Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF 2,2-DICHLORO-1,1,1-TRIFLUOROETHANE (HCFC-123)

Abstract This invention provides an improved process for the preparation of 2,2-dichloro-1,1,1-trifluoroethane by catalytic hydrogenolysis of chlorofluorocarbons (CFC-113a) using a catalyst containing Pd/Pt and of at least one or more metals selected consisting of Cobalt, Copper, Iron, Ruthenium, Rhodium supported on carbon typically constitutes between 0.1 and 5 percent by wt. of the catalyst. Suitable hydrogenolysis catalyst may be prepared by treating carbon support with hydrochloric acid or nitric acid and then washed thoroughly with demineralised water to bring down the ash content. The present invention comprises i) preparation and activation of the catalyst ii) hydrodehalogenation of chlorofluoro carbon (CFC-113a) to the formation of hydrochlorofluorocarbon (HCFC-123). The process is a continuous vapor phase reaction and typically achieved at atmospheric or superatmospheric pressures. Generally, in order to provide substantial hydrodehalogenation to promote high product yields, the amount of hydrogen used is at least about one mole per mole of CFC-113a. The reaction is suitably carried out at a temperature, which depends to some extent on the formation of by-products. The desired temperatures are in the range 120°-160°C where by-products formation is minimum and higher selectivity towards HCFC-123 is achieved. The contact time of raw materials on the surface of the catalyst plays an important role in conversions and selectivity and is preferably between 30-70 sec. The exit product stream of the reactor is bubbled in demineralised water, dried over molecular sieves and cooled in condenser, collected in receivers at -20 to -25°C.
Full Text FIELD OF THE INVENTION
The present invention relates to an improved process for the preparation of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) from 2,2,2-trichloro trifluoroethane (CFC-113a). More particularly, the present invention relates to an improved process for the hydrodehalogenation of 2,2,2-trichloro trifluoroethane (CFC-113a) by using a transition metal halide impregnated carbon catalyst.
BACKGROUND OF THE INVENTION
A number of chlorofluorocarbons (CFCs) used in refrigeration, air-conditioning, foam-blowing , degreasing solvent, flame retardant chemicals, etc., are detrimental to the earth's stratospheric ozone layer as they release chlorine radicals which consume large number of ozone molecules in a chain reaction. Hence, there is a conscious effort world-wide to develop alternative materials without chlorine or bromine that can serve as effective replacement for the CFCs. Hydrochlorofluorocarbons (HCFCs) have similar physical properties as CFCs, but decompose in the lower atmosphere before reaching the stratospheric zone and are considered as transitional replacements before other suitable materials are developed. 2,2-Dichloro-1,1,1-trifluoroethane with an ODP (ozone depletion potential) of 0.02 is identified as an alternative to CFC-11 with an ODP of 1.0.
Preparation of HCFC-123 is described in WO 91/05752(1996), where the hydrogenolysis of halocarbons was performed in the presence of silicon carbide with at least one metal selected from the group consisting of aluminium, molybdenum, titanium, nickel, iron, cobalt and their alloys coated on the inside surface of reaction vessel. The conversion is 33% and selectivity towards HCFC-123 is 95%. The drawback of the process is lower conversions of CFC-113a. Japanese patents 04,29,942 (1992) and 04,29,493(1992) disclosed the conversion of HCFC-122 in presence of fluorinated Y-AI2O3 to HCFC-123 and the selectivity was in the range 80-86%. US patent 5,300,712 (1994) described liquid phase batch reaction from 2,2,2-trichlorotrifluoroethane (CFC-113a) to HCFC-
123 in presence of triphenylphosphine-Rhodium chloride complex. The drawback of this invention was lower conversion (44.5%).
References may be made to, JP 01,319,441(1989) and WO 93,09,080 (1993), which described the hydrodehalogentation of CFC-113a to HCFC-123 using Pt, Pd, Ru chlorides on a support, and in all the cases the conversion or selectivity was low. JP 03,284,638 (1991) claimed the formation of HCFC-123 from CFC-113a by catalytic hydrodehalogenation method with 100% conversion and 70% selectivity. US patent No.5,155,082 (1992) and EP 282,005 (1988) disclosed the method of preparation of HCFC-123 from perchloroethylene using chromia/alumina as catalysts, however the conversions are only in the range of 25-30%.
Chlorination of 2-chloro-1,1,1-trifluoroethane (HCFC-133a) at higher temperature was reported by EP 407,990 (1989), US patent 5,414,166 (1995) and EP.881,201 (1998) with or without catalysts to give HCFC-123 with low selectivity.
