Trifluorotrichloroethane hydrogen reduction dechlorination catalyst, preparation method and application thereof

Abstract

This invention belongs to the field of fluorochemical catalysis technology, specifically relating to a catalyst for the hydrogenation reduction and dechlorination of trifluorotrichloroethane, its preparation method, and its application. The catalyst of this invention comprises a main catalyst, an auxiliary agent, and a support, wherein the main catalyst and the auxiliary agent are supported on the support; the main catalyst is palladium and copper; the auxiliary agent includes iridium, rhodium, chromium, rhenium, nickel, and potassium. The catalyst of this invention has abundant active sites and strong selectivity, effectively suppressing side reactions. It possesses advantages such as high feed conversion rate and excellent selectivity. Simultaneously, the catalyst has a stable structure, excellent high-temperature hydrogen reduction performance, is not easily deactivated, and has a long service life.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemical catalysis technology, specifically relating to a trifluorotrichloroethane hydrogenation reduction dechlorination catalyst, its preparation method, and its application. Background Technology

[0002] Chlorofluoroethylene (CFC) is an important organic compound with broad application prospects, primarily used in the manufacture of polychlorotrifluoroethylene (PTFE) resin. This resin maintains good physical properties and chemical stability over a wide temperature range, from extremely low to high temperatures, and is widely used in cryogenic liquid cooling seals, valves, and other fields.

[0003] Currently, the main methods for producing trifluorochloroethylene include zinc powder dechlorination and hydroreduction dechlorination. The zinc powder method is a mature technology, but its application is limited by high costs and environmental pollution. In contrast, hydroreduction dechlorination has the advantages of low cost and environmental friendliness, but the catalysts used in this method (such as Pd-Cu / C catalysts) have a lifespan of only about 300 hours, mainly due to poisoning and deactivation of the catalyst's active sites. Specifically, existing catalysts are often affected by reaction products or reaction conditions, leading to a rapid decline in catalytic activity. Furthermore, insufficient hydrogen supply and the occurrence of side reactions also accelerate catalyst degradation.

[0004] Therefore, developing a catalyst with a longer service life, higher activity, and greater selectivity is of great significance for reducing production costs, improving economic efficiency, and promoting the sustainable development of the fluorochemical industry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a catalyst for the hydrogenation reduction and dechlorination of trifluorotrichloroethane, its preparation method, and its applications. The catalyst of this invention has abundant active sites and strong selectivity, effectively suppressing side reactions. It possesses advantages such as high feed conversion rate and excellent selectivity. Furthermore, the catalyst exhibits stable structure, excellent high-temperature hydrogen reduction resistance, is not easily deactivated, and has a long service life.

[0006] The technical solution of this invention is: A hydrogenation reduction dechlorination catalyst for trifluorotrichloroethane, the catalyst comprising a main catalyst, an auxiliary agent, and a support, wherein the main catalyst and the auxiliary agent are supported on the support; the main catalyst is palladium and copper; the auxiliary agent comprises iridium, rhodium, chromium, rhenium, nickel, and potassium.

[0007] Furthermore, the amount of palladium used is 0.1-2.5% of the total mass of the catalyst, the amount of copper used is 0.2-3% of the total mass of the catalyst, the amount of the promoter is 0.1-5% of the total mass of the catalyst, and the remainder is a carrier.

[0008] Furthermore, the particle size of the carrier is 1-2 mm.

[0009] Furthermore, the carrier is activated carbon.

[0010] This invention also provides a method for preparing the above-mentioned trifluorotrichloroethane hydrogenation reduction dechlorination catalyst, comprising the following steps: S1 is subjected to acid washing, water washing until neutral, and then drying. S2 is used to prepare a mother liquor containing the main catalyst and auxiliary agents; S3. The carrier dried in step S1 is added to the mother liquor prepared in step S2, the pH is adjusted to 6.5-7.5, and impregnation is performed. S4 involves sequentially drying and reducing the crude catalyst impregnated in step S3 to obtain the final product.

[0011] Further, in step S1, the pickling treatment uses hydrochloric acid solution, the pickling temperature is 20-30℃, and the pickling time is 1-3 hours; the drying treatment temperature is 100-150℃, and the drying time is 4-8 hours.

