One-step process for hexafluoro-2-butene

This application claims domestic priority from commonly owned, U.S. Provisional Patent Application Ser. No. 62/028,851, filed 25 Jul. 2014, the disclosure of which is hereby incorporated herein by reference.

Hexafluoro-2-butene (CF 3 CH═CHCF 3 , HFO-1336) has zero ozone depletion potential (ODP) and low global warming potential (GWP) and is being used as a foam blowing agent, refrigerant and solvent. Reported methods for making HFO-1336 require multiple steps or give poor conversion or need raw materials that are not easily available. See for example, U.S. Pat. Nos. 8,426,655 and 8,530,709, and the references cited therein, the disclosures of which are hereby incorporated herein by reference. Thus, there is a continuing need to develop cost effective manufacturing processes which will circumvent the above issues regarding the production of HFO-1336.

Disclosed is a one step process for making of 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336). This includes both trans and cis (E and Z) isomers of HFO 1336.

In one embodiment, the invention is directed to a process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) from 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) comprising reacting HCFC-1233xf with a selected catalyst, at a sufficient temperature to afford HFO-1336.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) is conducted in the vapor phase.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) is conducted in a continuous manner.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) makes use of a catalyst which comprises Fe 2 O 3 /NiO.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) is conducted with the catalyst impregnated on carbon.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) is conducted wherein the carbon support for the catalyst is activated carbon.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) is conducted wherein the activated carbon catalyst support is granular with a mesh size of 4-14.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) is conducted wherein the activated carbon support for the catalyst is pelletized.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) includes a reaction temperature that ranges from 600° to 650° C.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) includes formation of both the trans and cis isomers of HFO-1336.

In certain embodiments of the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336), the predominant isomer of HFO-1336 formed is the trans isomer.

In certain embodiments of the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336), the ratio of the trans isomer to the cis isomer of HFO-1336 is about 88:12.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) includes a step wherein the trans isomer is converted into the cis isomer by reaction with an isomerization catalyst.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) makes use of an isomerization catalyst which comprises a fluorinated chromia catalyst.

In certain embodiments, the process for making 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) further comprises a step of using 1,1,1,4,4,4 hexafluoro-2-butene as a foam blowing agent, a refrigerant, or a solvent.

More particularly, the present invention provides a process for continuously preparing hexafluoro-2-butene (HFO-1336) from 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) using a specific type of catalyst, preferably a catalyst comprising Fe 2 O 3 /NiO (in about 98 wt % to 2 wt % ratio). A preferred ratio of Fe 2 O 3 to NiO is from about 95-99 wt % to 5-1 wt % impregnated on carbon; and a reaction temperature of from 600° to 650° C. Other catalysts such as oxides of Ru, Pd or Pt, having properties similar to the preferred Fe 2 O 3 /NiO impregnated on carbon may also be useful in this process.

When other suitable catalysts are employed (for example, RuO 2 , RuO 4 OsO 4 in combination with oxides of Pd or Pt (for example, PdO 2 , PtO 2 ), adjustments to the preferred 600° to 650° C. reaction temperature may be required. The skilled artisan will be able to adjust the reaction conditions using ordinary skill in this art.

It should be appreciated by those persons having ordinary skill in the art(s) to which the present invention relates that any of the features described herein in respect of any particular aspect and/or embodiment of the present invention can be combined with one or more of any of the other features of any other aspects and/or embodiments of the present invention described herein, with modifications as appropriate to ensure compatibility of the combinations. Such combinations are considered to be part of the present invention contemplated by this disclosure.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.

The present invention describes a process for producing HFO-1336 from 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf, CF 3 CCl═CH 2 ). HCFC-1233xf is available from many commercial sources or can be obtained by art recognized procedures.

When HCFC-1233xf in the vapor phase is passed over Fe 2 O 3 /NiO (in about 98 wt % to 2 wt % ratio) impregnated on carbon at from 600° to 650° C., the major product identified in the products exit stream is HFO-1336 with CF 3 CH═ClCF 3 as the minor product. Both the trans and cis isomers of HFO-1336 are formed and the predominant isomer under these conditions was trans (trans/cis=88/12). The trans isomer can be converted into the cis isomer by use of an appropriate isomerization catalyst, such as those described in U.S. Pat. No. 8,426,655.

Under identical vapor phase reaction conditions using other catalysts, (for example, activated carbon pellets) HCFC-1233xf yielded trifluoropropyne as the major product via dehydrochlorination, with only a trace amount (1-2%) of HFO-1336 being formed.

Thus, by selection of appropriate catalyst, one can get either CF 3 CH═CHCF 3 (HFO-1336) or trifluoropropyne as the major component in the reaction products, as depicted in Scheme 1, below.

Although one can rationalize the formation of trifluoropropyne with Cat. A by elimination of HCl from 1233xf, the formation of HFO-1336 with Cat. B as the major product was completely unexpected. Currently, the optimization of the reaction conditions for the above routes to make 1336 or trifluoropropyne has not yet been completed.

The process described here can be carried out in a tubular reactor made of stainless steel or inconel packed with appropriate catalyst with substrate HCFC in vapor phase at elevated temperature. Heating was accomplished by placing the tube reactor in a furnace; generally the portion of the tube containing the catalyst was heated. The reaction/process can be run in a continuous manner. Contact time can vary depending upon the size of the reactor, but includes from about 10 sec to 120 sec, preferably from about 20 sec to 60 sec, and most preferably from about 30 sec to 40 sec.

The preferred catalyst used herein was made by impregnating Fe 2 O 3 and NiO on activated granular carbon (4-14 mesh). Typically, the catalyst was prepared by mixing an aqueous suspension of Fe 2 O 3 /NiO with 4-14 mesh activated granular carbon. After mixing well, water from the catalyst was removed under reduced pressure.

Isomerization of the trans 1,1,1,4,4,4-hexafluoro-2-butene to its cis isomer can be accomplished using isomerization catalysts like fluorinated chromia as described in U.S. Pat. No. 8,426,655. The isomers can be separated by distillation since boiling points are 9° C. and 33° C. for the trans and cis isomer, respectively.

The following examples are merely illustrative of the present invention. They are not to be construed as limitations thereof.