Thus all methods cited above have disadvantages either in conversions or in selectivity towards desired product. Preparation of certain raw materials like HCFC-133a is time consuming and tedious. The present invention relates to a improved process for HCFC-123 from indigenously available CFC-113a by catalytic hydrodehalogenation method and can be used at commercial level.
The novelty of the present invention lies in the catalytic conversion of harmful CFCs (eg., CFC-113a) to highly value added products HCFCs (eg., HCFC-123, an exclusive substitute for CFC-11 refrigerant) by using a transition metal halide impregnated carbon catalyst.
OBJECTIVES OF THE INVENTION
The main object of the present invention is to provide a viable process for the preparation of HCFC-123 by catalytic hydrodehalogenation method.
Another object of the present invention is to provide a process for the preparation of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) by catalytic
hydrodehalogenation of 2,2,2-trichloro trifluoroethane (CFC-113a) by using a transition metal halide impregnated carbon catalyst.
SUMMARY OF THE INVENTION
Accordingly the present invention provides an improved process for the
preparation of 2,2-dichloro-1,1,1 -trifluoroethane from 2,2,2-
trichlorotrifluoroethane, which comprises reacting 2,2,2-trichlorotrifluoroethane (CFC 113a) reacting with hydrogen in a molar ratio of H2 to CFC 113a in the range of 1-6 in a conventional reactor, in the presence of a catalyst, at a constant flow rate of CFC 113a and H2 in the range of 0.01-10 cc/min and 10-70 cc/min, respectively, at a temperature in the range of 70-250°C, for a contact time period of 20-200 sec to obtain the product stream, followed by drying and condensation of the above said stream, at a temperature of -20 to -30°C to obtain the desired 1,1,1,2-tetrafluoroethane (HFC-134a).
In an embodiment of the present invention the mole ratio of H2 to CFC 114a used is in the range of 1-3.
In another embodiment the constant flow rate of H2 used is in the range of 10-40 cc/min.
In yet another embodiment the catalyst used is a metal salt impregnated carbon catalyst.
In yet another embodiment the metal salt used in catalyst is selected from metal halide, metal sulphate and combination thereof.
In yet another embodiment the metal used in catalyst is selected from transition metal and rare earth element selected from the group consisting of Pd, Cu, Fe, Co, Rh, Ru and a combination thereof.
In yet another embodiment the catalyst used is selected from the group consisting of (1% PdCI2 1% FeCI3 )/C, (1% PdCI2-1% FeCI3)/C, (0.75% PdCI2-0.75% FeCI3)/C and (0.475%PdCI2,0.025% CuS04 0.475% PdCI2, 0.025% CuS04, 0.033% FeCI3) /C.
In yet another embodiment the contact time is in the range of 20 to 100 seconds.
In yet another embodiment the process is a continuous vapor phase hydrodechlorination reaction.
In yet another embodiment the reaction temperature used is in the range 120-160°C.
In still another embodiment the selectivity of HCFC-123 obtained is in the range of 50-93%.
In still another embodiment the conversion of CFC-113a is in the range of 85-99%.
DETAIL DESCRIPTION OF THE INVENTION
This invention provides an improved process for the preparation of 2,2-dichloro-1,1,1-trifluoroethane by catalytic hydrogenolysis of chlorofluorocarbons (CFC-113a) using a catalyst containing Pd/Pt and of at least one or more metals selected consisting of Cobalt, Copper, Iron, Ruthenium, Rhodium supported on carbon typically constitutes between 0.1 and 5 percent by wt. of the catalyst. Suitable hydrogenolysis catalyst may be prepared by treating carbon support with hydrochloric acid or nitric acid and then washed thoroughly with demineralised water to bring down the ash content. The present invention comprises i) preparation and activation of the catalyst ii) hydrodehalogenation of chlorofluoro carbon (CFC-113a) to the formation of hydrochlorofluorocarbon (HCFC-123). The process is a continuous vapor phase reaction and typically achieved at atmospheric or superatmospheric pressures. Generally, in order to provide substantial hydrodehalogenation to promote high product yields, the amount of hydrogen used is at least about one mole per mole of CFC-113a. The reaction is suitably carried out at a temperature, which depends to some extent on the formation of by-products. The desired temperatures are in the range 120°-160°C where by-products formation is minimum and higher selectivity towards HCFC-123 is achieved. The contact time of raw materials on the surface of the catalyst plays an important role in conversions and selectivity and is preferably between 30-70 sec. The exit product stream of the reactor is bubbled in demineralised water, dried over molecular sieves and cooled in condenser,
collected in receivers at -20 to -25°C. The progress of the reaction is monitored by periodically analyzing samples by G.C.
Comparative data

