PROCESS FOR THE PREPARATION OF HALOGENATED ALKENES BY DEHYDROHALOGENATION OF HALOGENATED ALKANES

Abstract

The present invention provides a process for the preparation of a (hydro)(chloro)fluoroalkene by contacting a reagent stream comprising a hydrochlorofluoroalkane with a catalyst in a reactor to dehydrochlorinate at least a portion of the hydrochlorofluoroalkane to produce a product stream comprising the (hydro)(chloro)fluoroalkene and hydrogen chloride (NCI), wherein the catalyst is selected from the group consisting of metal oxide catalysts, metal halide catalysts, zero-valent metal catalysts, carbon-based catalysts and mixtures thereof, and wherein (i) the catalyst is chlorinated prior to contacting it with the reagent stream comprising the hydrochlorofluoroalkane; and/or (ii) the contacting step is carried out in the presence of a HCI co-feed.

Claims

1. A process for the preparation of a (hydro)(chloro)fluoroalkene, the process comprising contacting a reagent stream comprising a hydrochlorofluoroalkane with a catalyst in a reactor to dehydrochlorinate at least a portion of the hydrochlorofluoroalkane to produce a product stream comprising the (hydro)(chloro)fluoroalkene and hydrogen chloride (HCl), wherein the catalyst is selected from metal oxide catalysts, metal halide catalysts, zero-valent metal catalysts, carbon-based catalysts and mixtures thereof, and wherein: (i) the catalyst is chlorinated prior to contacting it with the reagent stream comprising the hydrochlorofluoroalkane; and/or (ii) the contacting step is carried out in the presence of a HCl co-feed.

2. A process according to claim 1, wherein step (i) the catalyst is chlorinated with a chlorinating agent comprising hydrogen chloride (HCl), chlorine (Cl.sub.2), or a mixture thereof.

3. A process according to claim 1 wherein step (i) comprises contacting the catalyst with a chlorinating agent at a temperature of from about 200° C. to about 600° C.

4. A process according to claim 3 wherein the catalyst is contacted by a fluid stream of the chlorinating agent haying a space velocity of from 0.1 min.sup.−1 to about 3 min.sup.−1 for about 1 hour to about 48 hours.

5. A process according to claim 2 wherein chlorinating agent is diluted by the presence of an inert gas, preferably wherein the inert gas is nitrogen.

6. A process according to claim 1, wherein the step (i) is combined with a catalyst drying step in a single procedure.

7. A process according to claim 1 wherein step (ii) the amount of HCl fed to the reactor is up to 50 mol % based on the combined amount of hydrochlorofluoroalkane and HCl fed to the reactor.

8. A process according to claim 1 wherein the amount of HCl fed to the reactor is at least 1 mol % based on the combined amount of hydrochlorofluoroalkane and HCl fed to the reactor.

9. A process according to claim 1 wherein at least a portion of the HCl in the product stream is recycled to the reactor to make up at least a portion of the HCl co-feed.

10. A process according to claim 1 wherein at least a portion of the HCl co-feed originates from a preceding process step of manufacturing the hydrochlorofluoroalkane.

11. A process according to claim 1 wherein the (hydro)(chloro)fluoroalkene is a C.sub.3-7 (hydro)(chloro)fluoroalkene and the hydrochlorofluoroalkane is a C.sub.3-7 hydrochlorofluoroalkane.

12. A process according to claim 11 wherein the C.sub.3-7 (hydro)(chloro)fluoroalkene is a (hydro)(chloro)fluoropropene and the C.sub.3-7hydrochlorofluoroalkane is a hydrochlorofluoroproane.

13. A process according to claim 12 wherein the (hydro)(chloro)fluoropropene is a hydrochlorofluoropropene selected from 1-chloro-3,3,3-trifluoropropene (CF.sub.3CH═CHCl, HCFO-1233rd) and 2-chloro-3,3,3-trifluoropropene (CF.sub.3CHCl═CH.sub.2, HCFO-1233xf).

14. A process according to claim 13 for preparing HCFO-1233zd, and wherein the hydrochlorofluoropropane is 1,1-dichloro-3,3,3-trifluoropropane (CF.sub.3CH.sub.2CHCl.sub.2, HCFC-243fa).

