Method of recycling byproduct-trifluoromethane in HCFC-22 production to prepare difluoromethane
A technology of trifluoromethane and difluoromethane is applied in the field of resource utilization of converting by-product trifluoromethane into difluoromethane, and can solve the problems of failure to convert trifluoromethane, high reaction temperature, many by-products, and the like, Achieve the effects of high catalyst selectivity, low reaction temperature, and no tail gas emissions
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Embodiment 1
[0062] Catalyst pretreatment: dichromium trioxide in N 2 Treat at 250°C for 5 hours, fluoride at 400°C for 2 hours in a mixed atmosphere of 10% hydrogen fluoride and 90% nitrogen, and finally treat at 400°C for 5 hours with hydrogen fluoride.
[0063] Reaction: Pass trifluoromethane and dichloromethane at a ratio of 1:1 (molar ratio) into a reactor containing 20ml of pretreated chromium oxide catalyst, at a temperature of 350°C, a pressure of 1bar, and a space velocity of 1000h -1 The reaction was carried out under the conditions to obtain the reaction product. During the reaction, all pipelines were kept warm to 60°C with heating tape. In the reaction product, the main product includes difluoromethane, chlorofluoromethane and chlorodifluoromethane, and its selectivity is 26.1%, 31.4% and 42.4% respectively, wherein the conversion ratios of trifluoromethane and dichloromethane are respectively 17.4% and 18.8%. The catalyst activity remained stable after 200 hours of reactio...
Embodiment 2
[0066] Catalyst pretreatment: dichromium trioxide in N 2 Treat at 200°C for 4 hours, fluoride at 350°C for 3 hours in a mixed atmosphere of 10% hydrogen fluoride and 90% nitrogen, and finally treat at 350°C for 5 hours with hydrogen fluoride.
[0067] Reaction: Pass trifluoromethane and dichloromethane at a ratio of 1:1 (molar ratio) into a reactor containing 20ml of pretreated chromium oxide catalyst, at a temperature of 450°C, a pressure of 2bar, and a space velocity of 2000h -1 The reaction was carried out under the conditions to obtain the reaction product. During the reaction, all pipelines were kept warm to 60°C with heating tape. In the reaction product, the main product includes difluoromethane, chlorofluoromethane and chlorodifluoromethane, and its selectivity is 22.5%, 25.2% and 40.5% respectively, wherein the conversion rates of trifluoromethane and dichloromethane are respectively 25.6% and 27.1%. The catalyst activity remained stable after 200 hours of reaction...
Embodiment 3
[0070] Catalyst pretreatment: dichromium trioxide in N 2 Treat at 250°C for 5 hours, fluoride at 400°C for 2 hours in a mixed atmosphere of 10% hydrogen fluoride and 90% nitrogen, and finally treat at 400°C for 5 hours with hydrogen fluoride.
[0071] Reaction: Pass trifluoromethane and dichloromethane at a ratio of 1:2 (molar ratio) into a reactor containing 20ml of pretreated chromium sesquioxide catalyst. -1 The reaction was carried out under the conditions to obtain the reaction product. During the reaction, all pipelines were kept warm to 60°C with heating tape. In the reaction product, the main product includes difluoromethane, chlorofluoromethane and chlorodifluoromethane, and its selectivity is 29.2%, 27.1% and 43.4% respectively, wherein the conversion ratios of trifluoromethane and dichloromethane are respectively 34.5% and 21.2%. The catalyst activity remained stable after 200 hours of reaction.
[0072] Rectification: The reaction product is subjected to rectif...
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