(TABLE REMOVED)

The present invention is described with reference to the following examples, which are explained by way of illustration and should not therefore be construed to limit the scope of invention.
Examples :
Preparation of water-washed carbon : The commercially available carbon extrudes (50 g) are soaked for 48 h at room temperature with occasional shaking in demineralised water in a 500 ml beaker. The carbon extrudes are collected on a fritted glass funnel and dried at 120°C followed by calcination at 300°C in air and obtained 45 g of dried calcined extrudes. The elemental analysis of carbon showed an ash content of 0.4%.
Preparation of HCI washed carbon : The commercially available carbon extrudes (50g) are soaked for 48 h with gentle stirring in 1M HCI. The extrudes
are collected on a fritted glass funnel and washed with demineralised water (10 lit). Finally, the extrudes are dried at 120°C followed by calcination at 300°C in air and obtained 44g of dried calcined extrudates which showed the ash content of 0.15%.
Catalyst preparation :
Catalyst - A : (1% PdCI2 1% FeCI3)/C : A solution of palladium chloride (0.25 g) in aq.hydrochloric acid solution (20 ml, 1M) is prepared and added slowly to water washed carbon extrudates (25g) using incipient impregnation method with occasional shaking and allowed for a period of 2h. The wet extrudates are dried at 120°C till getting the constant weight. A solution of FeCI3(0.25g) in aq.HCI solution is prepared and impregnated on above prepared catalyst with occasional shaking and dried at 120° till constant weight.
Catalyst - B : (1% PdCI2 - 1% FeCI3)/C : A solution of palladium chloride (0.25 g) dissolved in aq.hydrochloric acid (20 ml, 1M). The above prepared solution is impregnated on HCI-washed carbon extrudates (25 g) with occasional shaking at room temperature. After 2h, the wet extrudes are dried at 120° till constant weight. A solution of FeCI3(0.25 g) in aq.HCI is doped on the above prepared catalyst and dried at 120° till constant weight.
Catalyst-C : (0.75% PdCI2 - 0.75% FeCI3)/C : Acid washed carbon extrudates (25 g) are sequentially impregnated with solutions of palladium chloride (0.15 g) and Ferric chloride (0.15 g) in 1M Hydrochloric acid with occasional shaking. The wet catalyst is dried in oven at 120° till constant wt.
Catalyst-D : (0.475% PdCI2, 0.025% CuS04)/C : A mixture of palladium chloride ( 0.475 g) and copper sulphate (0.025 g) dissolved in aq. HCI and impregnated on acid washed carbon extrudates with occasional shaking. The wet catalyst is dried at 120°C till constant weight.
Catalyst-E : (0.475% PdCI2, 0.025% CuS04, 0.033% FeCI3)/C : Ferric chloride (0.005 g) is dissolved in aq. HCI solution (12 ml, 1M) and impregnated on catalyst-D extrudates (15 g) with occasional shaking. The catalyst is dried at 120°C till constant weight.
General procedure for hydrodehalogenation : SS tubular reactor of 15" x 3/4" o.d with provision for feeding CFC-113a and hydrogen gas independently with an additional line of nitrogen from top and product exit stream is from bottom side line. A thermowell is fixed from extreme bottom into the reactor with inside thermocouples to measure the bed temperature during the reaction. Electrical split furnace is used for heating the reactor to desired temperature and maintained by PID controller with in the range of ± 1°C for set temperature. The feed rate of CFC-113a is controlled by syringe pump and feed rates are in the range 0.01 - 10cc/min. The reactor exit line is connected to a bubbler, drier, condenser and receiver sequentially. Vapor sampling facility is also provided after drier for injecting the samples in GC.
Catalyst is loaded in the reactor and heated to a temperature of 175°C over a period of 5h, during which time nitrogen and hydrogen mixture is passed at a rate of 10cc/min each through the reactor bed. At the end of 5 hr, nitrogen flow is stopped, hydrogen flow increased to 20 cc/min, the reactor temperature raised to 275° C over 3 h and maintained at this temperature for an additional 16h. After this period, the reactor temperature was decreased to 120° C. CFC-113a and H2 feeding is started in predetermined molar ratios over catalyst bed and the exit stream is bubbled through water, dried over molecular sieves, condensed and collected in receivers at -20° to -25°C.
General procedure for product analysis : The acid free organic product leaving the reactor through bubbler is analysed on gas chromatograph. The column consisted 12" x 1/8" SS tube containing 5% porapak-Q and N2 is used as carrier gas. The product analysis are reported in area percent.
(TABLE REMOVED)

