Indian Patents. 193848:A PROCESS FOR THE GAS-PHASE HYDROGENOLYSIS OF CHLOROFLUOROCARBONS OR OF CHLOROFLUOROHYDROCARBONS

Title of Invention	A PROCESS FOR THE GAS-PHASE HYDROGENOLYSIS OF CHLOROFLUOROCARBONS OR OF CHLOROFLUOROHYDROCARBONS
Abstract	ABSTRACT PROCESS FOR THE HYDROGENOLYSIS OF CHLOROFLUOROCARBONS AND OF CHLOROFLUOROHYDROCARBONS The invention relates to the gas-phase hydrogenolysis of chlorofluorocarbons or of chlorofluorohydrocarbons in the presence of a palladixim based catalyst deposited on a support. Sulphur is incorporated into the catalyst in order to stabilize the catalytic activity.

Full Text	The present invention relates to a process for the gas-phase hydrogenolysis chlorofluorocarbons or of chlorofluorohydrocarbons. It appears to be clearly established that one factor responsible for the decrease of the ozone layer in the stratosphere is chlorofluorocarbons The reason for this is that liberated CFCs tend to percolate slowly up to the stratosphere, where they decompose by photodissociation releasing monoatomic chlorine. The chlorine atom destroys O3 (ozone) molecules in the course of catalytic cycles during which it is regenerated, thereby being able to affect several molecules. The international commxmity has thus decided to abandon the production of CFC and it has consequently become necessary to find and produce acceptable substitutes. CFCs are composed, as their cone suggests, of chlorine, fluorine and carbon atoms, but lack hydrogen. One strategy envisaged by producers is to replace them by molecules containing the same elements plus hydrogen, which are thus less stable and are capable of degrading rapidly in the lower atmosphere. The ultimate aim is to use compoxinds lacking chlorine, fluorohydrocarbons (FHCs), which should have no impact on ozone. Hydrogenolysis which comprises replacing a chlorine atom by a hydrogen atom in a molecule is a reaction which is particularly well suited to solving the problem posed. The importance of this reaction is shown by the nimbler of patents which relate to it. Thus, the hydrogenolysis of chlorodifluoromethane to difluoromethane is described in EP-A-0,508,660, and those of chlorotetrafluoroethane and dichlorotetrafluoroethane to tetrafluoroethane are mentioned in GB-A-1,578,933, EP-A-0,349,115 and US-A-4,873,3 81. This type of reaction also constitutes a good means of purifying the FHCs of the CFCs which may be present, as described in WO 94/02439 in the case of pentafluoroethane. However, the main drawback of hydrogenolysis processes lies in the stability of the catalytic activity over time. Indeed, cinder the often severe reaction conditions necessary for the complete conversion of the reactants, the catalyst becomes deactivated over time. It is thus necessary to replace it periodically or to find an effective means of regenerating the spent catalyst. In this respect, several techniques for regenerating hydrogenolysis catalysts are described in the literature. WO 93/24224 proposes oxidation of the spent catalyst with oxygen or an oxidizing agent. Treatments with chlorine (US-A-5,057,470) or with the CPC which may be the reactant to convert (US-A-4,980,324) also proved to be effective. However, these processes only reactivate the catalysts, which still have the same drawbacks after the treatment. It has now been fo\and that the incorporation of sulphur into a palladium-based catalyst deposited on a support imparts to this catalyst the property of being much more stable in gas-phase hydrogenolysis reactions, both in reactions for the synthesis of FHC from CFC or from CFHC, and in processes for the purifying of CFC impurities contained in the FHCs. The sulphur treatment of a hydrogenation/hydrogenolysis catalyst is known from FR-A-2,645,531, which describes the treatment of a Pd/C catalyst with sulphur-containing compounds in order to increase the selectivity for the liquid-phase hydrogenolysis of dichloroacetic acid (Click-COOH) to monochloroacetic acid (HjClC-COOH) . However, it was totally tm expected that treatment of the catalyst with a sulphur compound would allow its activity to be stabilized in the gas-phase hydrogenolysis of CFC or of CFHC, all the more so since the final research report from J.D. Park and J.R. Lacier published in 1959, which research was financed by the Air Force Office of Scientific Research (No. TR5899) and the Armed Services Technical In formations Agency (No. AD 162198), describes a treatment of the support in order to remove the sulphur before impregnation with palladium. According to the invention there is provided a process for the gas-phase hydrogenolysis of chlorofluorocarbons or of chlorofluorohydrocarbons in the presence of a palladium-based catalyst on a support, wherein sulphur is incorporated into the catalyst. In the catalyst used in the invention, the support may be charcoal, a fluoroalumina or aluminixan fluoride, and the palladium is advantageously deposited onto this support at a proportion of from 0.1 to 10% by weight relative to the total weight of the catalyst (Pd + support). The anoint of sulphur to be incorporated into the catalyst may range from 0.75 to 750 mg of sulphur per gram of palladium. It is preferably between 2 and 100 mg of sulphur per gram of and more particularly between 7.5 and 75 mg of sulphur per gram of The sulphur may be incorporated into the catalyst before and/or during its use. The incorporation may be performed in various ways depending on whether the sulphur-containing precursor compound is normally liquid (for example SClj, SjClj, CSj, thiophene, dimethyl sulphide, etc.) or gaseous (for example HjS, methyl mercaptan, etc.). When the sulphur-containing precursor compound is a liquid, the process may be performed by impregnation in the presence of a solvent whose choice depends on the nature of the sulphur-containing precursor. In the case of CS^, ethanol is particularly suitable; however, any solvent for CSj may be used. . After the impregnation, the catalyst is heat-treated under an atmosphere of a gas which may be inert, although hydrogen is preferably used, at a temperature of between 150 and 400"C to decompose the sulphur-containing composing. When the sulphur-containing precursor is normally gaseous (H2S, H3C-SH) or is a liquid which has a high vapour pressure (for example CSj) , it may be introduced onto the catalyst via the gaseous phase before or during admission of the hydrogen and the reactant to be hydrogenolysed. In this particularly advantageous technique for the "in situ" treatment of the catalyst in the reactor, the cutout of sulphur introduced onto the catalyst may be adjusted to the levels mentioned previously by varying the concentration of the sulphur-containing commoved in the gas, the flow rate of the gas and the duration of the treatment. Irrespective of the sulphur-containing compound and its mode of incorporation, the introduction of sulphur followed by a heat treatment leads to the formation of a solid phase of sulphur and palliatives of formula Pd4S. However, total conversion of the available palladium is not necessary to obtain a stable catalyst. The operating conditions for the hydrogenolysis reaction may vary within a wide range depending on the nature of the reactant to be hydrogenolysed (CFC or CFHC): • The reaction temperature is generally between 100 and 450°C, but it is preferred to work between 150 and 350°C. • The pressure may range from 1 to 50 bar; an increase in pressure has the effect of increasing the contact time and thus of making it possible to achieve high conversions for a given temperature. • The hourly flow rate of reactant fed continuously into the reactor may range from 0.01 to 12 mol per litre of catalyst. • The Hj/reactant molar ratio is generally between 0.5 and 10, preferably between 1 and 6. Examples of reactants to which the process according to the invention applies, include chloropentafluoroethane (F115), 1,1-dichloro-l,2,2,2-tetrafluoroethane {F114a), chlorodifluoromethane (F22), l-chloro-l,l-difluoroethane (F142b) and 1-chloro-1,2,2,2-tetrafluoroethane (F124), the hydrogenolysis of which leads respectively to pentafluoroethane (F125), 1,1,1,2-tetrafluoroethane (F134a), difluoromethane (F32), 1,1-difluoroethane (F152a) and 1,1,1,2-tetrafluoroethane {F134a). Mention may also be made of chlorofluoro(hydro)carbons such as 1,2,2-trichloro-l, 1, 3, 3, 3-pentaf luoropropane (F215aa) or 1,2-dichloro-1,1,3,3,3-pentafluoropropane (F225da) the hydrogenolysis of which leads to 1,1,1,3,3-pentafluoropropane (F245fa). Examples which follow illustrate the invention without limiting it. The percentages relating to the selectivities are expressed in moles. EXAMPLE 1: Comparative 75 ml of a commercial Pd/C catalyst containing 3% by weight of palladium are introduced into a ttibular Inconel reactor 45 cm in length and 2.72 cm in internal diameter. Prior to the introduction of the reactants, the catalyst is reduced at 300"C under an atmospheric pressure of hydrogen. 