BACKGROUND Commercial methods for the preparation of hexafluoropropene (CF3CF=CF2 or HFP), a fluoromonomer, typically involve temperatures greater than 600°C. The high reaction temperatures lead to the formation of perfluoroisobutylene, an extremely toxic compound which is costly to remove and destroy (e. g. , see European Patent Application No. 002,098).

Processes for the manufacture of HFP at lower temperatures based on the use of acyclic three-carbon hydrocarbons or partially halogenated three-carbon hydrocarbons are disclosed in U. S. Patent Nos. 5,043, 491, 5,057, 634 and 5,068, 472.

U. S. Patent No. 6,540, 933 discloses that 1, 2-dichloro- hexafluoropropane (CF3CCIFCCIF2 or CFC-216ba), or its azeotrope with HF, can be dechlorinated with hydrogen to afford HFP and that CFC- 216ba can be prepared by contacting 1,1, 2-trichloropentafluoropropane (CF3CCIFCC12F or CFC-215bb) with a mixture of HF and chlorine in the vapor phase in the presence of a catalyst.

There is a need for alternative methods of manufacturing CFC- 215bb which is useful for making hexafluoropropene.

SUMMARY OF THE INVENTION This invention provides a selective catalyst composition comprising Cr203 having a BET surface area of from about 1 to about 7 m2/g.

This invention also provides a method for preparing said selective catalyst composition. The method comprises calcining a-chromium oxide having a BET surface area of at least 10 m2/g at a temperature of from about 1000°C to about 1200°C for a time sufficient to produce Cr203 having a BET surface area of from about 1 to about 7 m2/g.

This invention also provides a selective catalyst composition prepared by treating a composition (e. g. , the above-referenced selective catalyst composition) comprising Cr203 having a BET surface area of from about 1 to about 7 m2/g with a fluorinating agent.

This invention also provides a process for the production of 1,1, 2- trichloropentafluoropropane (CFC-215bb). The process comprises reacting hydrogen fluoride (HF), chlorine (Cl2), and at least one halopropene of the formula CX3CCI=CCIX, wherein each X is independently selected from the group consisting of F and Cl, to produce a product comprising CF3CCIFCC12F, wherein said CF3CCIFCCI2F is produced in the presence of a catalyst composition selected from the group consisting of (i) catalyst compositions comprising Cr203 having a BET surface area of from about 1 to about 7 m2/g, and (ii) catalyst compositions of (i) which have been treated with a fluorinating agent (e. g., anhydrous hydrogen fluoride).

BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a schematic flow diagram of an embodiment of a process in accordance with this invention.

DETAILED DESCRIPTION The present invention provides a process for the production of CFC-215bb (CF3CCIFCC12F) by selective chlorofluorination of selected halopropenes. Ordinarily in chlorofluorinations of such halopropenes CFC-215aa (CF3CCI2CCIF2) is also produced in significant quantity.

However the use of selective catalyst compositions comprising Cr203 having a BET surface area of from about 1 to about 7 m2/g in accordance with this invention provides a means to obtain a high relative yield of CFC- 215bb compared to CFC-215aa. This can be a significant advantage <BR> <BR> where CFC-215bb is the desired isomer (e. g. , as a precursor compound in the manufacture of HFP).

Suitable starting materials of the formula CX3CCI=CCIX include E- and Z-CF3CCI=CCIF (CFC-1214xb), CF3CCI=CC12 (CFC-1213xa), CCIF2CCI=CC12 (CFC-1212xa), CC12FCCI=CCI2 (CFC-1211xa), and CC13CCI=CC12 (hexachloropropene, HCP), and mixtures thereof. Due to theiravailability, CF3CCI=CCI2 (CFC-1213xa) and CCI3CCI=CCI2 (hexachloropropene, HCP) are the preferred starting materials.

Preferably, the reaction of HF and C12 with CX3CCI=CCIX is carried out in the vapor phase in a heated tubular reactor. A number of reactor configurations are possible, including vertical and horizontal orientation of the reactor and different modes of contacting the halopropene starting material (s) with HF and chlorine. Preferably the HF and chlorine are substantially anhydrous.

In one embodiment of this invention, the halopropene starting material (s) are fed to the reactor containing the chlorofluorination catalyst.

The halopropene starting material (s) may be initially vaporized and fed to the first reaction zone as gas (es).

In another embodiment of this invention the halopropene starting material (s) may be contacted with HF in a pre-reactor. The pre-reactor may be empty (i. e. , unpacked), but is preferably filled with a suitable packing such as Monel or Hastelloy nickel alloy turnings or wool, or other material inert to HCI and HF which allows efficient mixing of CX3CCI=CCIX and HF vapor.

If the halopropene starting material (s) are fed to the pre-reactor as liquid (s), it is preferable for the pre-reactor to be oriented vertically with CX3CCI=CCIX entering the top of the reactor and pre-heated HF vapor introduced at the bottom of the reactor.

