USEFUL, LESS CHLORINATED ALKANES

The present invention relates generally to processes for converting chlorinated alkanes, and especially chlorinated alkanes produced as byproducts or waste products from useful chemical manufacturing processes, to less chlorinated alkanes which are directly useful in the same or a different process or salable

United States Patent No 3,892,818 to Scharfe et al (Scharfe) is illustrative of the known art and describes processes for converting hydrocarbon chlorides including 1 ,2- dichloropropane (a chief byproduct of the chlorohydrin process for producing propylene oxide) to hydrogen chloride and useful hydrocarbons such as propane These processes are conducted in the gas phase in the presence of rhodium-containing catalysts, with the rhodium being present in the catalysts in an elemental state or as a compound and preferably being utilized as part of a carrier catalyst While rhodium can be the sole catalytically active component of the earner catalysts, it is said that other metals or metal compounds can be included such as, for example, palladium, platinum, ruthenium, indium, iron, cobalt, nickel, copper, gold, vanadium, chromium, molybdenum and tungsten Suitable carriers can be aluminum oxide, silicic acid, aluminum silicate, spinel, active charcoal and titanium dioxide

United States Patents No 4,818,368 to Kalnes et al , 4,899,001 to Kalnes et al , and 5,013,424 to James, Jr et al are similar to Scharfe in broadly describing processes for the hydrogenation of halogenated hydrocarbons in the presence of metal or mixed metal catalysts involving combinations of Group VIB and Group VIII metals

The present invention provides novel and improved processes for the catalytic conversion of various less-desired chlorinated alkanes to reaction products including their corresponding, less-chlorinated alkanes in commercially substantial proportions (that is, at yields of at least 10 percent, but more preferably at least 20 percent and most preferably at least 30 percent, wherein the yield of a given product is calculated as the product of the conversion and of the selectivity to that product on a hydrogen- and hydrogen chloride-free basis), in which a chlorinated alkane is reacted with hydrogen in the presence of a catalyst including a selected Group IB metal or metals in an elemental or compound form with one or more Group VIII metals inclusive of platinum, indium, palladium or ruthenium in elemental or compound form The desired alkanes are then conventionally separated from the reaction products of these processes, and may be further processed in a conventional, known manner to be placed in condition for an appropriate use or for sale "Less chlorinated", as used above and elsewhere herein, embraces sti II- chlonnated alkanes as well as alkanes having no remaining chlorine atoms associated therewith

A preferred application of the present invention will be for the conversion in the gas phase ot 1 ,2-dιchloropropane to reaction products including propane in substantial proportion

Preferred catalysts for use in the inventi e processes will consist essentially of a combination of one or more Group IB metals in elemental or compound form with one or more Group VIII metals inclusive of platinum or iridium in elemental or compound form 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 VIII metals inclusive of platinum or indium

Preferably these catalysts comprise platinum in elemental or compound form as a

_{1 0} Group VIII metal, and silver or gold (with gold being preferred over silver) in elemental or compound form as a Group IB metal constituent on a support More preferably, the Group IB and Group VIII metals in the catalyst will consist substantially completely of gold (Group IB) and platinum (Group VIII) in their elemental or compound forms, and a most preferred catalyst will employ only gold and platinum in their elemental or compound forms as the respective Group

! 5 IB and Group VIII metals Especially preferred is a supported bimetallic catalyst of gold and platinum

The proportions and amounts of the selected Group VIII metal and selected Group IB metal in these preferred catalysts will vary depending on the particular chlorinated alkane or alkanes to be dechlonnated, but in general terms the Group IB metal component can be from

20 0 01 to 20 percent by weight (on an elemental basis) of the catalyst, with the selected Group Vlll metal comprising from 0 01 to 5 0 percent by weight (also on an elemental basis) of the catalyst

More preferably, the selected Group IB metal component will be from 0.05 to 15 percent by weight of the catalyst (on an elemental basis) and platinum or some other selected