Advantages :
The main advantage of the present invention is the conversion of harmful CFCs to value added HCFCs instead of chemical destruction by incineration.
Another advantage of the present invention is the high % conversion of harmful CFCs to HCFCs with good selectivity.
Another advantage of the process is that it is a continuous process desirable for commercial operation.






We claim
1. A improved process for the preparation of 2,2-dichloro-l,l,l-trifluoroethane from 2,2,2-trichlorotrifluoroethane, which comprises reacting 2,2,2trichlorotrifluoroethane (CFC 113a) reacting with hydrogen in a molar ratio of H2 to CFC 113a in the range of 1-6 in a conventional reactor, in the presence of a catalyst, at a constant flow rate of CFC 113a and H2 in the range of 0.01-1 Occ/min and 10-70 cc/min, respectively, at a temperature in the range of 70-250°C, for a contact time period of 20-200 sec to obtain the product stream, followed by drying and condensation of the above said stream, at a temperature of -20 to -30°C to obtain the 2,2, dichloro-1,1,1-trichlorotrifluoroethane
2. A process as claimed in claim 1, wherein the mole ratio of H2 to CFC 114a used is in the range of 1-3.
3. A process as claimed in claims 1&2, wherein the constant flow rate of H2 used is in the range of 10-40 cc/min.
4. A process as claimed in claim 1-3, wherein the catalyst used is a metal salt impregnated carbon catalyst.
5. A process as claimed in claim 1-4, wherein the metal salt used in catalyst is selected from metal halide, metal sulphate and combination thereof.
6. A process as claimed in claim 1-5, wherein the metal used in catalyst is selected from transition metal and rare earth element selected from the group consisting of Pd, Cu, Fe, Co, Rh, Ru and a combination thereof.
7. A process as claimed in claim 1-6, wherein the catalyst use is selected from the group consisting of (1% PdCL2 1% fEcL3)/c, (1% pDcL2-l% fEcL3)/C(0.75% PdCl2, 0.025%CuSO4, 0.033% FeCl3)/C.
8. A process as claimed in claim 1-7, wherein the contact time is in the range of 20 to 100 seconds.
9. A process as claimed in claim 1-8, wherein the process is a continuous vapor phase hydrodechlorination reaction.
10. A process as claimed in claim 1-9, wherein the reaction temperature used is in the range of 120-160°C.
11. An improved process for the preparation of 2,2-dichloro-1,1,1 -trifluoroethane from 2,2,2-trichlorotrifluoroethane substantially as here in described with reference to examples accompanying the this specification.

Documents:

474-del-2005-abstract.pdf

474-DEL-2005-Claims-(27-07-2011).pdf

474-del-2005-claims.pdf

474-DEL-2005-Correspondence Others-(27-07-2011).pdf

474-del-2005-correspondence-others.pdf

474-del-2005-description (complete).pdf

474-del-2005-form-1.pdf

474-del-2005-form-18.pdf

474-del-2005-form-2.pdf

474-del-2005-form-3.pdf

474-del-2005-form-5.pdf


Patent Number 249831
Indian Patent Application Number 474/DEL/2005
PG Journal Number 46/2011
Publication Date 18-Nov-2011
Grant Date 15-Nov-2011
Date of Filing 04-Mar-2005
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 PAMULAPARTHY SHANTHAN RAO INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
2 YADLA RAMBABU INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
3 SRIPATHI NARAYAN REDDY INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
4 MADABHUSHI SRIDHAR INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
5 PUNNAMRAJU VENKATA SATYA SRINIVAS INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
6 THALLAPALLY YAKAIAH INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
7 BODDUPALLY PEDDA VENKATA LINGAIAH INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA.
PCT International Classification Number C07C 17/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA