Process for producing 1,1-dichloro-2,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene

1. A process for producing tetrafluoropropenes, which comprises contacting a raw material composition comprising 1-chloro-2,3,3,3-tetrafluoropropane and dichloropentafluoropropane and 1,1-dichloro-2,2,3,3,3-pentafluoropropane and at least one of its isomers, with an alkali aqueous solution in the presence of a phase-transfer catalyst, to produce 1,1-dichloro-2,3,3,3-tetrafluoropropene from the 1,1-dichloro-2,3,3,3-pentafluoropropane and to produce 2,3,3,3-tetrafluoropropene from the 1-chloro-2,3,3,3-tetrafluoropropane,

wherein the reaction amount of 1 mol of the isomer of 1,1-dichloro-2,2,3,3,3-pentafluoropropane to form an isomer of 1,1-dichloro-2,3,3,3-tetrafluoropropene is less than 0.01 mol.

2. The process according to claim 1 , wherein the isomers of 1,1-dichloro-2,2,3,3,3-pentafluoropropane are 1,3-dichloro-1,2,2,3,3-pentafluoropropane, 2,2-dichloro-1,1,3,3,3-pentafluoropropane, 1,2-dichloro-1,2,3,3,3-pentafluoropropane and 2,3-dichloro-1,1,2,3,3-pentafluoropropane.

3. The process according to claim 1 or 2 , wherein in the raw material composition, the proportion of 1,1-dichloro-2,2,3,3,3-pentafluoropropane in the dichloropentafluoropropane is at most 99.5 mol %.

4. The process according to claim 1 or 2 , wherein the 1-chloro-2,3,3,3-tetrafluoropropane in the raw material composition is 1-chloro-2,3,3,3-tetrafluoropropane formed as a by-product in a reaction to produce 2,3,3,3-tetrafluoropropene by hydrolyzing 1,1-dichloro-2,3,3,3-tetrafluoropropene.

5. The process according to claim 1 or 2 , wherein in the raw material composition, the amount of the 1-chloro-2,3,3,3-tetrafluoropropane is from 0.01 to 20 parts by mass to 100 parts by mass of the dichloropentafluoropropane.

6. The process according to claim 1 or 2 , wherein the temperature for contacting the raw material composition with the alkali aqueous solution in the presence of a phase-transfer catalyst is from 0 to 20° C.

7. The process according to claim 1 or 2 , wherein the alkali concentration in the alkali aqueous solution is from 0.5 to 40 mass %.

8. The process according to claim 1 or 2 , wherein dichloropentafluoropropane is separated from the reaction product obtainable by the process according to claim 1 or claim 2 ; at least one of isomers other than 1,1-dichloro-2,2,3,3,3-pentafluoropropane in the separated dichloropentafluoropropane is isomerized to 1,1-dichloro-2,2,3,3,3-pentafluoropropane; and then, the dichloropentafluoropropane including 1,1-dichloro-2,2,3,3,3-pentafluoropropane obtained by the isomerization reaction is used as at least a part of the dichloropentafluoropropane in the raw material composition.

9. A process for producing 2,3,3,3-tetrafluoropropene, which comprises separating 1,1-dichloro-2,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene, respectively, from the reaction product obtainable by the process as defined in claim 1 or claim 2 , and reacting the separated 1,1-dichloro-2,3,3,3-tetrafluoropropene with hydrogen in the presence of a catalyst to produce 2,3,3,3-tetrafluoropropene.

10. The process for producing 2,3,3,3-tetrafluoropropene according to claim 9 , wherein from the hydrogenation reaction product, not only the 2,3,3,3-trafluoropropene is separated, but also a mixture comprising unreacted 1,1-dichloro-2,3,3,3-tetrafluoropropene, 1-chloro-2,3,3,3-tetrafluoropropene as an intermediate product and 1-chloro-2,3,3,3-tetrafluoropropane as a by-product, is separated; and the separated mixture is used as a part of the raw material composition in the process as defined in claim 1 .

11. A process for producing 2,3,3,3-tetrafluoropropene, which comprises:

a hydrogenation step of reacting 1,1-dichloro-2,3,3,3-tetrafluoropropene with hydrogen in the presence of a catalyst to produce 2,3,3,3-tetrafluoropropene, which is separated from the reaction product, and to obtain a mixture comprising unreacted 1,1-dichloro-2,3,3,3-tetrafluoropropene, 1-chloro-2,3,3,3-tetrafluoropropene as an intermediate product and 1-chloro-2,3,3,3-tetrafluoropropane as a by-product;

a mixing step of mixing dichloropentafluoropropane including 1,1-dichloro-2,2,3,3,3-pentafluoropropane and at least one of its isomers, and the mixture obtained in the above hydrogenation step to obtain a raw material composition comprising 1,1-dilchloro-2,2,3,3,3-pentafluoropropane and 1-chloro-2,3,3,3-tetrafluoropropane; and

a dehydrohalogenation step of contacting the raw material composition with an alkali aqueous solution in the presence of a phase-transfer catalyst to produce 1,1-dichloro-2,3,3,3-tetrafluoropropene from the 1,1-dichloro-2,2,3,3,3-pentafluoropropane and to produce 2,3,3,3-tetrafluoropropene from the 1-chloro-2,3,3,3-tetrafluoropropane, and separating the 1,1-dichloro-2,3,3,3-tetrafluoropene and the 2,3,3,3-tetrafluoropropene, respectively, from the reaction product;

wherein the 1,1-dichloro-2,3,3,3-tetrafluoropropene separated in the above dehydrohalogenation step is used as at least a part of the 1,1-dichloro-2,3,3,3-tetrafluoropropene in the above hydrogenation step, and

wherein the reaction amount of 1 mol of the isomer of 1,1-dichloro-2,2,3,3,3-pentafluoropropane to form an isomer of 1,1-dichloro-2,3,3,3-tetrafluoropropene is less than 0.01 mol.

12. The process for producing 2,3,3,3-tetrafluoropropene according to claim 11 , which further contains an isomerization step of isomerizing at least one of dichloropentafluoropropane other than 1,1-dichloro-2,2,3,3,3-pentafluoropropane to 1,1-dichloro-2,2,3,3,3-pentafluoropropane, wherein in the dehydrohalogenation step, from the reaction product, not only the 1,1-dichloro-2,3,3,3-tetrafluoropropene and the 2,3,3,3-tetrafluoropropene are, respectively, separated, but also dichloropentafluoropropane including at least one of dichloropentafluoropropane other than 1,1-dichloro-2,2,3,3,3-pentafluoropropane, is separated; the separated dichloropentafluoropropane is converted, by the isomerization step, to dichloropentafluoropropane including 1,1-dichloro-2,2,3,3,3-pentafluoropropane and at least one of its isomers; and the dichloropentafluoropropane obtained in the isomerization step is used as at least a part of the dichloropentafluoropropane in the above mixing step.