Description:FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“AN INTEGRATED PROCESS FOR PREPARATION OF 1,1-DIFLUOROETHANE AND 1,1-DIFLUOROETHYLENE”
The patent application is an alternative to the process filed in Indian patent application 202011006514 filed on 14 February 2020 by the same applicant.

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (INDIA)

The following specification particular describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention provides a process for preparation of 1,1-difluoroethane and 1,1-difluoroethylene.

BACKGROUND OF THE INVENTION
Mechanical refrigeration systems, and related heat transfer devices such as heat pumps and air conditioners, using refrigerant liquids are well known in the art for industrial, commercial and domestic uses. Chlorofluorocarbons (CFCs) were developed in the 1930s as refrigerants for such systems. However, since 1980s the effect of CFCs on the stratospheric ozone layer has received much attention. In 1987 a number of governments signed the Montreal Protocol to protect the global environment setting forth a timetable for phasing out the CFC products.
Thus, there is a requirement for a non-flammable, non-toxic alternative to replace these CFCs. In response to such demand industry has developed a number of hydrofluorocarbons (HFCs), which have a zero-ozone depletion potential.
Hydrofluorocarbons such as 1,1-difluoroethane (HFC-152a) have essentially no ozone depletion potential (ODP) and has low global warming potential (GWP), and therefore, they have been found to be acceptable refrigerants and, in some cases, as potential blowing agents in the production of plastic foams.
Various methods are known in the art for preparation of HFC-152a such as European Patent No. 2336101 provides a process for the production of 1,1-difluoroethane (HFC-152a), using strong Lewis acid fluorination catalyst such as halides of antimony impregnated on activated carbon.
The use of activated carbon impregnated with a strong Lewis acid fluorination catalyst makes the process costly at industrial scale.
The said EP patent also discloses that the pressure employed in the reaction zone is generally not critical and may be at atmospheric, super-atmospheric or under vacuum.
Similarly, U.S. Patent No. 5208395 also discloses a heterogeneously catalyzed gas phase process for producing 1,1-difluoroethane comprising contacting hydrogen fluoride and 1,1-dichloroethane in vapour phase in the presence of a costly solid catalyst consisting of tin tetrafluoride supported on activated carbon at atmospheric pressure to obtain a maximum of 74% 1,1-difluoroethane.
Indian Patent Application 202011006514, filed by the same applicant discloses a vapour phase process for the preparation of 1,1-difluoroethane by reacting 1,2-dichloroethane with anhydrous hydrogen fluoride in presence of a catalyst.
Indian Patent Application 202011006515, filed by the same applicant discloses a process for purification of 1,1-difluoroethane using swing distillation.
Beside other applications, 1,1-difluoroethane is also used a raw material for preparation of 1,1-difluoroethylene. So, inventors of the present invention developed an integrated route to coproduce 1,1-difluoroethane and 1,1-difluoroethylene from 1,2-dichloroethane in a single set up having provisions for recycling the unreacted starting materials and isolating each product having commercial value.

OBJECT OF THE INVENTION
The object of the present invention is to provide an alternative process for preparation of 1,1-difluoroethane and 1,1-difluoroethylene.

