Source: {"pile_set_name": "USPTO Backgrounds"}

Fluorocarbons, particularly fluorinated olefins, as a class, have many and varied uses, including as chemical intermediates and monomers. In particular, these products are useful as refrigerants, monomers or intermediates for preparing refrigerants, particularly those identified as having low global warming potential.
With concerns over global warming, hydrofluoroolefins (HFOs) are being commercialized as substitutes for chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) for use as refrigerants, heat transfer agents, blowing agents, monomers and propellants because HFOs do not deplete the ozone layer and have low global warming potential. Some HFOs are prepared by multiple steps that involve fluorinating a chlorinated organic compound with a fluorination agent such as hydrogen fluoride in the presence of a fluorination catalyst. These reactions may be conducted in either the liquid or gas phase or a combination of these. In processes to manufacture 2,3,3,3-tetrafluoropropene (1234yf), the following reaction sequence is known:                Step 1: TCP+3HF→1233xf+3HClwherein TCP is 1,1,2,3-tetrachloropropene, or CCl2═CClCH2Cl; and 1233xf is 2-chloro-3,3,3,-trifluoropropene, or CH2═CClCF3.        Step 2: 1233xf+HF→244bbwherein 244bb is 2-chloro-1,1,1,2-tetrafluoropropane, or CH3CClFCF3.A by-product of Step 2 can also form as follows: 1233xf+2HF→245cb+HCl, where 245cb is 1,1,1,2,2-pentafluoropropane, or CH3CF2CF3.        Step 3: 244bb→1234yf+HClwherein 1234yf is 2,3,3,3-tetrafluoropropene, or CH2═CFCF3.        
Whereas, in Step 2, a high conversion of 1233xf concurrent with low selectivity to the 245cb by-product is sought, it has been found, especially when an antimony chloride complex catalyst is used, that less than desirable conversion and selectivity is often obtained. There is thus a need to simultaneously achieve high conversion of 1233xf with low selectivity of 245cb and to gain the resultant economic and commercial benefits in, e.g. the production of 1234yf as a final product.