Process for manufacture of fluorinated olefins
View Patent ↗A process for the production of fluorinated olefins, preferably fluorinated propenes, by contacting a feed stream containing a fluorinated olefin and hydrogen with a first amount of catalyst to produce the hydrofluorocarbon, wherein a first exit stream contains unreacted fluorinated olefin and hydrogen; contacting the first exit stream with a second amount of catalyst to produce a hydrofluorocarbon, wherein the second amount of catalyst is preferably greater than the first amount of catalyst; and contacting the hydrofluorocarbon with a catalyst for dehydrohalogenation to produce a product stream of fluorinated olefin.
1. A process for the production of a fluorinated olefin comprising the steps of:
(a) contacting a feed stream comprising a fluorinated olefin reactant having an N degree of fluorination and hydrogen with a first hydrogenation catalyst to convert a portion of said fluorinated olefin reactant to a first amount of a hydrofluorocarbon at a first conversion rate and to produce a first exit stream comprising said hydrofluorocarbon, an unreacted portion of said fluorinated olefin reactant and an unreacted portion of said hydrogen;
(b) contacting said first exit stream with a second hydrogenation catalyst to convert a portion of said unreacted fluorinated olefin reactant to a second amount of said hydrofluorocarbon at a second conversion rate which is substantially greater than said first conversion rate;
(c) dehydrohalogenating at least a portion of said first and second amounts of said hydrofluorocarbon in the presence of a dehydrohalogenation catalyst to produce a product stream comprising a fluorinated olefin product having an N−1 degree of fluorination and HF; and
(d) optionally separating HF from said product stream.
2. The process of claim 1 wherein step (d) involves contacting at least a portion of said product stream with sulfuric acid to extract HF from said product stream.
3. The process of claim 2 wherein said sulfuric acid contacting step produces an effluent sulfuric acid stream containing at least a portion of the HF from the product stream and wherein said process further comprises the step of recycling at least a portion of said effluent sulfuric acid stream through an extraction tower.
4. The process of claim 2 wherein said fluorinated olefin reactant comprises a fluoropropene having from three to six fluorine substituents.
5. The process of claim 2 wherein said fluorinated olefin reactant is hexafluoropropene.
6. The process of claim 2 wherein said fluorinated olefin product is pentafluoropropene.
7. The process of claim 2 wherein said hydrofluorocarbon is pentafluoropropane (HFC-245).
8. The process of claim 2 wherein said hydrofluorocarbon is hexafluoropropane (HFC-236).
9. The process of claim 2 wherein said fluorinated olefin reactant is F 2 C=CFCF 3 .
10. The process of claim 2 wherein said fluorinated olefin product is CFH=CFCf 3 .
11. The process of claim 2 wherein said first and second hydrogenation catalysts comprise carbon-supported palladium.
12. The process of claim 2 wherein said dehydrohalogenating step comprises dehydrofluorination.
13. The process of claim 2 wherein said dehydrofluorination catalyst is selected from the group consisting of one or more fluorinated metal oxides, metal fluorides, carbon supported transition metals and combinations of these.