Catalyst for hexafluoropropane production, hexafluoropropane and method for its production

Abstract

The application provides a catalyst for preparing hexafluoropropane, hexafluoropropane and a preparation method thereof. The preparation method of the catalyst comprises the following steps: S100, sequentially performing acid washing treatment, alkali washing treatment and activation treatment on activated carbon to obtain impurity-removed activated carbon; S200, mixing the impurity-removed activated carbon obtained in S100 with chromium trichloride and granulating to obtain chromium trichloride microspheres; S300, using raw materials comprising a calcium source, a phosphorus source and the chromium trichloride microspheres obtained in S200 to prepare hydroxyapatite loaded with chromium trichloride; and S400, preparing a tin tetrafluoride aqueous solution, mixing the tin tetrafluoride aqueous solution with the hydroxyapatite obtained in S300 and preparing the catalyst. The application provides a solid-phase catalyst suitable for preparing hexafluoropropane, which is easy to separate from a reaction system and not easy to flow out with the reaction system, so that the yield of hexafluoropropane is improved, the production cost of hexafluoropropane is reduced, and the environmental friendliness of the reaction is improved.

Description

Technical Field

[0001] This invention relates to the technical field of chemical processes, and more specifically, to a catalyst for the preparation of hexafluoropropane, hexafluoropropane, and a method for its preparation. Background Technology

[0002] Hexafluoropropane (R236) is a chemical substance suitable for filling portable fire extinguishers. It is suitable for use in open and semi-open spaces, as well as in total flooding fire suppression systems in occupied areas.

[0003] In existing technologies, hexafluoropropane can generally be prepared through the following route: hydrogen fluoride is vaporized and fed into a reactor to be mixed with hexachloropropane, where it reacts under catalytic conditions to produce crude hexafluoropropane; subsequently, the crude hexafluoropropane, hydrogen chloride, and a small amount of residual hydrogen fluoride enter a hydrogen chloride distillation column to remove hydrogen chloride; then it enters a water-alkali washing system to remove most of the aqueous acid, and alkali washing removes residual acid, thus dehydrating the crude product and removing light components; finally, it enters a distillation column system to distill off the refined hexafluoropropane.

[0004] Referring to existing technologies such as DE69512250T2, US5545774A, and CN104803824A, the catalysts used in the aforementioned methods for preparing hexafluoropropane are generally halides of trivalent chromium, tetravalent tin, or pentavalent antimony. To facilitate catalyst recovery and reuse, it is essential to support the catalyst on a suitable support.

[0005] Currently, activated carbon with a porous structure is a common, inexpensive, and effective catalyst. However, when using activated carbon as a support, sulfur and iron impurities in the activated carbon can adversely affect the catalyst's activity. Therefore, for those skilled in the art, providing a porous supported catalyst with good catalytic performance and easy recycling is key to ensuring hexafluoropropane yield, reducing its production costs, and simplifying the catalyst recovery process. Summary of the Invention

[0006] The problem addressed by this invention is how to provide a solid-phase catalyst suitable for the preparation of hexafluoropropane that is easily separated from the reaction system and does not easily leak out with the reaction system, thereby improving the yield of hexafluoropropane, reducing its production cost, and improving the environmental friendliness of the reaction.

[0007] To address the above problems, this invention provides a method for preparing a catalyst for the preparation of hexafluoropropane, the method comprising:

[0008] S100: The activated carbon is subjected to acid washing, alkali washing and activation treatment in sequence to obtain impurity-removed activated carbon;

[0009] S200: The activated carbon obtained from S100 is mixed with chromium trichloride and granulated to obtain chromium trichloride microspheres, which are then dried.

[0010] S300: Using raw materials including calcium source, phosphorus source, and chromium trichloride microspheres obtained by S200, hydroxyapatite loaded with chromium trichloride is prepared.

[0011] S400: Prepare an aqueous solution of tin tetrafluoride, and mix the aqueous solution of tin tetrafluoride with the hydroxyapatite obtained by S300 to prepare a catalyst.

[0012] In any of the above technical solutions, S100 specifically includes:

[0013] S110. Place activated carbon in a hydrochloric acid aqueous solution with a volume concentration of 38% and a temperature of 36°C to 40°C, stir for 1 hour to 1.5 hours to perform acid washing treatment, then take it out and wash it with water to obtain the first acid-washed activated carbon.

[0014] S120. The first acid-washed activated carbon obtained in S110 is placed in hydrofluoric acid with a volume concentration of 25% and a temperature of 25°C to 30°C, stirred for 0.5h to 1h to perform acid washing again, then taken out and washed with water to obtain the second acid-washed activated carbon.