Suitable temperatures for the pre-reactor are within the range of from about 80°C to about 250°C, preferably from about 100°C to about 200°C. Under these conditions, for example, hexachloropropene may be converted to a mixture containing predominantly CFC-1213xa. The starting material feed rate is ordinarily determined by the length and diameter of the reactor, the temperature, and the degree of fluorination desired within the pre-reactor. Slower feed rates at a given temperature will increase contact time and tend to increase the amount of conversion of the starting material and increase the degree of fluorination of the products. The term"degree of fluorination"means the extent to which fluorine atoms replace chlorine substituents in the CX3CCI=CCIX starting materials. For example, CF3CCI=CCIF represents a higher degree of fluorination than CCIF2CCI=CC12 and CF3CC12CF3 represents a higher degree of fluorination than CCIF2CC12CF3.

The molar ratio of HF fed to the pre-reactor, or otherwise to the reaction zone, to halopropene starting material, is typically from about stoichiometric to about 50: 1. The stoichiometric ratio depends on the average degree of fluorination of the halopropene starting material (s) and is typically based on formation of C3CI3Fs. For example, if the halopropene is HCP, the stoichiometric ratio of HF to HCP is 5: 1; if the halopropene is CFC-1213xa, the stoichiometric ratio of HF to CFC-1213xa is 2: 1. Preferably, the molar ratio of HF to halopropene starting material is from about twice the stoichiometric ratio (based on formation of C3CI3Fs)

to about 30: 1. Higher ratios of HF to halopropene are not particularly beneficial. Lower ratios result in reduced yields of C3Cl3F5 isomers.

If the halopropene starting materials are contacted with HF in a pre- reactor, the effluent from the pre-reactor is then contacted with chlorine in the presence of a chlorofluorination catalyst.

In another embodiment of this invention, the halopropene starting material (s) may be contacted with C12 and HF in a pre-reactor. The pre- reactor may be empty (i. e. , unpacked) but is preferably filled with a suitable packing such as Monel or Hastelloy nickel alloy turnings or wool, activated carbon, or other material inert to HCI, HF, and C12 which allows efficient mixing of CX3CCI=CCIX, HF, and C12. Typically at least a portion of the halopropene starting material reacts with C12 and HF in the pre-reactor by addition of C12 to the olefinic bond to give a saturated halopropane as well as by substitution of at least a portion of the Cl substituents in the halopropropane and/or halopropene by F. Suitable temperatures for the pre-reactor in this embodiment of the invention are within the range of from about 80°C to about 250°C, preferably from about 100°C to about 200°C. Higher temperatures result in greater conversion of the halopropene (s) entering the reactor to saturated products and greater degrees of halogenation and fluorination in the pre-reactor products. The term"degree of halogenation"means the extent to which hydrogen substituents in a halocarbon have been replaced by halogen and the extent to which carbon-carbon double bonds have been saturated with halogen. For example, CF3CC12CCIF2 has a higher degree of halogenation than CF3CCI=CC12. Also, CF3CCI2CCIF2 has a higher degree of halogenation than CF3CHCICCIF2.

The molar ratio of C12 to halopropene starting material (s) is typically from about 1: 1 to about 10: 1, and is preferably from about 1: 1 to about 5: 1. Feeding C12 at less than a 1: 1 ratio will result in the presence of relatively large amounts of unsaturated materials and hydrogen-containing side products in the reactor effluent.

In a preferred embodiment of this invention, the halopropene starting materials are vaporized, preferably in the presence of HF, and contacted with HF and C12 in a pre-reactor and then contacted with the chlorofluorination catalyst. If the preferred amounts of HF and C12 are fed in the pre-reactor, additional HF and Cl2 are not required when the effluent from the pre-reactor contacts the chlorofluorination catalyst.

Suitable temperatures for catalytic chlorofluorination of halopropene starting material and/or their products formed in the pre- reactor are within the range of from about 200°C to about 450°C, preferably from about 250°C to about 400°C, depending on the desired conversion of the starting material and the activity of the catalyst. Reactor temperatures greater than about 350°C may result in products having a degree of fluorination greater than five. In other words, at higher temperatures, substantial amounts of chloropropanes containing six or more fluorine substituents (e. g., CF3CC12CF3 or CF3CCIFCCIF2) may be formed. Reactor temperatures below about 240°C may result in a substantial yield of products with a degree of fluorination less than five (i. e., underfluorinates).

Suitable reactor pressures for vapor phase embodiments of this invention may be in the range of from about 1 to about 30 atmospheres.

Reactor pressures of about 5 atmospheres to about 20 atmospheres may be advantageously employed to facilitate separation of HCI from other reaction products after the chlorofluorination.

The chlorofluorination catalysts which are used in the process of the present invention are compositions comprising Cr203 (chromium oxide) having a BET surface area of between about 1 m2/g and about 7 m2/g, or compositions obtained by treatment of said compositions comprising Cr203 with a fluorinating agent. "BET surface area"means a surface area measured by the well-known BET method, described for example in Journal of the American Chemical Society, Vol. 60, page 309 (1938). Of particular note are compositions comprising Cr203 having a BET surface area of between about 1 m2/g and about 5 m2/g, or compositions obtained by treatment of said compositions comprising Cr203 with a fluorinating agent. As described more fully herein, these chlorofluorination catalysts may be prepared by calcination of a-chromium oxide compositions having a BET surface area of at least 10 m2/g at a temperature of from about 1000°C to about 1200°C at a temperature of from about 1000°C to about 1200°C (followed by fluorination with a fluorinating agent, if desired). Of note are chlorofluorination catalysts prepared by calcination of a-chromium oxide compositions having a BET surface area of at least 20 m2/g.

