WO2009064022A2

WO2009064022A2 - Process for producing ( z) - and (e) -1, 1, 1, 2, 3-pentafluoropropene

Info

Publication number: WO2009064022A2
Application number: PCT/JP2008/071063
Authority: WO
Inventors: Kazuhiro Takahashi
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2007-11-16
Filing date: 2008-11-13
Publication date: 2009-05-22
Anticipated expiration: 2010-05-16
Also published as: WO2009064022A3

Abstract

A mixture comprising a Z-isomer and an E-isomer of 1,1,1,2,3-pentafluoropropene (HFC-1225ye) is distilled to separate it into a first stream composed substantially of either one of the Z-isomer and the E-isomer, and a second stream comprising the Z-isomer and the E-isomer; and the second stream is subjected to an isomerization reaction to obtain a third stream having an increased ratio of the one isomer therein from that in the second stream; and then the third stream is reused as at least a part of the above mixture as a raw material. The order of the isomerization reaction and the distillation may be reversed. Thus, either one of the Z-isomer and E-isomer can be efficiently produced.

Description

DESCRIPTION

PROCESS FOR PRODUCING PENTAFLUOROPROPENE

Technical Field

The present invention relates to a process for producing either one isomer of (Z) -I₁1, 1, 2, 3- pentafluoropropene and (E) -1, 1., 1, 2, 3-pentafluoropropene .

Background Art

CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons) were conventionally used as refrigerants. Since these substances can cause depletion of the ozone layer, HFCs (hydrofluorocarbons) , particularly HFC-125 (pentafluoroethane) and HFC-32 (difluoromethane) have widely been used as substitute refrigerants. However, HFC-125 and HFC-32 are potent global warming substances and cause concern of diffusion of these substances to adversely affect the global warming. Although these substances are recovered from disused apparatuses for the purpose of preventing their diffusion and consequently the global warming, all of these substances cannot be recovered. Also, diffusion caused by leaking or the like cannot be neglected. Although CO₂ and hydrocarbon compounds are studied to be used as other substitute refrigerants, there are a lot of problems in efficiency and safety.

Recently, intense interest has been shown towards, as a substitute refrigerant being able to solve these problems, 1, 1, 1,2,3-pentafluoropropene (CF₃CF=CHF, hereinafter also referred to as "HFC-1225ye") , which is a HFC of an olefin having a low warming coefficient. HFC-1225ye has two isomers, i.e. (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E)- 1, 1, 1,2, 3-pentafluoropropene (hereinafter also referred to as " (Z)-HFC-1225ye" and " (E) -HFC-1225ye", respectively), and these isomers have a boiling point of -19.5°C and - 15.3°C, respectively. Due to such difference in the boiling point, these two isomers have different applications as refrigerants and different performances.

HFC-1225ye can be obtained by a reaction of eliminating HF from 1, 1, 1, 2, 3, 3-hexafluoropropane (hereinafter also referred to as ^λΛHFC-236ea") (for example, see Patent Documents 1 and 2 listed below) . What is resulted from this reaction is a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye . These isomers can be separated from each other by subjecting the mixture to distillation. However, when only one isomer of them is desired, the separated other isomer is undesired and the undesired isomer is forced to be wasted, and thus only one isomer of them cannot be efficiently obtained. A process of selectively producing one isomer by a certain reaction has also been proposed (see Non-Patent Documents 1 and 2 listed below) . However, this process has a problem that it cannot be easily performed since, for example, the reaction must be carried out at a very low temperature of -78⁰C and requires using SbFs which is not easy to handle.

Patent Document 1: WO 93/25510

Patent Document 2: U.S. Patent Application Publication No. 2007/0179324 Non-Patent Document 1: Journal of Fluorine Chemistry, vol. 23 (1983) pp.339-357

Non-Patent Document 2: Journal of Fluorine Chemistry, vol. 44 (1989) pp.167-174

Disclosure of Invention

As described above, although various processes of obtaining a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye are known in the production process of HFC-1225ye, a process of efficiently obtaining only either one isomer of them is not proposed. An object of the present invention is to provide a process capable of producing either one isomer of the two isomers for HFC-1225ye ( (Z) -HFC-1225ye and (E)-HFC-1225ye) more efficiently.