[0015] S130. The second acid-washed activated carbon obtained in S120 is placed in ammonia water with a mass concentration of 26% and a temperature of 25°C to 30°C, and stirred for 1 hour to 1.5 hours to carry out alkaline washing treatment, and then taken out to obtain alkaline-washed activated carbon.

[0016] S140. The alkaline-washed activated carbon obtained in S130 is placed in a muffle furnace and subjected to heat treatment at a temperature of 360°C to 380°C for 2 to 3 hours. After natural cooling, it is ground and pulverized to obtain impurity-removed activated carbon.

[0017] In any of the above technical solutions, in S110, the mass ratio of activated carbon to hydrochloric acid aqueous solution is activated carbon: hydrochloric acid aqueous solution = (40-60): 100.

[0018] In any of the above technical solutions, in S120, the mass ratio of the first acid-washed activated carbon to hydrofluoric acid is first acid-washed activated carbon: hydrofluoric acid = (30-50): 100.

[0019] In any of the above technical solutions, in S130, the mass ratio of the second pickling activated carbon to ammonia water is second pickling activated carbon: ammonia water = (30-50): 100.

[0020] In any of the above technical solutions, in S140, an activation gas is introduced into the muffle furnace during the heat treatment process. The activation gas includes a mixture of carbon dioxide and water vapor in a volume ratio of 1:1.

[0021] In any of the above technical solutions, S200 specifically includes:

[0022] S210. Mix chromium trichloride in anhydrous ethanol solvent until homogeneous to prepare a 10wt% to 15wt% chromium trichloride ethanol solution.

[0023] S220, ammonium bicarbonate: impurity-removing activated carbon = (2-4): 100, ammonium bicarbonate and impurity-removing activated carbon obtained by S100 are mixed evenly, placed on a shaker and sprayed with chromium trichloride ethanol solution obtained by S210 for spray granulation, to obtain chromium trichloride microspheres with an average particle size of less than 100μm, and then dried.

[0024] The amount of chromium trichloride solution sprayed, by weight, is 30% to 60% of the weight of the activated carbon used for impurity removal.

[0025] In any of the above technical solutions, S300 specifically includes:

[0026] S310: Add 40% to 60% of the mass of calcium chloride obtained from S200 to a 0.15 mol / L to 0.3 mol / L calcium chloride aqueous solution and stir until homogeneous to obtain a calcium salt suspension.

[0027] S320, prepare a 0.05 mol / L to 0.1 mol / L aqueous solution of disodium hydrogen phosphate as a phosphate salt solution;

[0028] S330: Add the phosphate salt solution obtained in S320 to the calcium salt suspension obtained in S310 to obtain a mixture and stir simultaneously until the calcium / phosphorus molar ratio in the mixture reaches 1.67. Add ammonia water to adjust the pH value to 9 to 10, let it stand for 4 to 6 hours, filter, wash and dry the precipitate to obtain hydroxyapatite loaded with chromium trichloride.

[0029] In any of the above technical solutions, S400 specifically includes:

[0030] S410. Mix tin tetrafluoride and water evenly according to the mass ratio of tin tetrafluoride:water = (10-20):100 to obtain an aqueous solution of tin tetrafluoride.

[0031] S420. Hydroxyapatite loaded with chromium trichloride and tin tetrafluoride aqueous solution obtained in S300 are mixed in a reactor at a mass ratio of (40-60):100. The mixture is heated to 70°C to 90°C, pressurized to 2.2MPa to 2.5MPa by introducing nitrogen gas, and kept at the same temperature and pressure for 1 to 1.5 hours. After the holding time is completed, the pressure is released and the mixture is cooled. The solid is then filtered and dried to obtain the catalyst.

[0032] The present invention also provides a catalyst for the preparation of hexafluoropropane, wherein the catalyst is obtained by any of the above-described technical solutions.

[0033] This invention also provides a method for preparing hexafluoropropane, the method comprising:

[0034] S10. According to the mass ratio of catalyst: hexachloropropane = (2-6): 100, the catalyst and hexachloropropane are fed into the reactor, nitrogen is introduced to replace the air, and after the replacement is completed, the reactor is heated to 220°C to 240°C and kept at that temperature for 0.5 to 1 hour.

[0035] S20. Introduce gaseous hydrogen fluoride into the reactor and heat the reactor to 380°C to 420°C. Continue to introduce gaseous hydrogen fluoride and keep the temperature until the reaction is complete. Control the amount of gaseous hydrogen fluoride introduced so that the molar ratio of gaseous hydrogen fluoride to hexachloropropane is gaseous hydrogen fluoride: hexachloropropane = (550-650): 100.

