too high in the methyl dichloroacetate product, which has a strong impact on the product quality. b. The total reflux esterification reaction process is adopted, the reaction temperature is low, the reaction time is long, the equipment capacity is low, the methanol consumption is large, the ester product stays in the kettle for too long and decomposes, and the esterification operation is intermittent. c. The water content in the mixed ester product is too high, it is easy to be acidified and deteriorated, and the storage period is shortened. Other mother liquor treatment methods include: production of sodium oxalate and glycolic acid, production of carboxymethyl cellulose, production of chloroacetic acid and acetic acid by hydrogenation dechlorination reduction, production of dichloroacetic acid, trichloroacetic acid and chloroform by deep chlorination, generation of thioglycolic acid and dichloroacetic acid Chloroacetic acid, synthetic glyoxylic acid and other methods. Looking at the above methods, most of them belong to small-scale production, with complex and numerous procedures, and many of them have brought secondary pollution, which cannot be eradicated. In foreign countries, the process of producing chloroacetic acid and acetic acid by hydrogenation dechlorination reduction is often used, and dichloroacetic acid and trichloroacetic acid are hydrogenated to generate monochloroacetic acid and hydrogen chloride. There are no other impurities in the chlorination solution except monochloroacetic acid and acetic acid, and the mother liquor after the crystallization of monochloroacetic acid can be recycled in the chlorination process, which eliminates pollution and greatly improves product quality. Therefore, it is the preferred process for the follow-up treatment of monochloroacetic acid in large-scale acetic anhydride method. However, there are few domestic studies on this technology, and there is an urgent need to carry out research in this area to meet the needs of the development of chloroacetic acid, and the hydrogenation catalyst is precious metal palladium attached to activated carbon or porous silica gel. Due to the high cost of this catalyst, improper use will cause Therefore, it is of great significance to carry out the research on hydrogenation technology of chlorinated liquid to improve the development level of domestic chloroacetic acid.

Chinese patent CN1382680A discloses a method. Adding a chlorine inhibitor to the reaction system can inhibit the production of dichloroacetic acid. Available chlorine inhibitors include manganese acetate, manganous chloride, zinc chloride, zinc acetate or chromium acetate , the content of dichloroacetic acid in the product can be reduced to below 3%.

Chinese patent CN101528657A discloses a method, which is to treat a mixture of monochloroacetic acid and dichloroacetic acid at a pressure of 1-10 bar and a temperature of 130-170 ° C, and hydrogenolysis the latter under the use of a catalyst. In addition to these two substances, the reaction liquid in the production process of monochloroacetic acid also contains a certain amount of hydrochloric acid, water and acetic acid and other substances. This method does not mention whether it is applicable to this system.

Chinese patent CN1197838C adopts palladium as catalyst, is to make dichloroacetic acid under the conditions of atmospheric pressure 101.32kPa-100kPa (gauge pressure), 100～180°C, hydrogen and dichloroacetic acid molar ratio in the mixture to be treated as 1.2～15:1. A hydrogenation reaction occurs and the hydrogenation mixture is repeated to obtain monochloroacetic acid with a low dichloroacetic acid content. Although this method can remove dichloroacetic acid or reduce it to a lower content, but under low pressure, repeated hydrogenation takes a long time and the treatment efficiency is low.

German patent DE-A-1915037 discloses a process for hydrogenating a mixture of mono-, di- and trichloroacetic acids in the presence of a catalyst suspended in the mixture, thereby reducing the concentration of dichloroacetic and trichloroacetic acids. The disadvantage of this method is that a specific active agent soluble in the mixture needs to be added to the crude mixture, which increases the subsequent purification steps and consumes a large amount of hydrogen.

In the above patents, the removal effect of dichloroacetic acid is not satisfactory, or the treatment efficiency is low, and the hydrogen consumption is large, which inevitably affects the economic benefits of the product.

U.S. Patent No. 5,756,840 uses a Pd/C catalyst to hydrogenolyze ethyl chloride to the mixture at 1 bar and 130° C. to reduce the content of dichloroacetic acid from 3.2% to 0.35%.

European patent EP0537838 hydrogenolyzes the mixture of chloroacetic acid at 135°C and 1 bar pressure, and the content of dichloroacetic acid is reduced from 4% to 0.13%. After 200 hours of operation, the activity of the catalyst decreases and the content of formaldehyde increases significantly.

Although these patents have improved reaction effects, they still have the disadvantages of long reaction time, large hydrogen consumption, and rapid decline in catalyst activity, and they do not mention the applicability of chlorinated solutions containing hydrochloric acid, acetic acid and other substances.

Contents of the invention

The purpose of the present invention is just to overcome above-mentioned shortcoming and deficiency, provide a kind of method and its application of catalytic hydrogenolysis purification monochloroacetic acid in the production of monochloroacetic acid. It is a new catalytic hydrogenolysis process suitable for industrial practice. Under the atmosphere of nitrogen and hydrogen mixed gas, it can greatly improve the removal effect of dichloroacetic acid and trichloroacetic acid, increase the rate of hydrogenation, and the efficiency of dichloroacetic acid. Treatment efficiency and product purity, reduce catalyst deactivation trend and activity decline rate, shorten reaction time, reduce hydrogen consumption, improve raw material utilization and product yield, and further improve economic benefits.

In order to achieve the above object, the method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid of the present invention comprises processing the mother liquor after chlorination of acetic acid at a certain temperature and pressure. Also includes the following steps:

(1) In a catalytic reactor lined with polytetrafluoroethylene or zirconium material, one or a combination of Group VIII noble metals is installed as a hydrogenolysis catalyst bed, and the ratio of noble metals to the carrier is 0.1 to 3.5%;

(2) Under the gauge pressure of 100-800kPa and the temperature of 100-200°C, the chlorinated liquid in the production process of monochloroacetic acid flows through the fixed bed layer, and at the same time, the hydrogen-nitrogen mixed gas and the liquid phase flow into the bed;

(3) Under the action of the catalyst bed, make all or most of the polychloroacetic acid in the chlorinated solution undergo hydrogenolysis reaction to produce monochloroacetic acid;

(4) The material is discharged from the reactor, and separated by gas and liquid;

(5) crystallize and wash the chlorinated liquid liquid phase that does not contain or contain a very small amount of polychloroacetic acid after gas-liquid separation, to obtain a monochloroacetic acid product;

(6) The gas phase after gas-liquid separation is condensed, absorbed, and separated to recover hydrogen, hydrogen chloride, and acetic acid.

The invention uses one or a combination of Group VIII noble metals as a catalyst to hydrogenate polychloroacetic acid to generate monochloroacetic acid, and increase the yield of monochloroacetic acid while removing polychloroacetic acid.

The catalyst support can be activated carbon, silica, alumina, pumice or diatomaceous earth. The effect is best when activated carbon with a specific surface area of 500-1350m ² /g is used as the carrier. When palladium is used as the catalyst active component, the effect is better.

When the catalyst is a cylinder with a diameter of 0.2-15mm and a height of 0.3-30mm or a sphere with a diameter of 0.3-10mm, the effect is very good.

When the ratio of the noble metal to the carrier in the present invention is 0.5-1%, the effect is very good.

The effect is good when the pressure is a gauge pressure of 250 to 500kPa. When the temperature is 130 ~ 150 ℃, the effect is very good.

The hydrogenolysis reaction takes place under the atmosphere of pure hydrogen or a mixture of hydrogen and other inert gases. The inert gas can be one or a mixture of nitrogen, helium, argon, and carbon dioxide. The amount of hydrogen used is 1.2 to 8.0 times the molar amount of dichloroacetic acid, and the effect is very good when the molar ratio of inert gas to hydrogen is between 0 and 5. The amount of hydrogen used is 1.5 to 5.0 times the molar weight of dichloroacetic acid, and the effect is the best when the molar ratio of inert gas to hydrogen is between 2 and 3.

A residence time of 1.5 to 5 hours for the liquid phase in the catalyst bed works well. The effect is best when the residence time of the liquid phase in the catalyst bed is 2 to 4 hours.

In other words, the preferred hydrogenolysis process conditions of dichloroacetic acid in the present invention are: temperature 120-180°C; pressure 250-500kPa; hydrogen consumption is 1.5-5.0 times the molar weight of dichloroacetic acid; the molar ratio of nitrogen to hydrogen is (0-0.1): 1; the residence time of the liquid phase in the catalyst bed is 2 to 4 hours. The preferred process conditions are: temperature 150°C; pressure 360kPa; hydrogen consumption 3.5 times the molar amount of dichloroacetic acid; liquid phase residence time 2.5 hours.

Equipment and pipelines can be lined with PTFE, enamel, or made of corrosion-resistant metal materials such as zirconium, tantalum, and Hastelloy.

The purpose of the method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of the above-mentioned monochloroacetic acid is to be used for containing 75-95% of monochloroacetic acid, 0.5-6% of dichloroacetic acid, 0-3% of trichloroacetic acid, and 1-3% of hydrochloric acid. %, 5-15% chlorinated solution of acetic acid. After catalytic hydrogenolysis reaction, the content of dichloroacetic acid in the mixed liquid is less than 0.01% or lower.

The invention is a catalytic hydrogenolysis process for purifying chloroacetic acid, which is mainly used in the treatment of the mixed liquid after chlorination in the production process of monochloroacetic acid, so that dichloroacetic acid and trichloroacetic acid can be converted into monochloroacetic acid, and the product does not contain or Contains very small amounts of dichloroacetic acid.

The technical scheme of the present invention is: a catalyst bed is installed in a catalytic reactor lined with polytetrafluoroethylene or made of zirconium material, and at a certain temperature and pressure, the chlorinated liquid in the production process of monochloroacetic acid flows through the fixed bed layer. At the same time, the mixed gas of hydrogen and nitrogen flows into the bed with the liquid phase. Under the action of the catalyst, all or most of the polychloroacetic acid in the chlorinated liquid undergoes hydrogenolysis reaction to produce monochloroacetic acid. After the material leaves the reactor, it undergoes gas-liquid separation. The liquid phase is a chlorinated liquid that does not contain or contains a very small amount of polychloroacetic acid. After crystallization, washing and other processes, high-quality monochloroacetic acid products can be obtained. The gas phase is condensed, absorbed, separated, recovered hydrogen, hydrogen chloride and acetic acid and other materials.

Task of the present invention is accomplished like this.

After adopting the above process, the increase of hydrogen partial pressure accelerates the reaction speed, and the addition of nitrogen makes more hydrogen chloride gas generated by the raw materials and the reaction enter the gas phase, so that the hydrogenolysis reaction is carried out more completely; and the introduction of nitrogen makes the hydrogenolysis reaction proceed more smoothly. It is more stable, reduces the partial overload hydrogenolysis reaction of the catalyst, and is beneficial to prolong the life of the catalyst. At the same time, smooth hydrogenation is more conducive to reducing the hydrogenation side reaction of monochloroacetic acid. Therefore, under the process conditions of the present invention, the concentration of dichloroacetic acid in the mixed solution can be reduced to a very low level, and the impact of the hydrogen chloride contained in the chlorinated solution and generated by the hydrogenolysis reaction on the reaction is reduced to a minimum, and the utilization of raw materials is improved. rate and yield.

It is a new catalytic hydrogenolysis process suitable for industrial practice. Under the atmosphere of nitrogen and hydrogen mixed gas, it can greatly improve the removal effect of dichloroacetic acid and trichloroacetic acid, increase the rate of hydrogenation, and the efficiency of dichloroacetic acid. Treatment efficiency and product purity, reduce catalyst deactivation trend and activity decline rate, shorten reaction time, reduce hydrogen consumption, improve raw material utilization and product yield, and further improve economic benefits. The invention can be widely used in the purification of monochloroacetic acid in the production of monochloroacetic acid.

Detailed ways

Example 1. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. It includes treating the mother liquor after acetic acid chlorination under certain temperature and pressure. The following steps are also included: (1) in a catalytic reactor lined with polytetrafluoroethylene or zirconium material, one or a combination of Group VIII noble metals is installed as a hydrogenolysis catalyst bed, and the ratio of noble metals to the carrier is 3.5% (2) under the gauge pressure of 500kPa and the temperature condition of 150 DEG C, the chlorinated liquid in the monochloroacetic acid production process is made to flow through the fixed bed layer, and the hydrogen-nitrogen mixed gas and the liquid phase are co-flowed into the bed layer; (3) Under the action of the catalyst bed, make all or most of the polychloroacetic acid in the chlorinated liquid hydrogenolyze to produce monochloroacetic acid; (4) take the material out of the reactor and separate it through gas-liquid; ( 5) crystallize and wash the chlorinated liquid liquid phase after gas-liquid separation that does not contain or contain a very small amount of polychloroacetic acid, and obtain a monochloroacetic acid product; (6) condense, absorb, and separate the gas phase after gas-liquid separation, Hydrogen, hydrogen chloride and acetic acid are thereby recovered. good results.

Example 2. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. It includes treating the mother liquor after acetic acid chlorination under certain temperature and pressure. The following steps are also included: (1) in a catalytic reactor lined with polytetrafluoroethylene or zirconium material, one or a combination of Group VIII noble metals is installed as a hydrogenolysis catalyst bed, and the ratio of noble metals to the carrier is 2% (2) under the gauge pressure of 800kPa and the temperature condition of 100 DEG C, make the chlorinated liquid in the monochloroacetic acid production process flow through the fixed bed layer, and simultaneously make the hydrogen-nitrogen mixed gas and the liquid phase co-flow into the bed layer; (3) Under the action of the catalyst bed, make all or most of the polychloroacetic acid in the chlorinated liquid hydrogenolyze to produce monochloroacetic acid; (4) take the material out of the reactor and separate it through gas-liquid; ( 5) crystallize and wash the chlorinated liquid liquid phase after gas-liquid separation that does not contain or contain a very small amount of polychloroacetic acid, and obtain a monochloroacetic acid product; (6) condense, absorb, and separate the gas phase after gas-liquid separation, Hydrogen, hydrogen chloride and acetic acid are thereby recovered. good results.

Example 3. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. It includes treating the mother liquor after acetic acid chlorination under certain temperature and pressure. It also includes the following steps: (1) in a catalytic reactor lined with polytetrafluoroethylene or zirconium material, one or a combination of Group VIII noble metals is installed as a hydrogenolysis catalyst bed, and the ratio of noble metals to the carrier is 0.1% (2) under the gauge pressure of 100kPa and the temperature condition of 200 DEG C, the chlorinated liquid in the monochloroacetic acid production process is made to flow through the fixed bed layer, and the hydrogen-nitrogen mixed gas and the liquid phase are co-flowed into the bed layer; (3) Under the action of the catalyst bed, make all or most of the polychloroacetic acid in the chlorinated liquid hydrogenolyze to produce monochloroacetic acid; (4) take the material out of the reactor and separate it through gas-liquid; ( 5) crystallize and wash the chlorinated liquid liquid phase after gas-liquid separation that does not contain or contain a very small amount of polychloroacetic acid, and obtain a monochloroacetic acid product; (6) condense, absorb, and separate the gas phase after gas-liquid separation, Hydrogen, hydrogen chloride and acetic acid are thereby recovered. good results.

Example 4. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The catalyst carrier is one of activated carbon, silica, alumina, pumice or diatomaceous earth. All the other are with embodiment 1.

Example 5. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The catalyst carrier is activated carbon with a specific surface area of 500-1350m ² /g, and the rest are the same as in Example 1.

Example 6. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. It uses palladium as the catalyst active component, and all the other are the same as embodiment 1.

Example 7. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The catalyst is a cylinder with a diameter of 0.2-15mm and a height of 0.3-30mm or a sphere with a diameter of 0.3-10mm. All the other are with embodiment 1.

Example 8. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The proportion of the noble metal in the carrier is 0.5-1%, and the rest are the same as in Example 1.

Example 9. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The reaction conditions are: a gauge pressure of 300 kPa and a temperature of 150°C. All the other are with embodiment 1.

Example 10. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. Its hydrogenolysis reaction takes place under the mixture atmosphere of pure hydrogen or hydrogen and other inert gases, inert gas is nitrogen, and all the other are with embodiment 1.

Example 11. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. Its hydrogenolysis reaction takes place under the mixture atmosphere of pure hydrogen or hydrogen and other inert gases, helium, and all the other are the same as embodiment 1.

Example 12. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. Its hydrogen consumption is 1.2 times of dichloroacetic acid molar weight, and the mol ratio of inert gas and hydrogen is between 1, and all the other are with embodiment 1.

Example 13. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The amount of hydrogen used is 8.0 times the molar amount of dichloroacetic acid, and the molar ratio of inert gas to hydrogen is between 5. , all the other are with embodiment 1.

Example 14. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The amount of hydrogen used is three times the molar amount of dichloroacetic acid, and the molar ratio of inert gas to hydrogen is between 3. , all the other are with embodiment 1.

Example 15. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The residence time of its liquid phase in the catalyst bed was 1.5 hours, and all the other were the same as in Example 1.

Example 16. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The residence time of its liquid phase in the catalyst bed was 5 hours, and all the other were the same as in Example 1.

Example 17. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The residence time of its liquid phase in the catalyst bed was 3 hours, and all the other were the same as in Example 1.

Example 18. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. Its equipment and pipelines are made of zirconium, a metal material lined with polytetrafluoroethylene. All the other are with embodiment 1.

Example 19. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. It is used for chlorination solution containing 75-95% of monochloroacetic acid, 0.5-6% of dichloroacetic acid, 0-3% of trichloroacetic acid, 1-3% of hydrochloric acid and 5-15% of acetic acid. All the other are with embodiment 1. good results.

Example 20. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The reactor is loaded with 0.8% Pd/C catalyst, which is a cylinder with a diameter of 1mm and a height of 3mm, a bed height of 16000mm, a diameter of 800mm, a bed temperature of 171°C, and a reactor internal pressure of 400kPa. The chlorinated liquid and mixed gas are fed from the top of the reaction after preheating, and flow through the bed in parallel. The residence time of the liquid phase is 2.5h, the flow rate of hydrogen is 8.91kg/h, and the flow rate of nitrogen is 9kg/h. The gas-liquid mixture exits from the bottom of the reactor, enters the liquid separator, and the gas and liquid phases are processed and recovered separately. The composition of the chlorinated solution is shown in the attached table. When the device was running for 30 hours, 0.03% of dichloroacetic acid remained in the hydrogenolysis solution, and 1.7% of monochloroacetic acid reacted. After running for 300 hours, 0.06% of dichloroacetic acid remained in the hydrogenolysis solution, 1.3% of monochloroacetic acid reacted, and the effective component content in the catalyst was 0.7%.

Example 21. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The reactor is loaded with 0.8% Pd/C catalyst, which is a cylinder with a diameter of 1mm and a height of 3mm, a bed height of 16000mm, a diameter of 800mm, a bed temperature of 171°C, and a reactor internal pressure of 400kPa. The chlorinated liquid and mixed gas are fed from the top of the reaction after preheating, and flow through the bed in parallel. The residence time of the liquid phase is 2.5h, the flow rate of hydrogen is 8.91kg/h, and the flow rate of nitrogen is 9kg/h. The gas-liquid mixture exits from the bottom of the reactor, enters the liquid separator, and the gas and liquid phases are processed and recovered separately. The composition of the chlorinated solution is shown in the attached table. After the device runs for 300 hours, 0.042% of dichloroacetic acid remains in the hydrogenolysis solution, 1.1% of monochloroacetic acid reacts, and the effective component content in the catalyst is 0.7%.

Example 22. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The reactor is loaded with 0.8% Pd/C catalyst, which is a cylinder with a diameter of 1mm and a height of 3mm, a bed height of 16000mm, a diameter of 800mm, a bed temperature of 171°C, and a reactor internal pressure of 400kPa. Chlorinated liquid and hydrogen are fed from the top of the reaction after preheating, and flow through the bed in parallel. The residence time of the liquid phase is 2.5h, and the flow rate of hydrogen is 17.91kg/h. The gas-liquid mixture exits from the bottom of the reactor, enters the liquid separator, and the gas and liquid phases are processed and recovered separately. The composition of the chlorinated solution is shown in the attached table. When the device was running for 30 hours, 0.4% of dichloroacetic acid remained in the hydrogenolysis solution, and 3.1% of monochloroacetic acid reacted. After running for 300 hours, 1.0% of dichloroacetic acid remained in the hydrogenolysis solution, 2.7% of monochloroacetic acid reacted, and the effective component content in the catalyst was 0.5%.

Example 23. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The reactor is charged with 0.8% Pd/C catalyst, which is a cylinder with a diameter of 1mm and a height of 3mm, a bed height of 16000mm, a diameter of 800mm, a bed temperature of 130°C, and a reactor internal pressure of 800kPa. The chlorinated liquid and mixed gas are fed from the top of the reaction after preheating, and flow through the bed in parallel. The residence time of the liquid phase is 2.5h, the flow rate of hydrogen is 8.91kg/h, and the flow rate of nitrogen is 9kg/h. The gas-liquid mixture exits from the bottom of the reactor, enters the liquid separator, and the gas and liquid phases are processed and recovered separately. The composition of the chlorinated solution is shown in the attached table. When the device was running for 30 hours, 0.9% of dichloroacetic acid remained in the hydrogenolysis solution, and 1.3% of monochloroacetic acid reacted. After running for 300 hours, 1.2% of dichloroacetic acid remained in the hydrogenolysis solution, 1.2% of monochloroacetic acid reacted, and the effective component content in the catalyst was 0.7%.

