PROCESS FOR CONVERTING 2-CHLOROPROPANE TO PROPYLENE

Abstract: A process for the catalytic conversion of 2-chloropropane to propylene, characterized in that 2-chloropropane is reacted with hydrogen in the presence of a catalyst including a Group VIII metal such as platinum in elemental or compound form, and a Group IB metal such as copper in elemental or compound form.

Description: PROCESS FOR CONVERTING 2-CHLOROPROPANE TO PROPYLENE Isopropyl chloride, or 2-chloropropane, is formed as a byproduct in allyl chloride manufacture The conversion of this byproduct material to propylene for use in the production 5 of allyl chloride, or for other beneficial uses or for sale is a desirable end Several references are presently known which relate to the conversion of 1 ,2-dιchloropropane (or PDC) to propylene In German Patent Publication No 235,630 A1 (DE '630), for example, PDC is converted to propylene in a catalytic gas phase reaction at temperatures ranging from 170 ■ \ Q degrees Celsius to 450 degrees Celsius The catalyst is described as an activated carbon which has been treated with a suspension of iron oxides and/or iron oxide hydrates, and then dried at temperatures in the range of 80 degrees to 200 degrees Celsius Other methods described in DE '630 include the hydrogenation of PDC to propylene at 180-250 degrees Celsius via a rhodium catalyst, and the dechloπnation of PDC at T 5 normal temperatures to a mixture (9 1) of propylene and chloropropylene in the presence of a pure titanium catalyst The present invention provides a process for directly converting 2-chloropropane to propylene in a commercially substantial proportion (that is, at a yield (defined as the product of the conversion rate of 2-chloropropane and the selectivity to propylene, on a hydrogen 20 chloride- and hydrogen-free basis) of at least 10 percent, but preferably at least 20 percent, and more preferably still of at least 30 percent), in which 2-chloropropane 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 a selected Group VIII metal or metals, also in an elemental or compound form 25 The catalysts contemplated for use in the process of the present invention fundamentally comprise a selected Group IB metal or selected Group IB metals in elemental or compound form and a selected Group VIII metal or selected Group VIII metals in elemental or compound form on a support 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 30 Group VIII metals in 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 VIII metals on a support Preferred catalysts will comprise platinum in elemental or compound form and copper in elemental or compound form as a Group VIII metal and a Group IB metal, 35 respectively More preferably, the Group IB and Group VIII metals will consist substantially entirely of platinum and copper in their elemental or compound forms, and a most preferred catalyst will employ only copper and platinum in their elemental or compound forms as the respective Group IB and Group VIII metals In general terms, copper (as a preferred Group IB metal) can be from 0 01 to 20 percent by weight (on an elemental basis) of these preferred catalysts, with platinum (as a preferred Group VIII metal) comprising from 0 01 to 5 0 percent by weight (also on an elemental basis) of the catalyst 5 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 for the catalyst can be any of those conventionally employed in the ! o art, but is preferably silica or carbon, with carbon being more preferred A high surface area carbon support is especially preferred, 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 well-suited for use in the present invention is a coal-based carbon produced by ! 5 Calgon Carbon Corporation under the designation "BPLF3", and may generally be characterized as having a 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 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, 20 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 will vary, for example, depending on whether the process is 25 to be carried out in the gas phase or in the liquid phase (in either a batchwise or continuous mode) For gas phase processes, contemplated reaction pressures can range from atmospheric 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 2-chloropropane feed ratios ranging on a molar basis from 0 1 : 1 to 100 1 More preferably, reaction pressures will 30 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 2-chloroproρane feed ratios of from 0 5 1 to 20 1 Most preferably, reaction pressures in a gas phase process 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 35 seconds, and hydrogen to 2-chloropropane molar feed ratios of from 0 75 1 to 6 1 In a liquid phase process, it is anticipated that suitable reaction pressures will range from atmospheric pressure up to 3000 psig (20 6 Pa (gauge)), with temperatures of from 25 degrees Celsius to 350 degrees Celsius, residence times of from one to 30 minutes, and hydrogen to 2-chloropropane molar feed ratios of from 0 1. 1 to 100.1 Preferably the catalyst will have been pretreated by exposure to a chloride source, for example, hydrogen chloride, to improve initial selectivity to propylene over propane and to make the product stream immediately useful in an allyl chloride process (wherein impurity propane can react with chlorine to produce 1-chloropropane, which because of the similarity of its boiling point to allyl chloride's boiling point is difficult to remove therefrom), for example, or to minimize venting in a propylene oxide process of any propane in the product stream fed or recycled to the propylene oxide process In this regard, catalysts of the present invention which have been impregnated, dried and reduced under hydrogen have been observed to produce propane with decreasing selectivity and propylene with increasing selectivity over time The initial chloride source pretreatment is expected to substantially reduce, however, the amounts of venting or downstream processing involved in making use of the product stream in a propylene oxide process or allyl chloride process, respectively Catalysts that have been pretreated by exposure to a chloride source and not reduced, or which have been merely dried under nitrogen and started up (and which have been in essence treated with hydrogen chloride in situ on start up), have been observed to produce the least amount of propane initially, albeit with a substantial penalty in conversion For this reason, it is considered that it will generally be still more preferable to both reduce and pretreat (by exposure to a chloride source) a given catalyst, as opposed to reducing the catalyst solely, or not reducing the catalyst at all in favor of chloride-source pretreatment or treatment with HCI in situ It will also be preferred to employ hydrogen chloride in the feed to reduce coking and catalyst deactivation rates In this regard, the rate of conversion loss is preferably no more than about 0 03 percent per hour, and especially no more than about 0 01 percent per hour Illustrative Examples Examples 1 -9 A bimetallic platinum/copper on carbon catalyst was prepared containing 0 9 percent by weight of copper and 0 5 percent by weight on an elemental basis of platinum, for converting 2-chloropropane to reaction products including propylene in a commercially substantial proportion Initially H 2 tCl66H 2 0 (J T Baker, Inc , Baker Analyzed Grade, 37 6 percent Pt) was dissolved in distilled, deionized water A portion of this stock solution was added with swirling to a 50 mL Erlenmeyer flask containing a corresponding amount of CuCI 2 (Aldπch Chemical Co , Inc , 99 999 percent purity) until the CuCI 2 was dissolved The solution was diluted with additional distilled, deionized water, and then Calgon's BPLF3 activated carbon was added to the flask with sufficient agitation to coat the carbon fully with the solution The catalyst was air-dried at ambient temperatures for 18 hours and in an oven at 120 degrees Celsius for 2 hours A catalyst charge (0 6 grams) was placed on a glass wool support in the center of a tubular reactor (1/2 inch (1 27 cm) O D , 12 inches (30 5 cm) in length) located within an aluminum block supplied with a cartridge heater to achieve the desired 5 reaction temperature under computer control The catalyst was then covered with a plug of glass wool The charged 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 lowered to the o temperature setpomt of the particular catalyst run The reactor temperature and hydrogen gas flow were allowed to equilibrate for about 1 hour before the liquid 2-chloropropane flow was started into the apparatus The 2-chloroproρane was pumped via a high pressure syringe pump through 1/16th inch ( 1 6 mm) (O D ) Monel " nickel alloy tubing (unless specifically noted below all of ! 5 the components, tubing and fittings of the test reactor apparatus were also made of Monel " nickel alloy (Huntmgton 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 20 tracing Vaporization of the 2-chloropropane feedstock was accomplished in the feed line, so that the 2 chloropropane 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 to a preheater using a Model 8249 linear 5 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 0 Vaporized 2-chloropropane 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 at a pressure of 76 psig (0 52 Pa (gauge)), and at varying residence times (see Table 1 below), varying hydrogen to 5 2-chloroproρane molar feed ratios (Table 2) or varying temperatures (Table 3) The products from the reaction under a particular set of conditions were thereafter passed to a gas sampling valve, which provided gaseous a quots 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 lonization 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 gravimetncally-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 Selectivity to the individual reaction products was determined by dividing the number of moles of an individual reaction product by the number of moles of 2-chloropropane converted, and multiplying by 100 Percent conversion and thus individual component selectivities were calculated on a hydrogen- and hydrogen chloride-free basis The results from these various runs are reported in Tables 1-3, where " RT" is the residence time, "PE Sel " is the selectivity to propylene, and "PA Sel " is the selectivity to propane, and show a propylene yield in the last run of Table 3 of 43 5 percent ((49 0 x 88 8D/100) Table 1 Examples 10- 15 The procedures and apparatus described in Examples 1-9 were employed with a catalyst (prepared generally as described in Examples 1-9) which was 0.5 percent by weight of platinum, and 0 45 percent by weight of copper on the BPLF3 carbon The results of these runs (at residence times in the range of 4.6 to 5.6 seconds, at a pressure of 76 psig (0.52 Pa (gauge)), and at various temperature and hydrogen to 2-chloroproρane molar feed ratios) are as shown in Table 4 Table 4 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.