[0036] S30. Stop heating and depressurize, then allow to cool naturally to obtain hexafluoropropane;

[0037] The catalyst is obtained using any of the above-mentioned technical solutions.

[0038] Beneficial effects

[0039] This invention provides a catalyst for the preparation of hexafluoropropane, hexafluoropropane, and a method for preparing the same. First, activated carbon is subjected to acid washing, alkali washing, and activation treatment sequentially to remove impurities such as sulfur and iron and to increase its porosity. Then, the purified activated carbon is mixed with chromium trichloride and granulated to obtain chromium trichloride microspheres. Next, using raw materials including a calcium source, a phosphorus source, and chromium trichloride microspheres, hydroxyapatite loaded with chromium trichloride is prepared. Finally, an aqueous solution of tin tetrafluoride is prepared and mixed with hydroxyapatite to obtain the catalyst. The reason for using the above steps is that the applicant has found in practice that using chromium trichloride and tin tetrafluoride catalysts in combination is beneficial to improving their catalytic activity and effect. However, unlike tin tetrafluoride, chromium trichloride is less environmentally friendly, and due to its boiling point, solubility, and other physicochemical properties, its recovery is more difficult and costly. This invention aims to ensure the uniform distribution of tin tetrafluoride and chromium trichloride within the supporting material, while also reducing the loss of chromium trichloride in the reaction system and lowering recovery costs. To this end, chromium trichloride is mixed with and granulated from purified activated carbon to form chromium trichloride microspheres. These microspheres are then mixed with a calcium source and a phosphorus source is added dropwise. The purified activated carbon, loaded with chromium trichloride, acts as a solid-phase catalyst, uniformly solidified within the hydroxyapatite structure gradually formed through calcium-phosphorus mixing. This reduces the loss of chromium trichloride in the reaction system, thereby lowering the difficulty and cost of chromium trichloride recovery. Furthermore, this invention loads tin tetrafluoride onto porous hydroxyapatite, resulting in a simultaneous loading of tin tetrafluoride and chromium trichloride. Both are independently solidified within the support, preventing agglomeration and maintaining a uniform distribution, thus ensuring efficient catalysis. Furthermore, although activated carbon is the most cost-effective catalyst support, its sulfur and iron impurities can adversely affect the catalyst's activity. Therefore, this invention addresses this by firstly encapsulating activated carbon within hydroxyapatite, and secondly by further reducing its impurity content through acid-base washing. In summary, this invention provides a solid-phase catalyst that is easily separable from the reaction system, does not easily leak with the reaction system, is suitable for the preparation of hexafluoropropane, and exhibits good catalytic performance. This improves the yield of hexafluoropropane, reduces its production cost, and enhances the environmental friendliness of the reaction. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention will be provided below.

[0041] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available. Experimental methods in the following examples that do not specify particular conditions should be performed according to conventional methods and conditions, or as selected in the product instructions.

[0042] This invention first provides a method for preparing hexafluoropropane, the method comprising:

[0043] S10. According to the mass ratio of catalyst: hexachloropropane = (5-20): 100, the catalyst and hexachloropropane are fed into the reactor, nitrogen is introduced to replace the air, and after the replacement is completed, the reactor is heated to 220°C to 240°C and kept at that temperature for 0.5 to 1 hour.

[0044] S20. Introduce gaseous hydrogen fluoride into the reactor and heat the reactor to 380°C to 420°C. Continue to introduce gaseous hydrogen fluoride and keep the temperature until the reaction is complete. Control the amount of gaseous hydrogen fluoride introduced so that the molar ratio of gaseous hydrogen fluoride to hexachloropropane is gaseous hydrogen fluoride: hexachloropropane = (550-650): 100.

[0045] S30. Stop heating and depressurize, then allow to cool naturally to obtain hexafluoropropane.

[0046] In the above reactions, metal halides are generally chosen as catalysts. Metal halides include at least one or a combination of the following: halides of trivalent chromium, tetravalent tin, or pentavalent antimony. For example: chromium trichloride, tin tetrafluoride, and antimony pentafluoride.

[0047] The above reaction can be carried out in a reactor. Before starting the reaction, the oxygen in the reactor needs to be replaced with nitrogen. After the reaction is complete, crude hexafluoropropane can be obtained.

[0048] It is understandable that after obtaining crude hexafluoropropane, it is necessary to refine the crude hexafluoropropane and recover the catalyst and unreacted raw materials.

