WO1997003035A1 - Integrated process for handling saturated and unsaturated chlorinated hydrocarbonaceous waste and by-products from allyl chloride and propylene oxide processes - Google Patents

Abstract

A process for converting an unsaturated chlorinated hydrocarbon-containing stream which may further contain saturated chlorinated hydrocarbons to corresponding less-chlorinated hydrocarbonaceous products and hydrogen chloride, comprising (a) contacting the unsaturated chlorinated hydrocarbon-containing stream with hydrogen in the presence of a catalyst in a mild saturation reaction zone which is operated under conditions selected to saturate the unsaturated chlorinated hydrocarbons therein with a minimum of polymerization and coking, (b) contacting at least a portion of the effluent from the mild saturation reaction zone with hydrogen in the presence of a hydrodechlorination catalyst in a hydrodechlorination reaction zone to produce reaction products including a non-chlorinated olefinic product, hydrogen chloride and a less-chlorinated unsaturated hydrocarbon by-product fraction, (c) separating out and recovering non-chlorinated olefinic and hydrogen chloride products from the effluent from the hydrodechlorination reaction zone, and (d) recycling less-chlorinated unsaturated hydrocarbon by-product in said by-product fraction to the mild saturation reaction zone.

Description

INTEGRATED PROCESS FOR HANDLING SATURATED AND UNSATURATED CHLORINATED HYDROCARBONACEOUS WASTE AND BY-PRODUCTS FROM ALLYL CHLORIDE AND PROPYLENE

OXIDE PROCESSES

The present invention relates to processes for the conversion of chlorinated hydrocarbonaceous materials to less-chlorinated, higher value products, and more particularly to processes for the catalytic conversion of waste and by-product chlorinated hydrocarbonaceous materials comprised of saturated and unsaturated chlorinated hydrocarbons, to less-chlorinated materials and hydrogen chloride. United States Patents No. 4,895,995 to James, Jr. et al. and 4,899,001 to Kalnes et al. are illustrative of the art in this area, in describing processes for the "simultaneous hydroconversion of a first feedstock comprising unsaturated, halogenated organic compounds and a second feedstock comprising saturated, halogenated organic compounds" via particular unit operations and arrangements of such operations, each however involving the use of reactors in series for saturating the unsaturated feedstock under mild conditions designed to minimize polymerization or coking of the unsaturated feedstock, and for subsequently hydrogenating at least a portion of the saturated first feedstock and the second feedstock to produce a hydrocarbonaceous product and hydrogen halide in an effluent stream for further processing. United States Patents No. 4,818,368 to Kalnes et al., 4,882,037 to Kalnes et al.,

4,923,590 to Kalnes et al., 4,927,520 to Kalnes et al. and 5,013,424 to James, Jr. et al. are related but are somewhat differently directed, in describing various processes and arrangements of unit operations for, for example, "treating a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product while minimizing thermal degradation of the hydrocarbonaceous stream", see col. 1, lines 14-19 of United States Patent No.4,818,368. Acomparison ofthe contemplated "temperature-sensitive" hydrocarbonaceous streams of these references with the feedstocks, for example, of the 4,895,995 and 4,899,001 patents suggests that the arrangements described in these references can be employed for the same or essentially similar applications and uses, depending on whether a stream to be processed also contains non¬ volatile materials.

The present invention in one aspect concerns a novel process for converting an unsaturated chlorinated hydrocarbon-containing stream which may further contain saturated chlorinated hydrocarbons to corresponding less-chlorinated (including non-chlorinated) hydrocarbonaceous products and hydrogen chloride, comprising a) contacting the unsaturated chlorinated hydrocarbon-containing stream with hydrogen in the presence of a catalyst in a first, mild saturation reaction zone which is operated under conditions selected to saturate the unsaturated chlorinated hydrocarbons therein with a minimum of polymerization and coking. b) contacting at least a portion of the effluent from the first, mild saturation step with hydrogen in the presence of a catalyst in a second, hydrodechlorination reaction zone to produce reaction products including a non-chlorinated olefinic product, hydrogen chloride and a less-chlorinated unsaturated hydrocarbon by-product fraction, c) separating out and recovering non-chlorinated olefinic and hydrogen chloride produrts from the effluent from the second, hydrodechlorination step, and d) recycling less-chlorinated unsaturated hydrocarbon by-products in said by-product fraction to the first, mild saturation step.

In a second, related aspect, the process concerns the simultaneous processing of an unsaturated chlorinated hydrocarbon-containing stream (which may again further comprise saturated chlorinated hydrocarbons) with a separate feed stream including one or more saturated chlorinated hydrocarbons but which is substantially free of unsaturated chlorinated hydrocarbons, wherein the unsaturated chlorinated hydrocarbon-containing stream is processed in the manner ofthe preceding paragraph, while the separate saturated chlorinated hydrocarbon feed stream is directly fed to the second, hydrodechlorination step. In athird aspect, the process of the present invention includes separating the effluent from the first, mild saturation step into saturated chlorinated hydrocarbon portions with different degrees of chlorination, and processing or disposing of these portions by a plurality of different means, with at least one such portion being fed to the second, hydrodechlorination step and the olefinic and hydrogen chloride reaction products therefrom being recovered with recycling of less-chlorinated unsaturated hydrocarbon by-products to the first, mild saturation step as before.

In still a fourth aspect, the present invention concerns a process as described in the preceding paragraph, wherein the less-chlorinated unsaturated hydrocarbon by-products to be recycled to the first, mild saturation step and the saturated chlorinated hydrocarbon portion or portions to be fed to the second, hydrodechlorination step (from the separation performed on the effluent from the mild saturation step) are supplemented with a separate feed stream to the second, hydrodechlorination step which includes one or more saturated chlorinated hydrocarbons but which is substantially free of unsaturated chlorinated hydrocarbons. The present invention is further illustrated in the accompanying drawings, in which:

Figure 1 is a schematic illustration of the process of the present invention in a first preferred embodiment, as more particularly described below, for concurrently processing saturated and unsaturated chlorinated hydrocarbonaceous waste and by-products from allyl chloride and propylene oxide processes;

Figure 2 shows a preferred product separation section in the process ofthe present invention, for recovering the desired propylene and hydrogen chloride products from the saturated and unsaturated chlorinated hydrocarbonaceous waste and by-products from allyl chloride and chlorohydrin-based propylene oxide production;

Figure 3 is a schematic illustration of an alternate embodiment to that shown in Figure 1, wherein a different mix of waste and by-products is contemplated from an allyl chloride process;

Figure 4 schematically shows a more preferred arrangement for handling the streams of Figure 1 ;

Figure 5 shows a preferred apparatus for performing the mild saturation step in the process of the present invention as schematically illustrated in Figure 4; Figure 6 depicts a more preferred process for handling the different mix of waste and by-products handled in the embodiment of Figure 3, which process is analogous to the process arrangement of Figure 4;

Figure 7 schematically shows an alternate arrangement to the arrangement of Figure 4; and Figure 8 schematically illustrates a similar alternate arrangement to the arrangement of Figure 6.

A first preferred embodiment ofthe process of the present invention is shown in Figure 1, and designated bythe numeral 10. The process 10 schematically depicts a process for producing propylene and hydrogen chloride (preferably at least in part in anhydrous form, that is_» in a stream containing generally 50 parts per million byweight or less of water), from an unsaturated chlorinated hydrocarbon-containing stream 12 comprised of chlorinated propanes and chlorinated propenes, and from a feed stream 14 comprised of chlorinated propanes but which is substantially free of unsaturated chlorinated propenes.

Advantageously, the unsaturated chlorinated hydrocarbon-containing stream 12 is in Figure l derived in part from an intermediate boiling by-product fraction 16 of the product stream from an associated, same-site process of making allyl chloride by the chlorination of propylene, for example as disclosed in United States Patent No.4,319,062 to Boozalis et al. The intermediate boiling by-product fraction 16 from which the stream 12 is derived in part typically includes a variety of dichloropropanes and dichloropropenes, with 1,2- dichloropropane or PDC being present generally as a major component at from approximately 50 percent to 85 percent by weight, and typically from 60 to 75 percent by weight of the stream, and 3,3-dichloropropene being from 10 to 20 percent by weight of the stream.

As related in either of commonly-assigned, copending United States Patent Application Serial No. 08/499,694, entitled "Improved Catalyst for the Rearrangement of Allylic Geminal Dihalogen Compounds", filed July 7, 1995, or commonly-assigned United States Patent Application Serial No. 08/499,692, entitled "Improved Process for Rearranging Allylic Geminal Dihalogen Compounds" and also filed on July 7, 1995, the 3,3-dichloropropene component in the stream 16 is preferably isomerized to cis- and trans-1,3-dichioropropene in an isomerization step 18.

This isomerization step 18 can in one embodiment involve drying ofthe stream 16 according to the teachings of USSN 08/499,692, wherein the stream 16 has acquired in storage or otherwise an undesirable amount of watertherein, followed by contact with an isomerization catalyst which may be the improved, basic alumina, silica or zeolite catalyst of USSN 08/499,694 or which may be a known isomerization catalyst for example as described in United States Patent No. 5,072,063 to Langensee or as described in Japanese Patent No. 80- 69,523 (referenced in the Langensee patent). Alternatively and preferably, the stream 16 is processed directly from an adjacent allyl chloride process in a suitably dry condition, via an improved basic alumina, silica or zeolite catalyst as described in USSN 08/499,694, or less preferably via a known isomerization catalyst for converting 3,3-dichioropropene to 1,3-dichloropropene.

The isomerized product stream 20 from isomerization step 18 is then preferably distilled via conventional apparatus for accomplishing this step 22, to remove a heavies stream 24 (which is generally incinerated or otherwise disposed of) and a 1 ,3-dichloropropene stream 26 which possesses known utility as a soil fumigant and nematocide, thereby providing a stream 28 with a reduced level of unsaturated materials which in Figure 1 is augmented by a lower-boiling monochloropropenes stream 30 from the fractionation ofthe products ofthe allyl chloride process. Alternatively, a portion or all of the 1,3-dichloropropene stream 26 may be inciuded within the stream 28, for example, where the demand for 1 ,3-dichloropropene for use as a soil fumigant or for other uses is diminished or less than the amount of 1 ,3- dichloropropene produced from the allyl chloride process and by step 18.

In this regard, it has been found that the saturation products from cis- and trans- 1 ,3-dichloropropene in a subsequent saturation step 32 are more compatible than the saturation products of 3,3-dichloropropene with the catalyst of a downstream hydrodechlorination step 34 for converting, for example, 1,2-dichloropropane from the stream 16 from an allyl chloride process and from an associated, preferably same-site chlorohydrin- based process for making propylene oxide to propylene and hydrogen chloride, which hydrodechlorination step 34 is as taught in commonly-assigned United States Patent Application Serial No.08/112,042, filed Aug.26, 1993, now abandoned (which has been published as WO 94/07828 under the provisions of the Patent Cooperation Treaty), and its continuation-in-part application Serial No. 08/227,812, now allowed. Generally, then, even where there is no greater utility or demand for 1 ,3-dichloropropene as opposed to 3,3- dichloropropene, so that all of the 1,3-dichloropropene from the isomerization step 18 is to be combined with the stream 28 or must be disposed of by alternate means (such as incineration), it will still be preferable in the context of the present invention to employ an isomerization step 18for converting 3,3-dichloropropene in the stream 16to 1,3-dichloropropene. Feed stream 14 is preferably a finished 1,2-dichloropropane stream from a chlorohydrin process for manufacturing propylene oxide, but can more generally be comprised of any appropriate saturated chlorinated hydrocarbon wastes or by-products which may be generated in other commercially-significant processes or of combinations of these materials from a plurality of source processes. Thus, for example, feed stream 14 may additionally or alternately comprise 1,2,3-trichloropropane from an epichlorohydrin process or a combination of 1,2-dichloropropane and 1,2,3-trichloropropane from a chlorohydrin PO (propylene oxide) process and an epichlorohydrin process, respectively, for producing propylene and hydrogen chloride via the hydrodechlorination step 34 for recycle to the propylene oxide process giving rise to stream 14 and/or the allyl chloride process giving rise to stream 16.

Within the above-mentioned context, the stream 12 (from streams 28 and 30, diluted as appropriate and necessary with saturated chlorinated hydrocarbons to a level of unsaturated materials in the stream 12 allowing for the effective management of heat generated in the mild saturation reaction zone 32) is fed to the first, mild saturation reaction zone or section 32 for reaction with hydrogen supplied in a stream 36 in the presence of a suitable catalyst, for essentially completely saturating unsaturated materials in stream 12 which in an unsaturated condition have a tendency to form coke and cause unacceptable deactivation in the second, hydrodechlorination step 34. The mild saturation reaction zone 32 may in this regard employ any conventional catalyst and any appropriate process conditions for saturating the unsaturated materials within the stream 12 in this manner, with preferably a minimum of polymerization and coking. Processes conducted primarily in the liquid phase or in the gas phase are suitably employed, but a liquid phase process is presently preferred.

United States Patents No. 4,895,995 to James, Jr. et al. and 4,899,001 to Kalnes et al., as already indicated, broadly describe catalytic processes which may be conducted in the reaction zone 32. As related in the '001 patent particularly, the catalysts suitably employed therein are characterized as containing a metallic component having hydrogenation activity combined with a suitable refractory inorganic oxide carrier material of either synthetic or natural origin, preferred carrier materials being alumina, silica, carbon and mixtures of these. Metallic components identified as useful include those selected from Groups VIB and Vlll of the Periodic Table, as set forth in the Periodic Table of the Elements, E. H. Sargent and Company, 1964, with the VIB metals of chromium, molybdenum or tungsten generally being present in an amount of from 1 to 20 weight percent, the iron-group metals in an amount of from 0.2 to 10 weight percent, and the noble metals of Grp. Vlll in an amount of from 0.1 to 5 weight percent, all calculated on an elemental basis. Other metals contemplated include one or more of cesium, francium, lithium, potassium, rubidium, sodium, copper, gold, silver, cadmium, mercury and zinc.

Prescribed reaction conditions for these processes, as conducted with a fixed, ebulliated or fluidized catalyst bed, include a pressure of from atmospheric to 2,000 psig (13.8 MPa, gauge), maximum catalyst bed temperatures of 50 degrees Celsius to 343 degrees Celsius, liquid hourly space velocities of from 0.05 hr¹ to 20 hr¹, and hydrogen circulation rates from about 200 standard cubic feet per barrel (SCFB) (35 normal m3/m3) to about 100,000 SCFB (18,000 normal m³/m3). Preferred pressures are about 100 psig (690 kPa, gauge) to about 1800 psig (1.2 MPa, gauge), with preferred hydrogen circulation rates being from about 300 SCFB (53 normal m3/m3) to about 50,000 SCFB (9,000 normal m3/m3).

The effluent 38 from the first, mild saturation step 32 in Figure 1 is then conveyed to a separation means 40, for example, a conventional distillation apparatus, for recovering the several dichloropropanes (most preferably being predominantly 1,2-dichloropropane but generally also including some of the 1,1-, 2,2- and 1,3-dichloropropanes) from within the effluent 38 for being conveyed to the second, hydrodechlorination step 34 via stream 42 in a dry condition (that is, typically at a total concentration of water and water-precursors of 500 parts per million or less by weight), with any monochloropropanes (2-chloropropane (or, isopropyl chloride) and 1-chloropropane (n-propyl chloride)) being passed overhead in a stream 44to a separate distillation apparatus46 for removing a substantial portion 48 of the 1- chloropropane for disposal with any residual, tarry materials (stream 50) in the effluent 38 via any conventional means, for example, incineration.

The 2-chloropropane and any remaining 1-chloropropane not removed in the distillation apparatus 46 may be passed overhead in stream 52 to a cracking process 54 for producing propylene and hydrogen chloride therefrom in a stream 56, which is preferably suitable for feeding directly to the chlorination reactor (not shown) of an associated allyl chloride process or which is fed to a product separation section 58 downstream of the hydrodechlorination section 34. Alternatively, but less preferably, the stream 52 instead of being cracked can be fed directly to the hydrodechlorination step 34 wherein at least a portion of the 2-chloropropane is converted to propylene and hydrogen chloride in an equilibrium relationship.

Where the saturation of the olefinic components in stream 12 is incomplete, however, such that olefinic compounds from the effluent stream 38 are capable of being recycled to the hydrodechlorination reaction zone 34 via stream 42 in levels above those tolerated in the stream 14 (presently considered to be no more than 100 parts per million total of such undesired unsaturated materials for commercially acceptable catalyst life in the hydrodechlorination reaction zone 34, but more conservatively being limited to no more than 50 parts per million, preferably no more than 20 parts per million total and especially not more than 10 parts per million total), a means will preferably be employed (and may be preferred to the maintenance of more stringent saturation conditions in the mild saturation step 32) to remove these materials along with other possibly undesirable, saturated products in stream 91 (1,1-dichloropropane is presently believed to be an undesirable saturated material for the platinum/copper catalyst of the U.S. '042 and '812 applications). This means may conveniently be simply in the form of an added conventional distillation apparatus (not shown) between the mild saturation sertion 32 and the separation means 40, for distilling overhead the unwanted unsaturated materials, preferably also the 1,1-dichloropropane and for optionally further distilling overhead some or all of the propane which may be found in the effluent 38, for example, where this propane when combined with propane from the hydrodechlorination reaction zone 34 would cause the ultimate propylene product stream to be of an unacceptable quality or purity for direct use in an allyl chloride process.

Returning now to a discussion of the disposition of stream 52, one preferred embodiment of a cracking process 54 would employ a platinum/copper on carbon catalyst of a type described in the aforementioned commonly-assigned United States Patent Application Serial No. 08/1 12,042, and preferred for use in the second, hydrodechlorination section 34 as indicated below, at temperatures in the vicinity of about 280 degrees Celsius. It is expected that the 2-chloropropane material can under these conditions be converted at about an 80 percent conversion rate to propylene and hydrogen chloride with a selectivity of 90 percent or greater. Conceivably other thermal or catalytic processes could be used as well. The cracking of 1-chloropropane has been observed to be much more difficult to accomplish in high conversions and selectivities, so again, preferably the 1-chloropropane is removed insofar as feasible via distillation apparatus 46 where the stream 56 is to be passed to an associated allyl chloride process. Where the cracking process 54 is omitted, however, or where the cracking process is retained and the stream 56 fed to the produrt separation sertion 58 rather than an associated allyl chloride process, or conceivably where the 1 -chloropropane may be cracked in the cracking step 54 with sufficiently high conversions and selectivities to allow the resultant stream 56 to be passed to an associated allyl chloride process, the distillation apparatus 46 can optionally be omitted. Focusing now on the second, hydrodechlorination sertion or step 34, the dichloropropanes stream 42 from separation means/distillation apparatus 20 and the 1,2- dichloropropane feed stream 14 containing finished 1 ,2-dichloropropane are preferably fed to the hydrodechlorination reaction zone 34 in a dry condition. The saturated dichloropropanes in streams 14 and 42 are reacted with hydrogen supplied in a stream 60, preferably according to a hydrodechlorination process and in the presence of a preferred platinum/copper on carbon catalyst as described in the above-referenced '042 or '812 applications.

In this manner, 1 ,2-dichloropropane contained in streams 14 and 42 is converted to reaction produrts including propylene and hydrogen chloride, the dry effluent stream 62 from the hydrodechlorination step 34 typically comprising propylene, some amount of propane, hydrogen chloride, unreacted dichloropropanes and hydrogen, a less-chlorinated unsaturated hydrocarbon by-product fraction comprised of monochloropropenes (1- chloropropene, 2-chloropropene and 3-chloropropene), and monochloropropanes (1- chloropropane and 2-chloropropane). Hydrogen supplied via stream 60 is preferably derived in part from a larger hydrogen stream 64, a remaining portion of stream 64 being supplied to the first, mild saturation reaction zone 32 in the form of stream 36. Preferably also stream 60 is derived in part from a hydrogen chloride-containing, hydrogen-rich gaseous recycle stream 66 generated in product separation sertion 58 described more particularly hereafter, the presence of hydrogen chloride in the feed to hydrodechlorination section 34 being useful insofar as is known to reduce by-product formation as well as coking and catalyst deactivation rates, see the '042 application, for example, and United States Patent No. 5,314,614to Moseretal.

The hydrodechlorination process conducted in the hydrodechlorination reaction o zone 34 is fully and completely described in the '042 and '812 applications, so that a detailed description will not be undertaken herein. Briefly, however, the process reported in the '042 application fundamentally involves the reaction of a chlorinated alkane such as 1 ,2- dichloropropane with hydrogen in the presence of a catalyst consisting of one or more Group Vlll metals and one or more of the Group IB metals copper, silver or gold on a support, and 5 which is most preferably a bimetallic catalyst of platinum alloyed with copper (in elemental or compound form) on a coal-based, highly activated carbon support, to produce a corresponding less-chlorinated olefin such as propylene and hydrogen chloride as the desired produrts.

The '812 application still more broadly describes processes for reacting hydrogen and a chlorinated alkane in the presence of a supported catalyst of an active hydrogenating 0 metal (such as from the Group Vlll metals, chromium, tungsten or molybdenum) alloyed with a metal which surface segregates in a combination with the active hydrogenating metal (preferably being a Group IB metal of copper, silver or gold for the aforementioned Group Vlll active hydrogenating metals), to produce a corresponding less-chlorinated olefin and hydrogen chloride. A preferred application is again the conversion of 1 ,2-dichloropropane to 5 the non-chlorinated olefin propylene and hydrogen chloride, such conversion most preferably being accomplished by the same platinum/copper on carbon alloy catalyst as preferred in the '042 application.

A gas phase process such as described in the '812 application is particularly preferred for carrying out the hydrodechlorination step 34, employing a catalyst 0 coimpregnated with from 0.1 weight percent up to 5.0 weight percent on an elemental basis of platinum (in elemental or compound form) and from 0.01 weight percent to 15 weight percent of copper on a support, and especially containing from 0.20 to 1.0 weight percent of platinum and from 0.1 to 2.0 weight percent of copper on an elemental basis. The support is preferably a carbon support having a specific surface area of 200 square meters per gram or greater, though 5 more preferably the carbon support is characterized by a specific surface area of 500 square meters per gram or greater and still more preferably possesses a specific surface area of 800 square meters per gram or greater. A most preferred support is a commercially-available, highly activated coal-based carbon sold by Calgon Carbon Corporation, Pittsburgh, Pennsylvania under the designation "BPLF3", which is characterized by a specific surface area of 1 100 m2/g to 1300 m2/g, a pore volume of from 0.7 to 0.85 cm3/g, and an average pore radius of 12.3 to 14 angstroms, while an X-ray fluorescence analysis of the carbon suggests a typical bulk composition of: silicon, 1.5 weight 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, 0.28 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, o the remainder of course being carbon.

The catalyst in question is preferably additionally chloride source-pretreated and reduced at an elevated temperature in the manner of the '812 application, with a reducing and chloride source pretreating flow, for example, of hydrogen and hydrogen chloride (as the chloride source), before exposure to the PDC feedstock to carry out its conversion in the 5 hydrodechlorination section 34 to propylene and hydrogen chloride.

Preferred process conditions recited for such a gas phase process include pressures of from 40 to 300 psig (0.3 MPa, gauge to 2.0 MPa, gauge), temperatures of from 200 to 260 degrees Celsius, residence times of from 1 to 90 seconds, and hydrogen to 1,2-dichloropropane molar feed ratios from 0.75: 1 to 6: 1. 0 In a variation ofthe processes disclosed in the '042 and '812 applications and summarized briefly above, a zoned combination of a plurality ofthe catalysts taught in the '042 and '812 applications may be employed rather than a single such catalyst, in accordance with the teachings of commonly-assigned United States Patent Appl ication Serial No. 08/499,691, filed on July 7, 1995 and entitled "Improved Process for the Hydrodechlorination of 5 Chlorinated Alkanes to Corresponding Less-Chlorinated Olefinic Produrts". This zoned combination of catalysts such as are described in the '042 and '812 applications can, in the context of converting 1,2-dichloropropaneto propylene and hydrogen chloride, reduce yield losses to 2-chloropropane as a by-product (through the reaction of the propylene and hydrogen chloride produrts of step 34 via a simple addition process) by employing a catalyst in 0 that portion of a reactor wherein 2-chloropropane tends to be formed, which has a lesser tendency to form the 2-chloropropane by-product under reaction conditions.

It has been surprisingly found in this regard that the propensity of these catalysts to produce 2-chloropropane can be controlled by adjusting the total loading of platinum (as the hydrogenating metal component) and copper (as the surface segregating metal 5 component) in these catalysts at a given atomic ratio of these components to one another, such ratio being found to be principally determinative of the activity of the catalysts in this process and with substantially no penalty being paid in activity by manipulating the total metal loading, given a minimally sufficient level of platinum (for example, 0.1 percent by weight or greater of platinum) is maintained in the catalyst for carrying out the process. Thus, a catalyst can preferably be used in the exit end ofthe reactor which is characterized by a lower total loading of platinum and copper at a common copper to platinum atom ratio with a catalyst in the front end of the reactor, such lower total loadings favoring higher propane formation but lesser 2-chloropropane formation, and higher total loading catalysts conversely producing relatively greater amounts of 2-chloropropane and lesser amounts of propane. The various catalysts employed in the zoned combination are also preferably additionally chloride source- pretreated and reduced at an elevated temperature, as taught above.

A possible alternate means for reducing 2-chloropropane formation as well as catalyst expense is disclosed in commonly-assigned, copending United States Patent

Application Serial No. 08/499,683, filed July 7, 1995 and entitled "Preparation of Bimetallic Catalysts for Hydrodechlorination of Chlorinated Hydrocarbons, and Use of Same for Improved Hydrodechlorination". According to this application, a preferred platinum/copper on carbon catalyst for use in the hydrodechlorination reaction zone 34 can be prepared by impregnating the carbon support with a platinum salt solution, recovering and drying the thus-impregnated support, reducing the impregnated carbon support by exposure to hydrogen, and oxidizing the platinum to an oxidized state by exposure to an oxidizing environment (for example, oxygen at 300 degrees Celsius and greater), then impregnating the thus-treated support with a copper salt solution which preferably further comprises formalin or with a copper formate or chloroformate salt (omitting the formalin, and being however less preferred to use, for example, of a copper chloride salt with formalin), aging the support/salt solution mixture over a period of time at an elevated temperature (for example, at 50 degrees Celsius over a period of several hours), then cooling, recovering and drying the catalyst for subsequent chloride source pretreatment, reduction and use according to the teachings of the '042 and '812 applications.

Effluent stream 62 from the second, hydrodechlorination reaction zone 34 is preferably combined into stream 68 with the propylene and hydrogen chloride generated in the stream 56 from the cracking process 54, and stream 68 is thereafter fed in a dry condition to product separation sertion 58. Product separation sertion 58 is most preferably as described in commonly-assigned, copending United States Patent Application Ser. No. 08/344,186, filed Nov. 23, 1994, entitled "Process for Recovery of Anhydrous Hydrogen Chloride from Mixtures with Non-Condensable Gases", and as illustrated in Figure 2.

Referring now to Figure 2, the stream 68 containing principally hydrogen, hydrogen chloride and propylene is cross-exchanged in an exchanger 69 with a hydrogen chloride-containing, hydrogen-rich vapor stream 70 (the origin of which will be described subsequently, and from which hydrogen chloride-containing, hydrogen-rich gaseous recycle stream 66 is derived). The stream 68 is partially condensed, fed to a distillation apparatus 72 at a temperature on the order of, for example, 30 to 35 degrees Celsius, and distilled therein at a pressure which is substantially the same as the reaction pressure employed in the hydrodechlorination step 34. A compressor may be employed for compressing the stream 68 to a pressure which is greater than that in the hydrodechlorination step 34, and which may approach the pressure required given available refrigeration to achieve a selected proportion of liquid anhydrous hydrogen chloride from an overheads stream 74 from the distillation apparatus 72. Preferably, however, the stream 68 is distilled without a compression ofthe stream 68 as a whole rather than of the overheads stream 74 as described below, and consequently at a pressure which is substantially equal to that prevailing in the step 34.

Overheads stream 74 contains substantially all (for example, 95 percent or more by weight and especially 99.99 percent or more by weight) of the hydrogen chloride in the stream 68, together with the unreacted hydrogen in the stream 68 and any smaller amounts of other non-condensable gases present in the stream 68. A bottoms stream 76 is also produced containing substantially all (for example, 95 percent or more by weight, and especially 99.5 percent or more by weight) of the propylene from the stream 68, as well as propane which may be produced in the hydrodechlorination step 34, unreacted PDC and any other chlorinated hydrocarbons in the stream 68 (including partially hydrodechlorinated hydrocarbons) after the step 34.

The overheads stream 74 is compressed in a compressor apparatus 78 and preferably both air-cooled and refrigerated with an available refrigeration source (for example, by intermediated stage propylene refrigeration) in exchangers 80, while also preferably being cross-exchanged with a subsequently-produced liquid anhydrous hydrogen chloride produrt stream 82 in one or more exchangers 84.

Thereafter the overheads stream 74 is passed to a reflux drum 86 to produce a liquid anhydrous hydrogen chloride source stream 88 and a vapor stream 90 containing hydrogen, hydrogen chloride and any other non-condensable inerts which may have been present in the overheads stream 74, with the distribution between the hydrogen chloride recovered in the liquid anhydrous hydrogen chloride source stream 88 and hydrogen chloride remaining in the vapor stream 90 being controlled by selection of the compressor discharge pressure (a higher compressor discharge pressure resulting at the same refrigeration load in a greater proportion of the hydrogen chloride being recovered in liquid anhydrous hydrogen chloride source stream 88).

A reflux portion 92 of the liquid hydrogen chloride source stream 88 is refluxed back to the distillation apparatus 72. As the stream 88 rom the reflux drum 86 is saturated with hydrogen and any other non-condensables present in the overheads stream 74, that portion ofthe stream 88 not refluxed to the distillation apparatus 72 is preferably then conveyed in a stream 94 to be degassed or flashed in a vessel 96 at a lower pressure to remove residual hydrogen or other non-condensable materials. Residual hydrogen and other non- condensable materials which may be removed in this fashion are recycled to the hydrodechlorination step 34 in a vapor stream 98 along with vapor stream 90 from reflux drum 86. Vapor streams 90 and 98 from reflux drum 86 and vessel 96, respectively, thus combine in the embodiment of Figure 2 to form hydrogen chloride-containing, hydrogen-rich vapor stream 70. A portion or all of the stream 70 is recycled to the hydrodechlorination step 34 as hydrogen chloride-containing, hydrogen-rich gaseous recycle stream 66 per Figure 1 , with any remaining portion of the stream 70 being routed to a scrubber 100 in a stream 102 to produce concentrated aqueous hydrochloric acid (as described below).

A purified liquid anhydrous hydrogen chloride product stream 82 is thereby produced which again is preferably cross-exchanged with the compressed overheads stream 74 o in one or more exchangers 84, to reduce refrigeration requirements for condensing hydrogen chloride out of overheads stream 74 and recovering the same in reflux drum 86 through vaporization or partial vaporization of the liquid anhydrous hydrogen chloride product stream 82.

Hydrogen chloride not condensed from the overheads stream 74 and remaining 5 in the vapor streams 90 and 98 from the reflux drum 86 and vessel 96 is preferably recycled in the stream 66 to the hydrodechlorination section 34, or as just noted is passed in a stream 102 into a scrubber 100 for being absorbed in a flow 104 of water or an HCI-lean scrubbing solution, thus producing a concentrated hydrochloric acid produrt stream 106. Hydrogen and other non-condensables in the streams 90 and 98 are conveyed in a stream 108 to be burned. 0 Alternatively, the hydrogen chloride is conventionally neutralized in vessel 100 with a flow 104 of a base, conveniently, an aqueous solution of potassium hydroxide, calcium hydroxide or sodium hydroxide, to produce a brine solution 106. Preferably however the hydrogen chloride is recovered in the form of a concentrated aqueous hydrochloric acid stream 106, with the proportion of hydrogen chloride recovered in anhydrous form versus concentrated aqueous 5 form being determined by the selection of a compressor discharge pressure for compressor 78. The bottoms stream 76 from the distillation apparatus 72, containing substantially all of the propylene from the stream 68, as well as propane, unreacted PDC and any other chlorinated hydrocarbons, is preferably further processed in a conventional distillation apparatus 110 to recover an overhead propylene stream 112 (containing most ofthe 0 propane which may be produced in the stream 68 via the hydrodechlorination step 34) in an acceptable purity for subsequent sale or use. The chlorinated hydrocarbons in the bottoms stream 76 (including monochloropropenes produced in the step 34, 1-chloropropane, 2- chloropropane, PDC and other unreacted dichloropropanes and other trace components) are conveyed from the apparatus 110 in a bottoms stream 114 to a separation sertion 116 (shown 5 in the schematic of Figure 1), wherein the monochloropropanes, monochloropropenes and from 10 to 100 percent generally of the dichloropropanes therein are distilled in an overhead stream 118 and recycled to the first, mild saturation reaction zone 32, and the remaining dichloropropanes distilled in a bottoms stream 120 and passed to separation means 40 for eventual recycle to the second, hydrodechlorination reaction zone 34 in stream 42.

Other processes and apparatus could also be employed in the product separation section 58, for separating the hydrogen chloride in the stream 68 in anhydrous form from hydrogen and other non-condensable gases contained therein and for recovering at least the anhydrous hydrogen chloride product stream 82 and the propylene produrt stream 112. Suitable but less preferred alternate processes and apparatus are described, for example, in copending and commonly-assigned United States Patent Application Serial No.08/344,187, filed Nov. 23, 1994, entitled "Process for Extraction and Recovery of Anhydrous Hydrogen Chloride from Mixtures with Non-Condensable Gases" (involving removal of the hydrogen chloride and heavier materials in a chlorinated hydrocarbon solvent for preferentially absorbing the same, followed by distillation of the rich solvent stream, the chlorinated hydrocarbon solvent in the context of converting PDC and other chlorinated propanes and propenes from allyl chloride and propylene oxide processes to propylene being preferably and simply 1,2-dichloropropane), and in United States Patents No. 5,314,614 and 5,316,663.

In Figure 3, a preferred embodiment 122 is shown of a process of the present invention which is generally similar to the embodiment 10 of Figure 1 , but in which the unsaturated chlorinated hydrocarbon-containing stream 12 includes stream 28 as derived from an intermediate boiling by-product fraction ofthe stream 16 from an allyl chloride process, but does not add in the monochloropropenes from the stream 30.

As may be seen by a comparison of Figures 1 and 3, where the stream 28 is not augmented by monochloropropenes in the stream 30 from an allyl chloride process, then it is expected that the 1-chloropropane and 2-chloropropane in stream 44 from the separation means 40 will preferably not be separated in the distillation apparatus 46, cracked in a process 54 or recycled to the hydrodechlorination reartion zone 34 but will simply be incinerated or otherwise disposed of. Correspondingly, the stream 68 to the produrt separation section 58 is simply the dry effluent stream 62 from the hydrodechlorination sertion 34. Other features of the embodiment 122 in Figure 3 are as described with respect to the embodiment 10 of Figure 1 and to the product separation section 58 shown in Figure 2. Referring now to Figure 4, a more preferred embodiment 124 is shown of a process of the present invention for handling the waste and co-product streams handled in the embodiment 10 of Figure 1. The embodiment 124 essentially differs from the embodiment 10 of Figure 1, in the employment of a preferred apparatus 126 shown in Figure 5 for the mild saturation sertion 32 of the process ofthe present invention. The apparatus 126 is essentially comprised of a primary saturation reartor 128 for carrying most of the saturation load, a vapor- liquid separator 130 preferably operating at substantially the same pressure as the primary saturation reactor 128, a packed absorber vessel 132, and a plug flow-type polishing reartor 134, with a lower pressure vapor-liquid separator 136 being optionally employed downstream of the polishing reactor 134.

The incoming feed stream 12 to the apparatus 126 in Figure 5 is managed initially by dilution with an essentially saturated chlorinated hydrocarbonaceous stream (finished PDC, for example) and by the recycle of a more saturated recycle stream 138 to preferably contain no more than 5 percent by weight, and especially no more than 2 to 3 percent by weight of unsaturated materials in order to effectively manage the heat to be generated in the saturation of such unsaturated materials, and is fed to the primary saturation reactor 128 along with hydrogen stream 36. The recycle stream 138 will be more saturated than the stream 12, as has been just mentioned, but will in any event preferably contain any unsaturated materials in excess of 1000 parts per million by weight in the produrt stream 140 from the primary saturation reactor 128.

The primary saturation reactor 128 may again suitably employ any conventional catalyst and any appropriate process conditions for saturating any unsaturated materials within the stream 12 which would have an adverse effect on the catalyst employed in the hydrodechlorination step 34 if left unsaturated and not removed elsewhere in the process, with preferably a minimum of polymerization and coking. Processes conducted primarily in the liquid phase or in the gas phase are suitably employed, but a liquid phase process is presently preferred. Based on initial indications at a pressure of 260 psig (1.8 MPa, gauge), reartion temperatures of from 10 degrees Celsius to 100 degrees Celsius and preferably from 30 degrees to 60 degrees Celsius, a residence time of 0.5 to 1 hours and hydrogen to olefin molar feed ratios of from 1 : 1 to 50: 1 and preferably from 2: 1 to 10: 1, a preferred saturation catalyst for use in the apparatus 126 at least (and perhaps in a mild saturation reaction zone 32 employing a different apparatus, for example, with a significant liquid recycle stream) would comprise palladium or platinum on a support selected to possess an appropriate pore size for a liquid phase saturation process.

The produrt stream 140 is at least partially condensed in exchanger 142, and passed into the vapor-liquid separator 130 at substantially the same pressures prevailing in the primary saturation reactor 128, to produce a vapor stream 144 containing excess hydrogen, lighter chlorinated hydrocarbons and propane and hydrogen chloride produced through hydrodechlorination in the primary saturation reactor 128, as well as a liquid stream 146 which is split into the liquid recycle portion 138 (in an amount corresponding to a recycle ratio which is preferably from 6: 1 to 25: 1, more preferably is from 6: 1 to 15: 1 and most preferably is from 6: 1 to 12: 1) and a liquid feed portion 148 to absorber vessel 132.

Absorber vessel 132 preferably utilizes a chlorinated hydrocarbon solvent stream 150, which advantageously includes overhead stream 118 from separation sertion 116 and which preferably contains or is diluted with a more highly saturated chlorinated hydrocarbon material to contain less than 3.5 weight percent, especially less than 1 weight percent and most especially less than 0.25 weight percent of unsaturated materials (the overhead stream 118 will typically be 3.5 percent by weight of unsaturated materials), for separating overhead in stream 152 substantially all of the hydrogen and other residual non-condensable gases in the vapor stream 144 in the manner of commonly-assigned, copending United States Application Serial No. 08/344,187, filed Nov. 23, 1994 for "Process for Extraction and Recovery of Anhydrous Hydrogen Chloride from Mixtures with Non-Condensable Gases". The stream 152 is then useful for being recycled to the primary saturation reactor 128, or for being used in the hydrodechlorination section 34 as suggested in Figure 4. o Absorber vessel 132 can also be equipped with a reboiler if necessary to remove residual non-condensables, and preferably is designed to effectuate as complete a separation as possible between the hydrogen and other non-condensables in vapor stream 144 and the hydrogen chloride and heavier, chlorinated hydrocarbonaceous materials in the vapor stream 144 and liquid feed portion 148 from the product stream 140. 5 Typically the chlorinated hydrocarbon solvent stream 150 will be fed to the absorber vessel 132 in a ratio of from 4 to 5 parts by volume per part by volume of the liquid feed portion 1 8, at a temperature of from -10 degrees Celsius to 20 degrees Celsius and at substantially the pressures employed upstream of the absorber vessel 32.

Effluent stream 154 from the absorber vessel 132, containing preferably not more 0 than 0.25 weight percent of unsaturated materials and more typically containing 300 to 325 ppm by weight of unsaturated materials (corresponding to a chlorinated hydrocarbon solvent stream 150 containing 150 ppm by weight of such materials and which is passed into the vessel 132 in a feed ratio of from 4: 1 to 5: 1 with a liquid feed portion 148 containing 1000 ppm by weight of unsaturated materials), is fed then to the single pass, plug flow-type polishing 5 reactor 134 for essentially completely saturating the unsaturated materials in effluent stream 154. This polishing reartor 134 can utilize the same or a different saturation catalyst as employed in the primary saturation reactor 128, but it is expected that the same catalyst will preferably be employed and will have a significant lifetime before the catalyst will need to be replaced. As effluent stream 154 from absorber 132 is saturated with hydrogen 0 (corresponding to 50 parts per million by weight, or 2700 parts per million on a molar basis of hydrogen under typical conditions, for a hydrogen to olefin molar ratio in effluent stream 154 of about 9: 1 or greater (that is, 2700:325 or greater)), it is anticipated that no supplemental hydrogen will need to be added to the reartor 134 for achieving the desired saturation of the effluent stream 154. 5 By "essentially completely saturating" the unsaturated materials remaining in effluent stream 154 from the stream 12, it is intended that the polishing reartor produrt stream 156 contain not more than 100 parts per million of unsaturated materials, preferably not more than 50 parts per million of unsaturated materials, more preferably not more than 20 parts per million of such materials and most preferably not more than 10 parts per million of unsaturated materials total. The polishing reactor product stream 156 is then optionally passed to the second, low pressure vapor-liquid separator 136, wherein the stream 156 is degassed and primarily residual hydrogen and hydrogen chloride are separated overhead in a vent stream 158, and saturated effluent stream 38 from the mild saturation step 32 is formed for being further processed as shown in Figure 4.

The embodiment 160 shown in Figure 6 requires little additional explanation, and simply reflects the use ofthe mild saturation apparatus 126 of Figure 5 in the context of the process embodiment 122 shown in Figure 3, wherein the stream 12 is derived from an intermediate boiling by-product fraction 16 from an allyl chloride process and does not additionally comprise the monochloropropenes in stream 30 from the allyl chloride process.

The embodiment 162 of Figure 7 provides yet another variation on the processes described above, in which the feed stream 14 is processed initially in the mild saturation reartion zone 32 instead of the hydrodechlorination reaction sertion 34. In the context of the apparatus 126 of Figure s, the stream 14 can be suppl ied with the stream 12 to the primary saturation reactor 128 or can more preferably be suppl ied with the overhead stream 118 to the polishing reartor 134, or the stream 14 can be supplied in part with the stream 12 and in part with the stream 118. Finished 1,2-dichloropropane from a chlorohydrin-based propylene oxide manufacturing process can in regard to the embodiment of Figure 7 contain some undesired unsaturated chlorinated hydrocarbons, for example, 150 parts per million of 2,3- dichloropropene, so that it may be advantageous to pass finished 1 ,2-dichloropropane in a feed stream 14 over a saturation catalyst in the polishing reactor 134 to reduce the level of 2,3- dichloropropene in the finished 1,2-dichloropropane by-product stream 14, and to correspondingly reduce the rate of deartivation which may be seen with the preferred Pt/Cu on carbon hydrodechlorination catalysts in the reartion zone 34.

Finally, in Figure 8 a process embodiment 164 is shown which is fundamentally similar to the embodiment 160 of Figure 6, but in which the feed stream 14 is again processed initially in the mild saturation reaction zone 32 instead of the hydrodechlorination reaction sertion 34, per the embodiment 162 of Figure 7. As a closing observation, the various processes of Figures 1-8 have been described particularly with regard to the processing of saturated and unsaturated chlorinated hydrocarbon waste produrts and by-products from allyl chloride and chlorohydrin-based propylene oxide manufacturing processes. Those skilled in the art will however readily appreciate that the processes of Figures 1 -8 and the concepts embodied therein are more broadly applicable to the processing of saturated and unsaturated halogenated materials generally, and especially of saturated and unsaturated chlorinated hydrocarbons from other sources, with the isomerization and distillation steps 18 and 22 being omitted as inapplicable.

Claims

CLAIMS:

1. A process for converting an unsaturated chlorinated hydrocarbon- containing stream which may further contain saturated chlorinated hydrocarbons to corresponding less-chlorinated hydrocarbonaceous products and hydrogen chloride, comprising: contacting the unsaturated chlorinated hydrocarbon-containing stream with hydrogen in the presence of a catalyst in a mild saturation reaction zone which is operated under conditions selected to saturate the unsaturated chlorinated hydrocarbons therein with a minimum of polymerization and coking; contacting at least a portion of the effluent from the mild saturation reaction zone with hydrogen in the presence of a hydrodechlorination catalyst in a hydrodechlorination reaction zone to produce reartion products including a non-chlorinated olefinic product, hydrogen chloride and a less-chlorinated unsaturated hydrocarbon by-product fraction; separating out and recovering non-chlorinated olefinic and hydrogen chloride products from the effluent from the hydrodechlorination reaction zone; and recycling less-chlorinated unsaturated hydrocarbon by-products in said by¬ product fraction to the mild saturation reaction zone.

2. A process as defined in Claim 1 , further comprising feeding a separate feed stream, including one or more saturated chlorinated hydrocarbons but which is substantially free of unsaturated chlorinated hydrocarbons, to the hydrodechlorination reartion zone with the effluent portion from the mild saturation reartion zone.

3. A process as defined in Claim 1 or Claim 2, further comprising separating the effluent from the mild saturation reartion zone into saturated chlorinated hydrocarbon portions with different degrees of chlorination, and processing or disposing of these portions by a plurality of different means, with at least one such portion being fed to the second, hydrodechlorination reaction zone.

4. A process as defined in any one of Claims 1-3, wherein separating out and recovering hydrogen chloride from the hydrodechlorination reartion zone comprises: distilling the reartion produrts from such hydrodechlorination reaction zone at a pressure substantially equal to or greater than employed in said hydrodechlorination reaction zone, to produce a bottoms stream comprising about 95 percent by weight or more of the non- chlorinated olefinic product from the hydrodechlorination reaction zone and an overheads stream comprising about 95 percent by weight or greater of the hydrogen chloride, together with unreacted hydrogen and other non-condensable gases; and compressing and refrigerating the overheads stream to produce a desired proportion of the hydrogen chloride in the overheads stream in a liquid anhydrous form, and a vapor stream containing substantially all ofthe unreacted hydrogen and other non- condensable gases from said overheads stream, with some hydrogen chloride.

5. A process as defined in any one of Claims 1-4, wherein hydrogen chloride is a co-feed to the hydrodechlorination reaction zone.

6. A process as defined in any one of Claims 1-5, wherein a zoned combination of a plurality of hydrodechlorination catalysts are employed in the hydrodechlorination reaction zone.

7. A process as defined in any one of Claims 1-6, wherein the unsaturated chlorinated hydrocarbon-containing stream is saturated in said mild saturation reaction zone by: contacting said stream with hydrogen in the presence of a catalyst for carrying o out said saturation process in a first reartor; separating the effluent from the first reartor into a vapor portion and a liquid portion in a vapor-liquid separator at substantially the same pressure employed in said first reactor; dividing the liquid portion into a liquid recycle portion which is recycled to the 5 reactor and a liquid feed portion which is fed with the vapor portion into an absorber vessel; contacting the liquid feed and vapor portions from the vapor-liquid separator with a chlorinated hydrocarbon solvent stream at substantially the same pressures employed in the first reartor and vapor-liquid separator whereby excess hydrogen and other non- condensable gases contained in the effluent are removed overhead, and hydrogen chloride 0 and heavier materials including residual unsaturated chlorinated hydrocarbons are carried forward in a rich solvent stream; and saturating at least a portion ofthe residual unsaturated chlorinated hydrocarbons in said rich solvent stream by contart with the same or a different catalyst for this step, in a second, single-pass plug-flow type reactor. 5

8. A process as defined in Claim 7, wherein the chlorinated hydrocarbon solvent stream is the recycled by-product fraction from the hydrodechlorination reartion zone.

9. A process as defined in Claim 7 or Claim 8, wherein the product stream from the second, plug flow-type reartor is separated into a gaseous vent stream and a liquid portion which is thereafter contacted with the hydrodechlorination catalyst in the 0 hydrodechlorination reartion zone as a gas or liquid.

10. A process as defined in any one of Claims 7-9, wherein most of the saturation of the unsaturated chlorinated hydrocarbons in said unsaturated chlorinated hydrocarbon-containing stream occurs in the first reartor.

11. A process for converting a stream of waste or by-product chlorinated 5 propenes from an intermediate boiling by-product fraction from an allyl chloride process and/or in fractionation overheads from an allyl chloride process to propylene and hydrogen chloride, comprising: contacting a chlorinated propenes-containing stream with hydrogen in the presence of a catalyst in a mild saturation reaction zone which is operated under conditions selected to saturate the chlorinated propenes with a minimum of polymerization and coking; contacting at least a portion of the effluent from the mild saturation reaction zone with hydrogen in the presence of a hydrodechlorination catalyst in a hydrodechlorination reaction zone to produce reaction produrts including propylene, hydrogen chloride, 1- chloropropane, 2-chloropropane and a monochloropropenes fraction; separating out and recovering propylene and hydrogen chloride from the effluent from the hydrodechlorination reaction zone; and recycling the monochloropropenes fraction to the mild saturation reaction zone.

12. A process as defined in Claim 11, further comprising separating out the 1- chloropropane and 2-chloropropane from the other constituent materials ofthe reaction products stream from the hydrodechlorination reartion zone, then removing at least some of the 1-chloropropane, catalytically orthermally cracking at least a portion of the 2- chloropropane to propylene and hydrogen chloride and separating out and recovering propylene and hydrogen chloride from a cracking of the 2-chloropropane or feeding the cracked 2-chloropropane material directly to a reartor of a process for making allyl chloride by the chlorination of propylene.

13. A process as defined in Claim 11 or Claim 12, wherein the chlorinated propenes-containing stream is derived from an intermediate boiling by-product frartion from an allyl chloride process which includes 3,3-dichloropropene, by contacting said intermediate boiling by-product frartion with an effective catalyst for isomerizing 3,3-dichloropropene to one or both of cis- and trans- 1 ,3-dichloropropene.

14. A process as defined in Claim 13, wherein the isomerization catalyst is a basic alumina, silica or zeolite catalyst.

15. A process as defined in Claim 13, wherein the isomerization catalyst is an alkali metal- or alkaline earth metal-impregnated alumina.

16. A process as defined in any one of Claims 11-15, further comprising feeding a separate feed stream of waste or by-product chlorinated propanes derived from a chlorohydrin process for making propylene oxide, from an epichlorohydrin process or comprising waste or by-product chlorinated propanes from both a chlorohydrin propylene oxide process and an epichlorohydrin process to the hydrodechlorination reaction zone with the effluent portion from the mild saturation reaction zone.