DESC:PROCESS FOR THE PREPARATION OF 1,1,2,3-TETRACHLOROPROPENE

Field of the invention

The present invention provides a process for the preparation of a compound of Formula I. More particularly, the present invention provides a process for the preparation of 1,1,2,3-tetrachloropropene.

Background of the invention

The chlorinated propenes, particularly, 1,1,2,3-tetrachloropropene is an important precursor for the production of 2,3,3,3-tetrafluoropropene (HFO-1234yf). The fluorinated olefins are known to be effective refrigerants, fire extinguishers, heat transfer media, propellants, foaming agents, blowing agents, gaseous dielectrics, sterilant carriers, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, displacement drying agents and power cycle working fluids. Along with their innumerable applications, they have added advantage of posing no threat to the ozone layer as being devoid of chlorine atom.

U.S. Patent no. 3,446,859 mentions free radical initiators like oxygen, chlorine, chlorine yielding chlorocarbons.

U.S. Patent No.8,258,353 provides a process for the production of chlorinated and/or fluorinated propenes by reacting, at elevated pressures i) a chloroethylene or a chlorofluoroethylene and ii) a methane, chloromethane, fluoromethane or chlorofluoromethane, to provide at least one chlorinated and/or fluorinated propene. The reaction preferably takes place in the presence of initiators such as carbon tetrachloride, chlorine, hexachloroethane, benzotrichloride, hexachloroacetone or a combination of these.

The initiators are present as contaminants in the product which is to be purified for increasing the processing. Hence to minimise the process steps, the initiator has to be eliminated.

The present invention provides a process which is simple, economically viable and industrially doable.

Summary of the invention

The present invention provides a process for the preparation of a compound of Formula I
CYCl=CCl-CH2X,
comprising reacting a chlorinated olefin of Formula II
CYCl=CCl2
with a methyl halide of Formula III
CH3-X,
wherein Y is selected from chlorine and hydrogen and X is selected from chlorine, fluorine and bromine, and
wherein said reaction takes place in a vapour phase and at a temperature of not less than 460oC.

The present invention also provides a process of preparing 1,1,2,3-tetrachloropropene comprising reacting methyl chloride with 1,1,2,2-tetrachloroethene, wherein the said reaction takes place in a vapour phase, and at a temperature of not less than 460oC.

The inventors have observed that upon maintaining the conversion of 1,1,2,2-tetrachloroethene at around 6-8%, the selectivity of 1,1,2,3-tetrachloropropene so obtained is greater than 85 %. Further, the carbon lay down decreases thus increasing the cycle life of the reaction.

Detailed description of the invention

The present invention provides a process for the preparation of a compound of Formula I
CYCl=CCl-CH2X,
comprising reacting a chlorinated olefin of Formula II
CYCl=CCl2
with a methyl halide of Formula III
CH3-X,
wherein Y is selected from chlorine and hydrogen and X is selected from chlorine, fluorine and bromine, and
wherein said reaction takes place in a vapour phase and at a temperature of not less than 460oC.

The present invention also provides a process of preparing 1,1,2,3-tetrachloropropene comprising reacting methyl chloride with 1,1,2,2-tetrachloroethene, wherein the said reaction takes place in a vapour phase, at a temperature of not less than 460oC.

The 1,1,2,2-tetrachloroethene may be obtained commercially or can be prepared by any of the methods known in the art.
The process of the present invention is carried out at a temperature in the range of from about 460oC to 560oC.

The 1,1,2,3-tetrachloropropene prepared by virtue of the process of present invention has a selectivity greater than 80.0% by Gas chromatography.

The term ‘about’ refers to a variation of 10% on the higher and lower side of specified parameter.

While 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.

Examples
Example 1: Preparation of 1,1,2,3-tetrachloropropene

Methyl chloride (@ a feed rate of 341 g/hr) and 1,1,2,2-tetrachloroethene (@ a feed rate of 279 g/hr) was preheated to 180oC in a double pipe heat exchanger using high pressure steam and then vaporized in a 1”500 mm length electrical superheater where the temperature was brought to the reaction temperature, and then fed to a 1” Inconel hollow reactor of 750 mm length which is maintained at 460oC by electrical heaters and a pressure of 10 kg/cm2g. The molar ratio of methyl chloride to 1,1,2,2-tetrachloroethene was maintained at 4:1. The product stream was collected in a collection pot which was also maintained at 10kg/cm2g. The excess pressure which is mainly due to the by-product HCl was vented out to water scrubber. The sample from collection pot was analysed by Gas chromatography after venting methyl chloride.
Analysis:
1,1,2,2-tetrachloroethene conversion : 6-8 %
Selectivity of 1,1,2,3-tetrachloropropene : 85 %.

,CLAIMS:We claim:
1. A process for the preparation of a compound of Formula I
CYCl=CCl-CH2X
comprising reacting a chlorinated olefin of Formula II
CYCl=CCl2
with a methyl halide of Formula III
CH3-X,
wherein Y is selected from chlorine and hydrogen and X is selected from chlorine, fluorine and bromine, and
wherein said reaction takes place in a vapour phase and at a temperature of not less than 460oC.

2. The process as claimed in claim 1 is carried out at a temperature in the range of from 460oC to 560oC.
3. The 1,1,2,3-tetrachloropropene prepared by virtue of the process as claimed in claim 1 has a selectivity greater than 80.0% by Gas chromatography.