330°C 0.107 mol/hour 0.286 mol/hour 0.018 mol/hour A mixture of hydrogen, pentafluoroethane (F125} and chloropentafluoroethane (F115) are passed over the catalyst under the following operating conditions: Temperature Flow rate of hydrogen Flow rate of F125 Flow rate of F115 Analysis is performed by chromatography (6C) in line at the reactor outlet. The results collated in the following table show a rapid decrease in the activity of the catalyst over time. TIME (hours) CONVERSION (%) of F115 SELECTIVITY {% ) FOR F125 F134a Fl43a 11 90.3 93.8 1.4 4.a 32 88.0 94.9 1.0 4.1 40 86.2 95.1 1.0 3.9 60 83.3 95.3 1.0 3.7 68 82.3 95.3 1.1 3.6 80 81.3 95.4 1.0 3.6 92 77.9 95.6 1.0 3.4 100 77.9 95.6 0.9 3.5 108 76.5 95.7 1.0 3.3 122 75.1 95.6 1.0 3.4 130 73.7 95.5 1.1 3.4 148 70.9 95.7 0.9 3.4 170 67.8 95.7 1.0 3.3 190 64.3 95.5 1.0 3.5 208 61.3 95.7 0.9 3.4 230 57.2 95.9 0.8 3.3 252 54.8 95.8 0.9 3.3 268 52.0 95.9 0.9 3.2 289 49.0 95.8 0.8 3.4 308 45.0 96.0 0.9 3.1 EXAMPLE 2 a) Treatment of the catalyst 75 ml of the same commercial Pd/C catalyst as in the above example are loaded into a rotary evaporator, followed by introduction of 100 ml of an ethanol solution containing 0.011 mol/litre of CSj. The solid is maintained in contact with the solution at 20°C for 20 hours. The catalyst is then recovered by filtration, followed by reduction at 300°C under an atmospheric pressure of hydrogen for 4 hours. The amount of sulphur bound is 0.2% by weight and X-ray diffraction demonstrates the fozmation of a Pd4S phase. b) Purification of the F125 75 ml of the catalyst prepared above are introduced into the same tubular reactor as in Example 1, followed by passage of a mixture of hydrogen, pentafluoroethane (F125) and chloropentafluoroethane (F115) over this catalyst under the following operating conditions: Temperature : 33 0°C Flow rate of hydrogen : 0.107 mol/hour Flow rate of F125 : 0.2 86 mol/hour Flow rate of F115 : 0.018 mol/hour The results of the analysis performed by chromatography (GC) in line at the reactor outlet are collated in the following table. Appreciable stability of the catalytic activity is observed. TIME (hours) CONVERSION (%) of F115 SELECTIVITY (%) FOR F125 F134a F143a 27 59.4 76.2 6.4 17.4 35 60.4 76.9 6.2 16.9 45 60.0 81.9 6.4 11.7 65 63.8 84.4 5.9 9.7 77 61.6 84.6 6.0 9.4 79 63.7 84.8 5.7 9.5 95 60.8 84.2 6.3 9.5 105 63.0 85.2 5.6 9.2 115 62.7 84.3 5.9 9.8 125 62.7 84.8 5.6 9.6 143 62.5 84.7 5.6 9.7 157 62.8 83.0 5.4 11.6 164 65.9 86.7 5.1 8.2 197 65.6 86.7 5.1 8.2 208 62.8 87.5 5.2 7.3 212 61.4 85.8 5.5 8.7 234 62.6 85.6 5.1 9.3 254 62.0 85.9 5.1 9.0 265 62.7 86.7 5.2 8.1 292 63.1 87.6 5.1 7.3 296 63.5 87.5 4.9 7.6 313 63.5 88.5 5.0 6.5 EXAMPLE 3 a) Treatment of the catalyst The process is performed as in Example 2a^ but with 100 ml of an ethanol solution containing 0.001 mol/litre of CSj. X-ray diffraction detects no Pad’s crystallized phase, but the sulphur analysis shows the presence of 500 ppm by weight of sulphur on the catalyst. b) Purification of the F125 With the catalyst thus treated and the process being performed as in Example 2b, the results collated in the following table were obtained: TIME (hours) CONVERSION (%) of F115 SELECTIVITY (%) FOR F125 F134a F143a 21 65.8 86.7 4.9 8.4 46 62.6 87.6 4.6 7.8 70 62.7 88.5 4.6 6.9 80 62.8 88.7 4.4 6.9 96 61.0 88.2 4.5 7.3 101 61.6 89.2 4.3 6.5 115 58.9 88.6 4.5 6.9 127 59.9 88.8 4.0 7.2 176 61,2 89.4 3.8 6.8 185 62.6 90.6 3.5 5.9 195 61.9 90.2 3.4 6.4 205 62.0 90.8 3.5 5.7 215 61.0 90.2 3.5 6.3 243 61.6 91.1 3.1 5.8 251 61.6 90.7 3.1 6.2 273 58.4 90.5 3.3 6.2 315 58.7 90.7 3.1 6.2 325 61.0 91.0 3.0 6.0 The level of conversion is the same as in Example 2a with the same stability over time. An improvement in the selectivity for F125 is also noted. EXAMPLE 4; 75 ml of a commercial Pd/C catalyst containing 2% by weight of palladium are introduced^ into a tubular Income reactor 45 cm in length and 2.72 cm in internal diameter. Prior to the introduction of the reactants, the catalyst is reduced at 300°C under an atmospheric pressure of hydrogen. 250°C 0.103 mol/hour 0.281 mol/hour 0.018 mol/hour A mixture of hydrogen, pentafluoroethane (F125) and chloropentafluoroethane (F115) are passed over the catalyst tinder the following operating conditions: Temperature Flow rate of hydrogen Flow rate of F125 Flow rate of F115 The analysis performed by chromatography (GC) in line at the reactor outlet gives the results collated in the following table. A decrease in the activity of the catalyst over time is noted. TIME (hours) CONVERSION (%) of F115 SELECTIVITY (% ) FOR F143a F125 F134a 31 43.1 12.9 84.6 2.S 50 40.9 13.0 84.2 2.8 75 40.0 12.8 84.9 2.3 80 40.4 12.4 85.4 2.2 143 38.2 11.1 86.6 2.3 177 36.9 18.0 79.8 2.2 180 37.6 14.2 83.8 2.0 193 36.6 13.0 84.8 2.2 218 34.4 14.6 83.0 2.4 241 33.8 15.7 81.8 2.5 260 33.0 15.0 82.5 2.5 270 32.6 15.7 81.9 2.4 290 32.1 16.0 81.7 2.3 330 30.0 15.6 82.0 2.4 350 29.8 15.2 82.3 2.5 390 28.3 16.0 81.6 2.4 415 27.4 15.0 82.7 2.3 430 27.1 15.7 82.0 2.3 450 26.1 16.0 81.7 2.3 500 24.0 15.6 82.1 2.3 EXAMPLE 5 75 ml of the same commercial 2% Pd/C catalyst as in Example 4 are introduced into the same reactor as in Example 4. Prior to the introduction of the reactants, the catalyst is treated with hydrogen containing 100 ppm of hydrogen sulphide (HjS) at room temperature for 60 hours with a gas flow rate of 6 1/h. The catalyst is then reduced at 300°C