Of note are chromium oxide compositions prepared by pyrolyzing ammonium dichromate (preferably in accordance with the teaching of U. S.

Patent No. 5,036, 036) and calcining the resulting a-chromium oxide at a temperature of from about 1000°C to about 1200°C.

Also of note are chromium oxide compositions wherein the particle size of the crystallites are relatively uniform, with at least about 80% of the crystallites having a particle size close to a particular value between about 150 nm and about 600 nm. The average particle size of chromium oxide crystallites normally depends on the calcination temperature as exemplified in the Examples below.

The selective catalyst compositions of the present invention may be pressed into various shapes such as pellets for use in packing reactors.

They may also be used in powder form. Of note are porous structures of the selective catalyst compositions, and composite structures of the catalyst compositions and an inert material (e. g. , silicon carbide).

Porous structures of the selective catalyst compositions can be obtained for example by co-mixing (1) particles of the Cr203 obtained by calcination with (2) a powdered organic polymer (e. g., polyethylene), pressing the mixture into a desired shape, and subjecting the shaped mixture to thermolysis (e. g. at a temperature of from about 400°C to about 600°C) in the presence of air to remove the organic polymer component.

Under certain conditions the use of such porous structures can reduce the pressure drop during catalyst use.

Composite structures can be obtained, for example, by coating particles of the Cr203 obtained by calcination onto an inert (e. g. , silicon carbide) support. Coating can be accomplished by well-known techniques (e. g., slurry spray-coating in a manner similar to that used for automotive paints).

Typically, the selective catalyst compositions will be pre-treated with a fluorinating agent prior to use as catalysts for changing the fluorine content of halogenated carbon compounds. Typically this fluorinating agent is HF though other materials may be used such as sulfur tetrafluoride, carbonyl fluoride, boron trifluoride, and fluorinated carbon compounds such as trichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromethane, trifluoromethane, or 1,1, 2-trichlorotrifluoroethane.

This pretreatment can be accomplished, for example, by placing the catalyst in a suitable container which can be the reactor to be used to perform the process in the instant invention, and thereafter, passing HF over the catalyst so as to partially saturate the catalyst with HF. This is conveniently carried out by passing HF over the catalyst for a period of

time, for example, about 0.1 to about 10 hours at a temperature of, for example, about 200°C to about 450°C. Nevertheless, this pretreatment is not essential.

Compounds that are produced in the chlorofluorination process include the halopropane CF3CC12CCIF2 (CFC-215aa) as well as CF3CCIFCC12F (CFC-215bb). As detailed below, CFC-215aa and CFC- 215bb can be used together for the manufacture of HFP and optionally other useful products (e. g., CF3CH2CF3). Accordingly, a useful process for the preparation of both CFC-215aa and CFC-215bb is provided.

However, as illustrated in the Examples, the use of catalysts comprising chromium oxide compositions which have been calcined as disclosed herein to provide BET surface areas of between about 1 m2/g and about 5 m2/g, or fluorinated forms thereof, can actually result in reverse selectivity in the formation of these trichloropentafluoropropanes by chlorofluorination of CFC-1213xa. That is, use of a chromium oxide composition having a BET surface area of between about 1 m2/g and about 5 m2/g can result in the formation of more CFC-215bb than CFC- 215aa under conditions where a chromium oxide composition having a BET surface area of greater than about 5 m2/g results in the formation of more CFC-215aa than CFC-215bb.

Halopropane by-products that have a higher degree of fluorination than CFC-215bb and CFC-215aa that may be produced include CF3CCI2CF3 (CFC-216aa), CF3CCIFCCIF2 (CFC-216ba), CF3CF2CCI2F (CFC-216cb), CF3CCIFCF3 (CFC-217ba), and CF3CHCICF3 (HCFC- 226da).

Halopropane by-products that may be formed which have lower degrees of fluorination than CFC-215bb and CFC-215aa include CF3CC12CCI2F (HCFC-214ab).

Halopropene by-products that may be formed include CF3CCI=CF2 (CFC-1215xc), E-and Z-CF3CCI=CCIF (CFC-1214xb), and CF3CCI=CCI2 (CFC-1213xa).

Typically the effluent from reaction zone comprising CF3CC12CCIF2 (CFC-215aa) and CF3CCIFCC12F (CFC-215bb), and optionally HF, is separated from lower boiling components comprising HCI, Cl2, HF, over-fluorinated products comprising C3CIF7 and C3CI2F6 isomers, the under-halogenated components comprising C3CIF5 and C3CI2F4 isomers, and the under-fluorinated components comprising C3C4F4 isomers and CFC-1213xa.

