Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1998-06-30
2001-01-30
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S177000
Reexamination Certificate
active
06180840
ABSTRACT:
A method of producing 1,1,1,2,2-pentafluoroethane, a method of producing 2,2-dichloro-1,1,1-trifluoroethane, and a method of purifying 1,1,1,2,2-pentafluoroethane.
INDUSTRIAL FIELDS WHERE THE INVENTION CAN BE UTILIZED
This invention relates to a method of producing 1,1,1,2,2-pentafluoroethane that is useful as a substitute for freons and is expected to serve as a refrigerant, a method of producing 2,2-dichloro-1,1,1-trifluoroethane, and a method of purifying 1,1,1,2,2-pentafluoroethane.
PRIOR ART
1,1,1,2,2-pentafluoroethane (HFC-125) is expected to be applied as a refrigerant and is also useful as a substitute for freons.
In recent years, under circumstances whereby freons are regulated, the reduction plan for HCFCs has been determined after that of CFCs. At present, HCFC-22 (CHClF
2
) that is a kind of HCFC, is widely used as a refrigerant. It is therefore useful to determine and produce a substitute for HCFC-22. As its possible substitutes, HFC-32 (CF
2
H
2
), HFC-152a (CH
3
CHF
2
), HFC-143a (CH
3
CF
3
), HFC-134a (CF
3
CH
2
F), and HFC-125 are proposed. This invention relates to a method of producing HFC-125, one of the proposed substitutes.
As production methods of HFC-125, some reactions have been known: fluorination of perchloroethylene (Jap. Pat. Publication No. 17263/1964, U.S. Pat. No. 4,766,260); fluorination of HCFC-122 (Jap. Pat. Opening No. 172932/1990, Jap. Pat. Opening No. 29940/1992); fluorination of HCFC-123 (Jap. Pat. Opening No. 226927/1992, WO92/16482, EP513823); and reduction of CFC-115 (Jap. Pat. Opening No. 258632/1989). This invention relates to the reaction process of producing HFC-125 by fluorinating perchloroethylene.
As a method of producing HFC-125, it is reported that the fluorination reaction of a perchloroethylene as a starting material, especially perchloroethylene, is conducted at a temperature from 350° to 380° C. in the presence of a chromium-oxide catalyst (Jap. Pat. Publication No. 17263/1964). In Jap. Pat. Opening No. 178237/1990, reactions have been improved by changing catalysts. According to the improvement, the conversion of perchloroethylene has been raised, but the selectivity of HFC-125 still remains at a low level of about 15%. As shown in WO92/16479, the low selectivity is unchanged even if the catalyst is changed to one based on Zn.
Like this, in reactions using perchloroethylene as a raw material, the conversion of perchloroethylene has been improved. It cannot, however, be sufficiently confirmed at present whether technology to improve the selectivity of HFC-125 together with its conversion has been achieved.
Accordingly, a reaction starting from HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane) has been proposed. In Jap. Pat. Opening No. 226927/1992; it is shown that HCFC-124 (2-chloro-1,1,1,2-tetrafluoroethane) and HFC-125 can be obtained selectively by using a chromium catalyst having an valence number of three or more. In WO92/16482, a reaction with a catalyst mainly comprised of Zn is explained, showing a result of the high selectivity of HCFC-124. In EP513823, a reaction with a chrom-manganese catalyst is attempted. In any case, these proposals are aimed at a high yield of HFC-125 by improving their catalysts.
When HFC-125 is produced, 1-chloro-1,1,2,2,2-pentafluoroethane (CFC-115) is formed as an impurity, for example, in the process of producing HFC-125 by fluorinating perchloroethylene.
Inasmuch as CFC-115 is one of specified freons whose production must be discontinued in 1995, it is necessary to lower the content of CFC-115 as little as possible in the production of HFC-125. There exists a limit, however, in raising the purity of HFC-125 by rectification because HFC-125 and CFC-115 form an azeotrope-like composition.
The reaction itself of reducing CFC-115 to HFC-125 is already known. Jap. Pat. Opening No. 258632/1989 shows that this reaction is conducted by using a catalyst, in which a metal chosen from the platinum and iron groups or from rhenium is carried on active carbon or alumina. Jap. Pat. Opening No. 29941/1992 shows a method to control the formation of excessively reduced products. WO91/05752 shows a method of performing the reaction by changing a kind of catalyst with a catalyst comprised of a metal chosen from Al, Mo, Ti, Ni, Fe, or Co, on a silicon-carbide carrier. A reaction by using a palladium catalyst on a carrier from the alumina group is shown in EP506525.
All these known technologies are aimed at decreasing the formation of excessively reduced products by improving catalysts to attain a high selectivity of HFC-125. Accordingly, severe selection of a catalyst is needed to raise reaction activity (conversion) and the product's selectivity.
OBJECTIVES OF THE INVENTION
A purpose of this invention is to offer an HFC-125 production method that can attain not only a high conversion of perchloroethylene used as a starting material but also a high efficiency in HFC-125 production.
Another purpose of this invention is to offer a method of efficiently producing an HCFC-123 that can be used to produce HFC-125.
A further purpose of this invention is to offer a purification method enabling to produce HFC-125 efficiently and with high selectivity while mitigating the reaction conditions, including the selection of a catalyst in connection with the conversion and selectivity of the reaction.
THE CONSTITUTION OF THE INVENTION
The inventors found that high pressure and high temperature are effective to increase the conversion of perchloroethylene, and that low pressure and high temperature are effective to improve the selectivity of HFC-125. Accordingly, the increase in pressure will exert conflicting effects on the reaction processes of directly producing HFC-125 by fluorinating perchloroethylene. Furthermore, the increase in reaction temperature that is a common condition to improve the yield of HFC-125 has a detect that may cause catalytic deterioration. Under these conditions the inventors ascertained the reaction process for the effective formation of HFC-125, having created this invention.
This invention thus relates to the method of producing 1,1,1,2,2-pentafluoroethane (HFC-125) in which reactions are conducted in two reaction regions. In the first reaction regions mainly perchloroethylene reacts with hydrogen fluoride in a vapor phase in the presence of a catalyst. In the second reaction region, mainly 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) and/or 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124) react with hydrogen fluoride in a vapor phase in the presence of a catalyst. The first reaction region is kept at a higher pressure than the second reaction region.
In the reactions of forming HFC-125 by fluorinating perchloroethylene with hydrogen fluoride, the reaction processes of this invention are divided into two reaction regions. One region is where mainly perchloroethylene reacts with HF in a vapor phase in the presence of a catalyst. The other region is where mainly HCFC-123 (CF
3
CHCl
2
) and/or HCFC-124 (CF
3
CFHCl) react with HF in a vapor phase in the presence of a catalyst. It is characteristic that the first region is kept at a higher pressure and the second region at a lower pressure while the reactions proceed to produce HFC-125(CF
3
CF
2
H).
In the production method based on this invention, dividing reaction regions and the difference in their pressure conditions make it possible in the high-pressure stage to keep the conversion of perchloroethylene at a high level by securing the catalyst's life through maintaining a relatively low temperature. Conversely, in the low-pressure stage, it is possible to increase the selectivity of HFC-125 because a reaction can be conducted at a lower pressure by setting its reaction conditions independently from those of the high-pressure stage.
In the fluorination reaction of perchloroethylene, it is first necessary to use a catalyst of high activity to improve the conversion of perchloroethylene. With such a catalyst, increasing the temperature, maintaining a long contact time, raising the mole ratio of HF to perchloroethylene, and increasing the pre
Homoto Yukio
Komatsu Satoshi
Shibanuma Takashi
Yoshimura Toshikazu
Armstrong, Westerman Hattori, McLeland & Naughton
Daiken Industries Ltd.
Parsa J.
Richter Johann
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