A gas-phase dehydrofluorination catalyst for producing 2,3,3,3-tetrafluoropropene from 1,1,1,2,2-pentafluoropropane

Abstract

The application discloses a gas-phase dehydrofluorination catalyst for preparing 2,3,3,3-tetrafluoropropene from 1,1,1,2,2-pentafluoropropane, which is a supported catalyst and is composed of a carrier magnesium fluoride and an active component; the catalyst is prepared by the following steps: preparing the carrier magnesium fluoride by reacting hydrofluoric acid or an aqueous solution of ammonium fluoride with magnesium carbonate, loading soluble salts of any one of iron, aluminum, zinc or nickel by using an equal-amount impregnation method, and preparing the catalyst by drying and high-temperature calcination. The catalyst has excellent performance, does not contain noble metals and heavy metal chromium in the composition, has low cost, is green and environment-friendly, has high activity, and has industrial application value. When the reaction is carried out at 300 DEG C, the conversion rate of 1,1,1,2,2-pentafluoropropane can reach more than 70%, the catalyst has long service life and can be stably operated for 360 hours.

Description

Technical Field

[0001] This invention relates to a catalyst and its preparation method, specifically to a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane and its preparation method. Background Technology

[0002] 2,3,3,3-Tetrafluoropropene (HFO-1234yf) has an ozone depletion potential (ODP) of zero and a global warming potential (GWP) of 4, exhibiting excellent environmental performance and being used as a next-generation environmentally friendly refrigerant. The synthesis of HFO-1234yf has been extensively studied, with the gas-phase fluorination of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) to prepare HFO-1234yf being a crucial route among numerous synthetic methods. 1,1,1,2,2-Pentafluoropropane (HFC-245cb) is the main byproduct in the synthesis of HFO-1234yf from HCFO-1233xf. The applications of HFC-245cb are limited; the main application route for HFC-245cb is the gas-phase catalytic defluorination to prepare HFO-1234yf.

[0003] Patent CN101868436B discloses chromium fluoride as a catalyst for the defluorination of HFC-245cb to produce HFO-1234yf. The reaction is carried out at 350℃, with a conversion rate of 60.9% for HFC-245cb and a selectivity of 99.7% for HFO-1234yf. The reaction temperature is relatively high, and the catalyst composition contains the heavy metal chromium, which poses a potential environmental risk.

[0004] Patent US9102579B2 discloses 0.5% Pd / C and 0.5% Pt / C as catalysts for the defluorination of HFC-245cb to prepare HFO-1234yf. The reaction is carried out at 550°C, and the conversion rates of HFC-245cb are 92% and 93%, respectively. However, the selectivity of HFO-1234yf is low, at 53% and 33%, respectively. The reaction temperature is high, and the catalysts used are Pd / C and Pt / C, which results in high cost.

[0005] Currently, the gas-phase defluorination catalysts used to prepare HFO-1234yf from HFC-245cb contain precious metals or heavy metals such as chromium, which pose problems such as high cost and significant potential environmental risks. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane. This catalyst, HFC-245cb, is low-cost, environmentally friendly, and has a long service life, eliminating the need for expensive precious metal compounds and environmentally hazardous heavy metal chromium during the preparation process.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for preparing a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropene from 1,1,1,2,2-pentafluoropropane, wherein the gas-phase defluorination catalyst is a supported catalyst comprising a magnesium fluoride support and an active component, wherein the molar ratio of the active component to magnesium fluoride is 1:10 to 40. The catalyst is prepared by reacting an aqueous solution of hydrofluoric acid or ammonium fluoride with magnesium carbonate to prepare magnesium fluoride support, controlling the molar ratio of fluorine to magnesium to be 2 to 2.4:1, loading soluble salts of any one of iron, aluminum, zinc or nickel using an equal-volume impregnation method, drying at 90℃ to 120℃, and finally calcining at 330℃ to 380℃ to obtain a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane.

