Title of Invention

A PROCESS FOR THE PREPARATION OF 1,1,1,2-TETRA FLUOROETHANE FROM 1,1,-DICHLORO TETRAFLUORO ETHANE

Abstract The invention relates to a process for producing 1,1,1,2-tetrafluoroethane (HFC-134a) from the hydrogenolysis of 1,1-dichloro-tetrafluoroethane (CFC-114a). The process involve hydrodehalogenation of 1,1-dichloro tetrafluoroethane (CFC-114a) by reacting it with hydrogen in a molar ratio of H2 to CFC 114a in the range of 1-10 in a conventional flow system in the presence of a catalyst, at a constant flow rate of CFC 114a and H2 in the range of 2-10 g/hr and 10-70 cc/min., respectively, at a temperature in the range of 100-300°C, for a contact period of 5-80 sec to obtain the organic compound followed by drying and condensation at a temperature of-50 to -80°C to obtain the desired 1,1,1,2-tetrafluoroethane (HFC-134a).
Full Text FIELD OF THE INVENTION
The present invention relates to a process for the preparation of 1,1,1,2-tetrafluoroethane from 1,1-dichloro-tetrafluoroethane. More particularly the present invention relates to a process for the preparation of 1,1,1,2-tetrafluoroethane (HFC-134a) by catalytic hydrogenolysis of 1,1-dichloro-tetrafluoroethane (CFC-114a) using a metal halide impregnated v-Alumina / carbon catalyst.
BACK GROUND OF THE INVENTION
Reference may be made to British patent 1,578,935, wherein the catalytic hydrogenation of 1,1-dichloro-tetrafluoroethane at 280°C on a catalyst containing 5% of a palladium On charcoal yields a product mixture containing 70% of 1,1,1,2-tetrafluoroethane. As the concentration of palladium and temperature of reaction being high with low selectivity the method has disadvantage for commercial production of HFC-134a.
Reference may be made to JP 56-38131, shows obtaining R-134a from CFC-114a by reaction with hydrogen in the presence of palladium on active carbon support. The reported yield of R-134a is about ~7% with side products 1,1,1-trifluoroethane (HFC-143a) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) to the extent of 10% each respectively.
Another reference may be made to US 5602288, where hydrogenolysis of CFC-114a is disclosed. The palladium (0.5%) on carbon support in presence of hydrogen resulted 52% conversion with 87% selectivity towards the formation of HFC-134a. The disadvantage of the process is lower conversion and lower reaction time ~26 h.
Yet another references may be made to US patent 5,053,564 (1991) and EP 379396 (1990) wherein the preparation of HFC-134a is reported from CFC-114a using Pd/C (5%) catalyst with quantitative conversion and selectivity (95%). However the palladium content being high the commercial application may not be economical.
E.Kemnitz et.al [catalysis today, 85,153-168(2004)] investigated the mechanistic aspects of hydrodechlorination of CFC-114a to HFC-134a using metal fluoride supported on Pt/Pd catalysts. The palladium catalysts performed well. The conversion and selectivities are 92-97 and 74-79% respectively.
The hydrogenolysis of 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124) was disclosed by EP 03847830 using two or more combination of carbon supported Pd-Cu, Rh-Cu, Rh-Cu-W, Pd-Cu-La and Pd-Ag-W catalysts resulted high conversions (95%) and selectivity 97%. Though the results are good, another process is required for the preparation of HCFC-124 from CFC-114a. All the methods discussed have inherent limitations and drawbacks in terms of economies or lower conversions and selectivity. It is an object of the present invention to provide a better method of preparing HFC-134a by hydrodehalogenation of CFC-114a.
Comparative data of the present invention with the prior art references:
(TABLE REMOVED)
OBJECTIVES OF THE INVENTION
The main object of the present invention is to provide a process for the preparation of 1,1,1,2-tetrafluoroethane (HFC-134a) by catalytic hydrodehalogenation of 1,1-dicloro tetrafluoroethane (CFC-114a)
Another object of the present invention is the use of catalyst prepared by impregnating one or more metal halides on γ-Alumina / carbon by incipient wetness method.
The novelty of the present invention is in the preparation of 1,1,1,2-tetrafluoroethane by hydrodechlorination of CFC-114a using a trimetalic component on carbon furnished good conversion to the extent 96% and moderate selectivity 56%. The inventive step of the process is using lower content of palladium (1%) on alumina support gave good conversion (84%) and selectivity (86%). Usage of the lower content of palladium is commercially viable.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a process for the preparation of 1,1,1,2-tetrafluoroethane from 1,1-dichloro tetrafluoroethane, which comprises reacting 1,1-dichloro tetrafluoroethane with hydrogen in a molar ratio of H2 to 1,1-dichloro tetrafluoroethane in the range of 1-10 in a conventional flow system, in the presence of a catalyst, at a constant flow rate of 1,1-dichloro tetrafluoroethane and H2 in the range of 2-10 g/hr and 10-70 cc/min., respectively, at a temperature in the range of 100-300°C, for a contact period of 5-80 sec to obtain the organic compound followed by drying and condensation at a temperature of -50 to -80°C to obtain the desired 1,1,1,2-tetrafluoroethane.