[0049] To facilitate catalyst separation after the reaction, this invention provides a special solid-phase catalyst that is easy to separate from the reaction system and does not easily leak with the reaction system. When applied to the preparation of hexafluoropropane, it can reduce the production cost of hexafluoropropane and improve the environmental friendliness of the reaction.

[0050] Specifically, the preparation method of the catalyst for hexafluoropropane preparation provided in the embodiments of the present invention includes:

[0051] S100: The activated carbon is subjected to acid washing, alkali washing and activation treatment in sequence to obtain impurity-removed activated carbon;

[0052] S200: The purified activated carbon obtained from S100 is mixed with chromium trichloride and granulated to obtain chromium trichloride microspheres;

[0053] S300: Using raw materials including calcium source, phosphorus source, and chromium trichloride microspheres obtained by S200, hydroxyapatite loaded with chromium trichloride is prepared.

[0054] S400: Prepare an aqueous solution of tin tetrafluoride, and mix the aqueous solution of tin tetrafluoride with the hydroxyapatite obtained by S300 to prepare a catalyst.

[0055] In the above process, porous activated carbon serves as the support for the chromium trichloride catalyst. Acid washing and alkali washing are mainly used to remove impurities such as sulfur and iron from the activated carbon. Activation treatment is used to improve the porosity and adsorption performance of the activated carbon.

[0056] In some embodiments of the present invention, S100 specifically includes:

[0057] S110. Place activated carbon in a hydrochloric acid aqueous solution with a volume concentration of 38% and a temperature of 36°C to 40°C, stir for 1 hour to 1.5 hours to perform acid washing treatment, then take it out and wash it with water to obtain the first acid-washed activated carbon.

[0058] S120. The first acid-washed activated carbon obtained in S110 is placed in hydrofluoric acid with a volume concentration of 25% and a temperature of 25°C to 30°C, stirred for 0.5h to 1h to perform acid washing again, then taken out and washed with water to obtain the second acid-washed activated carbon.

[0059] S130. The second acid-washed activated carbon obtained in S120 is placed in ammonia water with a mass concentration of 26% and a temperature of 25°C to 30°C, and stirred for 1 hour to 1.5 hours to carry out alkaline washing treatment, and then taken out to obtain alkaline-washed activated carbon.

[0060] S140. The alkaline-washed activated carbon obtained in S130 is placed in a muffle furnace and subjected to heat treatment at a temperature of 360°C to 380°C for 2 to 3 hours. After natural cooling, it is ground and pulverized to obtain impurity-removed activated carbon.

[0061] Preferably, in S110, the mass ratio of activated carbon to hydrochloric acid aqueous solution is activated carbon: hydrochloric acid aqueous solution = (40-60): 100.

[0062] Preferably, in S120, the mass ratio of the first pickled activated carbon to hydrofluoric acid is first pickled activated carbon: hydrofluoric acid = (30-50): 100.

[0063] Preferably, in S130, the mass ratio of the second pickling activated carbon to ammonia water is second pickling activated carbon: ammonia water = (30-50): 100.

[0064] More preferably, in S110, the mass ratio of activated carbon to hydrochloric acid aqueous solution is activated carbon: hydrochloric acid aqueous solution = 45:100.

[0065] More preferably, in S120, the mass ratio of the first acid-washed activated carbon to hydrofluoric acid is 40:100.

[0066] More preferably, in S130, the mass ratio of the second acid-washed activated carbon to ammonia water is 35:100.

[0067] Preferably, in S140, an activation gas is introduced into the muffle furnace during the heat treatment process. The activation gas includes a mixture of carbon dioxide and water vapor in a volume ratio of 1:1.

[0068] The process involves two acid washes using hydrochloric acid and hydrofluoric acid, followed by an alkaline wash using weakly alkaline ammonia. After these two washes, activation is achieved through heating. It should be noted that this invention, after obtaining the ammonia-treated alkaline-washed activated carbon, does not perform a water wash. Instead, the activated carbon is directly placed in a muffle furnace and heated to a specified temperature for heat treatment. Thus, weakly alkaline ammonia can be used as an auxiliary activator. During the furnace heating process, the ammonia assists in the etching and thermal decomposition of the activated carbon surface, increasing the pore structure of the activated carbon. Furthermore, the ammonia leaves no residue after decomposition, unlike alkaline substances such as sodium hydroxide or potassium hydroxide, which increase impurities in the activated carbon.

[0069] In some embodiments of the present invention, S200 specifically includes:

[0070] S210. Mix chromium trichloride in anhydrous ethanol solvent until homogeneous to prepare a 10wt% to 15wt% chromium trichloride ethanol solution.