[0009] The present invention also includes the following technical features: Specifically, the process of preparing magnesium fluoride carrier by reacting hydrofluoric acid with magnesium carbonate is as follows: water is added to magnesium carbonate and stirred to form a slurry. Hydrofluoric acid is added dropwise to the slurry while stirring. After the addition is complete, stirring is continued for 1 to 5 hours. Ammonia water is added dropwise to adjust the pH of the solution to 8 to 10. Stirring is continued for 2 to 4 hours. The solution is then filtered or centrifuged, and the filter cake or precipitate is washed with deionized water until the pH of the filtrate or supernatant is 6 to 7. The obtained filter cake or precipitate is dried at 90°C to 120°C to obtain magnesium fluoride carrier.

[0010] Specifically, the process of preparing magnesium fluoride carrier by reacting an aqueous solution of ammonium fluoride with magnesium carbonate is as follows: water is added to magnesium carbonate and stirred to form a slurry. While stirring, an aqueous solution of ammonium fluoride is added dropwise to the slurry. After the addition is complete, stirring is continued for 3 to 9 hours. The mixture is then filtered or centrifuged, and the filter cake or precipitate is washed with deionized water until the pH of the filtrate or supernatant is 6 to 7. The resulting filter cake or precipitate is dried at 90°C to 120°C to obtain the magnesium fluoride carrier.

[0011] Specifically, the soluble salts of iron, aluminum, zinc, or nickel are the corresponding nitrates or chlorides.

[0012] A gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane is prepared by the same method described above.

[0013] Compared with the prior art, the present invention has the following technical effects: (1) Existing catalysts contain precious metals such as palladium or platinum, which are expensive. In the catalyst preparation process of this invention, it is not necessary to use precious metal compounds, but only to use inexpensive non-precious metal soluble salts such as iron, aluminum, zinc or nickel, which are low in cost.

[0014] (2) Existing catalysts contain heavy metal chromium, which poses a high environmental risk. The catalyst preparation process in this invention does not require the use of heavy metal chromium, making it green and environmentally friendly. Detailed Implementation

[0015] This invention provides a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane. To obtain a high-performance catalyst with low preparation cost, environmental friendliness, and long service life, it is envisioned to prepare magnesium fluoride by reacting an aqueous solution of hydrofluoric acid or ammonium fluoride with magnesium carbonate in an aqueous phase as a support, and then impregnate it with a non-precious metal active component to modulate the surface acidity, alkalinity, and other physicochemical properties to obtain the desired catalyst.

[0016] The present invention provides a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene (HFO-1234yf) from 1,1,1,2,2-pentafluoropropane (HFC-245cb). The catalyst is a supported catalyst, comprising magnesium fluoride support and an active component, wherein the molar ratio of the active component to magnesium fluoride is 1:10 to 40.

[0017] The catalyst is prepared by reacting an aqueous solution of hydrofluoric acid or ammonium fluoride with magnesium carbonate to prepare magnesium fluoride support, controlling the molar ratio of fluorine to magnesium to be 2 to 2.4:1, loading soluble salts of any one of iron, aluminum, zinc or nickel using an equal-volume impregnation method, drying at 90℃ to 120℃, and finally calcining at 330℃ to 380℃ to obtain a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane.

[0018] The process of preparing magnesium fluoride by reacting hydrofluoric acid with magnesium carbonate is as follows: water is added to magnesium carbonate and stirred to form a slurry. Hydrofluoric acid is added dropwise to the slurry while stirring. After the addition is complete, stirring is continued for 1 to 5 hours. Ammonia water is added dropwise to adjust the pH of the solution to 8 to 10. Stirring is continued for 2 to 4 hours. The solution is then filtered or centrifuged, and the filter cake or precipitate is washed with deionized water until the pH of the filtrate or supernatant is 6 to 7. The resulting filter cake or precipitate is dried at 90°C to 120°C to obtain magnesium fluoride carrier.

[0019] The process of preparing magnesium fluoride by reacting an aqueous solution of ammonium fluoride with magnesium carbonate is as follows: water is added to magnesium carbonate and stirred to form a slurry. While stirring, an aqueous solution of ammonium fluoride is added dropwise to the slurry. After the addition is complete, stirring is continued for 3 to 9 hours. The mixture is then filtered or centrifuged, and the filter cake or precipitate is washed with deionized water until the pH of the filtrate or supernatant is 6 to 7. The resulting filter cake or precipitate is dried at 90°C to 120°C to obtain the magnesium fluoride carrier.