SUMMARY OF THE INVENTION
The present invention provides an integrated process to coproduce 1,1-difluoroethane and 1,1-difluoroethylene from 1,2-dichloroethane.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the three integrated reactor lines used in one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
In an embodiment, the presence invention provides an integrated process to coproduce 1,1-difluoroethane and 1,1-difluoroethylene, comprising the steps of:
a) in a thermal cracking reactor, 1,2-dichloroethane was converted to vinyl chloride in absence of a catalyst;
b) in a fluorination reactor, performing liquid phase fluorination of vinyl chloride in presence of anhydrous hydrogen fluoride to isolate a portion of 1,1-difluoroethane;
c) in a chlorination reactor, performing chlorination of a portion of 1,1-difluoroethane to isolate 1,1-difluoroethylene.
In another embodiment of the present invention, the thermal cracking is carried out at a temperature of 350 to 550 °C.
In another embodiment of the present invention, the thermal cracking is carried out at a pressure of 0 to 10 kg/cm2.
In another embodiment of the present invention, the step of fluorination is carried out in presence of a catalyst selected from a group consisting of Tin and Antimony halides, such as the chlorides, fluorides and chlorofluorides. The catalyst can be used as such or is used after activating by passing hydrogen fluoride over it.
In an embodiment, the process of the present invention is carried out at an organic feed rate of 25g per hour to 200g per hour for every 100g of catalyst.
In another embodiment of the present invention, the step of fluorination is carried out in a solvent selected from a group consisting of perchloroethene, 1,1,1,3,3-pentafluorobutane and trichloroethene or the like
In another embodiment of the present invention, the step of fluorination is carried out at a temperature of 40 to 120°C.
In another embodiment of the present invention, the step of fluorination is carried out at a pressure of 0 to 15 kg/cm2.
In another embodiment, the product mixture of 1,1-difluoroethane (HFC-152a) contains additional components selected from unreacted 1,2-dichloroethane, and vinyl chloride which may be recycled back to the appropriate step of the reactor.
In another embodiment, the molar ratio of anhydrous hydrogen fluoride to that of vinyl chloride is selected in the range of 2:1 to 3:1.
In another embodiment of the present invention, 1,1-difluoroethane is isolated using swing distillation to remove vinyl chloride.
In another embodiment of the present invention, the chlorination is carried out using elemental chlorine.
In another embodiment of the present invention, the chlorination is carried out in presence of a radical initiator selected from a group consisting of chloroform, and carbon tetrachloride, or the like.
In another embodiment of the present invention, the chlorination is carried out at a temperature of 300°C to 550°C.
In another embodiment of the present invention, the chlorination is carried out using elemental chlorine at a molar ratio of 1 to 2 with respect to 1,1-difluoroethane.
In another embodiment of the present invention, the chlorination is carried out using carbon tetrachloride in a molar ratio of 2:1 to 4:1 with respect to 1,1-difluoroethane.
In another embodiment of the present invention, the residence time in the step of chlorination was maintained at 0.1 to 10 seconds.
In another embodiment of the present invention, the 1-chloro-1,1-difluoroethane formed as a by-product in the chlorination step is recycled back to the chlorination reactor.
The process of the present invention is carried out using reactors made up of Inconel or Monel alloys. The chlorination if carried out in presence of UV light is performed in a glass reactor.
The products 1,1-difluoroethan and 1,1-difluoroethylene is separated in a series of distillation column, wherein hydrochloride and 1,1-difluoroethylene are separated in the first column and 152a is separated in the second column and subsequently scrubbed using water scrubber, alkali scrubber, and acid scrubber.
The completion of the reaction may be monitored by gas chromatography (GC).
The 1,2-dichloroethane which is used herein as starting material can be prepared by any of the methods known in the art or can be obtained commercially.
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
Example: 1- Preparation of vinyl chloride
1,2-Dichloroethane (EDC; 300 g/h) was subjected to a temperature of 350 to 550°C at a pressure of 3 to 5 kg/cm2 in a non-catalytic vapor phase reactor for a residence time of 45 seconds to obtain vinyl chloride monomer (VCM). The un-reacted EDC was recycled back into the reactor after distillation. Pure VCM is collected after distillation and was fed as the raw material for Step-2 reaction. Selectivity: vinyl chloride- 98-99%.