[0071] S220, ammonium bicarbonate: impurity-removing activated carbon = (2-4): 100, ammonium bicarbonate and impurity-removing activated carbon obtained by S100 are mixed evenly, placed on a shaker and sprayed with chromium trichloride ethanol solution obtained by S210 for spray granulation, to obtain chromium trichloride microspheres with an average particle size of less than 100μm, and then dried.

[0072] The amount of chromium trichloride solution sprayed, by weight, is 30% to 60% of the weight of the activated carbon used for impurity removal.

[0073] Preferably, S200 specifically includes:

[0074] S210. Chromium trichloride is mixed evenly in anhydrous ethanol solvent to prepare a 12wt% chromium trichloride ethanol solution.

[0075] S220, ammonium bicarbonate: activated carbon for impurity removal = 2:100 mass ratio, ammonium bicarbonate and activated carbon for impurity removal obtained by S100 are mixed evenly, placed on a shaker and sprayed with chromium trichloride ethanol solution obtained by S210 for spray granulation, to obtain chromium trichloride microspheres with an average particle size of less than 100μm, and then dried.

[0076] The amount of chromium trichloride solution sprayed is 40% of the weight of the activated carbon used for impurity removal, by weight.

[0077] In some embodiments of the present invention, S300 specifically includes:

[0078] S310: Add 40% to 60% of the mass of calcium chloride obtained from S200 to a 0.15 mol / L to 0.3 mol / L calcium chloride aqueous solution and stir until homogeneous to obtain a calcium salt suspension.

[0079] S320, prepare a 0.05 mol / L to 0.1 mol / L aqueous solution of disodium hydrogen phosphate as a phosphate salt solution;

[0080] S330: Add the phosphate salt solution obtained in S320 to the calcium salt suspension obtained in S310 to obtain a mixture and stir simultaneously until the calcium / phosphorus molar ratio in the mixture reaches 1.67. Add ammonia water to adjust the pH value to 9 to 10, let it stand for 4 to 6 hours, filter, wash and dry the precipitate to obtain hydroxyapatite loaded with chromium trichloride.

[0081] Preferably, S300 specifically includes:

[0082] S310. Add 45% of the mass of calcium chloride obtained from S200 to a 0.15 mol / L calcium chloride aqueous solution and stir until homogeneous to obtain a calcium salt suspension.

[0083] S320, prepare a 0.05 mol / L disodium hydrogen phosphate aqueous solution as a phosphate salt solution;

[0084] S330: Add the phosphate salt solution obtained in S320 to the calcium salt suspension obtained in S310 to obtain a mixture and stir simultaneously until the calcium / phosphorus molar ratio in the mixture reaches 1.67. Add ammonia water to adjust the pH value to 9, let it stand for 6 hours, filter, wash and dry the precipitate to obtain hydroxyapatite loaded with chromium trichloride.

[0085] In some embodiments of the present invention, S400 specifically includes:

[0086] S410. Mix tin tetrafluoride and water evenly according to the mass ratio of tin tetrafluoride:water = (10-20):100 to obtain an aqueous solution of tin tetrafluoride.

[0087] S420. Hydroxyapatite loaded with chromium trichloride and tin tetrafluoride aqueous solution obtained in S300 are mixed in a reactor at a mass ratio of (40-60):100. The mixture is heated to 70°C to 90°C, pressurized to 2.2MPa to 2.5MPa by introducing nitrogen gas, and kept at the same temperature and pressure for 1 to 1.5 hours. After the holding time is completed, the pressure is released and the mixture is cooled. The solid is then filtered and dried to obtain the catalyst.

[0088] Preferably, S400 specifically includes:

[0089] S410. Mix tin tetrafluoride and water evenly according to the mass ratio of tin tetrafluoride:water = 15:100 to obtain an aqueous solution of tin tetrafluoride.

[0090] S420: Hydroxyapatite loaded with chromium trichloride and tin tetrafluoride aqueous solution obtained in S300 are mixed in a reactor at a mass ratio of 45:100. The mixture is heated to 75°C, pressurized to 2.4 MPa by introducing nitrogen gas, and kept at the same temperature and pressure for 1 hour. After the holding period, the pressure is released and the mixture is cooled. The solid is then filtered and dried to obtain the catalyst.

