CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. Provisional Application 60/956,188, filed Aug. 16, 2007.

BACKGROUND

1. Field of the Disclosure

The disclosure herein relates in general to processes for the catalytic isomerization between E and Z isomers of 1,2,3,3,3-pentafluoropropene (HFC-1225ye).

2. Description of Related Art

As a result of the Montreal Protocol phasing out ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), industry has been working for the past few decades to find replacement refrigerants. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants. The new hydrofluorocarbon refrigerants, HFC-134a being the most widely used at this time, have zero ozone depletion potential and thus are not affected by the current regulatory phase out as a result of the Montreal Protocol. The production of other hydrofluorocarbons for use in applications such as solvents, blowing agents, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishants and power cycle working fluids has also been the subject of considerable interest.

There is also considerable interest in developing new refrigerants with reduced global warming potential for the mobile air-conditioning market.

HFC-1225ye, having zero ozone depletion and a low global warming potential, has been identified as a potential refrigerant. HFC-1225ye can also find use in other applications such as solvents, cleaning agents, foam expansion agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing agents, sterilants and power cycle working fluids. HFC-1225ye may also be used to make polymers. HFC-1225ye may exist as one of two configurational isomers, E or Z, which boil at different temperatures. Depending on the applications, HFC-1225ye may be preferably used as the Z-isomer or the E-isomer or a mixture thereof. It is known that Z-HFC-1225ye is thermodynamically more stable than E-HFC-1225ye.

The liquid phase SbF₅catalyzed isomerization of E-HFC-1225ye to Z-HFC-1225ye has been described by Burton et al. in Journal of Fluorine Chemistry, 44, 167-174 (1989). This article shows that the isomerization between E-HFC-1225ye and Z-HFC-1225ye is an equilibrium reaction.

There is a need for new catalytic isomerization processes for the isomerization between E-HFC-1225ye and Z-HFC-1225ye.

SUMMARY

Applicants have found that the Z/E ratio of 1,2,3,3,3-pentafluoropropene can be increased by decreasing the temperature of the HFC-1225ye in the vapor phase in presence of aluminum catalysts, or that the Z/E ratio can be decreased by increasing the temperature of the HFC-1225ye in the vapor phase in the presence of aluminum catalysts.

Therefore, in accordance with the present invention, a process has been provided to increase the Z/E ratio of 1,2,3,3,3-pentafluoropropene. The process comprises: contacting a starting material comprising 1,2,3,3,3-pentafluoropropene in the vapor phase with an aluminum catalyst selected from the group consisting of fluorided alumina and high surface area amorphous aluminum fluoride to obtain a final product comprising 1,2,3,3,3-pentafluoropropene, wherein the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in the final product is increased relative to the Z/E ratio of 1,2,3,3,3-pentafluoropropene in said starting material.

Further in accordance with the present invention, a process has also been provided to decrease the Z/E ratio of 1,2,3,3,3-pentafluoropropene. The process comprises: contacting a starting material comprising 1,2,3,3,3-pentafluoropropene in the vapor phase with an aluminum catalyst to obtain a final product comprising 1,2,3,3,3-pentafluoropropene, wherein the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in the final product is decreased relative to the Z/E ratio of 1,2,3,3,3-pentafluoropropene in said starting material.

In either process, the ratio of isomers will depend on the temperature at which the starting material is allowed to equilibrate. Thus, by varying this temperature in the presence of an aluminum catalyst, applicants have found that the Z/E ratio can be increased or decreased.

The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as defined in the appended claims.

DETAILED DESCRIPTION

Before addressing details of embodiments described below, some terms are defined or clarified.

1,2,3,3,3-pentafluoropropene (CF3CFâ• CHF), also referred to as HFC-1225ye, may exist as one of two configurational isomers, E or Z. HFC-1225ye (with no isomer designation) as used herein refers to either of the isomers, E-1225ye (CAS reg no. 5595-10-8) or Z-1225ye (CAS reg. no. 5528-43-8), as well as any combinations or mixtures of such isomers. HFC-1225ye may be prepared by methods known in the art, such as those described in U.S. Pat. Nos. 5,396,000, 5,679,875, 6,031,141, and 6,369,284.

The term â€œisomerization processâ€ is intended to mean any process by which the Z/E ratio of HFC-1225ye is changed, either increased or decreased.

The term â€œZ/E ratioâ€ is intended to mean the molar ratio of Z isomer to E isomer of an olefin. For example, the term â€œZ/E ratio of HFC-1225yeâ€ is intended to mean the molar ratio of Z-1225ye to E-1225ye.

The term â€œan elevated temperatureâ€ is intended to mean a temperature higher than room temperature.