[0012] Furthermore, in step S1, the drying process employs an integral jacketed heat exchanger, using heat transfer oil for constant-temperature drying, while simultaneously introducing high-purity nitrogen gas for dehydration.

[0013] Furthermore, in step S3, the temperature of the impregnation treatment is 35-55°C, and the impregnation time is 0.5-2.5 hours.

[0014] Furthermore, in step S4, the drying process is divided into two stages: the first stage drying temperature is 100-140℃ and the drying time is 2-4 hours; the second stage drying temperature is 200-250℃ and the drying time is 1-3 hours; the hydrogen reduction process is carried out at a temperature of 280-340℃ and for a processing time of 1.5-3 hours.

[0015] Furthermore, in step S4, the drying process employs an integral jacketed heat exchanger to dry the material at a constant temperature using heat transfer oil.

[0016] During the pickling and drying processes, surface impurities on the support are effectively removed, enhancing its adsorption properties. During impregnation, the metal components of the main catalyst and auxiliary agents are uniformly distributed on the activated carbon surface, enhancing catalytic activity. The reduction reaction, facilitated by the introduction of hydrogen, promotes metal reduction, ultimately forming a catalyst with excellent catalytic performance.

[0017] This invention relates to a carrier and crude catalyst drying equipment that employs an integrated jacketed heat exchanger. Constant temperature drying is achieved using heat transfer oil, while high-purity nitrogen is simultaneously introduced for purging and dehydration. This minimizes the moisture content of the activated carbon carrier, addressing the industry pain point of deep dehydration and drying of the carrier and crude catalyst. It effectively improves the carrier's adsorption performance, significantly enhances the catalyst's catalytic activity and reaction selectivity, and exhibits superior stability during catalyst regeneration and recycling. This invention can effectively improve the production efficiency of trifluorochloroethylene and reduce overall production costs, with broad prospects for industrialization. Precise control of drying and reaction process parameters ensures the repeatability and operational stability of the catalytic reaction process, laying a solid technical foundation for the large-scale application of this type of catalyst.

[0018] Through extensive and creative experiments, this invention has discovered that by employing a two-stage drying process (first stage drying temperature 100–140°C; second stage drying temperature 200–250°C) on the impregnated crude catalyst, free water is slowly removed in the low-temperature stage to prevent the active components from migrating to the support surface with the water vapor, ensuring that the main catalyst and promoters are uniformly distributed within the pores. The high-temperature stage removes chemically bound water and surface hydroxyl groups, effectively preventing the collapse of the support pores, the decrease in specific surface area, and the thermal cracking and pulverization of catalyst particles caused by one-time high-temperature drying. At the same time, it allows the main catalyst and promoter precursors to be uniformly spread and loaded on the surface of the support pores, enhancing the interaction between the active components and the support, while avoiding agglomeration caused by the rapid decomposition of metal salts. This step-drying process can significantly improve the dispersion of active components, forming fine and uniform active crystals after reduction, fully preserving the excellent pore structure and specific surface area of ​​the support, increasing the number of active sites for hydrodechlorination, strengthening the synergistic effect of the main and auxiliary agents, improving the catalytic activity, reaction selectivity and structural thermal stability of trifluorotrichloroethane hydroreduction dechlorination, while enhancing the mechanical strength of the catalyst, reducing sintering carbon deposits and loss of active components during operation, and extending the service life of the catalyst.

[0019] Another object of the present invention is to provide the application of the above-mentioned trifluorotrichloroethane hydrogenation reduction dechlorination catalyst or the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst prepared according to the above-mentioned preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst in the preparation of trifluorochloroethylene by trifluorotrichloroethane hydrogenation reduction dechlorination.

[0020] Furthermore, when the catalyst is used to prepare trifluorochloroethylene by hydrogenation-reduction dechlorination of trifluorotrichloroethane, the reaction pressure is 0.5-2.0 MPa, the reaction temperature is 150-250 °C, and the molar ratio of hydrogen to trifluorotrichloroethane is 1-5:1.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The present invention uses a Pd-Cu-based multi-metal auxiliary compound system, which has abundant active sites and high selectivity. It can effectively inhibit side reactions, and the conversion rate can reach more than 99% and the selectivity can reach 85%.

[0022] (2) The present invention adopts an integral jacketed heat exchanger + constant temperature of heat transfer oil + high-purity nitrogen dehydration drying method, which is thorough dehydration and uniform and controllable temperature. It can not only significantly improve the adsorption performance and metal dispersion of activated carbon carrier, but also improve the activity and selectivity of catalyst.

[0023] (3) The catalyst of the present invention has a stable structure and excellent stability in the high-temperature hydrogen reduction process, which reduces the deactivation of the catalyst during the reaction process and has a service life of up to 2500 hours.

[0024] (4) The preparation process of this invention is stable and controllable, and has strong scalability, making it suitable for continuous industrial production. It significantly reduces production costs and improves economic benefits. Detailed Implementation

[0025] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0026] Example 1: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst includes the following steps: S1 uses a 10% hydrochloric acid solution to acid-wash activated carbon with a particle size of 1-2 mm at a temperature of 25°C for 2 hours. After washing with distilled water until neutral, it is then dried using an integral jacketed heat exchanger with constant temperature drying via heat transfer oil at a temperature of 120°C for 6 hours. Simultaneously, high-purity nitrogen (with a purity of 99.99% or higher) is introduced for dehydration. S2 prepares a mother liquor containing the main catalyst and auxiliary agents. The concentrations of palladium chloride, copper chloride, iridium chloride, rhodium chloride, chromium chloride, rhenium chloride, nickel chloride, and potassium chloride in the mother liquor are 0.01 mol / L, 0.15 mol / L, 0.02 mol / L, 0.015 mol / L, 0.015 mol / L, 0.02 mol / L, 0.002 mol / L, and 0.05 mol / L. S3. Add 2.7 kg of the dried activated carbon from step S1 to 3.6 L of the mother liquor prepared in step S2, stir evenly, add ammonia water to adjust the pH value to 6.5, and perform impregnation treatment using the equal volume impregnation method. The impregnation treatment temperature is 40℃ and the impregnation time is 1 hour. S4 involves drying the crude catalyst impregnated in step S3 using an integral jacketed heat exchanger with constant-temperature drying of heat transfer oil and nitrogen assistance. The drying process is divided into two stages. Specifically, the crude catalyst impregnated in step S3 is placed in the jacketed tube of the integral jacketed heat exchanger. The first stage drying temperature is 120℃, and the drying time is 3 hours. The heat transfer oil is then heated to 230℃ at a heating rate of 8℃ / min, and the second stage drying temperature is 230℃ for 1 hour. The heat transfer oil is then heated to 300℃ at a heating rate of 10℃ / min, and hydrogen is introduced to carry out a reduction reaction for 2 hours. Finally, nitrogen is introduced to cool the catalyst down to room temperature, yielding a trifluorotrichloroethane hydrogenation reduction dechlorination catalyst.

[0027] Example 2: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst includes the following steps: S1 uses a 10% hydrochloric acid solution to acid-wash activated carbon with a particle size of 1-2 mm at a temperature of 25°C for 2 hours. After washing with distilled water until neutral, it is then dried using an integral jacketed heat exchanger with constant temperature drying via heat transfer oil at a temperature of 120°C for 6 hours. Simultaneously, high-purity nitrogen (with a purity of 99.99% or higher) is introduced for dehydration. S2 prepares a mother liquor containing the main catalyst and auxiliary agents. The concentrations of palladium chloride, copper chloride, iridium chloride, rhodium chloride, chromium chloride, rhenium chloride, nickel chloride, and potassium chloride in the mother liquor are 0.02 mol / L, 0.1 mol / L, 0.01 mol / L, 0.01 mol / L, 0.01 mol / L, 0.02 mol / L, 0.002 mol / L, and 0.05 mol / L. S3. Add 2.7 kg of the dried activated carbon from step S1 to 3.6 L of the mother liquor prepared in step S2, stir evenly, add ammonia water to adjust the pH value to 7.5, and perform impregnation treatment using the equal volume impregnation method. The impregnation treatment temperature is 45℃ and the impregnation time is 1.5 hours. S4 involves drying the crude catalyst impregnated in step S3 using an integral jacketed heat exchanger with constant-temperature drying of heat transfer oil and nitrogen assistance. The drying process is divided into two stages. Specifically, the crude catalyst impregnated in step S3 is placed in the jacketed tube of the integral jacketed heat exchanger. The first stage drying temperature is 120℃, and the drying time is 3 hours. The heat transfer oil is then heated to 230℃ at a heating rate of 11℃ / min, and the second stage drying temperature is 230℃ for 1 hour. The heat transfer oil is then heated to 300℃ at a heating rate of 10℃ / min, and hydrogen is introduced to carry out a reduction reaction for 2 hours. Finally, nitrogen is introduced to cool the catalyst down to room temperature, yielding a trifluorotrichloroethane hydrogenation reduction dechlorination catalyst.

[0028] Example 3: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst includes the following steps: S1 uses a 10% hydrochloric acid solution to acid-wash activated carbon with a particle size of 1-2 mm at a temperature of 25°C for 2 hours. After washing with distilled water until neutral, it is then dried using an integral jacketed heat exchanger with constant temperature drying via heat transfer oil at a temperature of 120°C for 6 hours. Simultaneously, high-purity nitrogen (with a purity of 99.99% or higher) is introduced for dehydration. S2 prepares a mother liquor containing the main catalyst and auxiliary agents. The concentrations of palladium chloride are 0.03 mol / L, copper chloride is 0.1 mol / L, iridium chloride is 0.01 mol / L, rhodium chloride is 0.01 mol / L, chromium chloride is 0.01 mol / L, rhenium chloride is 0.02 mol / L, nickel chloride is 0.002 mol / L, and potassium chloride is 0.05 mol / L. S3. Add 2.7 kg of the dried activated carbon from step S1 to 3.6 L of the mother liquor prepared in step S2, stir evenly, add ammonia water to adjust the pH value to 7.0, and perform impregnation treatment using the equal volume impregnation method. The impregnation treatment temperature is 50℃ and the impregnation time is 2 hours. S4 involves drying the crude catalyst impregnated in step S3 using an integral jacketed heat exchanger with constant-temperature drying of heat transfer oil and nitrogen assistance. The drying process is divided into two stages. Specifically, the crude catalyst impregnated in step S3 is placed in the jacket tube of the integral jacketed heat exchanger. The first stage drying temperature is 120℃, and the drying time is 3 hours. The heat transfer oil is then heated to 230℃ at a heating rate of 10℃ / min, and the second stage drying temperature is 230℃ for 1 hour. The heat transfer oil is then heated to 320℃ at a heating rate of 10℃ / min, and hydrogen is introduced to carry out a reduction reaction for 2.5 hours. Finally, nitrogen is introduced to cool the catalyst down to room temperature, yielding a trifluorotrichloroethane hydrogenation reduction dechlorination catalyst.

[0029] Comparative Example 1: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst is similar to that of Example 3, except that rhenium is not added to the additive.

[0030] Comparative Example 2: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst is similar to that of Example 3, except that rhenium is replaced with nickel in the auxiliary agent.

[0031] Comparative Example 3: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst is similar to that of Example 3. The difference is that the drying process in step S1 is carried out in a vacuum drying oven at a temperature of 120°C for 6 hours.

[0032] Comparative Example 4: Preparation of a catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst is similar to that of Example 3. The difference is that the drying process in step S4 is carried out in a vacuum drying oven.

[0033] Experimental Example 1: Catalyst Conversion and Selectivity Test The catalysts prepared in Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 were added to a reactor and reacted under the conditions of a reaction pressure of 1.0 MPa, a reaction temperature of 200 °C, and a hydrogen to trifluorotrichloroethane molar ratio of 3:1. The conversion rate and selectivity of the catalysts were obtained by sampling and analysis after 500 hours of continuous production operation. The test results are shown in Table 1.