[0091] The purpose of steps S200 to S400 is to load and solidify chromium trichloride (Chromium trichloride), which is environmentally unfriendly and has high recycling costs, onto purified activated carbon to form Chromium trichloride microspheres. These microspheres are then added during the gradual formation of hydroxyapatite using a mixture of calcium and phosphorus sources. This ensures that the microspheres containing Chromium trichloride and impurities from the activated carbon are uniformly solidified within the hydroxyapatite structure. Finally, this invention loads tin tetrafluoride aqueous solution onto hydroxyapatite. Hydroxyapatite, as a porous inorganic material, can adsorb and load tin tetrafluoride, thus obtaining a product simultaneously loaded with both tin tetrafluoride and Chromium trichloride. Both are independently solidified within the support, preventing agglomeration and maintaining a uniform distribution, thereby ensuring catalytic efficiency. Furthermore, by solidifying activated carbon containing Chromium trichloride into the hydroxyapatite structure, this invention reduces the loss of Chromium trichloride in the reaction system, thereby lowering the difficulty and cost of Chromium trichloride recovery.

[0092] Example 1

[0093] This embodiment provides a method for removing impurities from activated carbon, which includes the following steps:

[0094] S110. Activated carbon is placed in a hydrochloric acid aqueous solution with a volume concentration of 38% and a temperature of 36°C, stirred for 1 hour to carry out the acid washing treatment, and then taken out and washed with water to obtain the first acid-washed activated carbon; the mass ratio of activated carbon to hydrochloric acid aqueous solution is activated carbon: hydrochloric acid aqueous solution = 45:10.

[0095] S120. The first acid-washed activated carbon obtained in S110 is placed in hydrofluoric acid with a volume concentration of 25% and a temperature of 25°C, stirred for 0.5 h to perform the acid washing treatment again, then taken out and washed with water to obtain the second acid-washed activated carbon; the mass ratio of the second acid-washed activated carbon to ammonia water is second acid-washed activated carbon: ammonia water = 35: 100.

[0096] S130. The second acid-washed activated carbon obtained in S120 is placed in ammonia water with a mass concentration of 26% and a temperature of 25°C, stirred for 1 hour to carry out the alkaline washing treatment, and then taken out and washed with water to obtain alkaline-washed activated carbon; the mass ratio of the second acid-washed activated carbon to ammonia water is second acid-washed activated carbon: ammonia water = 35: 100.

[0097] S140. The alkaline-washed activated carbon obtained in S130 is placed in a muffle furnace and subjected to heat treatment at 360°C for 2 hours. After natural cooling, it is ground and pulverized to obtain the impurity-removed activated carbon. During the heat treatment, an activation gas is introduced into the muffle furnace. The activation gas includes a mixture of carbon dioxide and water vapor in a volume ratio of 1:1.

[0098] Example 2

[0099] This embodiment provides a method for preparing microsphere materials containing activated carbon and a catalyst, which includes the following steps:

[0100] S210. Chromium trichloride is mixed evenly in anhydrous ethanol solvent to prepare a 12wt% chromium trichloride ethanol solution.

[0101] S220, ammonium bicarbonate and activated carbon were mixed evenly at a mass ratio of 2:100. The mixture was placed on a shaker and sprayed with the chromium trichloride ethanol solution obtained in S210 for spray granulation to obtain chromium trichloride microspheres with an average particle size of less than 100 μm, and then dried.

[0102] In Example 2, the activated carbon used for impurity removal was the same activated carbon obtained in Example 1, and the amount of chromium trichloride solution sprayed was 40% of the weight of the activated carbon.

[0103] Example 3

[0104] This embodiment provides a method for preparing a mixture containing activated carbon and a catalyst, which includes the following steps:

[0105] S210, according to the mass ratio of chromium trichloride: ammonium bicarbonate: activated carbon for impurity removal = 5:2:100, the above three are mixed evenly by dry grinding to obtain a mixture with an average particle size of less than 100μm;

[0106] In Example 3, the activated carbon used for impurity removal was the same activated carbon obtained in Example 1.

[0107] Example 4

[0108] This embodiment provides a method for preparing a catalyst for the preparation of hexafluoropropane, which includes the following steps:

[0109] S310. Add 45% of the mass of calcium chloride microspheres to a 0.15 mol / L calcium chloride aqueous solution and stir until homogeneous to obtain a calcium salt suspension.

[0110] S320, prepare a 0.05 mol / L disodium hydrogen phosphate aqueous solution as a phosphate salt solution;

[0111] S330. Add the phosphate salt solution obtained in S320 to the calcium salt suspension obtained in S310 to obtain a mixture and stir simultaneously until the calcium / phosphorus molar ratio in the mixture reaches 1.67. Add ammonia water to adjust the pH value to 9, let it stand for 6 hours, filter, wash and dry the precipitate to obtain hydroxyapatite loaded with chromium trichloride.