In one embodiment of the invention, the reactor effluent from the reaction zone may be delivered to a distillation column in which HCI, Cl2 and any HCI azeotropes are removed from the top of column while the higher boiling components are removed at the bottom of the column (see <BR> <BR> e. g. , Figure 1, distillation column (300) as further described below). The products recovered at the bottom of the first distillation column are then delivered to a second distillation column in which HF, CF3CC12CF3 (CFC- 216aa), CF3CCIFCCIF2 (CFC-216ba), CF3CF2CC12F (CFC-216cb), CF3CCIFCF3 (CFC-217ba), CF3CF2CCIF2 (CFC-217ca), CF3CCI=CF2 (CFC-1215xc), and CF3CHCICF3 (HCFC-226da) and their HF azeotropes are recovered at the top of the column and CFC-215aa and CFC-215bb, and any remaining HF and the higher boiling components are removed <BR> <BR> from the bottom of the column (see e. g. , Figure 1, distillation column (400) as further described below). The products recovered from the bottom of the second distillation column may then be delivered to further distillation columns to separate the under-fluorinated by-products and intermediates <BR> <BR> and to isolate CFC-215aa and CFC-215bb (see e. g. , Figure 1, distillation column (500) as further described below).

Optionally, after distillation and separation of HCI from the reactor effluent, the resulting mixture of HF and halopropanes and halopropenes may be delivered to a decanter controlled at a suitable temperature to permit separation of a liquid HF-rich phase and a liquid organic-rich phase. The organic-rich phase may then be distilled to isolate the CFC- 215aa and CFC-215bb. The HF-rich phase may then be recycled to the reaction zone, optionally after removal of any organic components by distillation. The decantation step may be used at other points in the CFC- 215aa/CFC-215bb separation scheme where HF is present.

In one embodiment of the present invention said underfluorinated <BR> <BR> and underhalogenated components (e. g. , CFC-214ab, CFC-1212xb, and CFC-1213xa) are returned to the reaction zone.

In another embodiment of the present invention, the lower boiling by-products and over fluorinated products comprising CF3CC12CF3 (CFC- 216aa), CF3CCIFCCIF2 (CFC-216ba), CF3CF2CC12F (CFC-216cb), CF3CCIFCF3 (CFC-217ba), CF3CF2CCIF2 (CFC-217ca), CF3CCI=CF2 (CFC-1215xc), and CF3CHCICF3 (HCFC-226da), their HF azeotropes and HF, if present, are further reacted with HF, or if HCFC-226da is present, HF and Cl2, to give CF3CCIFCF3 (CFC-217ba) which in turn may

be converted to hexafluoropropene (HFP) as disclosed in U. S. Patent Nos 5,068, 472 and 5,057, 634.

In another embodiment of the present invention, the HCFC-226da, CFC-216aa, CFC-216ba, CFC-217ba, and by-products are further reacted with hydrogen (H2) to give 1,1, 1,3, 3, 3-hexafluoropropane (HFC-236fa), 1,1, 1,2, 3, 3-hexafluoropropane (HFC-236ea), and 1,1, 1,2, 3,3, 3- heptafluoropropane (HFC-227ea) (see e. g. , U. S. Patent No. 6,291, 729 and U. S. Patent Application 60/511,355 filed October 14,2003).

This invention also provides a process for the manufacture of hexafluoropropene (HFP). The process comprises (a) reacting hydrogen fluoride (HF), chlorine (Cl2), and at least one halopropene of the formula CX3CCI=CCIX, wherein each X is independently selected from the group consisting of F and Cl, to produce a product comprising CF3CCIFCC12F and CF3CCI2CCIF2, wherein said CF3CCIFCC12F and CF3CCI2CCIF2 are produced in the presence of a catalyst composition selected from the group consisting of (i) catalyst compositions comprising Cr203 having a BET surface area of from about 1 to about 7 m2/g, and (ii) catalyst compositions of (i) which have been treated with a fluorinating agent (e. g., anhydrous hydrogen fluoride) ; (b) recovering CF3CCIFCCI2F and CF3CC12CCIF2 produced in (a); (c) reacting CF3CCIFCC12F and CF3CC12CCIF2 recovered in (b) with hydrogen fluoride (HF), and optionally chlorine (C12), to produce a product comprising CF3CCIFCCIF2 and CF3CC12CF3, wherein said CF3CCIFCCIF2 and CF3CCI2CF3 are produced in the presence of a fluorination catalyst ; (d) recovering CF3CCIFCCIF2 and CF3CCI2CF3 produced in (c), (e) reacting CF3CCIFCCIF2 and CF3CC12CF3 recovered in (d) with hydrogen to produce CF3CF=CF2 and CF3CH2CF3, and ( recovering CF3CF=CF2 produced in (e).

The CF3CH2CF3 produced in (e) may also be recovered.

Accordingly, a process for the manufacture of both HFP and HFC-236fa is also provided by this invention.

The step (a) chlorofluorination is accomplished in the manner described above in connection with the process of this invention for producing CFC-215bb.

In step (b), CFC-215aa and CFC-215bb (and optionally HF and/or Cl2) from step (a) are typically separated from the low-boiling components of the step (a) effluent (which typically comprise HCI, C12, HF and over- fluorinated products) and under-fluorinated components of the step (a)

effluent. The under-fluorinated components may be recycled to the step (a) reaction zone (s).

In step (c) of the process, the CFC-215bb and CFC-215aa are reacted with additional HF, and optionally chlorine, in a second reaction zone to produce a product mixture comprising CF3CCIFCCIF2 (CFC- 216ba) and CF3CC12CF3 (CFC-216aa). Accordingly, this invention provides a process for the preparation of mixtures of CF3CCIFCCIF2 (CFC-216ba) and CF3CCI2CF3 (CFC-216aa) from readily available starting materials.

Preferably, the reaction of HF, and optionally Cl2, with CFC-215bb and CFC-215aa in step (c) is carried out in the vapor phase in a heated tubular reactor. As above, a number of reactor configurations are possible including horizontal or vertical orientation of the reactor and different modes of contacting the trichloropentafluoropropane starting materials (i. e. , CFC-215bb and CFC-215aa) with HF and chlorine. Preferably the HF and chlorine are substantially anhydrous.

In one embodiment of step (c), the trichloropentafluoropropane starting materials are fed to the reactor containing the fluorination catalyst.

The starting materials may be initially vaporized and fed to the reactor as gas (es).

The molar ratio of HF to trichloropentafluoropropanes fed to the reaction zone of step (c) is typically from about 5: 1 to about 50: 1.

Preferably, the ratio of HF to trichloropentafluoropropanes is from about 5: 1 to about 30: 1. Higher ratios of HF to trichloropentafluoropropanes are not particularly beneficial ; lower ratios result in reduced yields of dichlorohexafluoropropanes.

Chlorine (C12) may be co-fed to the reaction zone of step (c). The molar ratio of trichloropentafluoropropanes starting materials to chlorine is typically from about 1: 1 to about 4: 1.

Suitable temperatures in the reaction zone of step (c) are within the range of from about 200°C to not more than 400°C, preferably from about 250°C to about 350°C. Higher temperatures result in greater conversion of the trichloropentafluoropropanes starting materials, but also result in formation of overfluorinated products such as CF3CCIFCF3 and contribute to reduced catalyst life. Temperatures lower than about 250°C result in low yields of CFC-216ba and CFC-216aa. Unconverted starting materials may be recycled back to the reaction zone.

Suitable reactor pressures for step (c) may be in the range of from about 1 to about 30 atmospheres. Reactor pressures of about 5 atmospheres to about 20 atmospheres may be advantageously employed to facilitate separation of HCI from other reaction products.

While various known fluorination catalysts may be employed in step (c), preferred vapor phase fluorination catalysts for step (c) comprise trivalent chromium. Typically, the catalyst compositions used in step (a) as well as the catalyst compositions used in step (c) will each be pre- treated with a fluorinating agent prior to their use as catalysts.

Compounds that are produced in the fluorination process of step (c) include the halopropanes CF3CCIFCCIF2 (CFC-216ba) and CF3CC12CF3 (CFC-216aa).

Halopropane by-products that have a higher degree of fluorination than CFC-216ba and CFC-216aa that may be produced in step (c) include CF3CCIFCF3 (CFC-217ba), CF3CF2CCIF2 (FC-217ca) and CF3CF2CF3 (FC-218).

Halopropane and halopropene by-products that may be formed in step (c) which have lower degrees of fluorination and/or halogenation than CFC-216ba and CFC-216aa include unconverted starting materials, (CFC- 215bb and CFC-215aa), CF3CC12CC12F (CFC-214ab), and CF3CCI=CF2 (CFC-1215xc).

In step (d), CFC-216ba and CFC-216aa, (and optionally HF) from step (c) are typically separated from the low boiling components of the step (c) effluent (which typically comprise HCI, C12, HF, and over- fluorinated products such as CF3CCIFCF3) and the under-fluorinated components of the step (c) effluent. The under-fluorinated components may be returned to the step (a) and/or the step (c) reaction zone (s).

In one embodiment of step (d), the reactor effluent from step (c) is delivered to a distillation column in which HCI, C12 and any HCI azeotropes are removed from the top of the column while the higher boiling components are removed from the bottom of the column. The products removed from the bottom of the first distillation column are then delivered to a second distillation column in which HF and any products having a higher degree of fluorination than CFC-216ba abd CFC-216aa are removed at the top of the second distillation column and remaining HF and organic products, comprising CF3CCIFCCIF2 and CF3CC12CF3, are removed at the bottom of the distillation column. The products removed from the bottom of the second distillation column may be delivered to

further distillation columns or may be delivered to a decanter controlled at a suitable temperature to permit separation of an organic-rich phase and an HF-rich phase. The HF-rich phase may be distilled to obtain HF which is then recycled to step (a). The organic-rich phase may then be delivered to step (e).

CFC-217ba may be recovered as an over-fluorinated by-product in step (d) and may be converted to hexafluoropropene (HFP) as disclosed in U. S. Patent Nos. 5,068, 472 and 5,057, 634.

In step (e) of the process, CFC-216ba and CFC-216aa are contacted with hydrogen (H2) in a second reaction zone. The CFC- 216ba and CFC-216aa may be fed to the reactor zone at least in part as their azeotropes with HF.

In one embodiment of step (e), a mixture comprising CF3CCIFCCIF2 and CF3CC12CF3 is delivered in the vapor phase, along with hydrogen, to a reactor fabricated from nickel, iron, titanium, or their alloys, as described in U. S. Patent No. 6,540, 933; the teachings of this disclosure are incorporated herein by reference. A reaction vessel of these materials (e. g. , a metal tube) optionally packed with the metal in suitable form may also be used. When reference is made to alloys, it is meant a nickel alloy containing from 1 to 99.9% (by weight) nickel, an iron alloy containing 0.2 to 99.8% (by weight) iron, and a titanium alloy containing 72-99.8% (by weight) titanium. Of note is use of an empty (unpacked) reaction vessel made of nickel or alloys of nickel such as those containing 40% to 80% nickel, e. g., Inconel 600 nickel alloy, HastelloyT" C617 nickel alloy, or HastelloyT" C276 nickel alloy.

When used for packing, the metal or metal alloys may be particles or formed shapes such as perforated plates, rings, wire, screen, chips, pipe, shot, gauze, or wool.

The temperature of the reaction in this embodiment of step (e) can be between about 350°C to about 600°C, and is preferably at least about 450°C.

The molar ratio of hydrogen to the CFC-216ba/CFC-216aa mixture fed to the reaction zone should be in the range of about 0.1 mole H2 per mole of CFC-2 16 isomer to about 60 moles of H2 per mole of CFC-216 isomer, more preferably from about 0.4 to 10 moles of H2 per mole of CFC-216 isomer. Under these conditions the major products produced are HFP and HFC-236fa.

Alternatively, the contacting of hydrogen with the mixture of CFC- 216ba and CFC-216aa, and optionally HF, is carried out in the presence of a hydrogenation catalyst. In this embodiment of step (e), said mixture is delivered in the vapor phase, along with hydrogen, to the reaction zone containing a hydrogenation catalyst. Hydrogenation catalysts suitable for use in this embodiment include catalysts comprising at least one metal selected from the group consisting of rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, and platinum. Said catalytic metal component is typically supported on a carrier such as carbon or graphite or a metal oxide, fluorinated metal oxide, or metal fluoride where the carrier metal is selected from the group consisting of magnesium, aluminum, titanium, vanadium, chromium, iron, and lanthanum. If the desired products are HFP and HFC-236fa, the preferred catalysts are those containing ruthenium, rhenium, or their mixtures (see e. g. , U. S.

Patent No. 6,127, 585). If the desired products are HFC-236ea and HFC- 236fa, the preferred catalysts are those containing palladium (see e. g., U. S. Patent No. 6,291, 729 or U. S. Patent Application 60/511,355).

The supported metal catalysts may be prepared by conventional methods known in the art such as by impregnation of the carrier with a soluble salt of the catalytic metal (e. g., palladium chloride or rhodium nitrate) as described by Satterfield on page 95 of-Heterogenous Catalysis in Industrial Practice, 2nd edition (McGraw-Hill, New York, 1991). The concentration of the catalytic metal (s) on the support is typically in the range of about 0. 1 % by weight of the catalyst to about 5% by weight.

Suitable temperatures for the reaction zone containing said hydrogenation catalyst are in the range of from about 110°C to about 400°C, preferably from about 125°C to about 350°C.

The amount of hydrogen (H2) fed to the reaction zone containing said hydrogenation catalyst is typically from about 1 mole of H2 per mole of dichlorohexafluoropropane to about 20 moles of H2 per mole of dichlorohexafluoropropane, preferably from about 2 moles of H2 per mole of dichlorohexafluoropropane to about 10 moles of H2 per mole of dichlorohexafluoropropane.

The pressure used in the step (e) reaction zone is not critical and may be in the range of from about 1 to about 30 atmospheres. A pressure of about 20 atmospheres may be advantageously employed to facilitate separation of HCI from other reaction products.

The effluent from the step (e) reaction zone typically includes HCI, unreacted hydrogen, CF3CF=CF2 (HFP), CF3CH2CF3 (HFC-236fa), and CF3CHFCHF2 (HFC-236ea), as well as any HF carried over from step (a) or step (c). In addition, small amounts of CF3CF2CH2F (HFC-236cb), CF3CCI=CF2 (CFC-1215xc), and partially chlorinated by-products such as C3HCIF6 isomers including CF3CHCICF3 (HCFC-226da), CF3CCIFCHF3 (HCFC-226ba), CF3CHFCCIF2 (HCFC-226ea), may be formed.

In step (f), the HFP recovered. Optionally, HFC-236fa and/or HFC- 236ea (a hydrogenation product of HFP) may also be recovered. The reactor effluent from step (e) may be delivered to a separation unit to recover CF3CF=CF2 and optionally CF3CH2CF3, and/or CF3CHFCHF2, individually, as a mixture, or as their HF azeotropes.

The partially chlorinated by-products, including any unconverted CFC-216ba and CFC-216aa, may be recovered and returned to steps (a), (c), or (e).

Figure 1 is illustrative of one method of practicing this invention.

Referring to Figure 1, a feed mixture comprising HF, C12, and at least one halopropene of the formula CX3CCI=CCIX (wherein each X is independently selected from the group consisting of F and Cl) is passed through line (110) into pre-reactor (100).

The reactor effluent from pre-reactor (100) is passed through line (120) into line (710) where it is combined with the effluent from fluorination reactor (700) described below and line (510), the column bottoms from distillation column (500) described below. The column (500) bottoms comprise unconverted starting halopropenes and under-fluorinated chlorofluoropropanes such as CF3CC12CCI2F (CFC-214ab) and CF3CCI=CC12 (CFC-1213xa).