In a first aspect of the present invention, there is provided a process for producing either one isomer of (Z)- 1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3- pentafluoropropene, which comprises the steps of: a) subjecting a mixture comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene to distillation to separate it into a first stream comprising either one isomer of (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene and having an increased ratio of the one isomer therein from that in the mixture, and a second stream comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene; b) subjecting the second stream to an isomerization reaction to obtain a third stream comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene and having an increased ratio of the one isomer therein from that in the second stream; and c) reusing the third stream as at least a part of the mixture of the step a) , whereby the one isomer is obtained in the first stream.

According to the present invention, either one isomer can be efficiently produced from a mixture comprising two isomers for HFC-1225ye by appropriately combining distillation and an isomerization reaction.

Regarding the order of conducting the distillation and the isomerization reaction, the distillation may be conducted followed by the isomerization reaction as described above, and vice versa.

Thus, in a second aspect of the present invention, there is provided a process for producing either one isomer of (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3- pentafluoropropene, which comprises the steps of: p) subjecting a mixture comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene to an isomerization reaction to obtain a fourth stream comprising (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E)- 1, 1, 1, 2, 3-pentafluoropropene and having an increased ratio of either one isomer therein from that in the mixture; q) subjecting the fourth stream to distillation to separate it into a fifth stream comprising the one isomer and having an increased ratio of the one isomer therein from that in the fourth stream, and a sixth stream comprising (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E)- 1,1,1,2, 3-pentafluoropropene; and r) reusing the sixth stream as at least a part of the mixture of the step p) , whereby the one isomer is obtained in the fifth stream.

The process of the present invention can attain a similar effect even when the distillation and the isomerization reaction are conducted in any order.

In the present invention, the "ratio" of the one isomer in a stream or mixture means mol% of the one isomer on the basis of both isomers in the stream or mixture.

Furthermore, the present inventor has intensively studied to obtain unique finding that a dehydrofluorination reaction from 1, 1, 1, 2, 3, 3-hexafluoropropane can be allowed to proceed simultaneously with the isomerization reaction.

Therefore, in the process of the present invention, the mixture comprising (Z) -1, 1, 1, 2, 3-pentafluoropropene and

(E) -1, 1, 1, 2, 3-pentafluoropropene may further contain

1, 1, 1, 2, 3, 3-hexafluoropropane (hereinafter also referred to as "HFC-236ea") .

More specifically, with respect to the first aspect of the present invention described above, the second stream may be subjected together with 1,1,1,2,3,3- hexafluoropropane to the isomerization reaction of the step b) , and hydrogen fluoride may be eliminated from 1, 1, 1, 2, 3, 3-hexafluoropropane under conditions for the isomerization reaction to produce (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene . The reaction mixture resulted from the step b) may contain unreacted 1, 1, 1, 2, 3, 3-hexafluoropropane in addition to (Z)- 1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3- pentafluoropropene. The unreacted 1,1,1,2,3,3- hexafluoropropane may be appropriately separated by distillation and returned to the step b) , if necessary. With respect to the second aspect of the present invention described above, the mixture to be used in the step p) may further comprise 1, 1, 1, 2, 3, 3-hexafluoropropane, and hydrogen fluoride may be eliminated from 1,1,1,2,3,3- hexafluoropropane under conditions for the isomerization reaction to produce (Z) -1, 1, 1, 2, 3-pentafluoropropene and

(E) -1, 1, 1, 2, 3-pentafluoropropene. The reaction mixture resulted from the step p) may contain unreacted

1, 1, 1, 2, 3, 3-hexafluoropropane in addition to Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene. The unreacted 1, 1, 1, 2, 3, 3-hexafluoropropane may be appropriately separated by distillation and returned to the step p) , if necessary.

In one manner of the present invention, the reaction may be carried out in the presence of a metal oxide catalyst. The reaction may be carried out, for example, at a temperature of about 100⁰C to 400⁰C.

According to the present invention, either one of two isomers for 1, 1, 1, 2, 3-pentafluoropropene ( (Z) -HFC-1225ye and (E) -HFC-1225ye) can be produced more efficiently.

Brief Description of Drawings

Fig. 1 is a schematic diagram for explaining a process for producing (Z) -1, 1, 1, 2, 3-pentafluoropropene in one embodiment of the present invention. Fig. 2 is a schematic diagram for explaining a process for producing (E) -1, 1, 1, 2, 3-pentafluoropropene in another embodiment of the present invention.

