The material 1,1,1 ,2-tetrachloroethane is produced as a byproduct in the manufacture of 1,2-dichloroethane or EDC, and is a known, useful intermediate for the

5 production of vinyl chloride. Because of increasing regulatory pressures and reduced demands for such chlorinated solvents generally, however, it is increasingly advantageous to be able to convert materials such as 1 , 1 , 1 ,2-tetrachloroethane to other useful or salable products such as vinylidene chloride. The present invention provides an effective means for accomplishing this particular conversion.

1 o European Patent Application EP 0496- 46A, published on July 29, 1992, describes the preparation of chlorotrifluoroethylene and trifluoroethylene from 1, 1,2-trichloro- 1,2,2- -trifiuoroethane via a catalyst comprised of copper and a Group Vlll metal (palladium and platinum being preferred) on a carbon support. Several prior publications address the same conversion and describe the same or different catalysts, see, for example EP 025341 OB, EP

15 0355907B and EP 0459463A. All of these references appear however to be directed specifically to the chlorofluorocarbon art.

Outside of the chlorofluorocarbon art, EP 015665 describes the conversion of 1,1,2-trichloroethane to ethylene and vinyl ϊ loride via a catalyst including a noble metal chloride, an alkali metal chloride, iron chloride and optionally copper chloride.

20 According to the process of the present invention, 1 ,1,1,2-tetrachloroethane is converted to reaction products including vinylidene chloride in a commercially substantial proportion (that is, at a yield (defined as the product of the conversion rate of 1,1,1,2- -tetrachloroethane and the selectivity to vinylidene chloride, on a hydrogen chloride- and hydrogen-free basis) of at least 10 percent, but preferably at least 20 percent, and more

25 preferably at least 30 percent), by reacting the 1,1,1,2-tetrachloroethane with hydrogen in the presence of a catalyst including a selected Group IB metal or metals in an elemental or compound form with a selected Group Vlll metal or metals, also in an elemental or compound form. Preferred catalysts will, however, consist essentially of a combination of one or more Group IB metals in elemental or compound form with one or more Group Vlll metals in

30 elemental or compound form on a support. More preferably, the catalysts employed in the processes of the present invention will consist of one or more Group IB metals with one or more Group Vlll metals on a support.

Preferably platinum in elemental or compound form will be employed in these catalysts as a selected Group Vlll metal, with copper in elemental or compound form being

35 employed as a Group IB metal. More preferably, the Group IB and Group Vlll metals will consist substantially entirely of platinum and copper in their elemental or compound forms, and a most preferred catalyst will employ only platinum and copper in their elemental or compound forms as the Group IB and Group Vlll metals. Especially preferred is a supported bimetallic

catalyst of copper and platinum on a neutral support such as silica or carbon, with carbon being preferred.