under an atmospheric pressure of hydrogen. X-ray diffraction demonstrates the formation of a Pd4S phase. A mixture of hydrogen, pentafluoroethane (F125) and chloropentafluoroethane (F115) are passed over the catalyst \inder the following operating conditions: Temperature : 250°C Flow rate of hydrogen : 0.103 mol/hour Flow rate of F125 : 0.281 mol/hour Flow rate of F115 : 0.018 mol/hour The analysis performed by chromatography (GC) in line at the reactor outlet gives the results collated in the following table. Constant activity of the catalyst over time is noted. TIME (hours) CONVERSION (%) of F115 SELECTIVITY {% ) FOR F143a F125 F134a 10 32.4 35.2 64.8 1.0 21 31.8 36.8 62.2 1.0 30 32.8 34.9 63.7 1.4 40 32.5 35.1 63.8 1.1 72 32.0 32.6 65.9 1.5 140 31.3 33.3 65.5 1.2 150 32.3 27.3 71.3 1.4 165 32.0 27.5 71.2 1.3 189 32.0 26.5 72.0 1.5 250 32.1 24.8 73.7 1.5 280 32.6 22.0 76.5 1.5 290 31.8 21.5 77.0 1.5 306 33.0 21.1 77.4 1.5 350 32.3 19.5 79.0 1.5 395 31.8 19.0 79.5 1.5 430 32.4 18.1 80.4 1.5 450 31.5 18.0 80.5 1.5 500 32.2 17.6 80.9 1.5 EXAMPLE 6 a) Treatment of the catalyst 75 ml of the same commercial 2% Pd/C catalyst as in Example 4 are loaded into a rotary evaporator, followed by introduction of 100 ml of an ethanol solution containing 0.007 mol/litre of CSj. The solid is maintained in contact with the solution at 20°C for 2 0 hours. The catalyst is then recovered by filtration, followed by reduction at 300**C under an atmospheric pressure of hydrogen for 4 hours. The amount of sulphur bound is 0.15% by weight and X-ray diffraction demonstrates the formation of a Pd4S phase. b) Synthesis of the F125 75 ml of the catalyst prepared above are introduced into the same tubular reactor as in Example 4, followed by passage of a mixture of hydrogen and chloropentafluoroethane (F115) into the reactor iinder the following operating conditions: Temperature : 250°C Flow rate of hydrogen : 0.147 mol/hour Flow rate of F115 : 0.026 mol/hour The results of the analyses performed by chromatography (GO in line at the reactor outlet are collated in the following table. Good stability of the activity of the catalyst over time is noted. TIME (hours) CONVERSION (%) of F115 SELECTIVITY (% ) FOR F125 F143a F134a 175 47.8 81.7 16.2 2.1 181 47.4 82.1 15.9 2.0 191 47.1 82.5 15.5 2.0 201 46.9 83.0 15.0 2.0 211 47.3 83.7 14.4 1.9 219 47.2 83.8 14.3 1.9 229 47.0 83.9 14.1 2.0 239 45.8 83.2 14.7 2.1 251 45.8 83.3 14.6 2.1 261 45.4 83.3 14.6 2.1 271 45.4 83.1 14.7 2.2 281 45.2 83.1 14.7 2.2 300 46.0 83.4 14.5 2.1 310 46.9 83.0 15.0 2.0 We Claim: 1. A process for the gas-phase hydrogenolysis of chlorofluorocarbons or of chlorofluorohydrocarbons in the presence of a palladium-based catalyst on a support, wherein sulphur is incorporated into the catalyst. 2. The process according to claim 1, in which the amount of sulphur per gram of palladium is between 0 75 and 750 mg. 3. The process according to claim 2, in which the amount of sulphur per gram of palladium is from 2 to 100 mg. 4. The process according to claim 2, in which the amount of sulphur per gram of palladium is from 7.5 to 75 mg. 5. The process according to any one of the preceding claims, in which the palladium represents from 0.1 to 10% of the total weight of the catalyst. 6. The process according to any one of the preceding claims, in which the sulphur is incorporated into the catalyst using a precursor chosen from sulphur chloride, sulphur dichloride, carbon disulphide, thiophene, hydrogen sulphide, methyl mercaptan and dim ethyl sulphide. 7. The process according to any one of the preceding claims, in which the sulphur is incorporated into the catalyst by impregnation using a solution of a precursor which is normally liquid, and treatment under hydrogen at a temperature of between 150 and 400°C. 8. The process according to claim 7, in which an ethanolic solution of carbon disulphide is used. 9. The process according to any one of the preceding claims, in which the sulphur is introduced into the catalyst via the gaseous phase before and/or during the hydrogenolysis reaction. 10. The process according to claim 9, in which the precursor introduced in gaseous form is hydrogen sulphide, methyl mercaptan or carbon disulphide. 11. The process according to any one of the preceding claims, in which chloropentafluoroethane is subjected to the gas-phase hydrogenolysis with the formation of pentafluoroethane. 12. The process according to any one of claims 1 to 10, in which chloropentafluoroethane, present in crude pentafluoroethane, is subjected to the gas- phase hydrogenolysis with conversion of the chloropentafluoroethane to pentafluoroethane, 13. A process for the gas-phase hydrogenolysis of chlorofluorocarbons or of chlorofluorohydrocarbons substantially as herein described and exemplified.

Full Text

The present invention relates to a process for the gas-phase hydrogenolysis chlorofluorocarbons or of chlorofluorohydrocarbons.
It appears to be clearly established that one factor responsible for the decrease of the ozone layer in the stratosphere is chlorofluorocarbons The reason for this is that liberated CFCs tend to percolate slowly up to the stratosphere, where they decompose by photodissociation releasing monoatomic chlorine. The chlorine atom destroys O3 (ozone) molecules in the course of catalytic cycles during which it is regenerated, thereby being able to affect several molecules. The international commxmity has thus decided to abandon the production of CFC and it has consequently become necessary to find and produce acceptable substitutes.
CFCs are composed, as their cone suggests, of chlorine, fluorine and carbon atoms, but lack hydrogen. One strategy envisaged by producers is to replace them by molecules containing the same elements plus hydrogen, which are thus less stable and are capable of degrading rapidly in the lower atmosphere. The ultimate aim is to use compoxinds lacking chlorine, fluorohydrocarbons (FHCs), which should have no impact on ozone.

Hydrogenolysis which comprises replacing a chlorine atom by a hydrogen atom in a molecule is a reaction which is particularly well suited to solving the problem posed.
The importance of this reaction is shown by the nimbler of patents which relate to it. Thus, the hydrogenolysis of chlorodifluoromethane to difluoromethane is described in EP-A-0,508,660, and those of chlorotetrafluoroethane and dichlorotetrafluoroethane to tetrafluoroethane are mentioned in GB-A-1,578,933, EP-A-0,349,115 and US-A-4,873,3 81. This type of reaction also constitutes a good means of purifying the FHCs of the CFCs which may be present, as described in WO 94/02439 in the case of pentafluoroethane.
However, the main drawback of hydrogenolysis processes lies in the stability of the catalytic activity over time. Indeed, cinder the often severe reaction conditions necessary for the complete conversion of the reactants, the catalyst becomes deactivated over time. It is thus necessary to replace it periodically or to find an effective means of regenerating the spent catalyst.
In this respect, several techniques for regenerating hydrogenolysis catalysts are described in the literature. WO 93/24224 proposes oxidation of the spent catalyst with oxygen or an oxidizing agent. Treatments with chlorine (US-A-5,057,470) or with the

CPC which may be the reactant to convert (US-A-4,980,324) also proved to be effective. However, these processes only reactivate the catalysts, which still have the same drawbacks after the treatment.
It has now been fo\and that the incorporation of sulphur into a palladium-based catalyst deposited on a support imparts to this catalyst the property of being much more stable in gas-phase hydrogenolysis reactions, both in reactions for the synthesis of FHC from CFC or from CFHC, and in processes for the purifying of CFC impurities contained in the FHCs.
The sulphur treatment of a hydrogenation/hydrogenolysis catalyst is known from FR-A-2,645,531, which describes the treatment of a Pd/C catalyst with sulphur-containing compounds in order to increase the selectivity for the liquid-phase hydrogenolysis of dichloroacetic acid (Click-COOH) to monochloroacetic acid (HjClC-COOH) . However, it was totally tm expected that treatment of the catalyst with a sulphur compound would allow its activity to be stabilized in the gas-phase hydrogenolysis of CFC or of CFHC, all the more so since the final research report from J.D. Park and J.R. Lacier published in 1959, which research was financed by the Air Force Office of Scientific Research (No. TR5899) and the Armed Services Technical In formations Agency (No. AD 162198), describes a treatment of the support in order to remove the sulphur before impregnation with palladium.

According to the invention there is provided a process for the gas-phase hydrogenolysis of chlorofluorocarbons or of chlorofluorohydrocarbons in the presence of a palladium-based catalyst on a support, wherein sulphur is incorporated into the catalyst.
In the catalyst used in the invention, the support may be charcoal, a fluoroalumina or aluminixan fluoride, and the palladium is advantageously deposited onto this support at a proportion of from 0.1 to 10% by weight relative to the total weight of the catalyst (Pd + support).
The anoint of sulphur to be incorporated into the catalyst may range from 0.75 to 750 mg of sulphur per gram of palladium. It is preferably between 2 and 100 mg of sulphur per gram of and more particularly between 7.5 and 75 mg of sulphur per gram of
The sulphur may be incorporated into the catalyst before and/or during its use. The incorporation may be performed in various ways depending on whether the sulphur-containing precursor compound is normally liquid (for example SClj, SjClj, CSj, thiophene, dimethyl sulphide, etc.) or gaseous (for example HjS, methyl mercaptan, etc.).
When the sulphur-containing precursor compound is a liquid, the process may be performed by impregnation in the presence of a solvent whose choice

depends on the nature of the sulphur-containing precursor. In the case of CS^, ethanol is particularly suitable; however, any solvent for CSj may be used. . After the impregnation, the catalyst is heat-treated under an atmosphere of a gas which may be inert, although hydrogen is preferably used, at a temperature of between 150 and 400"C to decompose the sulphur-containing composing.
When the sulphur-containing precursor is normally gaseous (H2S, H3C-SH) or is a liquid which has a high vapour pressure (for example CSj) , it may be introduced onto the catalyst via the gaseous phase before or during admission of the hydrogen and the reactant to be hydrogenolysed. In this particularly advantageous technique for the "in situ" treatment of the catalyst in the reactor, the cutout of sulphur introduced onto the catalyst may be adjusted to the levels mentioned previously by varying the concentration of the sulphur-containing commoved in the gas, the flow rate of the gas and the duration of the treatment.
Irrespective of the sulphur-containing compound and its mode of incorporation, the introduction of sulphur followed by a heat treatment leads to the formation of a solid phase of sulphur and palliatives of formula Pd4S. However, total conversion of the available palladium is not necessary to obtain a stable catalyst.