[0112] S410. Mix tin tetrafluoride and water evenly according to the mass ratio of tin tetrafluoride:water = 15:100 to obtain an aqueous solution of tin tetrafluoride.

[0113] S420: Hydroxyapatite loaded with chromium trichloride and tin tetrafluoride aqueous solution obtained in S330 are mixed in a reactor at a mass ratio of 45:100. The mixture is heated to 75°C, pressurized to 2.4 MPa by introducing nitrogen gas, and kept at the same temperature and pressure for 1 hour. After the holding period, the pressure is released and the mixture is cooled. The solid is then filtered and dried to obtain the catalyst.

[0114] In Example 4, the chromium trichloride microspheres used were the same as those obtained in Example 2. The catalyst obtained in Example 4 is designated as Sample 1.

[0115] Example 5

[0116] This embodiment provides a method for preparing a catalyst for the preparation of hexafluoropropane. The preparation process is the same as in Example 4, except that in Example 5, chromium trichloride microspheres are not used. Instead, chromium trichloride microspheres are replaced with an equal weight of a mixture containing activated carbon and catalyst obtained in Example 3. The catalyst obtained in Example 5 is designated as Sample 2.

[0117] Example 6

[0118] This embodiment provides a method for preparing a catalyst for the preparation of hexafluoropropane. The preparation process is the same as that in Example 4, except that in Example 6, chromium trichloride microspheres are not used; instead, the chromium trichloride microspheres are replaced with an equal weight of activated carbon obtained in Example 1. The catalyst obtained in Example 6 is designated as Sample 3.

[0119] Performance testing

[0120] To evaluate the catalytic performance of the catalyst obtained in this invention during the preparation of hexafluoropropane, samples 1 to 3 were used as catalysts in the preparation process of hexafluoropropane. Specifically, the method for preparing hexafluoropropane is as follows:

[0121] S10. According to the mass ratio of catalyst to hexachloropropane = 20:100, the catalyst and hexachloropropane of samples 1 to 3 are respectively fed into a 600ml titanium alloy reactor equipped with a stirrer. First, nitrogen is introduced to replace the air. After the replacement is completed, the reactor is heated to 240℃ and kept at that temperature for 1 hour.

[0122] S20. Gas-phase hydrogen fluoride is introduced into the titanium alloy reactor, and the reactor is gradually heated to 400°C. The gas-phase hydrogen fluoride is continuously introduced and kept at the temperature until the reaction is completed. The amount of gas-phase hydrogen fluoride introduced is controlled so that the molar ratio of gas-phase hydrogen fluoride to hexachloropropane is gas-phase hydrogen fluoride: hexachloropropane = 550:100.

[0123] S30. Stop heating and depressurize, then allow to cool naturally to obtain hexafluoropropane.

[0124] When using samples 1 to 3 as catalysts, the reaction times to the endpoint were essentially similar. After nine consecutive trials using samples 1 to 3 as catalysts to prepare hexafluoropropane, and recovering unreacted raw materials and catalysts, a tenth trial was conducted using samples 1 to 3 as catalysts, and the yields were statistically analyzed. The yields using samples 1 to 3 as catalysts were 89%, 85%, and 78%, respectively.

[0125] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a catalyst for the preparation of hexafluoropropane, characterized in that, The preparation method includes: S100: The activated carbon is subjected to acid washing, alkali washing and activation treatment in sequence to obtain impurity-removed activated carbon; S200: The impurity-removing activated carbon obtained in S100 is mixed with chromium trichloride and granulated to obtain chromium trichloride microspheres; S300: Using raw materials including calcium source, phosphorus source, and the chromium trichloride microspheres obtained in S200, hydroxyapatite loaded with chromium trichloride is prepared. S400: Prepare an aqueous solution of tin tetrafluoride, and mix the aqueous solution of tin tetrafluoride with the hydroxyapatite obtained in S300 to prepare the catalyst; S100 specifically includes: S110. Activated carbon is placed in a hydrochloric acid aqueous solution with a volume concentration of 38% and a temperature of 36°C to 40°C, and stirred for 1 hour to 1.5 hours to carry out the acid washing treatment. After the acid washing treatment, the activated carbon is taken out and washed with water to obtain the first acid-washed activated carbon. S120. The first acid-washed activated carbon obtained in S110 is placed in hydrofluoric acid with a volume concentration of 25% and a temperature of 25°C to 30°C, and stirred for 0.5h to 1h to perform the acid washing treatment again. After that, it is taken out and washed with water to obtain the second acid-washed activated carbon. S130. The second acid-washed activated carbon obtained in S120 is placed in ammonia water with a mass concentration of 26% and a temperature of 25°C to 30°C, and stirred for 1 hour to 1.5 hours to carry out the alkaline washing treatment, and then taken out to obtain alkaline-washed activated carbon. S140. The alkaline washed activated carbon obtained in S130 is placed in a muffle furnace and subjected to heat treatment at 360°C to 380°C for 2 to 3 hours. After natural cooling, it is ground and pulverized to obtain the impurity-removed activated carbon. In S140, during the heat treatment process, an activation gas is introduced into the muffle furnace, the activation gas comprising a mixture of carbon dioxide and water vapor in a volume ratio of 1:

1.

