Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1996-06-07
1998-12-15
Rotman, Alan L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
570168, 570169, 570170, C07C 17158, C07C 1720, C07C 1706
Patent
active
058499636
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERNCE
This application is a 371 of PCT/IP94/02070 filed Dec. 09, 1994.
FIELD OF THE INVENTION
The present invention relates to a method for producing difluoromethane and 1,1,1,2-tetrafluoroethane. Difluoromethane and 1,1,1,2-tetrafluoroethane are alternative fluorocarbons, and are useful as a cooling medium and the like.
DESCRIPTION OF RELATED ART
As the method for producing difluoromethane (CH.sub.2 F.sub.2, HFC-32), a liquid phase synthesis process (cf. U.S. Pat. No. 2,749,373) and vapor phase synthesis process (cf. Japanese Patent Publication Nos. 3004/1967 and 2251321/1984) comprising using methylene chloride (CH.sub.2 Cl.sub.2, HCC-30) as a raw material are known.
It is a known fact that it is difficult to react methylene chloride in good conversion according to the vapor phase synthesis process (cf. "Chemistry and Industry of Fluorine Compound", page 267, published on December 1977 and Japanese Patent Publication No. 3004/1967). It is possible to increase the conversion of methylene chloride by using excess HF relative to methylene chloride. However, a large amount of HF must be disposed or recovered and, therefore, an economical disadvantage arises (cf. Japanese Patent Kokai Publication No. 2251321/1984).
Japanese Patent Kokai Publication No. 2942371/1991 discloses a process comprising reacting 1,1,1-trifluorochloroethane (HCFC-133a) with HF to obtain 1,1,1,2-tetrafluoroethane (HFC-134a), adding 1,1,2-trichloroethylene (HCC-1120) to a crude reaction gas to conduct the reaction from HCC-1120 into HCFC-133a in another reactor without exerting an influence on the other gas and recycling the formed 133a and a HF, as a process for producing efficiently 1,1,1-trifluorochloroethane (HCFC-133a) and 1,1,1,2-tetrafluoroethane (HFC-134a).
The conversion reaction from HCC-1120 into HCFC-133a is a largely exothermic reaction, and it is suggested that the prevention of a heat spot formation in a catalyst layer by the reaction is useful to prolong the catalytic life.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for effectively and simultaneously producing difluoromethane and 1,1,1,2-tetrafluoroethane in one apparatus.
The present invention provides a method for producing difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of:
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at a reaction temperature of 180.degree. to 320.degree. C. in the presence of a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen fluoride to give 1,1,1-trifluorochloroethane, in a first reactor,
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor phase at a reaction temperature of 280.degree. to 400.degree. C., which is higher than the reaction temperature of the first reactor, in the presence of a fluorinating catalyst to give 1,1,1,2-tetrafluoroethane in a second reactor, and supplying the reaction mixture from the second reactor to the first reactor;
(3) recovering difluoromethane, 1,1,1,2-tetrafluoroethane and hydrogen chloride from the reaction mixture of the first reactor; and
(4) supplying the remainder of the reaction mixture containing 1,1,1-trifluorochloroethane from the first reactor to the second reactor after recovering in the step (3).
In addition, the present invention provides a method for producing difluoromethane and 1,1,1,2-tetrafluoroethane, comprising the steps of:
(1) reacting methylene chloride with hydrogen fluoride in a vapor phase at a reaction temperature of 180.degree. to 320.degree. C. in the presence of a fluorinating catalyst and 1,1,1,2-tetrafluoroethane to give difluoromethane, and reacting 1,1,2-trichloroethylene with hydrogen fluoride to give 1,1,1-trifluorochloroethane, in a first reactor,
(2) reacting 1,1,1-trifluorochloroethane with hydrogen fluoride in a vapor phase at a reaction temperature of 280.degree. to 400.degree. C. which is higher than the reaction temperature of the first reactor in the presence of a f
REFERENCES:
patent: 2749373 (1956-06-01), Meyer
"Chemistry and Industry of Fluorine Compound", p. 267, published Dec. 1977.
Homoto Yukio
Komatsu Satoshi
Koyama Satoshi
Shibanuma Takashi
Tanaka Kunitada
Daikin Industries Ltd.
Rotman Alan L.
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