Example: 2- Preparation of 1,1-difluoroethane at 5.0 kg/cm2 pressure and 70°C
VCM (70 g/hour; 1 mol equivalent) and hydrogen fluoride (2 moles equivalent) were fed to a liquid phase reactor containing stannic chloride as catalyst and perchloroethane (500g) as a solvent at a temperature at 70°C and reaction pressure at 5.0 kg/cm2. The reactor outlet was scrubbed in a water scrubber and the gas was collected in a condenser, which was then analysed. R-152a selectivity: 95.35%; VCM Conversion: 98.77%.
Example: 3- Preparation of 1,1-difluoroethane at 5.0 kg/cm2 pressure and 80°C
VCM (70g/hour; 1 mol equivalent) and hydrogen fluoride (2 moles equivalent) were fed to a Liquid Phase Reactor containing Stannic Chloride as catalyst and perchloroethane (500g as the solvent at a temperature at 80°C and reaction pressure at 5.0 kg/cm2. The reactor outlet was scrubbed in a water scrubber and the gas was collected in a condenser, which was then analysed. R-152a selectivity: 97.75%; VCM Conversion: 99.17%.
Example: 4- Preparation of 1,1-difluoroethane at 8.0 kg/cm2 pressure and 80°C
VCM (70g/hour; 1 mol equivalent) and hydrogen fluoride (2 moles equivalent) were fed to a liquid phase reactor containing stannic chloride as catalyst and perchloroethane (500g) as the solvent at a temperature of 80°C and reaction pressure of 8.0 kg/cm2. The reactor outlet was scrubbed in a water scrubber and the gas was collected in a condenser, which was then analysed. R-152a selectivity: 98.75%; VCM Conversion: 99.87%.
Example: 5- Preparation of 1,1-difluoroethylene
1,1-Difluoroethane and chlorine were fed into an Inconel reactor in vapor phase at a temperature of 400°C, at atmospheric pressure. Residence time maintained was 6.25 seconds, with a molar ratio of 1.49 (Cl2 : r-152a). Carbon tetrachloride was fed into the reactor at a ratio of 0.31 w.r.t r-152a. The reactor outlet was connected to a caustic scrubber. Gas was collected from the scrubber outlet and analysed in a gas chromatograph, based on which conversion and selectivity was calculated. R-152a Conversion: 93.81%; VDF Selectivity: 45.94%
Example: 6- Preparation of 1,1-difluoroethylene.
1,1-Difluoroethane and chlorine were fed into an Inconel reactor in vapor phase at a temperature of 425°C, at atmospheric pressure. Residence time maintained was 6.3 seconds, with a molar ratio of 1.5 (Cl2 : r-152a). CTC was fed into the reactor at a ratio of 0.4 w.r.t r-152a. The reactor outlet was connected to a caustic scrubber. Gas was collected from the scrubber outlet and analysed in a gas chromatograph, based on which conversion and selectivity was calculated. R-152a Conversion: 97.0%; VDF Selectivity: 51.13%
Example: 7- Preparation of 1,1-difluoroethylene.
1,1-Difluoroethane and chlorine were fed into an Inconel reactor in vapor phase at a temperature of 450°C, at atmospheric pressure. Residence time maintained was 8.18 seconds, with a molar ratio of 0.85 (Cl2 : r-152a). CTC was fed into the reactor at a ratio of 0.5 w.r.t r-152a. The reactor outlet was connected to a caustic scrubber. Gas was collected from the scrubber outlet and analysed in a gas chromatograph, based on which conversion and selectivity was calculated. R-152a Conversion: 99.89%; VDF Selectivity: 60%.
Example: 8- Preparation of 1,1-difluoroethylene.
1,1-Difluoroethane and chlorine were fed into an Inconel reactor in vapor phase at a temperature of 500°C, at atmospheric pressure. Residence time maintained was 7 seconds, with a molar ratio of 1 (Cl2 : r-152a). CTC was fed into the reactor at a ratio of 1.0 w.r.t r-152a. The reactor outlet was connected to a caustic scrubber. Gas was collected from the scrubber outlet and analysed in a gas chromatograph, based on which conversion and selectivity was calculated. R-152a Conversion: 99.89%; VDF Selectivity: 76%.
, Claims:WE CLAIM:
1. An integrated process to coproduce 1,1-difluoroethane and 1,1-difluoroethylene, comprising the steps of:
a) in a thermal cracking reactor, 1,2-dichloroethane was converted to vinyl chloride in absence of a catalyst;
b) in a fluorination reactor, performing liquid phase fluorination of vinyl chloride in presence of anhydrous hydrogen fluoride to isolate a portion of 1,1-difluoroethane;
c) in a chlorination reactor, performing chlorination of a portion of 1,1-difluoroethane to isolate 1,1-difluoroethylene.
2. The process as claimed in claim 1, wherein the thermal cracking is carried out at a temperature of 350 to 550°C.
3. The process as claimed in claim 1, wherein the thermal cracking is carried out at a pressure of 0 to 10 kg/cm2.
4. The process as claimed in claim 1, wherein the fluorination is carried out in presence of a catalyst selected from a group consisting of Tin and Antimony halides, such as the chlorides, fluorides and chlorofluorides.
5. The process as claimed in claim1, wherein the fluorination is carried out in a solvent selected from a group consisting of perchloroethene, 1,1,1,3,3-pentafluorobutane, and trichloroethene.
6. The process as claimed in claim 1, wherein the fluorination is carried out at a temperature of 40 to 120°C.
7. The process as claimed in claim 1, wherein the fluorination is carried out at a pressure of 0 to 15 kg/cm2.
8. The process as claimed in claim1, wherein 1,1-difluoroethane is isolated using swing distillation.
9. The process as claimed in claim 1, wherein the chlorination is carried out using elemental chlorine.

10. The process as claimed in claim 1, wherein the chlorination is carried out in presence of a radical initiator selected from a group consisting of chloroform, and carbon tetrachloride.
Dated this 15th December 2022.