Process for the preparation of C3-7 fluoroalkenes by base-mediated dehydrohalogenated C3-7 fluoroalkenes
The invention relates to a process for preparing a compound of formula CF 3 CF═CHX, CHX 2 CX═CX 2 or a linear or branched C 4-7 (hydro)fluoroalkene, wherein each X is, independently, H or F provided that in CHX 2 CX═CX 2 at least one X is F, which process comprises dehydrohalogenating a compound of formula CF 3 CFYCH 2 X, CF 3 CFHCYHX, CHX 2 CXYCX 2 H, CHX 2 CXHCX 2 Y, or a linear or branched C 4-7 hydro(halo)fluoroalkane, wherein each X is, independently, H or F provided that in CHX 2 CXYCX 2 H and CHX 2 CXHCX 2 Y at least one X is F, wherein Y is F, Cl, Br, or I, in the presence of a base.
1. A process for preparing a C 3 -C 7 (hydro)fluoroalkene, which process comprises dehydrohalogenating a linear or branched C 3 -C 7 hydro(halo)fluoroalkane, in the presence of a base,
wherein the process is carried out in the presence of a polar aprotic solvent comprising N-methyl pyrrolidone (NMP).
2. A process according to claim 1 carried out at a temperature of from −50 to 300° C. and a pressure of from 0 to 30 bara.
3. A process according to claim 1 wherein the base is selected from a metal hydroxide, a metal amide and mixtures thereof.
4. A process according to claim 1 wherein the process is carried out in the presence of a catalyst.
5. A process according to claim 4 wherein the catalyst is a crown ether.
6. A process according to claim 4 , wherein the catalyst is fluorinated.
7. A process according to claim 4 for preparing a (hydro)fluoropropene selected from 1,2,3,3,3-pentafluoropropene (CF 3 CF═CFH, HFC-1225ye), 2,3,3,3-tetrafluoropropene (CF 3 CF═CH 2 , HFC-1234yf) and mixtures thereof.
8. A process according to claim 7 wherein CF 3 CF═CH 2 is prepared by dehydrohalogenating a compound of formula CF 3 CFYCH 3 or CF 3 CFHCYH 2 .
9. A process according to claim 8 wherein CF 3 CF═CH 2 is prepared by dehydrofluorinating 1,1,1,2,2-pentafluoropropane (CH 3 CF 2 CF 3 , HFC-245ca) and/or dehydrochlorinating 1,1,1,2-tetrafluoro-2-chloropropane.
10. A process according to claim 8 wherein CF 3 CF═CH 2 is prepared by dehydrofluorinating 1,1,1,2,3-pentafluoropropane (CH 2 FCHFCF 3 , HFC-245eb) and/or dehydrochlorinating 1,1,1,2-tetrafluoro-3-chloropropane.
11. A process according to claim 10 comprising the step of converting a trifluorodichloropropane or a difluorotrichloropropane or a fluorotetrachloropropane to CH 3 CF 2 CF 3 , 1,1,1,2-tetrafluoro-2-chloropropane, CH 2 FCHFCF 3 , and/or 1,1,1,2-tetrafluoro-3-chloropropane.
12. A process according to claim 11 wherein the trifluorodichloropropane is selected from 1,1,1-trifluoro-2,2-dichloropropane (CF 3 CCl 2 CH 3 ) and 1,1,1-trifluoro-2,3-dichloropropane (CF 3 CHClCH 2 Cl).
13. A process according to claim 12 comprising the step of chlorinating 3,3,3-trifluoropropene to produce CF 3 CHClCH 2 Cl.
14. A process according to claim 13 comprising the step of dehydrofluorinating 1,1,1,3-tetrafluoropropane to produce 3,3,3-trifluororopropene.
15. A process according to claim 14 comprising the step of fluorinating 1,1,1,3-tetrachloropropane to produce 1,1,1,3-tetrafluoropropane.
16. A process according to claim 15 comprising the step of telomerising carbon tetrachloride and ethylene to produce 1,1,1,3-tetrachloropropane.
17. A process according to claim 12 comprising the step of fluorinating 1,1,1,2,2-pentachloropropane to produce CF 3 CCl 2 CH 3 .
18. A process according to claim 17 comprising the step of chlorinating 1,1,1-trichloroacetone (CCl 3 C(O)CH 3 ) to produce 1,1,1,2,2-pentachloropropane.
19. A process according to claim 18 comprising the step of chlorinating acetone (CH 3 C(O)CH 3 ) to produce 1,1,1-trichloroacetone (CCl 3 C(O)CH 3 ).
20. A process according to claim 3 wherein the base is selected from an alkali metal hydroxide and an alkaline earth metal hydroxide.
21. A process according to claim 20 wherein the base is an alkali metal hydroxide.
22. A process according to claim 21 wherein the alkali metal hydroxide is selected from sodium hydroxide or potassium hydroxide.
23. A process according to claim 21 wherein the alkali metal hydroxide is calcium hydroxide.
24. A process according to claim 5 wherein the crown either is 18-crown-6.
25. A process according to claim 4 wherein the catalyst is quaternary ammonium salt.