The present invention provides a process for preparing 3,3,3-trifluoropropene (1243zf), the process comprising: (a) fluorinating CCl.sub.3CH.sub.2CH.sub.2Cl (250fb) to produce a reaction product comprising CF.sub.3CH.sub.2CH.sub.2Cl (253fb) in the liquid phase in a first reactor, using HF as the fluorinating agent; and (b) (i) dehydrohalogenating 253fb to produce 1243zf in the vapour phase in the present of a catalyst in a second reactor; or (b)(ii) dehydrohalogenating 253fb to produce 1243zf in a second reactor, wherein the reaction product comprising 253fb produced in step (a) has subjected to one or more purification steps before step (b).

The present invention also provides an azeotropic or near-azeotropic composition comprising HF and 253fb.

This invention provides a method capable of efficiently producing 2,3,3,3-tetrafluoropropene (HFO-1234yf) with a recycling step using substantially a single reaction step. A method for producing 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising a reaction step of reacting at least one chlorine-containing starting compound selected from the group consisting of chlorine-containing alkanes represented by formula (1): CX.sub.2YCHClCH.sub.2Z (wherein X, Y and Z independently represent H, F or Cl) and chlorine-containing alkenes represented by formula (2): CX.sub.2YCCl═CZ.sub.2 (wherein X, Y and Z independently represent H, F or Cl) with a fluorinating agent, wherein the molar ratio of the chlorine-containing starting compound represented by formula (1) or (2) newly supplied to the reactor inlet is less than 1.2 relative to 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) in components obtained from the reactor outlet.

This invention provides a method capable of efficiently producing 2,3,3,3-tetrafluoropropene (HFO-1234yf) with a recycling step using substantially a single reaction step. A method for producing 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising a reaction step of reacting at least one chlorine-containing starting compound selected from the group consisting of chlorine-containing alkanes represented by formula (1): CX.sub.2YCHClCH.sub.2Z (wherein X, Y and Z independently represent H, F or Cl) and chlorine-containing alkenes represented by formula (2): CX.sub.2YCCl═CZ.sub.2 (wherein X, Y and Z independently represent H, F or Cl) with a fluorinating agent, wherein the molar ratio of the chlorine-containing starting compound represented by formula (1) or (2) newly supplied to the reactor inlet is less than 1.2 relative to 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) in components obtained from the reactor outlet.

A process for the dehydrochlorination of a chlorinated hydrocarbon comprising at least one chlorine atom and at least one hydrogen atom on vicinal carbon atoms to yield the corresponding unsaturated hydrocarbon, said process comprising contacting the chlorinated hydrocarbon with a guanidinium salt or its guanidine precursor.

A process for the dehydrochlorination of a chlorinated hydrocarbon comprising at least one chlorine atom and at least one hydrogen atom on vicinal carbon atoms to yield the corresponding unsaturated hydrocarbon, said process comprising contacting the chlorinated hydrocarbon with a guanidinium salt or its guanidine precursor.

A process for the dehydrochlorination of a chlorinated hydrocarbon comprising at least one chlorine atom and at least one hydrogen atom on vicinal carbon atoms to yield the corresponding unsaturated hydrocarbon, said process comprising contacting the chlorinated hydrocarbon with a guanidinium salt or its guanidine precursor.

The invention relates to a composition comprising at least 99% by weight of 1,1,1,2,3-pentachloropropane, and comprising at least one compound chosen from a list of additional compounds consisting of trichloropropanes, tetrachloropropanes, pentachloropropanes other than 1,1,1,2,3-pentachloropropane, hexachloropropanes, heptachloropropanes, dichloropropenes, trichloropropenes, tetrachloropropenes, pentachloropropenes and hexachloropropene, said compound being present in the composition in a weight content of less than or equal to 500 ppm.

The invention also relates to the use of this composition for manufacturing 2,3,3,3-tetrafluoropropene.

The invention relates to a composition comprising at least 99% by weight of 1,1,1,2,3-pentachloropropane, and comprising at least one compound chosen from a list of additional compounds consisting of trichloropropanes, tetrachloropropanes, pentachloropropanes other than 1,1,1,2,3-pentachloropropane, hexachloropropanes, heptachloropropanes, dichloropropenes, trichloropropenes, tetrachloropropenes, pentachloropropenes and hexachloropropene, said compound being present in the composition in a weight content of less than or equal to 500 ppm.

The invention also relates to the use of this composition for manufacturing 2,3,3,3-tetrafluoropropene.

The invention relates to a composition comprising at least 99% by weight of 1,1,1,2,3-pentachloropropane, and comprising at least one compound chosen from a list of additional compounds consisting of trichloropropanes, tetrachloropropanes, pentachloropropanes other than 1,1,1,2,3-pentachloropropane, hexachloropropanes, heptachloropropanes, dichloropropenes, trichloropropenes, tetrachloropropenes, pentachloropropenes and hexachloropropene, said compound being present in the composition in a weight content of less than or equal to 500 ppm.

The invention also relates to the use of this composition for manufacturing 2,3,3,3-tetrafluoropropene.

A dehydrochlorination process is disclosed. The process involves contacting R.sub.fCHClCH.sub.2Cl with a chromium oxyfluoride catalyst in a reaction zone to produce a product mixture comprising R.sub.fCCl═CH.sub.2, wherein R.sub.f is a perfluorinated alkyl group.