Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1,

Details Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1, Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1,

1993-07-21

1995-06-20

Siegel, Alan

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

570178, C07C 1708, C07C 1738

Patent

active

054262518

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a process for preparing 1,1,1-trifluoro-2-chloroethane (referred to as R-133a hereinafter) and/or 1,1,1,2-tetrafluoroethane (referred to as R-134a hereinafter), which comprises reacting trichloroethylene and/or R-133a with hydrogen fluoride (referred to as HF hereinafter) in the presence of a fluorinating catalyst, and separating R-133a, HF, and optionally trichloroethylene, from the reaction mixture, and recycling them to the reaction process.
R-133a is useful as an intermediate of fluorinated organic compounds. R-134a is used as a coolant and a blowing agent as a substitute for dichlorodifluoroethane which is one of the recently regulated halocarbons.


DESCRIPTION OF THE PRIOR ART

R-133a and R-134a are usually produced by fluorinating trichloroethylene with HF in a gas phase in the presence of a catalyst which comprises chromium. R-134a is also produced from R-133a and HF by a similar way to the above method. These reactions proceed stepwise and are shown by the following scheme: ##STR1##
There is a reverse reaction of from the right side to the left side in the reaction (2) which provides R-134a. Moreover, it proceeds about 100 times as fast as the reaction of from the left to the right. Therefore, HF must be used in large excess even in a relatively efficient gas phase reaction. However, it is difficult to obtain R-133a in a conversion of more than 30%. Accordingly, it is necessary to separate unreacted R-133a and HF from the reaction mixture and to recycle them to the reaction process. However, the prior arts only describe a method in which the whole reaction mixture is washed with water. There has been known no method in which the unreacted R-133a and HF can be efficiently separated and recycled.
The reaction mixture obtained in the process comprising the gas phase reaction contains R-133a, R-134a, hydrogen chloride, HF, and optionally trichloroethylene. When trichlroethylene is completely fluorinated in the reaction process, or when R-133a is fluorinated, substantially no trichloroethlene is contained in the reaction mixture. However, even in those cases, the reaction mixture is seldom completely free from trichloroethylene and usually contains as much as 0.1 mole % trichloroethylene. In addition, the mixture inevitably contains a small amount of water which is present in the starting materials. Water, even in a small amount, lowers the activity of the catalyst used and prevents the reaction.
In a usual way, the reaction mixture which has been cooled is charged to a distillation tower. The low-boiling mixture consisting of hydrogen chloride which shifts the equlibrium of the reaction (2) to the left side and an azeotropic mixture of R-134a and HF is discharged from the top of the distillation tower, and the high-boiling mixture, consisting predominantly of R-133a and HF, and optionally trichloroethylene, is discharged from the bottom of the tower. Thereafter, the high-boiling mixture is vaporized with a vaporizer and recovered as a recycling gas in the reaction system. In this method, a vaporiser is required in addition to the distillation tower, which makes equipment very complicated. Moreover, in this method, the small amount of water which is contained in the reaction mixture is also recyled to reaction step and accumulated in the reaction system. Thus the method in which R-133a and HF are separated from the reaction mixture and recycled to the reaction step has the problems that impurities are incorporated into reaction system, and that a great deal of equipment to provide heat is required.


SUMMARY OF THE INVENTION

The inventors have made intense studies to solve the above problems and found the following facts: R-133a and HF, and trichloroethylene and HF form azeotropic compositions respectively, which, moreover, are minimum boiling mixtures, different from the azeotropic composition of water and HF; under a certain pressure, a mixture of any composition consisting of HF, R-133a and trichloroethylene has an equilibrium temperature be

REFERENCES:
patent: 3558438 (1971-01-01), Schoenbeck
patent: 4944846 (1990-07-01), Manzer et al.

Affiliated with

Also associated with

Rating

Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1, does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1,, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1, will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1845421