The operating conditions for the hydrogenolysis reaction may vary within a wide range depending on the nature of the reactant to be hydrogenolysed (CFC or CFHC):
• The reaction temperature is generally between 100 and 450°C, but it is preferred to work between 150 and 350°C.
• The pressure may range from 1 to 50 bar; an increase in pressure has the effect of increasing the contact time and thus of making it possible to achieve high conversions for a given temperature.
• The hourly flow rate of reactant fed continuously into the reactor may range from 0.01 to 12 mol per litre of catalyst.
• The Hj/reactant molar ratio is generally between 0.5 and 10, preferably between 1 and 6.
Examples of reactants to which the process according to the invention applies, include chloropentafluoroethane (F115), 1,1-dichloro-l,2,2,2-tetrafluoroethane {F114a), chlorodifluoromethane (F22), l-chloro-l,l-difluoroethane (F142b) and 1-chloro-1,2,2,2-tetrafluoroethane (F124), the hydrogenolysis of which leads respectively to pentafluoroethane (F125), 1,1,1,2-tetrafluoroethane (F134a), difluoromethane (F32), 1,1-difluoroethane (F152a) and 1,1,1,2-tetrafluoroethane {F134a). Mention may also be made of

chlorofluoro(hydro)carbons such as 1,2,2-trichloro-l, 1, 3, 3, 3-pentaf luoropropane (F215aa) or 1,2-dichloro-1,1,3,3,3-pentafluoropropane (F225da) the hydrogenolysis of which leads to 1,1,1,3,3-pentafluoropropane (F245fa).
Examples which follow illustrate the invention without limiting it. The percentages relating to the selectivities are expressed in moles.
EXAMPLE 1: Comparative
75 ml of a commercial Pd/C catalyst containing 3% by weight of palladium are introduced into a ttibular Inconel reactor 45 cm in length and 2.72 cm in internal diameter. Prior to the introduction of the reactants, the catalyst is reduced at 300"C under an atmospheric pressure of hydrogen.
330°C
0.107 mol/hour 0.286 mol/hour 0.018 mol/hour
A mixture of hydrogen, pentafluoroethane (F125} and chloropentafluoroethane (F115) are passed over the catalyst under the following operating conditions:
Temperature
Flow rate of hydrogen
Flow rate of F125
Flow rate of F115
Analysis is performed by chromatography (6C) in line at the reactor outlet. The results collated in the following table show a rapid decrease in the activity of the catalyst over time.

TIME (hours) CONVERSION (%) of F115 SELECTIVITY {% ) FOR

F125 F134a Fl43a
11 90.3 93.8 1.4 4.a
32 88.0 94.9 1.0 4.1
40 86.2 95.1 1.0 3.9
60 83.3 95.3 1.0 3.7
68 82.3 95.3 1.1 3.6
80 81.3 95.4 1.0 3.6
92 77.9 95.6 1.0 3.4
100 77.9 95.6 0.9 3.5
108 76.5 95.7 1.0 3.3
122 75.1 95.6 1.0 3.4
130 73.7 95.5 1.1 3.4
148 70.9 95.7 0.9 3.4
170 67.8 95.7 1.0 3.3
190 64.3 95.5 1.0 3.5
208 61.3 95.7 0.9 3.4
230 57.2 95.9 0.8 3.3
252 54.8 95.8 0.9 3.3
268 52.0 95.9 0.9 3.2
289 49.0 95.8 0.8 3.4
308 45.0 96.0 0.9 3.1
EXAMPLE 2
a) Treatment of the catalyst
75 ml of the same commercial Pd/C catalyst as in the above example are loaded into a rotary evaporator, followed by introduction of 100 ml of an ethanol solution containing 0.011 mol/litre of CSj. The solid is maintained in contact with the solution at 20°C for 20 hours. The catalyst is then recovered by filtration, followed by reduction at 300°C under an atmospheric pressure of hydrogen for 4 hours. The amount of sulphur bound is 0.2% by weight and X-ray diffraction demonstrates the fozmation of a Pd4S phase.
b) Purification of the F125
75 ml of the catalyst prepared above are introduced into the same tubular reactor as in

Example 1, followed by passage of a mixture of
hydrogen, pentafluoroethane (F125) and
chloropentafluoroethane (F115) over this catalyst under
the following operating conditions:
Temperature : 33 0°C
Flow rate of hydrogen : 0.107 mol/hour
Flow rate of F125 : 0.2 86 mol/hour
Flow rate of F115 : 0.018 mol/hour
The results of the analysis performed by
chromatography (GC) in line at the reactor outlet are
collated in the following table. Appreciable stability
of the catalytic activity is observed.