2. The preparation method according to claim 1, characterized in that, In S110, the mass ratio of activated carbon to the hydrochloric acid aqueous solution is activated carbon: hydrochloric acid aqueous solution = (40-60): 100; and / or In S120, the mass ratio of the first acid-washed activated carbon to the hydrofluoric acid is first acid-washed activated carbon: hydrofluoric acid = (30-50): 100; and / or In S130, the mass ratio of the second acid-washed activated carbon to the ammonia water is second acid-washed activated carbon: ammonia water = (30-50):

100.

3. The preparation method according to any one of claims 1 to 2, characterized in that, S200 specifically includes: S210. Mix chromium trichloride in anhydrous ethanol solvent until homogeneous to prepare a 10wt% to 15wt% chromium trichloride ethanol solution. S220. According to the mass ratio of ammonium bicarbonate: impurity-removing activated carbon = (2-4): 100, ammonium bicarbonate and the impurity-removing activated carbon obtained in S100 are mixed evenly, placed on a shaker and sprayed with the chromium trichloride ethanol solution obtained in S210 for spray granulation to obtain chromium trichloride microspheres with an average particle size of less than 100 μm, and then dried. The amount of chromium trichloride ethanol solution sprayed, by weight, is 30% to 60% of the weight of the activated carbon used for impurity removal.

4. The preparation method according to claim 3, characterized in that, The S300 specifically includes: S310. Add 40% to 60% of the mass of calcium chloride obtained in S200 to a 0.15 mol / L to 0.3 mol / L aqueous solution of calcium chloride and stir until homogeneous to obtain a calcium salt suspension. S320, prepare a 0.05 mol / L to 0.1 mol / L aqueous solution of disodium hydrogen phosphate as a phosphate salt solution; S330. Add the phosphate solution obtained in S320 to the calcium salt suspension obtained in S310 to obtain a mixture and stir simultaneously until the calcium / phosphorus molar ratio in the mixture reaches 1.

67. Add ammonia water to adjust the pH value to 9 to 10, let it stand for 4 to 6 hours, filter, wash and dry the precipitate to obtain the hydroxyapatite loaded with chromium trichloride.

5. The preparation method according to claim 4, characterized in that, The S400 specifically includes: S410. Mix tin tetrafluoride and water evenly according to the mass ratio of tin tetrafluoride:water = (10-20):100 to obtain the tin tetrafluoride aqueous solution. S420. The chromium-containing hydroxyapatite supported on S300 and the tin tetrafluoride aqueous solution obtained in S410 are mixed in a reactor at a mass ratio of (40-60):

100. The mixture is heated to 70°C to 90°C, pressurized to 2.2 MPa to 2.5 MPa by introducing nitrogen gas, and kept at the same temperature and pressure for 1 to 1.5 hours. After the heat and pressure holding is completed, the pressure is released and the mixture is cooled, filtered, and the solid is dried to obtain the catalyst.

6. A catalyst for the preparation of hexafluoropropane, characterized in that, The catalyst is obtained by the preparation method according to any one of claims 1 to 5.

7. A method for preparing hexafluoropropane, characterized in that, The preparation method includes: S10. According to the mass ratio of catalyst: hexachloropropane = (2-6): 100, the catalyst and hexachloropropane are fed into the reactor, nitrogen is introduced to replace the air, and after the replacement is completed, the reactor is heated to 220℃ to 240℃ and kept at the temperature for 0.5 to 1 hour. S20. Introduce gaseous hydrogen fluoride into the reactor and heat the reactor to 380°C to 420°C. Continue to introduce the gaseous hydrogen fluoride and maintain the temperature until the reaction is complete. The amount of gaseous hydrogen fluoride introduced is controlled so that the molar ratio of gaseous hydrogen fluoride to hexachloropropane is gaseous hydrogen fluoride: hexachloropropane = (550-650):

100. S30. Stop heating and depressurize, then allow to cool naturally to obtain hexafluoropropane; The catalyst is obtained by the preparation method according to any one of claims 1 to 5.