[0020] The soluble salts of iron, aluminum, zinc, or nickel used are the corresponding nitrates or chlorides.

[0021] In this invention, the catalyst performance was evaluated as follows: 30 mL of catalyst was measured and loaded into a reaction tube. After drying with nitrogen and activation with hydrogen fluoride, the reaction temperature was maintained at 300 °C. HFC-245cb and nitrogen were introduced, with a nitrogen to HFC-245cb molar ratio of 4:1 and a contact time of 18 s. The reaction was run for 24 h. The reaction product was washed with water, washed with alkali to absorb HF, and then dried. Gas chromatography was used for analysis. A 7890B gas chromatograph was used with a GS-GasPro column, nitrogen as the carrier gas, and an FID detector at a detector temperature of 220 °C. The column oven was kept at 140 °C for constant temperature injection. Peak area normalization was used for quantification to obtain the raw material conversion rate and the selectivity data of HFO-1234yf.

[0022] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0023] Example 1: This embodiment provides a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane and its preparation method. Water is added to magnesium carbonate and stirred to form a slurry. Hydrofluoric acid is added dropwise to the slurry while stirring, controlling the fluorine to magnesium molar ratio to be 2:1. After the addition is complete, stirring is continued for 3 hours. Ammonia water is added dropwise to adjust the pH of the solution to 9, and stirring is continued for 2 hours. The solution is then filtered, and the filter cake is washed with deionized water until the pH of the filtrate is 7. The obtained filter cake is dried at 90°C to obtain a magnesium fluoride support.

[0024] Magnesium fluoride support was added to a beaker, and Fe(NO3)3•9H2O was impregnated using an equal-volume impregnation method, with a molar ratio of Fe(NO3)3•9H2O to magnesium fluoride of 1:12.5. The mixture was dried in an oven at 100℃ and calcined in a muffle furnace at 350℃ for 4 hours to prepare the catalyst. Evaluation showed that the conversion rate of HFC-245cb was 77.0%, and the selectivity of HFO-1234yf was 99.2%.

[0025] Example 2: This embodiment provides a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane and its preparation method. Water is added to magnesium carbonate and stirred to form a slurry. Hydrofluoric acid is added dropwise to the slurry while stirring, controlling the fluorine to magnesium molar ratio to be 2.2:1. After the addition is complete, stirring is continued for 2 hours. Ammonia water is added dropwise to adjust the pH of the solution to 10, and stirring is continued for 3 hours. The solution is centrifuged, and the precipitate is washed with deionized water until the pH of the supernatant is 6. The obtained precipitate is dried at 100°C to obtain magnesium fluoride support.

[0026] Magnesium fluoride support was added to a beaker, and AlCl3•6H2O was impregnated using an equal-volume impregnation method, with a molar ratio of AlCl3•6H2O to magnesium fluoride of 1:10. The mixture was dried in an oven at 90℃ and calcined in a muffle furnace at 330℃ for 5 hours to prepare the catalyst. Evaluation showed that the conversion rate of HFC-245cb was 74.6%, and the selectivity of HFO-1234yf was 99.5%.

[0027] Example 3: This embodiment provides a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane and its preparation method. Water is added to magnesium carbonate and stirred to form a slurry. While stirring, an aqueous solution of ammonium fluoride is added dropwise to the slurry, controlling the fluorine to magnesium molar ratio to be 2.4:1. After the addition is complete, stirring is continued for 9 hours. The mixture is then filtered, and the filter cake is washed with deionized water until the pH of the filtrate is 7. The resulting filter cake is dried at 110°C to obtain a magnesium fluoride support.