15. A process according to claim 13 for preparing HCFO-1233xf, and wherein the hydrochlorofluoropropane is 1,2-dichloro-3,3,3-trifluoropropane (CF.sub.3CHClCH.sub.2Cl, HCFC-243db).

16. A process according to claim 12 wherein the (hydro)(chloro)fluoropropene is a hydrofluoropropene selected from 1,3,3,3-tetrafluoropropene (CF.sub.3CH═CHF, HFO-1234ze) and 2,3,3,3-tetrafluoropropene (CF.sub.3CF═CH.sub.2, HFO-1234yf).

17. A process according to claim 16 for preparing HFO-1234yf, and wherein the hydrochlorofluoropropane is 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb).

18. A process according claim 16 for preparing HFO-1234ze, and wherein the hydrochlorofluoropropane is 3-chloro-1,1,1,3-tetrafluoropropane (HCFC-244fa).

19. A process according to claim 1, wherein the catalyst comprises a metal oxide and wherein the metal is selected from Li, Na, K, Ca, Mg, Cs, Sc, Al, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, La and Ce.

20. A process according to claim 19 wherein the metal oxide comprises one or more of Cr.sub.2O.sub.3, ZrO.sub.2, Li.sub.2O, Na2O, K.sub.2O, CaO, MgO or Cs.sub.2O.

21. A process according to claim 1, wherein the catalyst comprises a zinc/chromia catalyst.

22. A process according to claim 1, wherein the dehydrochlorination is carried out at a pressure of from about 0.1 to about 40 bara, preferably from about 1 to about 5 bara.

23. A process according to claim 1, wherein the dehydrochlorination is carried out at a temperature of from about 100° C. to about 600° C., preferably from about 180° C. to about 420° C.

24. A process according to claim 1, wherein the reagent stream comprising a hydrochlorofluoroalkane contacting the catalyst has a space velocity of from about 0.1 min.sup.−1 to about 10 min.sup.−1.

25. A process according to claim 1 wherein the process is continuous, and wherein the catalyst is periodically regenerated by one or more of regenerative oxidation, regenerative oxyfluorination, regenerative reduction or regenerative chlorination.

26. A process according to claim 25 wherein the catalyst is regenerated by (i) regenerative oxidation or (ii) regenerative oxyfluorination, and then (iii) regenerative chlorination.

27. A process according to claim 26 wherein the catalyst is regenerated regenerative oxychlorination.

28. (canceled)

Description

EXAMPLE

[0076] Sintered Ni pellets were produced by reducing NiF.sub.2 with H.sub.2. The catalyst was then loaded to a reactor and re-reduced in the reactor with H.sub.2 prior to starting 244bb flow over the pellets, conditions: [0077] Temp=400° C. [0078] 244bb flow rate=5 ml/min [0079] Reactor=glass lined stainless steel with glass wool and rod support [0080] 1.2 g sintered Ni pellets

[0081] Initially, conversion of 244bb was poor. The 244bb feed was switched off and after reducing the pellets with H.sub.2 for a second time. Conversion temporarily increased to about 14% but the reaction was not very selective to 1234yf and 244bb conversion reduced significantly in under 3 hours. The 244bb feed was switched off and the pellets were treated with HCl (50% in N.sub.2 for 2.5 hours at 400° C.), this increased 244bb conversion to 17% and the reaction was highly selective to 1234yf. Moreover, relatively high 244bb conversion and 1234yf selectivity were maintained for about 4 hours. The results are summarised below.

TABLE-US-00005 244bb 1234yf 1233xf Experiment Conversion Selectivity Selectivity Details/Events Time/h % % % After 1st reduction 0.5 2.56 69.92 20.20 3 days 0.13 49.20 42.34 After 2nd reduction 0.5 13.85 38.21 38.84 3.0 0.48 65.95 34.05 After HCl treatment 1 17.08 98.17 1.05 4 15.62 98.57 0.86

[0082] The results show the surprising beneficial effect on conversion and, particularly, selectivity, for 244bb dehydrochlorination to 1234yf by chlorinating the catalyst prior to contacting it with the 244bb reagent stream.

[0083] The invention is defined by the following claims.