TIME (hours) CONVERSION (%) of F115 SELECTIVITY (%) FOR

F125 F134a F143a
27 59.4 76.2 6.4 17.4
35 60.4 76.9 6.2 16.9
45 60.0 81.9 6.4 11.7
65 63.8 84.4 5.9 9.7
77 61.6 84.6 6.0 9.4
79 63.7 84.8 5.7 9.5
95 60.8 84.2 6.3 9.5
105 63.0 85.2 5.6 9.2
115 62.7 84.3 5.9 9.8
125 62.7 84.8 5.6 9.6
143 62.5 84.7 5.6 9.7
157 62.8 83.0 5.4 11.6
164 65.9 86.7 5.1 8.2
197 65.6 86.7 5.1 8.2
208 62.8 87.5 5.2 7.3
212 61.4 85.8 5.5 8.7
234 62.6 85.6 5.1 9.3
254 62.0 85.9 5.1 9.0
265 62.7 86.7 5.2 8.1
292 63.1 87.6 5.1 7.3
296 63.5 87.5 4.9 7.6
313 63.5 88.5 5.0 6.5

EXAMPLE 3
a) Treatment of the catalyst
The process is performed as in Example 2a^ but with 100 ml of an ethanol solution containing 0.001 mol/litre of CSj. X-ray diffraction detects no Pad’s crystallized phase, but the sulphur analysis shows the presence of 500 ppm by weight of sulphur on the catalyst.
b) Purification of the F125
With the catalyst thus treated and the process being performed as in Example 2b, the results collated in the following table were obtained:

TIME (hours) CONVERSION (%) of F115 SELECTIVITY (%) FOR

F125 F134a F143a
21 65.8 86.7 4.9 8.4
46 62.6 87.6 4.6 7.8
70 62.7 88.5 4.6 6.9
80 62.8 88.7 4.4 6.9
96 61.0 88.2 4.5 7.3
101 61.6 89.2 4.3 6.5
115 58.9 88.6 4.5 6.9
127 59.9 88.8 4.0 7.2
176 61,2 89.4 3.8 6.8
185 62.6 90.6 3.5 5.9
195 61.9 90.2 3.4 6.4
205 62.0 90.8 3.5 5.7
215 61.0 90.2 3.5 6.3
243 61.6 91.1 3.1 5.8
251 61.6 90.7 3.1 6.2
273 58.4 90.5 3.3 6.2
315 58.7 90.7 3.1 6.2
325 61.0 91.0 3.0 6.0
The level of conversion is the same as in Example 2a with the same stability over time. An improvement in the selectivity for F125 is also noted.

EXAMPLE 4;
75 ml of a commercial Pd/C catalyst containing 2% by weight of palladium are introduced^ into a tubular Income reactor 45 cm in length and 2.72 cm in internal diameter. Prior to the introduction of the reactants, the catalyst is reduced at 300°C under an atmospheric pressure of hydrogen.
250°C
0.103 mol/hour 0.281 mol/hour 0.018 mol/hour
A mixture of hydrogen, pentafluoroethane (F125) and chloropentafluoroethane (F115) are passed over the catalyst tinder the following operating conditions:
Temperature
Flow rate of hydrogen
Flow rate of F125
Flow rate of F115
The analysis performed by chromatography (GC) in line at the reactor outlet gives the results collated in the following table. A decrease in the activity of the catalyst over time is noted.

TIME (hours) CONVERSION (%) of F115 SELECTIVITY (% ) FOR

F143a F125 F134a
31 43.1 12.9 84.6 2.S
50 40.9 13.0 84.2 2.8
75 40.0 12.8 84.9 2.3
80 40.4 12.4 85.4 2.2
143 38.2 11.1 86.6 2.3
177 36.9 18.0 79.8 2.2
180 37.6 14.2 83.8 2.0
193 36.6 13.0 84.8 2.2
218 34.4 14.6 83.0 2.4
241 33.8 15.7 81.8 2.5
260 33.0 15.0 82.5 2.5
270 32.6 15.7 81.9 2.4
290 32.1 16.0 81.7 2.3
330 30.0 15.6 82.0 2.4
350 29.8 15.2 82.3 2.5
390 28.3 16.0 81.6 2.4
415 27.4 15.0 82.7 2.3
430 27.1 15.7 82.0 2.3
450 26.1 16.0 81.7 2.3
500 24.0 15.6 82.1 2.3
EXAMPLE 5
75 ml of the same commercial 2% Pd/C catalyst as in Example 4 are introduced into the same reactor as in Example 4. Prior to the introduction of the reactants, the catalyst is treated with hydrogen containing 100 ppm of hydrogen sulphide (HjS) at room temperature for 60 hours with a gas flow rate of 6 1/h. The catalyst is then reduced at 300°C under an atmospheric pressure of hydrogen. X-ray diffraction demonstrates the formation of a Pd4S phase.
A mixture of hydrogen, pentafluoroethane (F125) and chloropentafluoroethane (F115) are passed over the catalyst \inder the following operating conditions:
Temperature : 250°C

Flow rate of hydrogen : 0.103 mol/hour
Flow rate of F125 : 0.281 mol/hour
Flow rate of F115 : 0.018 mol/hour
The analysis performed by chromatography (GC) in line at the reactor outlet gives the results collated in the following table. Constant activity of the catalyst over time is noted.