Claims: 1 A process for the conversion of 2-chloropropane to propylene in a commercially substantial proportion, characterized in that 2-chloropropane is reacted with hydrogen in the presence of a supported catalyst including one or more Group IB metals in elemental or compound form and one or more Group VIII metals in elemental or compound 5 form 2 A process as defined in Claim 1 , wherein hydrogen chloride is incorporated in the feed to the process. 3 A process as defined in Claim 1 , wherein propylene is produced at a yield of at least 20 percent ■ \ Q 4. A process as defined in Claim 3, wherein propylene is produced at a yield of at least 30 percent. 5 A process as defined in Claim 1 , wherein the catalyst consists essentially of one or more Group IB metals in elemental or compound form and of one or more Group VIII metals in elemental or compound form on the support • 5 6 A process as defined in Claim 5, wherein the catalyst consists of one or more Group IB metals in elemental or compound form and of one or more Group VIII metals in elemental or compound form on the support 7 A process as defined in Claim 6, wherein the one or more Group IB metals includes copper and wherein the one or more Group VIII metals includes platinum 20 8 A process as defined in Claim 7, wherein the Group IB and Group VIII metals in the catalyst consist substantially entirely of copper and platinum. 9 A process as defined in Claim 8, wherein the Group IB and Group VIII metals consist of copper and platinum. 10 A process as defined in Claim 9, wherein the catalyst comprises from 0.01 to 25 5.0 percent by weight of platinum on an elemental basis and from 0.01 to 20 percent by weight of copper, also on an elemental basis, and the catalyst support is a carbon having a specific surface area of at least 200 m 2 /g. 1 1 A process as defined in Claim 10, wherein the catalyst comprises from 0 03 to 3 0 percent by weight of platinum on an elemental basis and from 0.05 to 15 percent by 30 weight of copper, also on an elemental basis, and the catalyst support is a carbon having a specific surface area of at least 400 m 2 /g. 12 A process as defined in Claim 1 1 , wherein the catalyst comprises from 0 05 to 1 0 percent by weight of platinum on an elemental basis and from 0.1 to 10 percent by weight of copper, also on an elemental basis, and the catalyst support is a carbon having a 35 specific surface area of at least 600 m 2 /g. 13 A process as defined in Claim 10, wherein the catalyst has been pretreated by exposure to a chloride source. 14 A process as defined in Claim 1 1 , wherein the catalyst has been pretreated by exposure to a chloride source. 15 A process as defined in Claim 12, wherein the catalyst has been pretreated by exposure to a chloride source 16 A process as defined in any one of Claims 10-15, wherein the reaction is conducted in the gas phase at a pressure of from atmospheric pressure to 10.3 Pa (gauge), at a temperature of from 100 degrees Celsius to 350 degrees Celsius, a residence time of from 0.25 seconds to 180 seconds, and a hydrogen to 2-chloropropane molar feed ratio of from 0 1 : 1 to 100: 1 17 A process as defined in any one of Claims 10-15, wherein the reaction is conducted in the gas phase at a pressure of from 0.03 Pa (gauge) psig to 3 4 Pa (gauge), at a temperature of from 180 degrees Celsius to 300 degrees Celsius, a residence time of from 0 5 seconds to 120 seconds, and a hydrogen to 2-chloropropane molar feed ratio of from 0 5: 1 to 20: 1 18 A process as defined in any of Claims 10-15, wherein the reaction is conducted in the gas phase at a pressure of from 0.28 Pa (gauge) to 2 1 Pa (gauge), at a temperature of from 200 degrees Celsius to 260 degrees Celsius, a residence time of from 1 second to 90 seconds, and a hydrogen to 2-chloropropane molar feed ratio of from 0 75: 1 to 6. 1.

Inventors: CISNEROS MARK D, HARLEY A DALE, HOLBROOK MICHAEL T, ITO LARRY N, MURCHISON CRAIG B, SMITH DAVID D, CISNEROS, MARK, D., HARLEY, A., DALE, HOLBROOK, MICHAEL, T., ITO, LARRY, N., MURCHISON, CRAIG, B., SMITH, DAVID, D.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1993
Main classification: C07C1
IPC codes: B01D53, B01J23, C07B61, C07C1, C07C5, C07C11, C07C17, C07C21