Fig. 3 is a schematic diagram for explaining a process for producing (Z) -1, 1, 1, 2, 3-pentafluoropropene in yet another embodiment of the present invention.

Fig. 4 is a schematic diagram for explaining a process for producing (E) -1, 1, 1, 2, 3-pentafluoropropene in yet another embodiment of the present invention.

Following numerals denote the following elements: 1, 3, 5, 7, 9... line; T ...distillation column (or tower); R... reactor; F... feed (mixture); Sl... first stream; S2... second stream; S3... third stream; S4... fourth stream; S5... fifth stream; and S6... sixth stream.

Best Mode for Carrying Out the Invention

Some embodiments of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) The present embodiment relates to a manner of a process for producing (Z) -HFC-1225ye in which distillation is conducted and then an isomerization reaction is conducted as shown in Fig. 1.

First, a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye to be used as a raw material in the present embodiment is prepared. The mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye may be obtained, for example, by an elimination reaction of hydrogen fluoride (HF) from HFC-236ea (see Patent Documents 1 and 2 listed above) , although the mixture can be obtained according to an any appropriate method.

Referring to Fig. 1, the previously prepared mixture of (Z)-HFC-1225ye and (E) -HFC-1225ye is supplied as the raw material from the outside to a line 1, and a third stream

(S3) extracted from a reactor R described below through a line 7 is recycled to the line 1. The third stream (S3) is also composed of the mixture of (Z) -HFC-1225ye and (E)-HFC- 1225ye. Thus, the mixture of (Z) -HFC-1225ye and (E)-HFC- 1225ye is fed as a feed (F) to a middle of a distillation column T through the line 1. The mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye fed as the feed (F) is subjected to distillation in the distillation column T, thereby separated into a first stream (Sl) comprising (Z) -HFC-1225ye and having an increased ratio of (Z) -HFC-1225ye therein from that in the mixture of the feed (F), and a second stream (S2) comprising (Z) -HFC-1225ye and (E) -HFC-1225ye . It is preferred that the first stream (Sl) is substantially composed of the one isomer which is desired ( (Z) -HFC-1225ye in the present embodiment) . The ratio of the one isomer in the first stream (Sl) can be, for example, 90 mol% or more, and preferably 99 mol% or more. However, the present invention is not limited thereto, and the first stream (Sl) can also contain other component (s) other than the desired one component, such as the other components ((E)-HFC- 1225ye) in the present embodiment) .

The temperature, pressure and number of plates for such separation by distillation can be appropriately selected. (Z) -HFC-1225ye and (E) -HFC-1225ye have a normal boiling point (a boiling point under a pressure of 0.1013 MPa (1 atm) ) of -19.5°C and -15.3°C, respectively. In usual distillation operation conditions, since (Z)-HFC- 1225ye has a lower boiling point than that of (E)-HFC- 1225ye, the first stream (Sl) is taken out from the column top through a line 3, while the second stream (S2) is taken out from the column bottom through a line 5.

The resultant second stream (S2) is transferred to the reactor R as it is, where it is subjected to an isomerization reaction. The isomerization reaction between (Z) -HFC-1225ye and (E) -HFC-1225ye proceeds by exposure to a high temperature in the presence of a catalyst. As the catalyst, for example, at least one selected from the group consisting of metal-supported catalysts, metal oxides

(including metal oxyfluorides) and metal fluorides can be used, mainly. For example, the catalyst may be platinum- supported zirconium oxide, alumina oxide, molybdenum oxide, chromium oxyfluoride, aluminum oxyfluoride, niobium fluoride, magnesium fluoride, tantalum fluoride, or antimony fluoride. The catalyst is preferably a metal oxide catalyst, and particularly preferably a metal oxyfluoride catalyst. The metal oxyfluoride can be obtained by fluorinating a metal oxide. The reaction temperature may be usually within a range from 100⁰C to 600⁰C, and preferably a range from 100⁰C to 400⁰C.

The isomerization reaction between (Z) -HFC-1225ye and (E) -HFC-1225ye carried out by using the above-mentioned catalyst is an equilibrium reaction as shown in the following formula, and reaches to its equilibrium composition after an appropriate time, for example, after about 1 to 20 minutes, and preferably after about 1 to 5 minutes.