[0028] Magnesium fluoride support was added to a beaker, and Zn(NO3)2•6H2O was impregnated using an equal-volume impregnation method, with a molar ratio of Zn(NO3)2•6H2O to magnesium fluoride of 1:25. The mixture was dried in an oven at 120℃ and calcined in a muffle furnace at 380℃ for 2 hours to prepare the catalyst. Evaluation showed that the conversion rate of HFC-245cb was 73.6%, and the selectivity of HFO-1234yf reached 99.6%.

[0029] Example 4: This embodiment provides a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane and its preparation method. Water is added to magnesium carbonate and stirred to form a slurry. While stirring, an aqueous solution of ammonium fluoride is added dropwise to the slurry, controlling the fluorine to magnesium molar ratio at 2.1:1. After the addition is complete, stirring continues for 6 hours. The mixture is then centrifuged, and the precipitate is washed with deionized water until the pH of the supernatant reaches 6. The resulting precipitate is dried at 120°C to obtain a magnesium fluoride support.

[0030] Magnesium fluoride support was added to a beaker, and NiCl2•6H2O was impregnated using an equal-volume impregnation method. The molar ratio of NiCl2•6H2O to magnesium fluoride was 1:40. The mixture was dried in an oven at 110℃ and calcined in a muffle furnace at 340℃ for 4 hours to prepare the catalyst. Evaluation showed that the conversion rate of HFC-245cb was 73.5%, and the selectivity of HFO-1234yf reached 99.1%.

[0031] The catalyst prepared in Example 1 was subjected to a lifetime test, and the evaluation results are shown in Table 1.

[0032] Table 1 Life Test

Claims

1. A method for preparing a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane, characterized in that, The gas-phase defluorination catalyst is a supported catalyst, consisting of magnesium fluoride support and an active component, with a molar ratio of active component to magnesium fluoride of 1:10 to 40. The catalyst is prepared by reacting an aqueous solution of hydrofluoric acid or ammonium fluoride with magnesium carbonate to prepare magnesium fluoride support, controlling the molar ratio of fluorine to magnesium to be 2 to 2.4:1, loading soluble salts of any one of iron, aluminum, zinc or nickel using an equal-volume impregnation method, drying at 90℃ to 120℃, and finally calcining at 330℃ to 380℃ to obtain a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane.

2. The method for preparing a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane as described in claim 1, characterized in that, The process of preparing magnesium fluoride carrier by reacting hydrofluoric acid with magnesium carbonate is as follows: water is added to magnesium carbonate and stirred to form a slurry. Hydrofluoric acid is added dropwise to the slurry while stirring. After the addition is complete, stirring is continued for 1 to 5 hours. Ammonia water is added dropwise to adjust the pH of the solution to 8 to 10. Stirring is continued for 2 to 4 hours. The solution is then filtered or centrifuged, and the filter cake or precipitate is washed with deionized water until the pH of the filtrate or supernatant is 6 to 7. The obtained filter cake or precipitate is dried at 90℃ to 120℃ to obtain magnesium fluoride carrier.

3. The method for preparing a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane as described in claim 1, characterized in that, The process of preparing magnesium fluoride carrier by reacting an aqueous solution of ammonium fluoride with magnesium carbonate is as follows: water is added to magnesium carbonate and stirred to form a slurry. While stirring, an aqueous solution of ammonium fluoride is added dropwise to the slurry. After the addition is complete, stirring is continued for 3 to 9 hours. The mixture is then filtered or centrifuged, and the filter cake or precipitate is washed with deionized water until the pH of the filtrate or supernatant is 6 to 7. The resulting filter cake or precipitate is dried at 90°C to 120°C to obtain the magnesium fluoride carrier.

4. The method for preparing a gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane as described in claim 1, characterized in that, The soluble salts of iron, aluminum, zinc, or nickel are the corresponding nitrates or chlorides.

5. A gas-phase defluorination catalyst for the preparation of 2,3,3,3-tetrafluoropropylene from 1,1,1,2,2-pentafluoropropane, characterized in that, The 2,3,3,3-tetrafluoropropylene was prepared by the gas-phase defluorination hydrogen catalyst preparation method according to any one of claims 1 to 4, which is used to prepare 1,1,1,2,2-pentafluoropropane.

Images