The present invention relates to a process for separating chlorocarbon from olefin feed. BACKGROUND OF THE INVENTION
Refrigerant is the substance which is used as working fluid in a thermodynamic cycle, undergoes a phase change from liquid to vapour and produces cooling. These are used in refrigeration, air conditioning, and heat pumping systems. They absorb heat from one area, such as an air conditioned space, and reject it into another, such as outdoors, usually through evaporation and condensation, respectively. These phase changes occur both in absorption and mechanical vapour compression refrigeration systems, but they do not occur in systems operating on a gas cycle using a fluid such as air.
Fluorocarbon based fluids have found widespread use in industry in a number of applications, including as refrigerants, aerosol propellants, blowing agents, heat transfer media, and gaseous dielectrics. Tetrafluoropropenes, having zero ozone depletion and low global warming potential, have been identified as favorable refrigerant over other refrigerants. One tetrafluoropropene having valuable properties is 2,3,3,3-tetrafluoropropene (R-1234yf).
However, the production of these and other organofluorine compounds often require substantial separation steps to isolate the compounds from other components present in the reaction product, including unreacted feedstock, undesirable byproducts, and coproducts.
Production of organofluorine compounds often results in the formation of other organofluorine compounds, organochlorines, and chlorofluorocarbons (collectively referred to herein as "coproducts of organofluorine production" or simply "coproducts"), as both intermediate products and coproducts that appear in the final reaction mixture.

In prior art several methods have been disclosed for preparing R-1234yf, wherein by-products have been removed by using several techniques such as distillation, azeotropic distillation, adsorption, absorption, membrane separation and a like or combination thereof to achieve high yield.
U.S. Pat. No. 2,931,840 describes a reaction involving the pyrolysis of chloromethane with tetrafluoroethylene, or alternatively chloromethane with chlorodifluoromethane. It is very difficult to remove unreacted chloromethane from the reaction product stream since the boiling point of chloromethane (-24°C) is relatively close to the boiling point of the desired 2,3,3,3-tetrafluoropropene (-28°C). It does not mention the process for removing unreacted chloromethane from the reaction mixture.
PCT publication no. WO2017/050686 discloses a process for purifying and drying a stream comprising a hydrofluoroolefin, water and impurities based on halogenated carbon compounds by contacting the stream with adsorbent selected from membrane and/or molecular sieve.
Further, U.S. Pat. No. 9,725,384 discloses a process for separating an organofluorine compound from inorganic compounds and/or other organofluorine compounds having at least two carbon atoms.
Chlorocarbon compounds such as chloromethane forms a low boiling azeotrope with R-1234yf and are difficult to separate by conventional distillation. The above references are silent on an efficient method for separation and recovery of chlorocarbon compounds such as chloromethane.
There is therefore a need to develop a process for separating chlorocarbon compounds from a feed used in the preparation of fluoroolefinic compounds. SUMMARY OF THE INVENTION
A first aspect of the present invention provides a process for separating chlorocarbon from a feed comprising at least one fluoroolefinic compound and chlorocarbon by contacting the feed with a semipermeable membrane.

A second aspect of the present invention provides a process for separating chlorocarbon from a feed comprising at least one fluoroolefinic and chlorocarbon by contacting the feed with a semipermeable membrane to obtain a feed substantially free of the chlorocarbon. DETAILED DESCRIPTION
The term "feed" used in the present invention refers to crude composition obtained by the reaction of tetrafluoroethylene/ chlorodifluoromethane with chloromethane.
The term "fluoroolefinic compounds" used in the present invention refers to unsaturated organofluorine compound. Examples of unsaturated organofluorine compounds includes R-1234yf, R-1234ze, R-1243zf, HCFO-1233zd, HCFO-1233xf, R-1225zc and mixtures thereof.
The term "chlorocarbon" used in the present invention refers to chlorinated hydrocarbons and chlorofluorocarbons (CFCs). Examples of CFCs includes CFC-11 (CCbF), CFC-12 (CCI2F2), HCFC-21 (CHCI2F), HCFC-22 (R22; CHCIF2), HCFC-23 (CHF3). Examples of chlorinated hydrocarbons includes chloromethane, methylene chloride, and carbon tetrachloride.
The term "semipermeable membrane" as used in the present invention refers
to polymeric membrane that allows selective permeability of one compound over the
other in the feed. Examples of polymeric membrane include polyethene,
polypropylene, polyester, polyamide, nylon, nitrile rubber, neoprene,
polydimethylsiloxane (silicone rubber), chlorosulfonated polyethylene, polysilicone-carbonate copolymers, fluoroelastomer, polyvinylchloride, plasticized polyvinylchloride, polyurethane, cis-polybutadiene, cis-polyisoprene, poly(butene-l), polystyrene-butadiene copolymers, styrene/butadiene/styrene block copolymers, styrene/ethylene/butylene block copolymers, thermoplastic polyolefin elastomers, and block copolymers of polyethers and polyesters.