(Z)-HFC-1225ye (E) -HFC-1225ye

(Cis) (Trans)

This equilibrium composition varies depending on the reaction temperature. The equilibrium compositions (mol% of (Z)-HFC-1225ye and (E) -HFC-1225ye) obtained by carrying out the isomerization reaction at various reaction temperatures under a normal pressure (about 0.1 MPa) are shown in Table 1.

Table 1

Therefore, when a proper reaction temperature is selected, a ratio of the either one isomer which is desired can be increased by the isomerization reaction. In the present embodiment, since (Z) -HFC-1225ye is desired, the ratio of (Z) -HFC-1225ye can be increased by allowing the isomerization reaction to proceed at a relatively low temperature (for example, about 100⁰C to 300⁰C) .

The third stream (S3) taken out of the reactor R through the line 7 is composed of (Z) -HFC-1225ye and (E)- HFC-1225ye, and has an increased ratio of (Z) -HFC-1225ye therein from that in the second stream. In the present embodiment, a substantial reaction other than the isomerization reaction does not arise, and normally only the ratio between (Z) -HFC-1225ye and (E) -HFC-1225ye varies in the third stream (S3) .

The third stream (S3) thus obtained flows from the line 7 into the line 1, and is reused as at least a part of the feed (F) as described above. The amount of the mixture supplied to the line 1 from the outside is adjusted according to, for example, the amount of the third stream (S3) to be reused, and the supply from the outside may be stopped, if appropriate.

As described above, according to the present embodiment, (Z) -HFC-1225ye can be efficiently obtained in the first stream. The production process of the present embodiment is preferably conducted in a continuous process, and ideally operated so as to make the whole mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye used as the raw material into (Z)-HFC-1225ye to be obtained.

Various modifications of the present embodiment are possible. For example, while the mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye is used as the raw material in the present embodiment, HFC-236ea can be used in place of the mixture.

More specifically, in this modification, HFC-236ea is firstly supplied as the raw material from the outside to the reactor R through a line 9 (indicated by a dotted line) . In the reactor R under conditions for the isomerization reaction, a dehydrofluorination reaction of HFC-236ea arises to produce a mixture of (Z) -HFC-1225ye and (E)-HFC- 1225ye and the isomerization reaction concurrently arises and reaches to its equilibrium composition. The reaction mixture taken out of the reactor R through the line 7 contains unreacted HFC-236ea and produced HF in the reaction in addition to (Z) -HFC-1225ye and (E) -HFC-1225ye, and is preferably subjected to a deacidification treatment to remove HF (indicated by a dotted line) , and if necessary subjected to another distillation operation to remove HFC- 236ea, and results in the third stream (S3) . The third stream (S3) thus obtained flows from the line 7 into the line 1, and is fed to the distillation column T as a feed (F), and subjected similarly in Embodiment 1 to the distillation and the subsequent isomerization reaction (and dehydrofluorination reaction) . In this case, the second stream (S2) is subjected to the isomerization reaction in the reactor R together with HFC-236ea supplied through the line 9. When the unreacted HFC-236ea is removed by another distillation operation, the separated HFC-236ea may be supplied again to the reactor R as the raw material. When the unreacted HFC-236ea is not removed by another distillation operation, the third stream (S3) and the second stream (S2) contain HFC-236ea in addition to (Z)- HFC-1225ye and (E) -HFC-1225ye . The amount of HFC-236ea supplied to the line 9 from the outside is adjusted according to, for example, the amount of the third stream

(S3) to be reused, and the supply from the outside may be stopped, if appropriate. The production process of this modification is also preferably conducted in a continuous process.

(Embodiment 2)

The present embodiment relates to a manner of a process for producing (E) -HFC-1225ye in which distillation is conducted and then an isomerization reaction is conducted as shown in Fig. 2. Unless otherwise specified, descriptions for this embodiment is similar to Embodiment 1 described above.

In the present embodiment, referring to Fig. 2, a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye fed as a feed (F) is subjected to distillation in a distillation column T, thereby separated into a first stream (Sl) comprising (E)- HFC-1225ye and having an increased ratio of (E) -HFC-1225ye therein from that in the mixture of the feed (F) , and a second stream (S2) comprising (Z) -HFC-1225ye and (E)-HFC- 1225ye. The first stream (Sl) is taken out from the column bottom through a line 5, while the second stream (S2) is taken out from the column top through a line 3. It is preferred that the first stream (Sl) is substantially composed of the one isomer which is desired ( (E) -HFC-1225ye in the present embodiment) . The ratio of the one isomer in the first stream (Sl) can be, for example, 90 mol% or more, and preferably 99 mol% or more.