25 Group Vlll metal will be from 0.03 to 3.0 percent by weight of the catalyst. Most preferably, the Group IB metal can be from 0J to 10 percent by weight of the catalyst (on an elemental basis) and the Group Vlll metal 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, with carbon being preferred to silica The carbon is preferably a

30 high surface area carbon, for example, a carbon having a specific surface area in an unimpregnated condition of 200 m ² /g or more, especially 400 m ² /g or more, and most especially 600 m ² /g or more. An example of a commercially-available carbon which has been found to be of 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

35 specific surface area of 1 100 m ² /g to 1300 m ² /g, a pore volume of 0.7 to 0.85 cm3/g, and an average pore radius of 12.3 to 14 angstroms. A typical bulk composition for the BPLF3 carbon as determined by X-ray fluorescence is as follows (percents given are weight percents). 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)

5 The reaction conditions to be preferred will again vary, depending for example on the particular catalyst and the particular chlorinated alkane or alkanes involved, as well as on whether the process in question is to be carried out in the gas phase or in the liquid phase In general however, reaction pressures for gas-phase processes can range from atmospheric up to 1 500 psig ( 10 3 Pa (gauge)), with temperatures of from 100 deg C to 350 deg C , residence

! 0 times of from 0 25 seconds to 180 seconds, and hydrogen/chlorinated alkane feed ratios ranging on a molar basis from 0 1 1 to 100 1 More preferably, reaction pressures will range trom 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/chlorinated alkane feed ratios of from 0 5 1 to 20 1 Most preferably, reaction pressures will range from 40

! 5 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/chlorinated alkane molar feed ratios of from 0 75 1 to 6 1 Reaction pressures in liquid-phase processes (which can be conducted in a batchwise or continuous manner, as desired) will in general range from atmospheric pressure to 3000 psig (20 6 Pa (gauge)), at temperatures of from 25 degi ees Celsius

20 up to 300 degrees Celsius, residence times of from one to thirty minutes, and hydrogen to chlorinated alkane molar feed ratios ranging from 0 1 1 to 100 1 Both batchwise and continuous liquid-phase processes are contemplated

Although the chlorinated alkane feedstock and hydrogen are necessarily fed to the process, preferably hydrogen chloride is also employed in the feed to reduce coking and

25 catalyst deactivation rates to a loss in conversion of no more than about 0 03 percent per hour, and preferably no more than 0 01 percent per hour Illustrative Examples Example 1

In this example as in Example 2 below, catalysts were prepared involving a

30 combination of platinum with a group IB metal on a carbon support, and were evaluated under several conditions for converting 1,2-dιchloropropane to reaction products including propane Several parameters were measured and/or calculated, including PDC conversion ( 100 minus the mol percent of PDC in the test reactor effluent, excluding unreacted hydrogen and the hydrochloric acid produced by the reaction), selectivity to a given component (mols of

35 component divided by mols PDC converted, multiplied by 100), liquid hourly space velocity (in hr i , the volume of liquid PDC fed per hour to the reactor divided by the packed bed volume of catalyst in the reactor), and catalyst productivity (on a basis of kilograms of propane produced per hour per cubic meter of catalyst used)

For each example, PDC was converted to propane by flowing hydrogen and PDC in the gas phase over a given catalyst to be evaluated. Liquid PDC was pumped via a piston pumr nrough 1/16th ιnch (1 6 mm) (0.D.) nickel tubing to a Monel ^' " alloy (Huntington Alloys, Inco Alloys International, Inc ) gas sample cylinder packed with glass beads (unless specifically

5 noted, all fittings and tubing were of Monel'" alloy) The 1/6th inch tubing extended to the center of the sample cylinder, with the sample cylinder being heated to a vaporization temperature of 1 10 degrees Celsius by electrical heat tracing A thermocouple was used to monitor the in temperature of the sample cylinder

The flow of the hydrogen feed stream was controlled by a pre-calibrated mass

* _j 0 flow controller The desired flow of hydrogen was passed through the heated sample cylinder, where mi xing of the gaseous PDC and hydrogen occurred The mixed gases were then passed into a charged Monel '" tubular reactor (0 75 in ( 1 9 cm ) O D , 18 inches (45 7 cm ) in length) heated by ceramic lined electric elements to a desired reaction temperature