TIME (hours) CONVERSION (%) of F115 SELECTIVITY {% ) FOR

F143a F125 F134a
10 32.4 35.2 64.8 1.0
21 31.8 36.8 62.2 1.0
30 32.8 34.9 63.7 1.4
40 32.5 35.1 63.8 1.1
72 32.0 32.6 65.9 1.5
140 31.3 33.3 65.5 1.2
150 32.3 27.3 71.3 1.4
165 32.0 27.5 71.2 1.3
189 32.0 26.5 72.0 1.5
250 32.1 24.8 73.7 1.5
280 32.6 22.0 76.5 1.5
290 31.8 21.5 77.0 1.5
306 33.0 21.1 77.4 1.5
350 32.3 19.5 79.0 1.5
395 31.8 19.0 79.5 1.5
430 32.4 18.1 80.4 1.5
450 31.5 18.0 80.5 1.5
500 32.2 17.6 80.9 1.5
EXAMPLE 6
a) Treatment of the catalyst
75 ml of the same commercial 2% Pd/C catalyst as in Example 4 are loaded into a rotary evaporator, followed by introduction of 100 ml of an ethanol solution containing 0.007 mol/litre of CSj. The solid is maintained in contact with the solution at 20°C for 2 0 hours. The catalyst is then recovered by filtration, followed by reduction at 300**C under an atmospheric

pressure of hydrogen for 4 hours. The amount of sulphur
bound is 0.15% by weight and X-ray diffraction
demonstrates the formation of a Pd4S phase.
b) Synthesis of the F125
75 ml of the catalyst prepared above are
introduced into the same tubular reactor as in
Example 4, followed by passage of a mixture of hydrogen
and chloropentafluoroethane (F115) into the reactor
iinder the following operating conditions:
Temperature : 250°C
Flow rate of hydrogen : 0.147 mol/hour
Flow rate of F115 : 0.026 mol/hour
The results of the analyses performed by chromatography (GO in line at the reactor outlet are collated in the following table. Good stability of the activity of the catalyst over time is noted.

TIME (hours) CONVERSION (%) of F115 SELECTIVITY (% ) FOR

F125 F143a F134a
175 47.8 81.7 16.2 2.1
181 47.4 82.1 15.9 2.0
191 47.1 82.5 15.5 2.0
201 46.9 83.0 15.0 2.0
211 47.3 83.7 14.4 1.9
219 47.2 83.8 14.3 1.9
229 47.0 83.9 14.1 2.0
239 45.8 83.2 14.7 2.1
251 45.8 83.3 14.6 2.1
261 45.4 83.3 14.6 2.1
271 45.4 83.1 14.7 2.2
281 45.2 83.1 14.7 2.2
300 46.0 83.4 14.5 2.1
310 46.9 83.0 15.0 2.0

We Claim:
1. A process for the gas-phase hydrogenolysis of chlorofluorocarbons or of chlorofluorohydrocarbons in the presence of a palladium-based catalyst on a support, wherein sulphur is incorporated into the catalyst.
2. The process according to claim 1, in which the amount of sulphur per gram of palladium is between 0 75 and 750 mg.
3. The process according to claim 2, in which the amount of sulphur per gram of palladium is from 2 to 100 mg.
4. The process according to claim 2, in which the amount of sulphur per gram of palladium is from 7.5 to 75 mg.
5. The process according to any one of the preceding claims, in which the palladium represents from 0.1 to 10% of the total weight of the catalyst.
6. The process according to any one of the preceding claims, in which the sulphur is incorporated into the catalyst using a precursor chosen from sulphur chloride, sulphur dichloride, carbon disulphide, thiophene, hydrogen sulphide, methyl mercaptan and dim ethyl sulphide.
7. The process according to any one of the preceding claims, in which the sulphur is incorporated into the catalyst by impregnation using a solution of a precursor which is normally liquid, and treatment under hydrogen at a temperature of between 150 and 400°C.

8. The process according to claim 7, in which an ethanolic solution of carbon
disulphide is used.
9. The process according to any one of the preceding claims, in which the sulphur
is introduced into the catalyst via the gaseous phase before and/or during the
hydrogenolysis reaction.
10. The process according to claim 9, in which the precursor introduced in gaseous
form is hydrogen sulphide, methyl mercaptan or carbon disulphide.
11. The process according to any one of the preceding claims, in which
chloropentafluoroethane is subjected to the gas-phase hydrogenolysis with the
formation of pentafluoroethane.
12. The process according to any one of claims 1 to 10, in which
chloropentafluoroethane, present in crude pentafluoroethane, is subjected to the gas-
phase hydrogenolysis with conversion of the chloropentafluoroethane to
pentafluoroethane,
13. A process for the gas-phase hydrogenolysis of chlorofluorocarbons or of
chlorofluorohydrocarbons substantially as herein described and exemplified.

Documents:

0415-mas-1996 abstract.pdf

0415-mas-1996 claims.pdf

0415-mas-1996 correspondence-others.pdf

0415-mas-1996 correspondence-po.pdf

0415-mas-1996 descripiton(complete).pdf

0415-mas-1996 form-2.pdf

0415-mas-1996 form-26.pdf

0415-mas-1996 form-4.pdf

0415-mas-1996 form-6.pdf

0415-mas-1996 petition.pdf

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Patent Number

193848

Indian Patent Application Number

415/MAS/1996

PG Journal Number

20/2006

Publication Date

19-May-2006

Grant Date

25-Jan-2006

Date of Filing

15-Mar-1996

Name of Patentee

M/S. ELF ATOCHEM SA

Applicant Address

4 & 8 COURS MICHELET, LA DEFENSE 10, 92800 PUTEAUX

Inventors:

#	Inventor's Name	Inventor's Address
1	DOMINIQUE GUILLET	262 CHEMIN DES CORCELLES, 69390, VERNAISON
2	SERGE HUB	262 CHEMIN DES CORCELLES, 69390, VERNAISON

PCT International Classification Number

C07C17/23

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	9503117	1995-03-17	France