[0034] Table 1. Results of catalyst conversion and selectivity tests

[0035] As shown in Table 1, the catalysts prepared in Examples 1, 2, and 3 of this invention exhibit excellent conversion rates and selectivity, with Example 3 showing the best performance and thus being the optimal example of this invention. Compared to Comparative Examples 1-4, the catalyst prepared in Example 3 of this invention demonstrates higher conversion rates and selectivity.

[0036] Test Example 2: Service Life Test The catalysts prepared in Examples 3, 1, 2, 3, and 4 were added to a reactor and reacted under the conditions of a reaction pressure of 1.0 MPa, a reaction temperature of 200°C, and a hydrogen to trichlorofluoroethane molar ratio of 3:1. During the reaction, the composition of the reaction gas was periodically sampled and analyzed to determine the conversion rate and catalyst selectivity. The analysis frequency was set to once every 4 hours. After continuous operation, the catalyst lifespan was tested until the conversion rate was below 80% and the selectivity was below 70%. The catalyst lifespan test results are shown in Table 2.

[0037] Table 2 Catalyst lifespan test results

[0038] As can be seen from Table 2, the service life of the catalyst prepared in Example 3 of the present invention is significantly higher than that of Comparative Examples 1, 2, 3 and 4. This shows that the catalyst prepared in Example 3 of the present invention can effectively delay catalyst deactivation and improve long-term stable operation capability. It also shows that the catalyst formulation and preparation process have a significant impact on its service life.

Claims

1. A catalyst for the hydrogenation-reduction dechlorination of trifluorotrichloroethane, characterized in that, The catalyst comprises a main catalyst, an auxiliary agent, and a support, wherein the main catalyst and the auxiliary agent are supported on the support; the main catalyst is palladium and copper; the auxiliary agent comprises iridium, rhodium, chromium, rhenium, nickel, and potassium.

2. The trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 1, characterized in that, The amount of palladium used is 0.1-2.5% of the total mass of the catalyst, the amount of copper used is 0.2-3% of the total mass of the catalyst, the amount of the promoter is 0.1-5% of the total mass of the catalyst, and the remainder is a carrier.

3. The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 1 or 2, characterized in that, Includes the following steps: S1 is subjected to acid washing, water washing until neutral, and then drying. S2 is used to prepare a mother liquor containing the main catalyst and auxiliary agents; S3. The carrier dried in step S1 is added to the mother liquor prepared in step S2, the pH is adjusted to 6.5-7.5, and impregnation is performed. S4 involves sequentially drying and reducing the crude catalyst impregnated in step S3 to obtain the final product.

4. The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 3, characterized in that, In step S1, the pickling treatment uses hydrochloric acid solution, the pickling temperature is 20-30℃, and the pickling time is 1-3 hours; the drying treatment temperature is 100-150℃, and the drying time is 4-8 hours.

5. The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 3, characterized in that, In step S1, the drying process uses an integral jacketed heat exchanger, with heat transfer oil used for constant temperature drying, while high-purity nitrogen is introduced for dehydration.

6. The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 3, characterized in that, In step S3, the immersion temperature is 35–55°C and the immersion time is 0.5–2.5 hours.

7. The method for preparing the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 3, characterized in that, In step S4, the drying process is divided into two stages: the first stage drying temperature is 100-140℃ and the drying time is 2-4 hours; the second stage drying temperature is 200-250℃ and the drying time is 1-3 hours; the hydrogen reduction process is carried out at a temperature of 280-340℃ and for a time of 1.5-3 hours.

8. The preparation method of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 3, characterized in that, In step S4, the drying process uses an integral jacketed heat exchanger to dry the oil at a constant temperature.

9. The application of the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst according to claim 1 or 2, or the trifluorotrichloroethane hydrogenation reduction dechlorination catalyst prepared by the preparation method according to any one of claims 3 to 8, in the preparation of trifluorochloroethylene by the hydrogenation reduction dechlorination of trifluorotrichloroethane.

10. The application according to claim 9, characterized in that, The catalyst is used to prepare trifluorochloroethylene by hydrogenation-reduction dechlorination of trifluorotrichloroethane, with a reaction pressure of 0.5-2.0 MPa, a reaction temperature of 150-250 °C, and a molar ratio of hydrogen to trifluorotrichloroethane of 1-5:1.

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