In an embodiment of the present invention the mole ratio of H2 to CFC 114a
used is in the range of 1-6.
In another embodiment the catalyst used is a metal halide impregnated γ-
Alumina/carbon catalyst.
In yet another embodiment the metal halide impregnated y-Alumina/carbon catalyst used is selected from the group consisting of Pd-Zn/AI203, Pd/AI203, Pd,Cu,La/carbon, Pd-Fe/carbon and combination thereof.
In yet another embodiment the constant flow rate of CFC 114a used is in the range of 2-9 g/hr.
In yet another embodiment the constant flow rate of H2 used is in the range of 10-60 cc/min.
In yet another embodiment the temperature used in hydrodehalogination is in the range 150-275°C.
In yet another embodiment the condensation temperature used is in the range of-60to-70°C.
In still another embodiment the selectivity of HFC 134a obtained is in the range of 45-80%.
The process comprises series of heterogenous reactions on the catalyst surface, whereby adsorption of a reactant is essential. Though the micro mechanism is not clearly understood, it is believed that hydrogen molecules in the gas phase are adsorbed on the catalyst surface, and the adsorbed hydrogen atoms and the haloethane are reacted at the catalyst surface, whereby the reduction reaction proceeds. Based on these principles, optimization in combination of alloy elements, their proportions, parameters like temperature and mole ratios are studied. The process is conveniently divided as catalyst preparation and hydrodechlorination reaction of CFC-114a.
The following examples are given by the way of illustration and should not be construed to limit the scope of the invention.
Catalyst preparation:
Catalyst-A (Pd-Zn/Al203) : y-Alumina extrudates (surface area 150 m2/g) 20g are impregnated with zinc chloride (0.4 g) solution by incipient wetness method and allowed for 1h followed by it is dried at 150°C till constant weight. The extrudes are
treated with palladium chloride (0.2 g) solution and again dried at 200°C till constant weight.
Catalyst-B (Pd/Al203): Palladium chloride (0.3 g) is dissolved in dil.HCI solution (10.5 ml) and impregnated on y-Alumina (15 g) by incipient wetness method and allowed at ambient temperature for 2h. The wet catalyst is dried at 150°C for 10h till constant weight.
Catalyst-C: (Pd, Cu, La/Carbon): A mixture of palladium chloride (0.1187g) and copper sulphate (0.0062g) is dissolved in aq.hydrochloric acid solution (25%, 25ml) and impregnated on carbon extrudes (surface area 700 m2/g) by incipient wetness method. The wet catalyst is allowed to stay for 1h at ambient temperature and dried at 150°C for 10h till constant weight.
Catalyst-D (Pd - Fe): A mixture of palladium chloride (0.45g) and Ferric chloride (0.075g) were dissolved in aq.HCI solution (11.25 ml H20 + 3.75 ml HCI). The metal halide solution was impregnated on carbon extrudes (dried) by incipient wetness method. The wet extrudes were dried at 150°C till constant weight of catalyst.
General method of pretreatment of catalyst: Prior to each reaction, the catalyst was pretreated in flowing H2 & N2, 20 ml/min each from ambient temperature to 175°C over a period of 3h. The N2 flow is stopped and the temperature raised to 300°C in 5h and maintained at that temperature for 10h in presence of H2 flow. After reduction, the catalyst is cooled to the desired reaction temperature.
Hydrodechlorination reaction:
The hydrodechlorination of 1,1-dichloro tetrafluoroethane is conducted in a stainless-steel flow system at atmospheric pressure. Mass flow controllers maintain a constant flow of each reactant. The bed temperature maintained by electrically heated split furnaces controlled by PID instruments. The skin and bed temperatures are monitored by K-type thermocouples. Pressure monitoring and safety gadgets
provided to ensure safe operation of the reactor system. In a typical reaction experiment the total flow of the reactant mixture is in the range 5-25 cc/min consisted of 1,1-dichloro-tetrafluoroethane and hydrogen. The CF3CFCI2 is obtained from M/s. Navin Fluorine Industries, Surat and analysed by GC, determined that the purity was greater than 99%. The reaction is carried out in the range 100-300°C and the product exit stream is scrubbed with water. The acid free organic product is dried over molecular sieves and condensed in a receiver cooled at -60°C. Before condensing, the product stream was periodically withdrawn as vapor through gas tight syringe and analysed by GC. The results are tabulated in table-1.