As used herein, the terms â€œcomprises,â€ â€œcomprising,â€ â€œincludes,â€ â€œincluding,â€ â€œhas,â€ â€œhavingâ€ or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, â€œorâ€ refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, use of â€œaâ€ or â€œanâ€ are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety, unless a particular passage is cited. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

The present disclosure provides a process for increasing the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in a final product relative to the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in a starting material. The process comprises contacting the starting material comprising 1,2,3,3,3-pentafluoropropene in the vapor phase with an aluminum catalyst to obtain a final product comprising 1,2,3,3,3-pentafluoropropene. The result of this process is that the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in the final product is increased relative to the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in said starting material.

In this process, the HFC-1225ye in the starting material is either E-HFC-1225ye or a mixture of E-HFC-1225ye and Z-HFC-1225ye. The HFC-1225ye in the starting material has a lower Z/E ratio than the HFC-1225ye in the final product.

In one embodiment of this process, the Z/E ratio of 1,2,3,3,3-pentafluoropropene in the final product is at least 10. In another embodiment, the Z/E ratio of 1,2,3,3,3-pentafluoropropene in said final product is at least 20. In another embodiment, the Z/E ratio of 1,2,3,3,3-pentafluoropropene in the final product is at least 40.

In one embodiment of the process for increasing the Z/E ratio of 1,2,3,3,3-pentafluoropropene, the contacting is conducted at a temperature of from about âˆ’20Â° C. to about 150Â° C. In another embodiment, the contacting is conducted at a temperature of from about âˆ’10Â° C. to about 100Â° C. In another embodiment, the contacting is conducted at a temperature of from about 0Â° C. to about 50Â° C. In another embodiment, the contacting is conducted at about ambient, i.e., room temperature.

The present disclosure also provides a process for decreasing the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in a final product relative to the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in a starting material. The process comprises contacting the starting material comprising 1,2,3,3,3-pentafluoropropene in the vapor phase with an aluminum catalyst to obtain a final product comprising 1,2,3,3,3-pentafluoropropene. The result of the process is that the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in the final product is decreased relative to the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in said starting material.

In one embodiment of this process, the HFC-1225ye in the starting material is either Z-HFC-1225ye or a mixture of E-HFC-1225ye and Z-HFC-1225ye. The HFC-1225ye in the starting material has a higher Z/E ratio than the HFC-1225ye in the product.

In one embodiment of this process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is decreased, the contacting is conducted at an elevated temperature. In particular, the contacting is conducted at a temperature of from about 300Â° C. to about 450Â° C.

In either process where the Z/E ratio of 1225ye is increased or decreased, the catalyst is an aluminum catalyst which can be used in vapor phase reactions. In either process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is increased or decreased, the process occurs in the vapor phase, i.e., the 1,2,3,3,3-pentafluoropropene is in the vapor phase. The catalyst may be selected from the group consisting of high surface area amorphous aluminum fluoride and fluorided alumina. When the catalyst is fluorided alumina, it may be prepared by treatment of aluminum oxide (also known as alumina or Al₂O₃) with HF at elevated temperature (as described in Example 1). A high surface area amorphous aluminum fluoride may be prepared as described in US 2004/0052649 A1.

In either embodiment of the isomerization process, where the Z/E ratio is either increased or decreased, the Z/E ratio of the 1,2,3,3,3-pentafluoropropene in said product is at least 10. In another embodiment where the Z/E ratio is either increased or decreased, the Z/E ratio of 1,2,3,3,3-pentafluoropropene in said product is at least 20. In another embodiment where the Z/E ratio is either increased or decreased, the Z/E ratio of 1,2,3,3,3-pentafluoropropene in said product is at least 40.

In either process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is increased or decreased, the contact time for 1,2,3,3,3-pentafluoropropene with the catalyst is not critical. In one embodiment, the contact time may range from about 0.01 seconds to 100 seconds. In another embodiment, the contact time may range from about 5 seconds to about 60 seconds.

In either process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is increased or decreased, the pressure employed in the isomerization process can be subatmospheric, atmospheric or superatmospheric. In one embodiment, the isomerization pressure is near atmospheric. In another embodiment, the isomerization pressure is autogenous.

In certain embodiments of either process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is increased or decreased, the contacting may occur in any suitable vapor phase reaction vessel. In one particular embodiment, the reaction vessel is a tube packed with catalyst through which the gaseous HFC-1225ye may flow.