The selective permeability of a membrane is characterized by a separation factor a, which is a measure of the preferential permeability of one compound or type of compound over another compound or type of compound. The separation factor is the ratio of the relative amount of a compound that permeates through the membrane to the relative amount of another compound that permeates the membrane.
The separation factor
a = [ A ] permeate / [ B ] permeate [ A ] retantate / [ B ] retentate
The permeability is function of temperature, pressure and time.
The operable temperature ranges from 0°C to 50°C
The operable pressure ranges from 1 bar to 10 bars
The term "permeate" refers to the component of the feed that permeates through semipermeable membrane.
The term "retantate" refers to the component of the feed that does not permeates through semipermeable membrane.
The term "substantially free" used in the present invention refers to a composition that is 80% free of chlorocarbon compared to the feed.
The term "anhydrous" used in the present invention refers to water content of less than 50 ppm
A first aspect of the present invention provides a process for separating chlorocarbon from a feed comprising at least one fluoroolefinic compound and chlorocarbon by contacting the feed with a semipermeable membrane.
In an embodiment of this aspect, the present invention provides a process for separating chlorinated hydrocarbon from a composition comprising at least one fluoroolefinic compound by contacting the feed with a semipermeable membrane.
In an embodiment of this aspect, the present invention provides a process for separating chlorinated hydrocarbon from a composition comprising at least one R-1234yf and/or R-1234ze by contacting the feed with a semipermeable membrane.

In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising at least one R-1234yf and/or R-1234ze by contacting the feed with a semipermeable membrane.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane through semipermeable membrane, further recovering chloromethane and reusing recovered chloromethane for preparation of R- 1234yf
In an embodiment of this aspect, the present invention provides a continuous process for separating, recovering and reusing chloromethane comprising the step of contacting a feed containing at least one R-1234yf and/or R-1234ze with a semipermeable membrane.
In another embodiment, the present invention provides a process for separating
chloromethane (R-40) from a feed comprising R-1234yf, vinyledenefluoride, R-124a
(l-Chloro-l,l,2,2-tetrafluoroethane), HFP (hexafluoropropene), OFCB
(Octafluorocyclobutane), R-22 (Chlorodifluoromethane), R-1122 (2-Chloro-l,l-difluoroethylene), R-236ca (1,1,2,3,3,3- hexafluoropropane), R-226cb (1,1,1,2,3,3-Hexafluoro-3-chloropropane), R-32 (Difluoromethane), TFE (tetrafluoroethylene), trans R-1225ye (trans-l,3,3,3-tetrafluoroprop-l-ene), cis R-1225ye (cis-1,3,3,3-tetrafluoroprop-1-ene), R-1243zf (3,3,3-Tetrafluoroprop-l-ene), R-1234ze (1,3,3,3-Tetrafluoropropene) and R-40 (chloromethane) by contacting the feed with a semipermeable membrane.
A second aspect of the present invention provides a process for separating chlorocarbon from a feed comprising at least one fluoroolefinic and chlorocarbon by contacting the feed with a semipermeable membrane to obtain a retantate substantially free of the chlorocarbon.