The resultant second stream (S2) is transferred to a reactor R, where it is subjected to an isomerization reaction. In the present embodiment, since (E) -HFC-1225ye is desired, a ratio of (E) -HFC-1225ye can be increased by allowing the isomerization reaction to proceed at a relatively high temperature (for example, about 300⁰C to 600⁰C, preferably about 300 to 400⁰C) .

A third stream (S3) taken out of the reactor R through a line 7 is composed of (Z) -HFC-1225ye and (E) -HFC-1225ye, and has an increased ratio of (E) -HFC-1225ye therein from that in the second stream. As described above, according to the present embodiment, (E) -HFC-1225ye can be efficiently obtained in the first stream. The production process of the present embodiment is also preferably conducted in a continuous process . Various modifications of the present embodiment are also possible. For example, while the mixture of (Z)-HFC- 1225ye and (E) -HFC-1225ye is used as the raw material in the present embodiment, HFC-236ea can be used in place of the mixture. This modification can be similar to that described in Embodiment 1. However, in this modification, when the unreacted HFC-236ea is not removed by another distillation operation, the first stream (Sl) obtained from the distillation contains HFC-236ea in addition to (E)-HFC- 1225ye, and thus it is optionally subjected to a further distillation operation or the like to separate it into (E)- HFC-1225ye and HFC-236ea. The separated HFC-236ea may be supplied again to the reactor R as the raw material. The production process of this modification of the present embodiment is also preferably conducted in a continuous process.

(Embodiment 3)

The present embodiment relates to a manner of a process for producing (Z) -HFC-1225ye in which an isomerization reaction is conducted and then distillation is conducted as shown in Fig. 3. Unless otherwise specified, descriptions for this embodiment is similar to Embodiment 1 described above.

In the present embodiment, referring to Fig. 3, a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye fed as a feed

(F) is subjected to an isomerization reaction in a reactor

R. In the present embodiment, since (Z) -HFC-1225ye is desired, a ratio of (Z) -HFC-1225ye can be increased by allowing the isomerization reaction to proceed at a relatively low temperature (for example, about 100⁰C to 300⁰ C ) .

A fourth stream (S4) taken out of the reactor R through a line 7 is composed of (Z) -HFC-1225ye and (E)-HFC- 1225ye, and has an increased ratio of (Z) -HFC-1225ye therein from that in the mixture of the feed (F) .

The resultant fourth stream (S4) is subjected to distillation in a distillation column T, thereby separated into a fifth stream (S5) comprising (Z) -HFC-1225ye and having an increased ratio of (Z) -HFC-1225ye therein from that in the fourth stream, and a sixth stream (S6) comprising (Z) -HFC-1225ye and (E) -HFC-1225ye. The fifth stream (S5) is taken out from the column top through a line 3, while the sixth stream (S6) is taken out from the column bottom through a line 5. It is preferred that the fifth stream (S5) is substantially composed of the one isomer which is desired ( (Z) -HFC-1225ye in the present embodiment) . The ratio of the one isomer in the fifth stream (S5) can be, for example, 90 mol% or more, and preferably 99 mol% or more . The sixth stream (S6) thus obtained flows from the line 5 into a line 1, and is reused as at least a part of the feed (F) . The amount of the mixture supplied to the line 1 from the outside is adjusted according to, for example, the amount of the sixth stream (S6) to be reused, and the supply from the outside may be stopped, if appropriate .

As described above, according to the present embodiment, (Z) -HFC-1225ye can be efficiently obtained in the fifth stream. The production process of the present 5. embodiment is also preferably conducted in a continuous process, and ideally operated so as to make the whole mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye used as the raw material into (Z) -HFC-1225ye to be obtained.

Various modifications of the present embodiment are0 also possible. For example, while the mixture of (Z)-HFC- 1225ye and (E) -HFC-1225ye is used as the raw material in the present embodiment, HFC-236ea can be used in place of the mixture .