The particular catalyst to be evaluated ( 1 2 cubic centimeters) was in each case

15 charged into the reactor between 3 mm glass beads, and placed in the middle of the reactor The catalyst was thereafter dried under a flow of nitrogen for one hour at 130 degrees Celsius, and then reduced under a 5: 1 molar ratio of flowing nitrogen and hydrogen. In reducing the catalyst, itie temperature was ramped up from 130 to 220 degrees Celsius at 3 degrees per minute and then held at 220 degrees for a total reducing cycle time of about 2 hours o Upon reaction of the mixed hydrogen and PDC in the reactor at a prescribed reaction temperature, the effluent from the reactor 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 5 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 0 of individual components in the reactor effluent, and the selectivity to individual reaction products as described above

The catalyst tested in this Example 1 comprised 0 29 percent by weight on an elemental basis of platinum and 0 75 percent by weight of silver on a Calgon BPLF3 activated carbon support (6 x 16 mesh, Calgon Carbon Corp., Pittsburgh, Pa ), and was prepared first by

35 making an aqueous stock solution from 0.048 grams of Pt(NH ₃ ) (N03) ₂ , 0.1 16 grams of silver nitrate, and 12 43 grams of distilled, deionized water in a 50 mL Erlenmeyer flask. The activated carbon was then added (at 9.68 grams) to the flask containing the stock solution, and the flask agitated thoroughly to en- that the activated carbon was evenly coated with the

aqueous solution of Ft(NH3) ₄ (Nθ3)2 and silver nitrate. The catalyst was then air-dried at ambient temperature for 18 hours and then in an oven at 120 degrees Celsius for another 2 hours. A single 1.2 cubic centimeter charge (weighing 500.1 milligrams) of the catalyst was placed in the reactor and pretreated as described above, then tests were conducted sequentially with this catalyst at several hydrogen to PDC molar feed ratios.

The results from the testing are shown in Table 1 , with the highest propane yield under the conditions specified being 14.8 percent (or (25.5 x 58.1 )/100).

TABLE 1

a) LHSV = Liquid Hourly Space Velocity b) C3H6 = Propylene c) C3H8 = Propane d) 2-CPA = 2-Chloropropane e) 1-CPE = 1-Chloropropene

Example 2

For this example, an aqueous H ₂ l ^> tCl6 6H2O stock solution was prepared by dissolving 3.179 grams of H ₂ PtCI ₆ 6H ₂ 0 (J. T. Baker, Inc., Baker Analyzed Grade, 37.6 percent Pt) in 100 00 mL of distilled, deionized water. A portion (0.995 grams) of this stock solution was added with swirling to a 50 mL Erlenmeyer flask containing 0 134 grams of HAuCI ₄ 3H ₂ 0 (Aldrich Chemical Co., Inc , ACS purity) until the HAuCI ₄ 3H2O was dissolved The solution was diluted wi th 5 42 grams of distilled, deionized water, and then 4 79 grams of the same Calgon BPLF3 activated carbon were added to the flask with sufficient agitation to coat the carbon

1 Q fully with the solution.

T he catalyst was air-dried at ambient temperatures for 18 hours and in an oven at 120 degrees Celsius for 2 hours The catalyst thus prepared comprised 0.24 percent by weight of platinum (on an elemental basis) and 1.37 percent by weight of gold (on an elemental basis) on the activated carbon support, to give the same proportions as employed for the PXJAg

• _| 5 catalyst of the previous example.

A 1 2 cubic centimeter charge (again, about 500 mg in weight) of the catalyst was placed in the test reactor for being reduced and evaluated The results of the single run conducted witn this platinum/gold catalyst are summarized in Table 2.

20

25

30

35

TABLE 2

a) LHSV = Liquid Hourly Space Velocity b) C3H6 = Propylene c) C3H8 = Propane d) 2-CPA = 2-Cnloropropane e) 1-CPE = 1-Chloropropene

00

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.