In an embodiment of this aspect, the present invention provides a process for separating chlorinated hydrocarbon from a feed comprising at least one fluoroolefinic compound by contacting the feed with a semipermeable membrane to obtain a retantate substantially free of the chlorocarbon.
In an embodiment of this aspect, the present invention provides a process for separating chlorinated hydrocarbon from a feed comprising at least one R- 1234yf and/or R-1234ze by contacting the said composition with a semipermeable membrane to obtain a retantate substantially free of the chlorocarbon.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a feed comprising at least one R-1234yf and/or R-1234ze by contacting the said composition with a semipermeable membrane to obtain a retantate substantially free of the chlorocarbon.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane to obtain a retantate substantially free of the chlorocarbon.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane to obtain a retantate having not more than 10% of chlorocarbon compared to the feed.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane to obtain a retantate having not more than 5% of chloromethane compared to the feed.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane to obtain a retantate having not more than 2% of chlorocarbon compared to the feed.

In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane to obtain a retantate having not more than 2%, of chloromethane compared to the feed.
In an embodiment of this aspect, the present invention provides a process for separating chloromethane from a composition comprising R-1234yf by contacting the feed with a semipermeable membrane to obtain a retantate having not more than 0.5%, of chloromethane compared to the feed.
In another embodiment, the present invention provides a process for separating chloromethane (R-40) from a feed comprising R-1234yf, VdF, R-124a, HFP, OFCB, R-22, R-1122, R-236ca, R-226cb, R-32, TFE, trans R-1225ye, cis R-1225ye, R-1243zf, R-1234ze and R-40 by contacting the feed with a semipermeable membrane to obtain a retantate substantially free of R-40.
In another embodiment, the present invention provides a process of using the retantate for preparing single fluoroolefinic compound.
In another embodiment, the present invention provides a process of using the retantate for preparing R1234yf
The experiments were performed to show that the permeation of chloromethane from the feed is a function of temperature, pressure and time. Table 1 and Table 2 shows the results of permeation of chloromethane at 25°C and a pressure of 1.1 bars. In this experiment, feed was allowed to pass through polyethene and analyzed over a period of time.
Table 1

Time (hours) 0 4.25 9 13.5 17.5 46
Gas Weight 57 55 55 55 55 26
R-1234yf 21.73% 23.30% 25.11% 26.65% 28.23% 35.52%
R-22 19.27% 20.27% 21.23% 22.04% 22.69% 20.16%
R-40 33.40% 29.15% 24.26% 20.03% 15.92% 0.58%

Table 2

Time hours 0 4.25 9 13.5 17.5 46
Gas Weight 51 49 49 49 49 29
R-1234yf 15.07% 16.34% 17.90% 18.91% 19.91% 25.24%
R-22 31.10% 32.74% 34.60% 35.89% 36.80% 36.00%
R-40 30.42% 25.69% 20.38% 16.51% 13.16% 1.20%
A feed comprising organofluorine compounds and chlorocarbon, used in the present invention, is obtained by any process known in the prior art; wherein chloromethane is reacted with tetrafluoroethyelene optionally in the presence of initiator or catalyst; particularly the said composition may be obtained by the processes as disclosed in PCT publication no. WO2017/122222A1 or in Indian publication no. IN201611040763.
The present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLE:
Preparation of R-1234yf:
Chloromethane was added to tetrafluoroethene at an elevated temperature in the presence of initiator, the reactor outlet feed consists of mainly unreacted tetrafluoroethyelene, difluoromethane, vinylidenefluoride, trifluoromethane,

hexafluoropropene, octafluorocyclobutane, 2,3,3,3-tetrafluoropropene,
chlorodifluoromethane, unreacted Chloromethane.
The reactor outlet stream is passed through first distillation column, from where tetrafluoroethyelene, trifluoromethane, vinylidenefluoride and difluoromethane is removed from top and recycled back into reactor while the bottom feed is contacted with semipermeable (polymeric) membrane where chloromethane (R-40) permeate and the rest of the composition retains. Chloromethane (R-40) is recycled back into reactor and the rest of the composition which is retained (free of chloromethane) is passed to conventional distillation column from where chlorodifluoromethane (R-22) and octafluorocyclobutane (OFCB) is easily separated from 2,3,3,3-tetrafluoropropene (R-1234yf).

Composition Mol %
HFP 2.11
OFCB 33.85
R-1234yf 35.52
R-22 20.16
R-40 (C-l) 0.58
C-l
Permeate
Membrane Separation

Example 1:
Inlet Feed
Composition Mol %
HFP 1.21 »
OFCB 18.63

R-1234yf 21.73
R-22 19.27
R-40 33.40
Here the membrane can be a hollow cylinder made of polyethene or a supported membrane.
Example 2:
C-l


Inlet Feed
Composition Mol %
HFP 0.90 ►
OFCB 13.87

R-1234yf 15.07
R-22 31.10
R-40 30.42

Membrane Separation

Permeate

Composition Mol %

HFP 1.63
OFCB 25.46
R-1234yf 25.24
R-22 36.0
R-40 (C-l) 1.2
Here the membrane can be a hollow cylinder made of polyethene or a supported membrane.

Abbreviation Full-form Abbreviation Full-form
HFP Hexafluoropropene R-1225ye (cis) Cis 1,2,3,3,3-penta fluoropropene
OFCB Octafluorocyclobutan e R-1225ye (trans) Trans 1,2,3,3,3-pentafluoropropene
R-134a 1,1,1,2-Tetrafluoro ethane R-1243zf 1,1,1-
Tri fluoropropene
R-226cb 1-Chloro-l, 1,2,2,3,3-hexa fluoropropane R-1234ze 1,3,3,3-Tetrafluoro propene
R-227ea 1,1,1,2,3,3,3-Hepta fluoropropane CTFE Chlorotrifluoroethyl ene
R-227ca 1,1,1,2,2,3,3-Hepta fluoropropane R22 Chlorodifluorometh ane
R-1225zc 1,1,3,3,3-Penta fluoropropene R-40 (C-l) Chloromethane
R-1234yf 2,3,3,3-Tetrafluoro propene R-124a Chi orotetrafluoroeth ane
PFIB Perfluoroi sobutene R-236ca 1,1,2,2,3,3-Hexafluoro propane
R-134 1,1,2,2-tetrafluoro ethane R1122 l-Chloro-2,2-difluoro ethene

We Claim:

1.A process for separating chlorocarbon from a mixture comprising at least one fluoroolefinic compound and chlorocarbon by contacting the mixture with a semipermeable membrane.
2. The process as claimed in claim 1 wherein, fluoroolefinic compound is selected from a group comprising R-1234yf, R-1234ze, R-1243zf, R-1233zd, R-1233xf, R-1225zc and mixtures thereof.
3. The process as claimed in claim 1 wherein, chlorocarbon is selected from a group comprising CFC-11 (CCbF), CFC-12 (CCI2F2), HCFC-21 (CHCbF), HCFC-22 (R22; CHCIF2), HCFC-23 (CHF3).
4. The process of claim 1 wherein, chlorocarbon is selected from a group comprising chloromethane, methylene chloride, and carbon tetrachloride.
5. The process of claim 1 wherein, semipermeable membrane is selected from a group comprising polyethene, polypropylene, polyester, polyamide, nylon, nitrile rubber, neoprene, polydimethylsiloxane (silicone rubber), chlorosulfonated polyethylene, polysilicone-carbonate copolymers, fluoroelastomer, polyvinylchloride, plasticized polyvinylchloride, polyurethane, cis-polybutadiene, cis-polyisoprene, poly(butene-l), polystyrene-butadiene copolymers, styrene/butadiene/styrene block copolymers, styrene/ethylene/butylene block copolymers, thermoplastic polyolefin elastomers, and block copolymers of polyethers and polyesters.

6. The process as claimed in claim 1 wherein, the mixture comprises one of more selected from a group comprising R-1234yf, R-1234ze, vinyledenefluonde, R-124a, HFP, OFCB, R-22, R-1122, R-236ca, R-226cb, R-32, TFE, trans R-1225ye, cis R-1225ye, R-1243zf, R-1234ze and R-40.