More specifically, in this modification, HFC-236ea is5 firstly supplied as the raw material from the outside to the line 1, and the sixth stream (S6) taken out of the distillation column T through the line 5 is recycled to the line 1. Thus, a mixture of (Z) -HFC-1225ye, (E) -HFC-1225ye and HFC-236ea is fed as the feed (F) to the reactor R0 through the line 1. In the reactor R under conditions for the isomerization reaction, a dehydrofluorination reaction of HFC-236ea arises to produce a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye and the isomerization reaction concurrently arises and reaches to its equilibrium5 composition. The reaction mixture taken out of the reactor R through the line 7 contains unreacted HFC-236ea and produced HF in the reaction in addition to (Z) -HFC-1225ye and (E) -HFC-1225ye, and is preferably subjected to a deacidification treatment to remove HF (indicated by a dotted line), and results in the fourth stream (S4) . The fourth stream (S4) thus obtained is transferred to the distillation column T through the line 7, and subjected to distillation similarly to Embodiment 3. However, in this modification, the sixth stream (S6) obtained from the distillation contains HFC-236ea in addition to (Z)-HFC- 1225ye and (E) -HFC-1225ye . The amount of HFC-236ea supplied to the line 1 from the outside is adjusted according to, for example, the amount of the sixth stream (S6) to be reused, and the supply from the outside may be stopped, if appropriate. The production process of this modification of the present embodiment is also preferably conducted in a continuous process.

(Embodiment 4) The present embodiment relates to a manner of a process for producing (E) -HFC-1225ye in which an isomerization reaction is conducted and then distillation is conducted as shown in Fig. 4. Unless otherwise specified, descriptions for this embodiment is similar to Embodiment 3 described above. Referring to Fig. 4, a mixture of (Z) -HFC-1225ye and (E) -HFC-1225ye fed as a feed (F) is subjected to an isomerization reaction in a reactor R. In the present embodiment, since (E) -HFC-1225ye is desired, the ratio of (E) -HFC-1225ye can be increased by allowing the isomerization reaction to proceed at a relatively high temperature (for example, about 300⁰C to 600⁰C, preferably about 300 to 400°C) .

A fourth stream (S4) taken out of the reactor R through a line 7 is composed of (Z) -HFC-1225ye and (E)-HFC- 1225ye, and has an increased ratio of (E) -HFC-1225ye therein from that in the mixture of the feed (F) .

The fourth stream obtained from the reactor R is subjected to distillation in a distillation column T, thereby separated into a fifth stream (S5) comprising (E)- HFC-1225ye and having an increased ratio of (E) -HFC-1225ye therein from that in the fourth stream, and a sixth stream (S6) comprising (Z) -HFC-1225ye and (E) -HFC-1225ye . The fifth stream (S5) is taken out from the column bottom through a line 5, while the sixth stream (S6) is taken out from the column top through a line 3. It is preferred that the fifth stream (S5) is substantially composed of the one isomer which is desired ( (E) -HFC-1225ye in the present embodiment) . The ratio of the one isomer in the fifth stream (S5) can be, for example, 90 mol% or more, and preferably 99 mol% or more.

As described above, according to the present embodiment, (E) -HFC-1225ye can be efficiently obtained in the fifth stream. The production process of the present embodiment is also preferably conducted in a continuous process .

Various modifications of the present embodiment are also possible. For example, while the mixture of (Z)-HFC- 1225ye and (E) -HFC-1225ye is used as the raw material in the present embodiment, HFC-236ea can be used in place of the mixture. This modification can be similar to that described in Embodiment 3. However, in this modification, the fifth stream (S5) obtained from the distillation contains HFC-236ea in addition to (E) -HFC-1225ye, and thus it is optionally subjected to a further distillation operation or the like to separate it into (E) -HFC-1225ye and HFC-236ea. The separated HFC-236ea may be supplied again to the reactor R as the raw material. The production process of this modification of the present embodiment is also preferably conducted in a continuous process.