In certain embodiments of either process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is increased or decreased, the reaction vessel for the isomerization process and its associated feed lines, effluent lines, and associated units used in applying the disclosed processes should be constructed of materials resistant to corrosion. Typical materials of construction include stainless steels, in particular of the austenitic type, the well-known high nickel alloys, such as nickel-copper alloys commercially available under the trademark MonelÂ®, nickel-based alloys commercially available under the trademark HastelloyÂ® and nickel-chromium alloys commercially available under the trademark InconelÂ®, and copper-clad steel.

In either process where the Z/E ratio of the 1,2,3,3,3-pentafluoropropene is increased or decreased, the ratio of isomers will depend on the temperature at which the starting material is allowed to equilibrate. For example, if the E-isomer is desired, and the starting material is the Z-isomer, allowing the starting material to equilibrate at about 350Â° C. will produce about 10% E-isomer. In an embodiment wherein the starting material is 10% E-isomer and 90% Z-isomer (which is the case when the two isomers are made at about 350Â° C.) the Z-isomer can be increased to 99% by interconverting them at 25Â° C. Therefore, the equilibrium composition may be approached from either side.

EXAMPLES

The concepts described herein will be further described in the following Examples, which do not limit the scope of the invention described in the claims.

Example 1Isomerization of E-1225ye to Z-1225ye With Fluorided Alumina Catalyst

An Inconelâ„¢ tube (â… inch OD) was filled with 13 cc (8.01 gm) of Al₂O₃extrudate ground to 12/20 mesh. The temperature of the catalyst bed was raised to 200Â° C. for 20 minutes under a flow of nitrogen of 38 sccm (6.3Ã—10^âˆ’7m³/sec). The temperature was then raised to 325Â° C. for 13 minutes, to 400Â° C. for 27 minutes and to 300Â° C. for 80 minutes while maintaining the same nitrogen flow. The flow of nitrogen was then reduced to 26 sccm (4.3Ã—10^âˆ’7m³/sec) and the flow of HF added at 9 sccm (1.5Ã—10^âˆ’7m³/sec) for 46 minutes. The temperature was raised to 325Â° C. for 80 minutes, to 350Â° C. for 80 minutes, to 375Â° C. for 120 minutes, to 400Â° C. for 40 minutes, and to 425Â° C. for 53 minutes, all at the same flows. The nitrogen flow was reduced to 19 sccm (3.2Ã—10^âˆ’7m³/sec) and the HF increased to 15 sccm (2.5Ã—10^âˆ’7m³/sec) while maintaining the temperature at 425Â° C. for 27 minutes. The nitrogen flow was reduced to 11 sccm (1.8Ã—10^âˆ’7m³/sec) and the HF increased to 21 sccm (3.5Ã—10^âˆ’7m³/sec) while maintaining the temperature at 425Â° C. for 27 minutes. The nitrogen flow was reduced to 4 sccm (6.7Ã—10^âˆ’7m³/sec) and the HF increased to 27 sccm (4.5Ã—10^âˆ’7m³/sec) while maintaining the temperature at 425Â° C. for 27 minutes. The nitrogen flow was ceased and the HF flow increased to 30 sccm (5.0Ã—10^âˆ’7m³/sec) while maintaining the temperature at 425Â° C. for 161 minutes. The temperature was then cooled to 30Â° C. while under a nitrogen flow of 20 sccm (3.3Ã—10^âˆ’7m³/sec).

A mixture of E- and Z-1225ye containing 92.3% Z-1225ye, 4.2% E-1225ye and 2.6% unknowns was passed through the reactor at 30Â° C. at a flow rate of 20 sccm (3.3Ã—10^âˆ’7m³/sec) resulting in a contact time of 20 seconds. The effluent of the reactor was analyzed by GCMS and was found to contain 97.4% Z-1225ye, no detectable E isomer, and 2.6% unknowns. While maintaining a temperature in the reactor of 30Â° C., the flow of 1225ye was increased to 34 sccm (5.7Ã—10^âˆ’7m³/sec) resulting in a contact time of 22 seconds and the reactor effluent was found to be 97.4% Z-1225ye, no detectable E isomer and 2.6% unknowns.

Example 2 Isomerization of E-1225ye to Z-1225ye with Fluorided Alumina Catalyst

The catalyst was made from aluminum isopropoxide as described in WO 2004/060806 A1 and 15 cc were put into a flow reactor. A mixture of E- and Z-1225ye containing 45% Z-1225ye, 5% E-1225ye and 50% argon was passed through the reactor at 30Â° C. at a flow rate of 19 sccm (3.2Ã—10^âˆ’7m³/sec) resulting in a contact time of 47 seconds. The effluent of the reactor was analyzed by ¹⁹F NMR and was found to contain 98.5% Z-1225ye and 1.5% E isomer.

Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed.

In the foregoing specification, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.

It is to be appreciated that certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges include each and every value within that range.