The combination of lines (120), (510), and (710) is directed to reactor (200) which is preferably maintained at a temperature within the range of about 200°C to about 450°C. Reactor (200) contains a chlorofluorination catalyst composition selected from the group consisting of (i) catalyst compositions comprising Cr203 having a BET surface area of from about 1 to about 7 m2/g, and (ii) catalyst compositions of (i) which have been treated with a fluorinating agent. Additional HF may be co-fed to reactor (200) via line (230) if desired.

The effluent from the chlorofluorination reactor (200), comprising HF, HCI, unreacted Cl2, CFC-215bb, CFC-215aa, CFC-216ba, CFC- 216aa, CFC-217ba, HCFC-226da, CFC-1215xc, and CFC-214ab, is

directed through line (210) to distillation column (300). HCI and Cl2 are removed through line (320) and the remaining components of the reactor (200) effluent are directed through line (310) into a second distillation column (400).

HF, Cis, CFC-216ba, CFC-216aa, CFC-217ba, HCFC-226da, and CFC-1215xc are removed from the top of column (400) through line (410) and directed to distillation column (600). Lower boiling components are removed from the top distillation column (600) by line (610). CFC-216ba, CFC-216aa are removed from the bottom of distillation column (600) via line (620) and sent to reactor (800) where they are combined with hydrogen which is fed to reactor (800) through line (810). Reactor (800) is typically maintained at a temperature of about 350°C to about 600°C. The product comprising hexafluoropropene and HFC-236fa leaves reactor (800) through line (820) and is directed to product recovery units (not shown).

Materials taken from the bottom of distillation column (400) through line (420) comprise CFC-215bb, CFC-215aa, and higher boiling components. This stream is sent to distillation column (500) where the CFC-215bb and CFC-215aa are collected at the top of the column at line (520). Higher boiling materials are collected at the bottom of the column and sent back to reactor (200) via line (510). The stream in line (520) containing CFC-215bb and CFC-215aa is directed to reactor (700) where it is combined with HF added through line (720). Reactor (700) contains a fluorination catalyst and is typically maintained at a temperature of from about 200°C to about 400°C.

The effluent from reactor (700) is directed to reactor (200) through line (710). The effluent from reactor (700) contains CFC-216ba and CFC- 216aa, and these compounds typically pass through reactor (200) without significant further reaction and are directed on to the distillation columns.

The reactor, distillation columns, and their associated feed lines, effluent lines, and associated units used in applying the processes of this invention should be constructed of materials resistant to hydrogen fluoride and hydrogen chloride. Typical materials of construction, well-known to the fluorination art, include stainless steels, in particular of the austenitic type, the well-known high nickel alloys, such as MonelTM nickel-copper alloys, HastelloyTM nickel-based alloys and, lnconelTM nickel-chromium alloys, and copper-clad steel.

The following specific embodiments are to be construed as merely illustrative, and do not constrain the remainder of the disclosure in any way whatsoever.

EXAMPLES LEGEND 214ab is CF3CC12CC12F 215aa is CF3CC12CCIF2 215bb is CC12FCCIFCF3 216aa is CF3CC12CF3 216ba is CCIF2CCIFCF3 216cb is CC12FCF2CF3 217ba is CF3CCIFCF3 217ca is CF3CF2CCIF2 226da is CF3CHCICF3 1213xa is CF3CCI=CCI2 1214xb is CF3CCI=CCIF 1215yb is CF3CF=CCIF 1215xc is CF3CCI=CF2 Preparation of Chromium Oxide Compositions The chromium oxide compositions used in Examples 1-14 were prepared by calcining a-chromium oxide prepared by pyrolysis of ammonium dichromate (see U. S. Patent No. 5,036, 036) at 500°C, 700°C, 900°C, 1000°C, 1100°C, 1200°C and 1300°C for ten hours. The surface areas of the chromium oxide compositions resulting from the calcinations were determined by the BET method to be 30.2 m2/g, 18.2 m2/g, 8.2 m2/g, 4.6 m2/g, 2.5 m2/g, 1.7 mug and 0.3 m2/g, respectively. Dinitrogen adsorption/desorption measurements were performed using a Micromeritics ASAP model 2400/2405 porosimeter. Samples were degassed at 150°C overnight prior to data collection. Surface area measurements utilized a five-point adsorption isotherm collected over 0.05 to o. 20 p/p0 and analyzed via the BET method (see S. Brunauer, P. H.

Emmett and E. Teller, Journal of the American Chemical Society, Vol. 60, page 309 (1938) ). The surface area of the chromium oxide prepared by pyrolysis of ammonium dichromate that was used for the calcinations was about 42. 1 m2/g.

Images of the crystallites in the chromium oxide compositions resulting from calcination at 500°C, 1000°C, 1100°C and 1200°C were obtained using transmission electron microscopy (TEM). The images indicated that the particle sizes of the crystallites were relatively uniform for each calcination temperature, with an estimated 80% or more of the crystallites having a particle size close to about 30nm, about 150nm, about 370nm, and about 600nm, respectively for the compositions resulting from calcination at 500°C, 1000°C, 1100°C and 1200°C.