[Example 1]

The process of the present invention was carried out in accordance with Embodiment 1 described with reference to Fig. 1. As the raw material, a mixture of (Z) -HFC-1225ye and

(E) -HFC-1225ye (molar ratio of 85:15) was used. This raw material was combined with a third stream (S3) recycled from the reactor R, and then fed to the middle of the distillation column T as a feed (F) (Fig. 1) . As the distillation column T, a packed column (packing material:

HeIi Pack) was used. A first stream (Sl) was obtained from the column top of the distillation column T and a second stream (S2) was obtained from the column bottom. The resultant second stream (S2) was transferred to the reactor R. The reactor R was previously filled with chromium oxyfluoride (fluorine content: about 31% by weight) as a catalyst. The reaction conditions met W/F0 = 40 (g'Nml^"1* sec) , wherein FO (NmI ^• sec^"1) denotes the amount of the second stream (S2) supplied to the reactor R (the symbol "N" means conversion into a normal condition of 0⁰C and 1 atπi) , and W (g) denotes the amount of the catalyst filling the reactor R. The reaction temperature was 300°C. The third stream (S3) was obtained from the reactor R and the entire amount thereof was recycled as described above.

Compositions of the feed (F) and the first to the third streams (Sl to S3) were analyzed by gas chromatography. The results are shown in Tables 2 and 3. No by-product other than HFC-1225ye was detected. Table 2

Flow rate (kmol/hr)

F Sl S2 S3

(Z)-HFC-1225ye 1.13 1.00 0.13 0.27

(E)-HFC-1225ye 0.17 0.00 0.17 0.03

Table 3

Composition ratio (mol%)

F Sl S2 S3

(Z)-HFC-1225ye 87 100 43 90

(E)-HFC-1225ye 13 0 57 10

It is confirmed from Tables 2 and 3 that (Z)-HFC- 1225ye is obtained as the first stream (Sl) and the ratio of (Z)-HFC-1225ye in the third stream (S3) is higher than that in the second stream (S2) .

[Example 2]

The process of the present invention was carried out in accordance with Embodiment 2 described with reference to Fig. 2.

The distillation and the reaction were conducted under the same conditions as those in Example 1, except that the first stream (Sl) was obtained from the column bottom of the distillation column T and the second stream (S2) was obtained from the column top (Fig. 2) and that the reaction temperature in the reactor R was 400⁰C, . Compositions of the feed (F) and the first to the third streams (Sl to S3) were analyzed by gas chromatography. The results are shown in Tables 4 and 5. No by-product other than HFC-1225ye was detected.

Table 4

Table 5

It is confirmed from Tables 4 and 5 that (E)-HFC- 1225ye is obtained as the first stream (Sl) and the ratio of (E) -HFC-1225ye in the third stream (S3) is higher than that in the second stream (S2) .

[Example 3] The process of the present invention was carried out in accordance with Embodiment 3 described with reference to

Fig. 3.

As the raw material, a mixture of (Z) -HFC-1225ye and

(E) -HFC-1225ye (molar ratio of 85:15) was used. This raw material was combined with a sixth stream (S6) recycled from the distillation column T, and then fed to the reactor R as a feed (F) (Fig. 3) . The reactor R was previously filled with chromium oxyfluoride, which was same as that used in Example 1, as a catalyst. The reaction conditions met W/F0 = 40 (g'Nml^{"1 •} sec) , wherein FO (NmI -sec^"1) denotes the amount of the feed (F) fed to the reactor R, and W (g) denotes the amount of the catalyst filling the reactor R. The reaction temperature was 250⁰C. A fourth stream (S4) was obtained from the reactor R, and then supplied to the middle of the distillation column T. As the distillation column T, a packed column (packing material: HeIi Pack) was used. A fifth stream (S5) was obtained from the column top of the distillation column T and a sixth stream (S6) was obtained from the column bottom. The entire amount of the obtained sixth stream (S6) was recycled as described above.

Compositions of the feed (F) and the fourth to the sixth streams (S4 to S6) were analyzed by gas chromatography. The results are shown in Tables 6 and 7.

No by-product other than HFC-1225ye was detected.

Table 6

Flow rate (kmol/hr)

F S4 S5 S6

(Z)-HFC-1225ye 1.03 1.18 1.00 0.18

(E)-HFC-1225ye 0.27 0.12 0.00 0.12

Table 7

Composition ratio (mol%)

F S4 S5 S6

(Z)-HFC-1225ye 79 91 100 60

(E)-HFC-1225ye 21 9 0 40

It is confirmed from Tables 6 and 7 that (Z)-HFC- 1225ye is obtained as the fifth stream (S5) and the ratio of (Z) -HFC-1225ye in the fourth stream (S4) is higher than that in the mixture as the feed (F) .

[Example 4]

The process of the present invention was carried out in accordance with the process described as the modification of Embodiment 3.

