Disclosed are processes for the production of fluorinated olefins, preferably adapted to commercialization of CF3CF═CH2 (1234yf). Three steps may be used in preferred embodiments in which a feedstock such as CCl2═CClCH2Cl (which may be purchased or synthesized from 1,2,3-trichloropropane) is fluorinated (preferably with HF in gas-phase in the presence of a catalyst) to synthesize a compound such as CF3CCl═CH2, preferably in a 80-96% selectivity. The CF3CCl═CH2 is preferably converted to CF3CFClCH3 (244-isomer) using a SbCl5 as the catalyst which is then transformed selectively to 1234yf, preferably in a gas-phase catalytic reaction using activated carbon as the catalyst. For the first step, a mixture of Cr2O3 and FeCl3/C is preferably used as the catalyst to achieve high selectivity to CF3CCl═CH2 (96%). In the second step, SbCl5/C is preferably used as the selective catalyst for transforming 1233xf to 244-isomer, CF3CFClCH3. The intermediates are preferably isolated and purified by distillation and used in the next step without further purification, preferably to a purity level of greater than about 95%.