EXAMPLES 1-14 Chlorofluorination of CF3CCI=CC12 The results of CFC-1213xa chlorofluorination over the chromium oxide compositions which had been calcined at the indicated temperatures are shown in Table 1. A weighed quantity of pelletized chromium oxide was placed in a 5/8" (1. 58 cm) diameter Inconel nickel alloy reactor tube heated in a fluidized sand bath. The tube was heated from 50°C to 175°C in a flow of nitrogen (50 cc/min; 8.3 (10)-7m3/sec) over the course of about one hour. HF was then admitted to the reactor at a flow rate of 50 cc/min (8.3 (10)-7m3/sec). After 0.5 to 2 hours the nitrogen flow was decreased to 20 cc/min (3.3 (10)-7m3/sec) and the HF flow increased to 80 cc/min (1.3 (10)-6m3/sec) ; this flow was maintained for about 1 hour. The reactor temperature was then gradually increased to 400°C over 3 to 5 hours. At the end of this period, the HF flow was stopped and the reactor cooled to 300°C under 20 sccm (3.3 (10)- 7m3/sec) nitrogen flow. CFC-1213xa was fed from a pump to a vaporizer maintained at about 118°C. The CFC-1213xa vapor was combined with the appropriate molar ratios of HF and C12 in a 0.5 inch (1.27 cm) diameter Monel nickel alloy tube packed with Monel turnings. The mixture of reactants then entered the reactor. All reactions were conducted at a nominal pressure of one atmosphere. Analytical data is given in units of GC area %. In all cases the molar ratio of HF to CFC- 1213xa toCl2was 20: 1: 4 and contact time was five seconds.

EXAMPLES 15-18 Fluorination of CF3CCIFCC12F The results of CFC-215bb fluorination over a-chromium oxide prepared by pyrolysis of ammonium dichromate are shown in Table 2. A weighed quantity of pelletized catalyst (10.68 g, 8 cc) was placed in a 5/8" (1.58 cm) diameter Inconel nickel alloy reactor tube heated in a fluidized sand bath. The catalyst was pre-fluorinated using the procedure indicated above. CFC-215bb was fed from a pump to a vaporizer maintained at about 100°C. The CFC-215bb vapor was combined with the appropriate molar ratio of HF in a 0.5 inch (1.27 cm) diameter Monel nickel alloy tube packed with Monel turnings. The mixture of reactants then entered the reactor. All reactions were conducted at a nominal pressure of one atmosphere. Analytical data is given in units of GC area %. In all cases the molar ratio of HF to CFC-215bb was 20: 1 and contact time was five seconds.

TABLE 1<BR> EX. Reaction Calcination 1215xc 217ba 217ca 226da 216aa 216ba 216cb 215aa 215bb 1214xb 214ab 1213xa<BR> NO. Temp°C Temp°C<BR> 1 320 500 0.5 10.4 0.4 2.0 29.9 13.4 0.9 39.5 2.2 0.1 0.5 0.07<BR> 2 320 700 0.4 8.6 0.3 1.1 30.1 17.9 2.0 36.0 3.5 0.01 0. 1-<BR> 3 320 900 0.5 2.7 0.1 0.5 22.8 10.0 2.2 33.0 24.1 0.4 3.5 0.06<BR> 4 320 1000 7.3 1.9 0.02 0.3 21.2 7.7 1.7 26.3 27.1 3.8 2.0 0.2<BR> 5 320 1100 1.3 0.1-0. 1 5.3 1.2 1.3 19.3 44.4 3.2 17.2 4.8<BR> 6 320 1200 1.0 0. 01--0. 4 0.3 0.4 4.0 48.4 7.8 12.4 48.4<BR> 7 320 1300 0. 1---0. 1--0.2 2.0 2.0 1.7 93.9<BR> 8 350 500 0.2 15.9 1.0 1.6 45.6 12.5 0.8 21.5 0.6 0.01 0. 05-<BR> 9 350 700 0.2 12.9 0.9 1.0 42.5 16.6 1.6 23.6 0.6-0. 04-<BR> 10 350 900 0.3 3.5 0.2 0.4 32.6 19.5 2.7 30.9 9.3 0.1 0.4 0.02<BR> 11 350 1000 0. 3 1. 4 0.08 0.2 25. 6 17. 4,. A 2.1 29.8 21.6 0.3 1.0 0. 2<BR> 12 350 1100.'-0. 9 0. 1-0. 1 9.3 2. 5", 1. 7 27.2 41.4 1. 8. 12. 4.-2, 2<BR> 13 350 1200 1. 5 0.04--1. 5.0. 6t ~ 0. 7 8. 1 32.6 7.8 15.0 32.0<BR> 14 350 1300 0.1 0.02 0.1-0. 1 0.07 0.02 0.3 2.6 2.9 2.7 91.1 TABLE 2<BR> EX. Reaction HFP + 1215yb 217ba 217ca 226da 216aa 216ba 215aa 215bb<BR> NO. Temp°C 227ea<BR> 15 320 0.06 0.2 0.5 0.02 0.2 0.3 95.9 1.6 1.3<BR> 16 350 0.08 0.1 4.1 0.09 0.2 2.1 91.4 1.7 0.09<BR> 17 375 0.1 0.08 12.8 0.2 0.3 6.0 79.5 0.8 0.06<BR> 18 400 0.3 0.1 29.4 0.4 0.3 14.0 55.1 0.3 0.05