(TABLE REMOVED)

Although the invention has been described in conjunction with specific embodiments, it is evident that many alternatives and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, the invention is intended to embrace all the alternatives and variations that fall within the spirit and scope of the appended claims.




We claim:
1. A process for the preparation of 1,1,1,2-tetrafluoroethane from 1,1-dichloro tetrafluoroethane, which comprises reacting 1,1-dichloro tetrafluoroethane with hydrogen in a molar ratio of H2 to 1,1-dichloro tetrafluoroethane in the range of 1-10 in a conventional flow system, in the presence of a catalyst, at a constant flow rate of 1,1-dichloro tetrafluoroethane and H2 in the range of 2-10 g/hr and 10-70 cc/min., respectively, at a temperature in the range of 100-300°C, for a contact period of 5-80 sec to obtain the organic compound followed by drying and condensation at a temperature of -50 to -80°C to obtain the desired 1,1,1,2-tetrafluoroethane.
2. A process as claimed in claim 1, wherein the mole ratio of H2 to 1,1-dichloro tetrafluoroethane used is in the range of 1-6.
3 A process as claimed in claims 1&2, wherein the catalyst used is a metal halide impregnated γ-Alumina/carbon catalyst.
4. A process as claimed in claims 1-3, wherein the metal halide impregnated γ-
Alumina/carbon catalyst used is selected from the group consisting of Pd-Zn/AI203,
Pd/AI203, Pd.Cu,La/carbon, Pd-Fe/carbon and combination thereof.
5. A process as claimed in claims 1-4, wherein the constant flow rate of 1,1-dichloro
tetrafluoroethane used is in the range of 2-9 g/hr.
6. A process as claimed in claims 1-5, wherein the constant flow rate of H2 used is in the range of 10-60 cc/min.
7. A process as claimed in claims 1-6, wherein the temperature used in hydrodehaloginationis in the range 150-275°C.
8. A process as claimed in claims 1-7, wherein the condensation temperature used is in the range of -60 to -70°C.
9. A process as claimed in claims 1-8, wherein the selectivity of 1,1,1,2-tetrafluoroethane obtained is in the range of 45-80%.
10. A process for the preparation of 1,1,1,2-tetrafluoroethane from 1,1-dichloro tetrafluoroethane, as herein described with reference to the examples.


Documents:

475-del-2005-Abstract-(11-03-2011).pdf

475-del-2005-abstract.pdf

475-del-2005-Claims-(11-03-2011).pdf

475-del-2005-claims.pdf

475-del-2005-Correspondence-Others-(11-03-2011).pdf

475-del-2005-correspondence-others.pdf

475-del-2005-Description (Complete)-(11-03-2011).doc

475-del-2005-Description (Complete)-(11-03-2011).pdf

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

475-del-2005-form-1.pdf

475-del-2005-form-18.pdf

475-del-2005-form-2.pdf

475-del-2005-Form-3-(11-03-2011).pdf

475-del-2005-form-3.pdf

475-del-2005-form-5.pdf


Patent Number 247631
Indian Patent Application Number 475/DEL/2005
PG Journal Number 17/2011
Publication Date 29-Apr-2011
Grant Date 28-Apr-2011
Date of Filing 04-Mar-2005
Name of Patentee COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH
Applicant Address ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 SRIPATHI NARAYAN REDDY INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
2 PAMULAPARTHY SHANTHAN RAO INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
3 GUNDAMARAJU ANURADHA INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
4 BANDA NARSAIAH INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
5 YADLA RAMBABU INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
6 PUNNAMRAJU VENKATA SATYA SURYA SRINIVAS INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
7 KAJJAM RAVINDRANATH INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY, HYDERABAD, 500 007, INDIA
PCT International Classification Number C07C 17/37
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA