MXPA96005580A - Method to reduce the formation of polycolored organic composites during oxycellation of c1 hydrocarbons - Google Patents

Abstract

The present invention relates to a process for the manufacture of chlorinated hydrocarbons with reduced formation of chlorobenzenes, polychlorinated biphenyls (PCB), polychlorinated dibenzodioxines (PCDD) and polychlorinated dibenzofurans (PCDF), initiating the process with a hydrocarbon reagent of C1 to C3 selected from the group consisting of methane, ethane, ethylene, acetylene, propane, propylene, methylacetylene and halogen-substituted versions thereof, the process comprises: contacting the reagent with oxygen or oxygenated gas and hydrogen chloride, in which at least a portion of the hydrogen chloride to be consumed is obtained from an external source other than the recovery from the thermal disintegration of the product produced in the oxychlorination process, such contact being carried out in the presence of an oxychlorination catalyst in a heated reaction zone operated from 150 ° C to 600 ° C where the chlorinated hydrocarbon is recovered from the eff In the reaction zone, the process is characterized by the fact that hydrogen chloride is pretreated with a medium to remove aromatic hydrocarbons.

Description

METHOD TO REDUCE THE FORMATION OF POLYCHLORATED AROMATIC COMPOUNDS DURING OXYCOLORATION OF HYDROCARBONS OF C1-C3 DESCRIPTION The present invention relates to processes involving the oxychlorination of hydrocarbons of c? ~ C3 especially methane, ethane, propane, ethylene, propylene, acetylene and propyne using hydrogen chloride from sources other than the thermal disintegration of the product of the oxychlorination processes operated. Recent literature concerning the commercial use of chlorine has concentrated on small but measurable quantities of polychlorinated aromatics such as chlorobenzenes, polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), all which will be referred to hereinafter as the PCDD / F and which are considered environmentally toxic. These highly undesirable compounds (HUCs) are found in soil and lake sediments and their reduction or elimination from industrial production is gaining increasing importance. The literature contains many references regarding the formation of PCDD / F which in general support the position that the formation of trace amounts of PCDD / F 'is unavoidable in many chlorine-containing industrial processes, involving the addition or elimination of chlorine atoms of non-aromatic hydrocarbons. This is particularly true for oxychlorination processes, and especially true for the oxychlorination of ethylene to 1,2-dichloroethane, which is also referred to as ethylene dichloride (EDC), an important intermediate in the production of chloride monomer of vinyl (VCM). Due to concerns about the toxicity and bioaccumulation of polychlorinated aromatics, minor amounts have been monitored in a variety of industries including solid waste incinerators, EDC / VCM processes and other processes involving chlorination, oxychlorination or hydrochlorination of non-aromatic hydrocarbons, including reversible processes, that is, dechlorination or dehydrochlorination. A recent report compiled from case studies of emissions from EDC / VCM processes in Europe estimates annual emissions of what is referred to as toxic equivalents of 2,3,7,8-tetrachlorodibenzodioxine (TCDD) in 1.8 kg. See De Vormina van PCDFs. PCDDs in Gerelateerde verbindingen Bii from Oxichlorination van Etheen. Evers, E.H.G., Dept. of Environmental Toxicology, University of Amsterdam, Contract No. ZH4005, Nat. Water Service District of So. Holland (hereinafter referred to as the NWS Study) 1989. MTC Pub. No. MTC89EE. In addition, experts disagree on what levels of these toxins are generated from both natural and industrial processes. There are numerous citations in the research literature concerning the various synthetic routes that give rise to PCDD / F. Chemosphere, Vol. 23 Nos. 8-10, 0. Hutzinger, Editor, Pergamon Press, 1991. As a synthesis, significant precursors that can lead to the formation of PCDD / F reported in the literature include chlorophenol, benzene, chlorinated benzene and diphenyl ether. These species have been found to be converted to PCDD / F by means of condensation, free radical and ionic mechanisms. Chlorinated Dioxins and Related Compounds, O. Hutzinger, et. al, Editors, Pergamon Press, 1982. De novo synthesis of PCBs and PCDD / F from non-aromatic precursors (including elemental forms) has been reported in the literature for oxychlorination processes. Chemosphere, Eklund, G .; Pederson, J.R .; Stromberg, B., 17, 575, 1988. The NWS study has shown "that a number of the PCDD / F were detected in the gas phase and catalyst residue of a simulated oxychlorination process. The total amount of PCDD / F observed in the NWS experiments was 546 nanograms per 1.31 grams of EDC formed or 417 ng / g (ppb). The congener pattern of the PCDD / F formed in the NWS experiments was very similar to that found in the residual sludge of the VCM industries along the rim bank account and indicates that the laboratory study precisely models the process that occurs in commercial units. The authors of the NWS study concluded that copper catalyst plays a role in the formation of PCDD / F in the media in which carbon is present, chlorine, oxygen and other active catalytic surfaces. The data generated seem to confirm the conclusions of other researchers in that PCDD / F are formed de novo in the oxychlorination of alkanes and alkenes and especially with the oxychlorination of ethylene to form EDC. The term de novo is defined as the formation of PCDD / F directly from acyclic, aliphatic hydrocarbons, such as methane and ethylene, in the presence of oxygen and HCl. The researchers hypothesized that aromatization of simple carbon structures occurred to consider apparent de novo synthesis. The de novo formation of alkenes, benzenes, phenols and chlorinated biphenyls has been reported to be formed by the reaction of C02 and HCl in the presence of catalysts. Chemosphere, Stromberg, B. 27, 179, 1993; Chemosphere, 23, 1515, 1990. These catalysts include many materials used commercially as those used in the oxychlorination processes. In addition, fly ash from municipal solid waste incinerators has been shown to catalyze the formation of PCDD / F a) Chemosphere, Ross, B. J.; Naik adi, K. P .; Karasek, F.W., 19,291, 1989; b) Chemosphere, Benfenati, E .; Mariani, G .; Fanelli, R .; Zuccotti, S., 22, 1045, 1992; and Chemosphere, Born J. G. P.; Louw, R.; Mulder, P., 26, 2087, 1993. A study has shown that favorable conditions occur at temperatures between 280 ° C and 300 ° C, leading to a consensus among researchers of the incineration methods that PCDD / F are formed probably in post-combustion gas cooling zones of solid waste incinerators. Therefore, studies have shown that de novo synthesis of chlorinated aromatics occurs apparently under a variety of conditions. With the various reports of de novo training of PCDD / F in the process. industrial companies that consume chlorine, the reduction or elimination of these collateral products is intensively sought. Some approaches have focused on improving the selectivity of the reaction to achieve the desired product. For example, an approach that is considered from the perspective of the reduction in the level of collateral products produced in the EDC manufacture, is the improved direct chlorination process described in US Patent Number 3,410,747 ('747). This liquid phase reaction of ethylene and chlorine as indicated in '747 is carried out at the boiling point of the EDC liquid in the presence of a metal chloride catalyst and an added aromatic hydrocarbon, such as benzene. The side reactions that form the undesirable side products, mainly 1, 1, 2-trichloroethane, are reduced. Following the view that the de novo synthesis of PCDD / F is occurring, the improved reaction selectivity could reduce the level of PCDD / F formed. Other improvements have focused on the reduction in the volume of effluent discharged from the oxychlorination process. In the balanced process of ethylene oxychlorination to achieve EDC, the recapture and reuse of hydrogen chloride from the disintegration of 1,2-dichloroethane to vinyl chloride monomer is contemplated. The amount of waste effluent is reduced considerably in the reuse of HCl. This recycled HCl is referred to herein as "internally supplied" and this internally supplied HCl is typically separated from EDC, VCM and collateral products by distillation. Recent developments in the broad world of the chemical industry are leading to a shift in the manufacture of VCM away from balanced VCM processes and towards the increasing use of HCl from external processes, that is, from non-oxychlorination processes. The present invention relates to the use of this "external" HCl, ie from other sources than those obtained by separating HCl from the effluent generated in the thermal disintegration of the oxychlorination product, for example, EDC. The external HCl is produced in industrial processes such as incineration of chlorinated materials residues; the manufacture of organic isocyanates; the high temperature chlorolysis of C1-C3 hydrocarbons; and the dehydrochlorination of chlorinated materials such as chlorine-containing polymers, chlorinated hydrocarbons, chloroacetic acid, CFCs, HCFCs and other industrially useful materials. In accordance with the invention, an oxychlorination process operated for the manufacture of chlorinated hydrocarbons is provided. The process involves the catalytic oxychlorination of a fixed bed or fluid bed of a hydrocarbon reagent containing 1 to 3 carbon atoms. The oxychlorination process comprises the contact of a C1-C3 hydrocarbon reagent with oxygen or oxygenated gas and HCl, wherein at least a portion of the hydrogen chloride to be consumed is obtained from an external source other than the recovery of hydrogen chloride from the thermal pyrolysis of the product of the oxychlorination process operated. The feeds are reacted in the presence of oxychlorination catalyst in a heated reaction zone operated from 150 ° C to 600 ° C where the chlorinated hydrocarbon product is recovered from the effluents of the reaction zone. The process is characterized by the fact that the HCl is pretreated before using it in the oxychlorination process operated by means to remove the aromatic hydrocarbons. The present invention arises from the unexpected discovery that the de novo synthesis of PCDD / F is not a necessary result in the oxychlorination of non-aromatic hydrocarbons under industrially practiced conditions. In carefully controlled quantitative experiments, a laboratory oxychlorination process was monitored by initiating with externally supplied HCl, ethylene and air or oxygen in the presence of a copper catalyst. There, according to the literature, measurable quantities of PCBs and PCDD / F were observed. The measured levels of PCBs and PCDD / F observed in the oxychlorination effluent were surprisingly reduced after the external HCl was first treated to remove the aromatic hydrocarbons. Therefore, it has been shown that a greater amount of the PCDD / F found in the effluent of the oxychlorination process is provided not by de novo synthesis during the oxychlorination of aliphatic hydrocarbons but rather by a low level of aromatic compounds discovered in the feed of external HCl. It has also been shown that these aromatic compounds can be removed by conventional means, prior to the use of HCl in the oxychlorination process, thus preventing their conversion to PCBs and PCDD / F during oxychlorination.

The present invention provides an improved oxychlorination process for converting aliphatic hydrocarbons to chlorinated aliphatic hydrocarbons having reduced levels of PCBs and PCDD / F including contacting an oxychlorination catalyst with an aliphatic hydrocarbon reagent, a gas containing oxygen and part or all of the chlorine source of the external hydrogen chloride in a heated reaction zone operating from 150 ° C to 600 ° C, depending on the preferred temperature of the specific hydrocarbon feed, and recovering the chlorinated aliphatic hydrocarbon effluents from the reaction zone, consisting in the improvement of the use of external HCl (without degree of disintegration) that has been pretreated with a means to remove the aromatic compounds. Suitable means for removing the aromatic compounds from the hydrogen chloride include the fractional distillation of multistage, adsorption, absorption and reaction processes. The removal of the aromatic compounds from hydrogen chloride by distillation includes the steps of vaporization of the HCl in a vessel equipped with a reflux condenser, followed by the collection of condensed vapors virtually free of high or low boiling compounds. The vaporization and condensation steps preferably include a means for delivering a multistage counter-current fractionation as widely used in the distillation of a variety of liquids. Other means for removing the aromatics from the externally administered HCl involves the step of passing the HCl through a container containing a solid or liquid adsorbent. Solid adsorbents are known and used in the art and include, but are not limited to, activated carbon, zeolite, alumina, diatomaceous earth, various forms of silica such as silica gel; and supported adsorbent polymer or selective absorbent resin. Liquid absorbers include but are not limited to paraffins, for example aliphatic hydrocarbons such as pentanes, hexanes, distilled C5-Cg fractions and the like and water. Removal of the aromatic compounds from the external HCl can also be achieved by hydrogenation reactions including treatment by a metal hydrogenation catalyst such as nickel, platinum or palladium in the presence of a hydrogen source to convert the aromatic compounds to aliphatic compounds saturated cyclics. Catalytic oxidation on an oxidation catalyst in the presence of oxygen to convert the aromatics to carbon dioxide and water is another reaction process that can be used to remove the aromatic compounds from the HCl.

The particular method of removing the aromatic compounds from the HCl is not critical and can be selected by the technician merely on the basis of the available equipment and the preferred economy that are beyond the scope of this disclosure. Among the available pretreatment steps, preferred methods include treatment with an oxidation catalyst, passage of HCl, through an adsorbent column containing activated carbon, and extraction with paraffin liquids. In another aspect of the invention, an improved oxychlorination process effluent containing a reduced and preferably less than detectable level of polychlorinated aromatics is provided, the effluent is produced in an oxychlorination process by contacting it with an oxychlorination catalyst in an area of heated reaction operating from 150 ° C to 600 ° C, with a hydrocarbon reagent of C- ^ to C3 such as methane, ethane, ethylene, propane, propylene, acetylene, chloroethane, chloropropane, dichloromethane, dichloroethane and the like, in the presence of an oxygen-containing gas such as air, and hydrogen chloride, where a portion or all of the chlorine is provided by externally supplied hydrogen chloride, i.e., the HCl is obtained from a source outside the recovery of the aliphatic hydrocarbon oxychlorination process itself. The internally supplied HCl is obtained by thermal disintegration of the chlorinated hydrocarbon intermediate of that process. Thus, in the present invention at least a portion of the HCl used must be obtained from a process other than the thermal disintegration of the chlorinated aliphatic hydrocarbon intermediate of the oxychlorination process operated. In the present invention, the externally supplied hydrogen chloride used must be pretreated with a means for removing the aromatic compounds prior to entering the heated oxychlorination reaction zone. Suitable catalysts used in the oxychlorination process are known and are conventionally understood. Examples are described in U.S. Pat. Nos. 3,624, 170, 4,446,249, 4,740,642 and 5,011,808 and in European Patent Publication No. 0255156. The process conditions required in catalytic oxychlorination are also known and established in the art. Examples are described in the US Patent. No. 3,488,398 assigned to Harpring et al. The oxychlorination catalysts are suitable either in the form of the fixed bed or fluid bed types. In the case of oxychlorination of saturated hydrocarbons containing 1, 2 or 3 carbon atoms, the heated reaction zone is generally operated at 300 ° C to 600 ° C. In the case of oxychlorination of saturated nC hydrocarbons containing 2 6 3 carbon atoms, the heated reaction zone is operated from 150 ° C to 300 ° C. The halogenated derivatives can also be advantageously chlorinated using the present process and include chloromethane, dichloromethane, chloroethane, dichloroethane, trichloroethane, fluoromethane, fluoroethane, fluoropropane, chlorofluoromethane, chlorofluoroethane, chlorofluoropropane and substituted b-C-C-bromo hydrocarbons. The process is operated at atmospheric pressure or above atmospheric pressure. The molar ratios of reactive HCl / C2H4 / 02 feed gases are generally maintained at 2 / 1-1.5 / 0.5-1.0. The process can be operated as a one-step method without the reuse of the unreacted feed gases or the process can be operated by recycling the unreacted feed gases. Further treatment of the chlorinated product is possible using conventional thermal disintegration and / or purification means established in the art. Experiments Several experiments were carried out to demonstrate that the careful removal of the aromatic compounds from the HCl streams used as feeds to the oxychlorination processes will lead to a significant reduction in the amount of PCBs and PCDD / F. Reactions were made in laboratory scale fluid bed oxychlorination reactors operated between 210 ° C and 245 ° C, the contact time of 15 and 40 seconds and otherwise within the range of operation of the commercial units. The contact time is defined as the volume of the fluidized bed of the catalyst bed divided by the volumetric flow of the sum of all the feed gases at the reactor control temperature and the maximum reactor pressure. In some experiments, the previously measured levels of aromatics were allowed to enter the reactor with the feed gases. Other experiments involved the artificial addition of benzene, dichlorobenzene or toluene as model compounds. Baseline experiments were performed where no aromatic compounds were present in the feed or in the catalyst. It is reported in the scientific literature that deals with the quantitative analysis of PCBs and PCDD / F, that PCBs and particularly PCDD / F formed in oxychlorination and other processes accumulate and concentrate in the catalyst and are found in the extractable residues of the solid catalyst particles. From Vorming go PCDFs, PCDDs in Gerelateerde Verbindingen Bii from Oxychlorination van Etheen, Evers, E.H.G., Doctoral Thesis, University of Amsterdam, 1989. MTC Pub. No. MTC89EE. In the experimental work that is synthesized below, the analyzes were carried out both in the reactor effluent, (product and gases) and in the solid catalyst particles. For analytical consistency and simplicity, only the results of the analyzes on reductions of the catalyst samples are reported below. Oxychlorination Test Conditions A local scale laboratory scale fluidized bed reactor was used. Approximately 300 g of catalyst was charged and the temperature between 210 ° C and 245 ° C was controlled by resistance heating. The system was operated at atmospheric pressure. The feed gases C2H4, HCl and air or 2 and 02 were introduced to the reactor just below the catalyst bed. The feed cups were maintained using mass flow controllers so that the contact time of the fluidized bed was approximately 25 seconds and the molar feed ratio of HCl / C2H4 / 02 was approximately 1.96 / 1.0 / 1, respectively. The reactants and products pass upwards through the fluidized bed to a decoupling zone that separates the catalyst particles from the product gases. The product gases are then transported through a system attached to the liquid and gas sampling stations. When the analyzes were to be carried out, it was essential that the reactor and the downstream sampling lines were maintained above the dew point of the gases. The catalyst samples were removed from the reactor during the reaction conditions. A sampling port located near the base of the reactor was opened but above the point where the feed gases are introduced and the catalyst sample was taken in a clear glass container and sealed. The catalyst samples were extracted with toluene according to the following procedure: Five grams of catalyst were added in a 50 cc folded container. Toluene (25 ml) was added and the sample was mechanically stirred for 7 hours and then allowed to stand for about 15 hours. The catalyst and solvent were filtered through # 2 Whatman paper in a 6 dram amber container. 2, 4, 8-trichlorodibenzodioxin was added as a standard of internal recovery. The sample was then evaporated to dryness. The residue was reconstituted in 2-3 ml of isooctane, transferred to a 4 ml amber container and evaporated to dry without heating. The residue was then extracted in 0.1 ml of isooctane to be analyzed by GC. Two methods of CG analysis were employed. The qualitative selection was performed on a HP5890 series II CG equipped with an electron capture detector (ECD) and an RTX-5 column. The quantitative analysis was performed on a HP5870 CG equipped with an HP 5790 mass selective detector and a 30m XTI-5 capillary column (0.25 μm film). The sample size was 2 μl, and the conditions of the column were 70 ° C for two minutes, 15 ° C / per minute ramp at 300 ° C, and a wetting time of 17.7 minutes. The detection limits were 0.1 ng PCBs or PCDD / F per gram of catalyst removed from the reactor. The quantitative data reported below are listed in units of ng / g of the catalyst. The values of PCBs with 8, 9, and 10 chlorine atoms are added together and reported as "PCBs". Under the heading "OCDD" and "OCDF" are the octachlorinated dibenzodioxins and the octachlorinated dibenzofurans respectively. It is widely known in the art that the oxychlorination process favors the formation of the more highly chlorinated and therefore less toxic PCDFs, derived from less chlorinated products and environmentally more suspicious congeners. The experiments were conducted with fresh catalyst, with catalyst previously used in the oxychlorination reactor of the laboratory, and with catalyst previously used in the oxychlorination reactor of the laboratory in the presence of aromatic hydrocarbons and chlorinated aromatic hydrocarbons aggregates.

The experiments were also performed to determine if the chlorinated ethene derivatives would lead to aromatic compounds or their known precursors (butadiene derivatives). In all cases, no evidence was found of the aromatization of the C2 hydrocarbons or the production of PCBs or PCDD / F when the reactor feed contained only C2H4, HCl, 02 and N2. Example 1 Fresh Catalyst (Baseline) A sample of a fresh oxychlorination catalyst of the type described in US 5,292,703 was extracted as described above. Qualitative and quantitative CG analyzes indicated that the fresh catalyst contained only minor levels of PCBs and PCDD / F. The contamination levels found were in agreement with those reported in the literature. These are similar to the background levels found in a wide variety of commercial and non-commercial materials. This analysis was repeated on 5 additional samples of fresh catalyst to establish a baseline. The results are summarized in Table 1 below. Units are listed in nanograms per gram of EDC produced (ng / g).

TABLE 1 Catalyst PCBs ng / g OCDD (ng / g) OCDF (ng / g) 1-A < 0.1 not detected ~ 0.8 1-B < 5 not detected < 5 1-C 3.0 not detected 2.3 1-D < 1 not detected < 1 1-E < 1 not detected < 1 1-F < 1 not detected < 1 Example 2 A fresh catalyst sample is used in the laboratory oxychlorination reactor operating at 225 ° C, with molar ratios of HCl / C2H4 / 02 controlled at 1.97 / 1.0 / 1.1, and with approximately 25 seconds of contact time. HCl, ethylene and air were quantitatively pretreated to remove the aromatics. The catalyst was shown and extracted as described above. Surprisingly, no evidence of elevated levels (compared to baseline experiments) of PCBs or PCDD / F was found in the quantitative analysis of the catalyst particles. If unavoidable, de novo synthesis of the polychlorinated aromatics was occurring, detectable increases in PCBs and / or PCDD / F in the catalyst particles would have been readily observed. Therefore, without aromatic compounds present in HCl after treatment using a suitable medium to remove the aromatic compounds, the oxychlorination effluent will contain reduced levels of PCBs and PCDD / F. Example 3 The fresh catalyst was placed in the laboratory oxychlorination reactor under the above conditions. A mixture of aromatic hydrocarbons consisting mainly of C3 xylenes and benzenes was introduced at a combined level of approximately 200 ppb based on the HCl feed rate. The reaction was carried out for about 24 hours to allow a steady state to be established, and the catalyst was shown and analyzed as described above. CG-MSD results indicated elevated levels of PCBs and PCDD / F: PCBs = 21.2 ng / g; OCDD = not detected; OCDF = 94.2 ng / g. In a similar experiment we found the PCB = 23.9 ng / g; OCDD = not detected; OCDF = 14.6 ng / g. These observations illustrate that the aromatic compounds present in the HCl stream do not contribute to the amount of polychlorinated aromatics found in the oxychlorination effluent. Example 4 Following the same procedure as in Example 3, benzene was introduced at a rate of about 14% of the HCl feed rate for 6 hours. The catalyst was shown and analyzed as described above and high levels of PCBs and PCDD / F were found: PCB = 5.3 ng / g; OCDD = not analyzed; OCDF = 1137 ng / g: Example 5 Following the procedures of Example 4 above, toluene was introduced at a rate of about 4% based on the HCl feed. The analysis of the catalyst after approximately 6 hours of exposure gave the following results: PCB = 46.4 ng / g; OCDD = 42.3 ng / g; OCDF = 315.6 ng / g. Example 6 In an effort to determine if the hydrocarbons can bind to form butadiene and butadiene derivatives known to react with the olefins to produce the aromatic compounds, perchlorethylene was introduced to the laboratory oxychlorination reactor operating under conditions similar to those of the Example 5. The qualitative analysis of the product of the reaction by CG-MSD indicated the presence of all chlorinated derivatives of ethane and ethene. However, no evidence of C3, C4, or major hydrocarbons or their derivatives was found. This indicates that there is no aromatization occurring under typical oxychlorination conditions. The type of catalyst used in the above experiments is not unique in relation to the observed behavior and is merely illustrative of a typical oxychlorination catalyst in commercial use. DISCUSSION Example 1 illustrated that before being used in the oxychlorination reaction, it is observed that the fresh catalyst contains only trace amounts of the PCBs and the PCDD / F. Example 2 illustrated the surprising result that when all the feed components used in the process are free of aromatics and fresh catalyst is used, there is no de novo synthesis of PCBs and PCDD / F under the conditions that are suitable for industry-scale operation. There are advantages in preventing the formation of occurrence of PCBs and PCDD / F in the effluent of the oxychlorination process since the heavy end collateral products contained in the raw EDC and the accumulated wastewater sludge from the process can now be approximated or achieve zero levels of PCBs and PCDD / F. There are considerable economic advantages when eliminating the decontamination stages of the residual effluents. The environmental contamination is finally reduced. In view of the foregoing misunderstanding, one can appreciate the application of the invention in other similar processes such as chlorination, hydroxychlorination, and reversible processes. The ability to prevent the formation of PCBs and PCDD / F can be achieved for any industrial process involving chlorine, hydrogen chloride and aliphatic hydrocarbons under conditions that prevent the conversion of aliphatic hydrocarbons into aromatic hydrocarbons. The present invention is not applicable to those processes where the de novo synthesis of aromatic compounds and polychlorinated aromatic compounds occurs intrinsically or where the aromatic compounds are an integral part of the process.

Claims (6)

1. CLAIMS 1. An improved process for the manufacture of chlorinated hydrocarbons with a reduced formation of chlorobenzenes, polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), initiating the process with a hydrocarbon reagent of C - ^ to C3 of the group consisting of methane, ethane, ethylene, acetylene, propane, propylene, methylacetylene and substituted halogen versions thereof, the process comprising: contacting the reagent with oxygen or oxygenated gas and hydrogen chloride, wherein at least a portion of the hydrogen chloride to be consumed is obtained from an external source other than the recovery of the thermal disintegration of the product produced in the oxychlorination process, such contact being carried out in the presence of a catalyst of oxychlorination in a heated reaction zone operated from 150 ° C to 600 ° C where the chlorinated hydrocarbon is recovered from the effluents of the area of reaction, the process is characterized in that the hydrogen chloride is pretreated with a means to remove the aromatic hydrocarbons.
2. 2. The process according to claim 1, characterized in that "the means for the removal of the aromatic compounds of hydrogen chloride are selected from the group consisting of distillation, adsorption, absorption, hydrogenation and oxidation.
3. 3. The process according to claim 1 characterized in that the means for the removal of the aromatic compounds are selected from the group consisting of (a) passing the hydrogen chloride through a container containing activated carbon, (b) treating hydrogen chloride with activated carbon, (c) treating the hydrogen chloride with silica, (d) treating the hydrogen chloride with an aromatic compound adsorbent resin, (e) subjecting the hydrogen chloride to a hydrogenation process, ( f) extraction with an aliphatic liquid hydrocarbon, and (g) subjecting the hydrogen chloride to an oxidation process.
4. 4. The process in accordance with the claim 1 characterized in that the hydrocarbon is selected from the group consisting of methane, ethane and propane and characterized in that the heated reaction zone is operated from 300 ° C to 600 ° C.
5. 5. The process according to claim 1 characterized in that the hydrocarbon is selected from the group consisting of ethylene, acetylene, propylene, methylacetylene and wherein the heated reaction zone is operated from 150 ° C to 300 ° C.
6. 6. The process according to claim 1 characterized in that the hydrocarbon is ethylene.