| 摘要 |
A method of producing refrigerant compound 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising two or more reaction steps, at least one of said reaction steps comprising the production of 1,3,3,3-tetrafluoropropene (HFO-1234ze) and optionally precursors thereof having the formula F3C-CH2-CHX2 or F3C-CH=CHX (X = halogen), from one or more HFO-1234yf precursors of the formula F3C-CXX-CH2X (X = H or halogen) or F3C-CX=CH2 (X = halogen), wherein at least a portion of the HFO-1234ze is recovered. Preferred HFO-1234yf precursors are HCFC-243db, HFC-245cb, HCFC-244bb, 3-chloro-1,1,1,2-tetrafluoropropane (HCFC-244eb), 1,1,1,2,3-pentafluoropropane (HFC-245eb) and HCFO-1233xf. Preferred HFO-1234ze precursors are 1,1,1,3,3-pentafluoropropane (HFC-245fa), 3-chloro-1,1,1,3-tetrafluoropropane (HCFC-244fa), 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243fa) and 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd). A preferred process comprises the following steps: i) Direct chlorination (D) of 3,3,3-trifluoropropene (HFO-1243zf) to form 1,1,1-trifluoro-2,3-dichloropropane (HCFC-243db), ii) Dehydrochlorination (C) of the latter to form 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), iii) Hydrofluorination (B) of the latter to form 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) by saturation of double bond and subsequently 1,1,1,2,2-pentafluoropropane (HFC-245cb) by substitution of Cl by F, and iv) Dehydrofluorination (A), preferably through contact with a zinc/chromia catalyst, which leads to the conversion of HFC-245cb into 2,3,3,3-tetrafluoropropene (HFO-1234yf) as a main product, but also to the production of 1,3,3,3-tetrafluoropropene (HFO-1234ze) at a minor proportion from intermediate by-products. Other by-products may be recycled to earlier reaction steps. |