In general terms, a selected Group IB metal (copper) can be from 0.01 to 20 percent by v. eight (on an elemental basis) of these preferred catalysts, with a selected Group Vlll metal (platinum) comprising from 0.01 to 5.0 percent by weight (also on an elemental basis) of the catalyst. More preferably, copper will be from 0.05 to 15 percent by weight of the catalyst (on an elemental basis) and platinum will be from 0.03 to 3.0 percent by weight of the catalyst. Most preferably, the copper can be from 0.1 to 10 percent by weight of the catalyst (on an elemental basis) and platinum will be from 0.05 to 1.0 percent by weight of the catalyst. The support can be any of those conventionally employed in the art, but is preferably silica or carbon, and more preferably is carbon. Especially preferred is a high surface area carbon support, for example, a carbon having a specific surface area in an unimpregnated condition of 200 m ² /g or more, especially 400 m /g or more, and most especially 600 m2/g or more. An example of a commercially-available carbon which has been found suitable for use in the present invention is a coal-based carbon produced by Calgon Carbon Corporation under the designation "BPLF3", and may generally be characterized as having a specific surface area of 1100 m /g to 1300 m ² /g, a pore volume of 0.7 to 0.85 crτι3/g, and an average pore radius of 12.3 to 14 angstroms. Based on an X-ray fluorescence analysis of this carbon, a typical bulk composition of the BPLF3 carbon has been determined to be as follows (by weight percent): silicon, 1.5 percent; aluminum, 1.4 percent; sulfur, 0.75 percent; iron, 0.48 percent; calcium, 0.17 percent; potassium, 0.086 percent; titanium, 0.059 percent; magnesium, 0.051 percent; chlorine, 0.028 percent; phosphorus, 0.026 percent; vanadium, 0.010 percent; nickel, 0.0036 percent; copper, 0.0035 percent; chromium, 0.0028 percent; and manganese, 0.0018 percent (the remainder being carbon). Reaction conditions can vary, depending for example on whether the process is to be conducted in the gas phase or in the liquid phase (whether in a batchwise or continuous mode). For a gas phase process, reaction pressures can range from atmospheric pressure up to 1500 psig (10.3 Pa (gauge)), with temperatures of from 100 deg. C. to 350 deg. C, residence times of from 0.25 seconds to 180 seconds, and hydrogen to 1,1,1,2-tetrachloroethane feed ratios ranging on a molar basis from 0.1 : 1 to 100: 1. More preferably, reaction pressures in a gas phase process will range from 5 psig (0.03 Pa (gauge)) to 500 psig (3.4 Pa (gauge)), with temperatures of from 180 deg. C. to 300 deg. C, residence times of from 0.5 seconds to 120 seconds, and hydrogen to 1,1,1,2-tetrachloroethane feed ratios of from 0.5: 1 to 20: 1. Most preferably, reaction pressures will range from 40 psig (0.28 Pa (gauge)) to 300 psig (2.1 Pa (gauge)), with temperatures of from 200 deg. C. to 260 deg. C, residence times of from 1 second to 90 seconds, and hydrogen to 1,1,1,2-tetrachloroethane molar feed ratios of from 0.75: 1 to 6: 1. In a liquid phase process, reaction pressures are expected to be from atmospheric pressure up to 3000 psig (20.6 Pa (gauge)), at temperatures of from 25 to 350 degrees Celsius,

residence times from one to 30 minutes, and hydrogen to 1,1,1,2-tetrachloroethane molar feed ratios of from 0.1 : 1 to 100: 1.

Preferably hydrogen chloride will be included in the feed to the process to reduce coking and catalyst deactivation rates. In this regard, the rate of conversion loss will preferably be no more than about 0.03 percent per hour, and especially no more than about 0.01 percent per hour. Example 1

A catalyst was initially prepared containing 0.5 percent by weight of platinum and 0.9 percent by weight of copper on Calgon's BPLF3 carbon support. An aqueous H ₂ PtCl6 stock solution was first prepared by dissolving H ₂ tCl66H ₂ 0 (J. T. Baker, Inc.; Baker Analyzed Grade, 37.6 percent Pt) in deionized and distilled water. An amount of CuCI ₂ (Aldrich Chemical Company, Inc., 99.999 percent purity) was placed in a 250 mL Erlenmeyer flask, and the H ₂ tCl6 stock solution added in an appropriate proportion with swirling to dissolve the CuCI . The solution was then diluted with deionized, distilled water and swirled. Calgon BPLF3 activated carbon (6 x 16 mesh, Calgon Carbon Corp., Pittsburgh, Pa.) was added to the flask, and the flask was agitated rapidly so that the carbon carrier was evenly coated with the aqueous Pt/Cu solution. The catalyst preparation was dried in an evaporating dish in air at ambient temperatures for 18 hours, and then further dried in an oven in air at 120 degrees Celsius for 2 hours. A catalyst charge (0.6 grams) of the thus-dried catalyst was placed in a tubular reactor within an aluminum block equipped with a cartridge heater to achieve a desired reaction temperature under computer control, over a glass wool support contained in the center of the reactor tubing. The catalyst was then covered with a plug of glass wool.

The catalyst was dried for from 8 to 24 hours at 150 degrees Celsius under a nitrogen purge, and thereafter reduced by passing hydrogen through the reactor at a flow rate of 34 mL/minute for 24 hours. The reactor temperature was then adjusted to the desired temperature setpoint of 235 degrees Celsius (at 76 psig (0.52 Pa (gauge))). The reactor temperature and hydrogen gas flow were allowed to equilibrate for about 1 hour before the liquid 1,1,1,2-tetrachloroethane flow was started. The 1,1,1,2-tetrachloroethane was pumped via a high pressure syringe pump through 1/16 inch (1.6 mm) (O.D.) Monel'" nickel alloy tubing (unless specifically noted below all of the components, tubing and fittings of the test reactor apparatus were also made of Monel'" nickel alloy (Huntington Alloys, Inco Alloys International, Inc.)) into a packed sample cylinder serving as a feed evaporator. The 1/16th inch tubing extended almost to the center of the packed cylinder, which was heated to a vaporizing temperature of 180 degrees Celsius using electrical heat tracing. Vaporization of the 1,1,1,2-tetrachloroethane was accomplished in the feed line, so that the 1,1,1 ,2-tetrachloroethane was superheated when combined with the hydrogen feed

stream. Thermocouples were used to monitor the skin temperature of the feed evaporator and the temperature of the gas exiting the feed evaporator.

The hydrogen feed stream was metered (at a 1.6: 1 molar ratio with the 1 ,1,1 ,2- -tetrachloroethane) to a preheater using a Model 8249 linear mass flow controller from Matheson Gas Products, Inc. Secaucus, N.J., with the preheater consisting of a packed sample cylinder wrapped with electrical heat tracing. Thermocouples were used to monitor both the skin temperature of the preheater and the temperature of the gas exiting the preheater. The preheater temperature was set and maintained at 140 degrees Celsius.

Vaporized 1 , 1 ,1 ,2-tetrachloroethane exiting the evaporator was mixed with the hydrogen gas from the preheater in a 2 foot (0.61 meter) long section of 1/4 inch (0.64 cm) tubing maintained at a temperature of 140 degrees Celsius. The mixed gases then were passed into and reacted within the above-mentioned tubular reactor (1/2 inch (1.27 cm) O.D., 12 inches (30.5 cm) in length). The residence time was 4.0 seconds.

After thus reacting the 1,1,1,2-tetrachloroethane and hydrogen in the gas phase, the products from the reaction were passed to a gas sampling valve, which provided gaseous aliquots for online gas chromatographic analysis in a Hewlett-Packard Model 5890 Series II gas chromatograph (Hewlett-Packard Company). The gas chromatograph was equipped with a flame ionization detector, and used 30 meter by 0.53 millimeter (I.D.) 100 percent methyl silicone/fused silica and 30 meter by 0.53 millimeter (I.D.) porous polymer-lined fused silica columns to separate the various reaction products. Response factors were conventionally determined by injections of gravimetrically-prepared standards of the individual reaction products. These response factors were applied in conjunction with individual peak areas and the total mols of all reaction products to determine the mol percents of individual components in the reactor effluent, and the selectivity to individual reaction products. Virtually all of the 1,1,1,2-tetrachloroethane (99.95 percent) was shown by this analysis to be converted to reaction products including vinylidene chloride at 93 percent selectivity (for a yield of vinylidene chloride of 93 percent ((99.95 x 93)/100), vinyl chloride at 1 percent selectivity, trichloroethylene at 3 percent, and ethane and ethylene at 3 percent combined. Catalytic activity declined fairly rapidly thereafter due (it is believed) to polymerization of the vinylidene chloride on the catalyst.

While various embodiments of the processes and catalysts of the present invention have been described and/or exemplified herein, those skilled in the art will readily appreciate that numerous changes can be made thereto which are nevertheless properly considered to be within the scope or spirit of the present invention as more particularly defined by the claims below.