As the raw material, HFC-236ea was used. The distillation and the reaction were conducted under the same conditions as those in Example 3, except that this raw material was combined with a sixth stream (S6) recycled from the distillation column T, and then fed to the reactor R as a feed (F) (Fig. 3) , that a fourth stream obtained from the reactor R was subjected to a deacidification treatment to remove HF before being supplied to the distillation column T, and that the reaction temperature in the reactor R was 400⁰C.

Compositions of the feed (F) and the fourth to the sixth streams (S4 to S6) were analyzed by gas chromatography (the fourth stream was analyzed after the deacidification treatment) . The results are shown in Tables 8 and 9. No by-product other than HFC-1225ye was detected.

Table 8

Flow rate (kmol/hr)

F S4 S5 S6

HFC-236ea 1 .16 0.16 0.00 0 .16

(Z) -HFC-1225ye 0 .17 1.17 1.00 0 .17

(E)-HFC-1225ye 0 .21 0.21 0.00 0 .21

Table 9

In Table 9, the numerical value in parenthesis shows the composition ratio in the two-component system of (Z)-HFC- 1225ye and (E) -HFC-1225ye .

It is confirmed from Tables 8 and 9 that (Z)-HFC- 1225ye is obtained as the fifth stream (S5) and the ratio of (Z) -HFC-1225ye in the fourth stream (S4) is higher than that in the mixture as the feed (F) .

Industrial Applicability Either (Z) -1, 1, 1, 2, 3-pentafluoropropene or (E)- 1, 1, 1, 2, 3-pentafluoropropene can be used as a refrigerant. Whish one should be used is decided based on the purpose and specification of each apparatus that utilizes a refrigerant.

The present application claims a priority to United States Provisional Application No. 60/988,615 filed on November 16, 2007, entitled "PROCESS FOR PRODUCING PENTAFLUOROPROPENE". The contents of that application are incorporated herein by the reference thereto in their entirety.

Claims

1. A process for producing either one isomer of (Z)- 1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3- pentafluoropropene, which comprises the steps of: a) subjecting a mixture comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene to distillation to separate it into a first stream comprising either one isomer of (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1,2, 3-pentafluoropropene and having an increased ratio of the one isomer therein from that in the mixture, and a second stream comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene; b) subjecting the second stream to an isomerization reaction to obtain a third stream comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene and having an increased ratio of the one isomer therein from that in the second stream; and c) reusing the third stream as at least a part of the mixture of the step a) , whereby the one isomer is obtained in the first stream.

2. The process according to claim 1, wherein the second stream is subjected together with 1,1,1,2,3,3- hexafluoropropane to the isomerization reaction of the step b) , and hydrogen fluoride is eliminated from 1,1,1,2,3,3- hexafluoropropane under conditions for the isomerization reaction to produce (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene .

3. A process for producing either one isomer of (Z)- 1, 1, 1,2, 3-pentafluoropropene and (E) -1, 1, 1, 2, 3- pentafluoropropene, which comprises the steps of: p) subjecting a mixture comprising (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene to an isomerization reaction to obtain a fourth stream comprising (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E)- 1, 1, 1,2, 3-pentafluoropropene and having an increased ratio of either one isomer therein from that in the mixture; q) subjecting the fourth stream to distillation to separate it into a fifth stream comprising the one isomer and having an increased ratio of the one isomer therein from that in the fourth stream, and a sixth stream comprising (Z) -1, 1, 1, 2, 3-pentafluoropropene and (E)- 1, 1, 1,2, 3-pentafluoropropene; and r) reusing the sixth stream as at least a part of the mixture of the step p) , whereby the one isomer is obtained in the fifth stream.

4. The process according to claim 3, wherein the mixture to be used in the step p) further comprises 1,1,1,2,3,3- hexafluoropropane, and hydrogen fluoride is eliminated from 1, 1, 1, 2, 3, 3-hexafluoropropane under conditions for the isomerization reaction to produce (Z) -1, 1, 1, 2, 3- pentafluoropropene and (E) -1, 1, 1, 2, 3-pentafluoropropene .

5. The process according to any one of claims 1 to 4, wherein the reaction is carried out in the presence of a metal oxide catalyst.

6. The process according to any one of claims 1 to 5, wherein the reaction is carried out at a temperature of 100⁰C to 400⁰C.