The present invention provides a process for preparation of 1,1,1-trichloro-2,2,2-trifluoroethane.
Background of the invention
The present invention provides a process for preparation of 1,1,1-trichloro-2,2,2-trifluoroethane (R-113a). Several methods are known in the prior art for preparation of R-113a.
U.S. Pat. No. 2,644,845 discloses a non-catalytic process for the chlorination of 1,1,1-trihaloethane at a temperature in the range of 365° C to 500° C. The chlorination of 1,1,1-trifluoroethane (R-143a) at 497°C results in following selectivity.
R-113a: 45%, R-123: 33% and R-133a: 22%
U.S. Pat. No. 5,120,883 also discloses the preparation of R-113a by chlorination of 1,1,1-trifluoroethane (R-143a) using activated carbon catalyst, under a nitrogen flow at 300°C using chlorine to obtain the titled compound with the following selectivity.
R-113a-39.7%, R-143a- 57.1%
Thus all the prior arts cited above discloses the preparation of R-l 13a with very less selectivity.
So there is a need to develop a cost effective, economic and robust process for preparation of R-l 13 a.
Summary of the invention
The present invention provides a process for preparation of 1,1,1 -Trichloro-2,2,2-trifluoroethane (R-l 13a), comprising the steps of:

a) providing activated carbon in a reactor and heating to 200 to 250°C in presence of nitrogen;
b) providing preheated R-133a and chlorine at a temperature in the range of 150-300°C, separately or premixed into the reactor to obtain the first reaction mixture;
c) heating the first reaction mixture at 250 to 320°C in the catalyst bed to obtain second reaction mixture containing R-l 13a, R-123, R-l 12a and R-133a;
d) isolating R-l 13a from step c) and recycling R-123, R-l 12a and R-l33a into the reactor.
Object of the invention The object of the present invention is to provide a cost effective, economic and robust process for preparation of l,l,l-trichloro-2,2,2-trifluoroethane.
Detailed description of the invention
In accordance with the present invention, the process of preparation of R-113a is carried out by providing activated carbon in an Inconel reactor and calcination is done at a temperature in the range of 200 to 250°C in presence of nitrogen. After calcination l,l,l-Trifluoro-2-chloroethane (R-133a) and chlorine is pre-heated at a temperature in the range of 150 to 300°C using an electrical heater and fed into the reactor operating at 250 to 300°C. The molar ratio of R-133a to chlorine is maintained in the range of 1:2 to 1:8. Residence time maintained in the range of 1 to 50 Seconds.
In a preferred embodiment, the extrudates of activated carbon catalyst are used having surface area of at least 800m2/g.
The chlorination reaction of the present invention is carried out in a fixed bed reactor. The molar ratio of chlorine to R-133a is selected in the range of 2-8. The reaction temperature is selected in the range of 250-320°C. The residence time is maintained in the range of 1 to 50 Sec.
The crude product is collected from the reactor outlet and analysed by gas chromatography. The product selectivity is 95% or above.

According to the present invention, the process of preparation of R-l 13a is carried out by chlorination of R-l 33a in a continuous mode wherein, R-133a (1,1,1-Trifluoro-2-chloroethane), R-123 (2,2-dichloro-l,l,l-trifluoroethane), R-l 12a (tetrachloro-2, 2-difluoroethane), are recycled back into the reactor.
In a preferred embodiment, the crude product thus obtained is passed through a series of distillation columns to remove HC1, chlorine, R-133a, R-123, R-112a to get 99.9% pure R-l 13a. Chlorine, R-123 and R133a are recycled back into the reactor.
Unless stated to the contrary, any of the words "comprising", "comprises" and includes mean "including without limitation" and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLES
Preparation of l,l,l-trichloro-2,2,2-trifluoroethane (R-l 13a)
Activated carbon catalyst (200g) was charged in an Inconel reactor and calcined at 250°C in the presence of Nitrogen. After calcination R-133a and chlorine in the molar ratio of 1:4 were preheated at 165°C and then superheated at 250°C and passed into the reactor at a feed rate of 46g/h and lOlg/h respectively where the temperature is maintained at 300°C using electrical heaters. The residence time was maintained at 14 Sec. The crude product thus obtained was analysed by gas chromatography and was further condensed and collected by passing through a water scrubber and a caustic scrubber. The organic layer was

separated and neutralized by 10% sodium carbonate solution and was further subjected to distillation where the R-123, R112a and unreacted R-133a was recycled back into the reactor and the titled compound i.e., R-113a was obtained with a purity of 99.99%. GC results are tabulated below.
Table 1

GC analysis (crude product)
Components GC purity
R-133a(l,l,l -Trifluoro-2-chloroethane) 1.1225%
R-123 (2,2-dichloro-l,l,l-trifluoroethane) 0.6123%
R-l 13a (l,l,l-trichloro-2,2,2-trifluoroethane) 97.8939%
R-l 12a (l,l,l,2-tetrachloro-2,2-difluoroethane) 0.0325%
Table 2

GC analysis (pure product)
Components GC purity
R-l 13a (l,l,l-trichloro-2,2,2-trifluoroethane) 99.99%.

We Claim:

1.A process for preparation of l,l,l-trichloro-2,2,2-trifluoroethane
(R-l 13a), comprising the steps of:
a) providing activated carbon in a reactor and heating to 200 to 250°C in presence of nitrogen;
b) providing preheated R-l33a and chlorine at a temperature in the range of 150-300°C, separately or premixed into the reactor to obtain the first reaction mixture;
c) heating the first reaction mixture at 250 to 320°C in the catalyst bed to obtain second reaction mixture containing R-l 13a, R-123, R-l 12a and R-133a;
d) isolating R-l 13a from step c) and recycling R-123, R-l 12a and R-l33a into the reactor.

2. The process as claimed in claim 1, wherein activated carbon catalyst have surface area of at least 800m2/g.
3. The process as claimed in claim 1, wherein, chlorination reaction is carried out in a fixed bed reactor.

4. The process as claimed in claim 1, wherein, molar ratio of chlorine to R-133a is selected in the range of 2-8.