Example 24. A method for purifying monochloroacetic acid by catalytic hydrogenolysis in the production of monochloroacetic acid. The reactor is loaded with 0.8% Pd/C catalyst, which is a cylinder with a diameter of 1mm and a height of 3mm, a bed height of 16000mm, a diameter of 800mm, a bed temperature of 171°C, and a reactor internal pressure of 400kPa. The chlorinated liquid and mixed gas are fed from the top of the reaction after preheating, and flow through the bed in parallel. The residence time of the liquid phase is 2.5h, the flow rate of hydrogen is 16.3kg/h, and the flow rate of nitrogen is 17.9kg/h. The gas-liquid mixture exits from the bottom of the reactor, enters the liquid separator, and the gas and liquid phases are processed and recovered separately. The composition of the chlorinated solution is shown in the attached table. When the device was running for 30 hours, 0.01% of dichloroacetic acid remained in the hydrogenolysis solution, and 6.2% of monochloroacetic acid reacted. After running for 300 hours, 0.02% of dichloroacetic acid remained in the hydrogenolysis solution, 5.1% of monochloroacetic acid reacted, and the effective component content in the catalyst was 0.6%.

The composition ratio of chlorination solution is as follows in embodiment 20-24:

Embodiment 1-24 is a new catalytic hydrogenolysis process applicable to industrial practice. Under the atmosphere of nitrogen and hydrogen mixed gas, the removal effect of dichloroacetic acid and trichloroacetic acid can be greatly improved, and the hydrogenation speed, The treatment efficiency and product purity of dichloroacetic acid can reduce the deactivation tendency and activity decline rate of the catalyst, shorten the reaction time, reduce hydrogen consumption, improve the utilization rate of raw materials and the yield of products, and further improve economic benefits. It can be widely used in the purification of monochloroacetic acid in the production of monochloroacetic acid.

Claims (1)

1. the method for a purifying chloroacetic acid by catalytic hydrogenolysis in chloroacetic acid production, be included under certain temperature and pressure, process the mother liquor after acetic acid chlorination, described mother liquor is containing the chlorated liquid of Monochloro Acetic Acid 75-95%, dichloro acetic acid 0.5-6%, trichoroacetic acid(TCA) 0-3%, hydrochloric acid 1～3%, acetic acid 5～15%, characterized by further comprising following steps:

(1) in the catalyticreactor of inner liner polytetrafluoroethylene or zirconium material, device group VIII noble metals a kind of or its combine as hydrogenolysis catalyst bed, and the ratio that precious metal accounts for carrier is 0.5～1%;

(2) under the gauge pressure of 250～500kPa and under the temperature condition of 130～150 DEG C, make the chlorated liquid in Monochloro Acetic Acid production process flow through fixed bed, make hydrogen-nitrogen mixture gas and liquid phase simultaneously and flow to into bed;

(3) under the effect of beds, make whole in chlorated liquid or most many Mono Chloro Acetic Acids generation hydrogenolysis, produce Monochloro Acetic Acid;

(4) material is gone out to reactor, and through gas-liquid separation;

(5) by not containing or containing the how chloroacetic chlorated liquid liquid phase crystallization of minute quantity, washing, obtaining Monochloro Acetic Acid product after gas-liquid separation;

(6) by the gas phase after gas-liquid separation through condensation, absorption, separation, thereby recover hydrogen, hydrogenchloride and acetic acid;

Hydrogen usage is 1.5～5.0 times of dichloro acetic acid molar weight, and the mol ratio of rare gas element and hydrogen is between 2～3, and liquid phase is 2～4 hours in the residence time of beds; Catalyzer is that diameter is the spheroid that 0.2～15mm, the height right cylinder that is 0.3～30mm or diameter are 0.3～10mm; Support of the catalyst is that specific surface area is activated carbon, silicon-dioxide, aluminum oxide, float stone or the diatomite of 500～1350m2/g; Using palladium as catalyst activity component.