FR2883872A1 - Manufacture of 1,2-dichloroethane to produce vinyl chloride, by subjecting hydrocarbon source to cracking, conveying fractions to (oxy)chlorination reactor, separating 1,2-dichloroethane, and subjecting heavy fraction to pyrolysis - Google Patents

Abstract

1,2-Dichloroethane is manufactured by subjecting a hydrocarbon source to cracking that produces a mixture of products containing ethylene; separating the mixture into at least one fraction containing ethylene and a heavy fraction; conveying the fractions to chlorination and/or oxychlorination reactor; separating 1,2-dichloroethane; and conveying the heavy fraction to cracking or to the oven. Manufacture of 1,2-dichloroethane involves subjecting a hydrocarbon source to cracking that produces a mixture of products (1) containing ethylene and other constituents; separating the mixture of products into at least one fraction containing ethylene and into a heavy fraction (fraction C); conveying the fraction (3, 4, 6, 7) containing ethylene to a chlorination reactor and/or to an oxychlorination reactor, in which reactors most of the ethylene present is converted to 1,2-dichloroethane; separating the 1,2-dichloroethane from the streams of products derived from the chlorination and oxychlorination reactors and it is conveyed to the pyrolysis oven; and conveying the fraction C to cracking or to the oven for pyrolysis of 1,2-dichloroethane as fuel. Independent claims are also included for: (A) a process for the manufacture of vinyl chloride, comprising converting 1,2-dichloroethane obtained by the inventive process to VC in the pyrolysis oven; and (B) a process for the manufacture of polyvinyl chloride by polymerization of the vinyl chloride obtained by the above process.

Description

Process for the manufacture of 1,2-dichloroethane

  The present invention relates to a process for the manufacture of 1,2-dichloroethane (DCE), a process for the manufacture of vinyl chloride (VC) and a process for producing polyvinyl chloride (PVC).

  To date, more than 99.9% pure ethylene is usually used for the manufacture of DCE intended essentially for the manufacture of VCM. This ethylene of very high purity is obtained by cracking various petroleum products followed by many complex and expensive separation steps so as to isolate ethylene from other cracking products and to obtain a product of very high purity. The other products of cracking, in particular ethane and compounds containing at least 3 carbon atoms, are in this case generally isolated and valorized as pure product.

  In view of the high cost of obtaining ethylene of such high purity, various DCE manufacturing processes using ethylene of purity lower than 99.9% have been developed. These processes have the advantage of reducing costs by simplifying the separation of the product from the cracking and thus giving up complex and uninteresting separations for the manufacture of DCE. These processes nevertheless have the disadvantage that ethane and the compounds containing at least 3 carbon atoms entrained with the so-called impure ethylene fraction, possibly separated subsequently, are not upgraded, thus affecting the economy of the process.

  The present invention therefore aims to provide a simplified method which has the advantage of reducing costs by giving up complex separations to isolate ethylene from other cracking products of no interest for the manufacture of DCE but which also has the advantage to allow recovery of ethane and compounds containing at least 3 carbon atoms thus inducing a significant saving.

  To this end, the invention relates to a simplified process for producing DCE from a hydrocarbon source according to which: a) the hydrocarbon source is subjected to a cracking producing a mixture of products containing ethylene and other components; b) separating said product mixture into at least one fraction containing ethylene and a heavy fraction (fraction C); c) the ethylene-containing fraction (s) is fed into a chlorination reactor and / or an oxychlorination reactor, reactors in which most of the ethylene present is converted to DCE; d) separating the obtained DCE from the product streams from the chlorination and oxychlorination reactors and sending it to the pyrolysis furnace; and e) fraction C is sent to the pyrolysis cracking or pyrolysis furnace as a fuel.

  The hydrocarbon source considered may be any known hydrocarbon source. Preferably, the hydrocarbon source subjected to cracking (step a)) is chosen from the group consisting of naphtha, gas oil, natural gas liquid, ethane, propane, butane and isobutane. mixtures. Particularly preferably, the hydrocarbon source is selected from the group consisting of ethane, propane, butane and propane / butane mixtures. Most preferably, the hydrocarbon source is selected from the group consisting of ethane, propane and propane / butane mixtures. Good results have been obtained with a hydrocarbon source selected from the group consisting of propane and propane / butane mixtures. The propane / butane mixtures can exist as such or be formed by mixing propane and butane.

  20. Ethane, propane, butane and propane / butane mixture are intended, for the purposes of the present invention, to denote the commercially available products, namely consisting essentially of pure product (ethane, propane, butane or propane / butane in admixture). and secondarily other saturated or unsaturated hydrocarbons, lighter or heavier than the pure product itself.

  By cracking (step a)), the term "fms" of the present invention is intended to denote all the stages of treatment of the hydrocarbon source which lead to the formation of a mixture of products containing ethylene and other constituents. .

  Such cracking can be carried out according to any known technique as long as it makes it possible to obtain a mixture of products containing ethylene and other constituents. Advantageously, the cracking comprises a first step of pyrolysis (that is to say a transformation under the action of heat) of the hydrocarbon source in the presence or absence of third compounds such as water, oxygen, a derivative sulfur and / or a catalyst. This step advantageously takes place in a furnace called cracking oven. This first step is preferably followed by steps of separation of the heavy products (for example via organic quenching and aqueous quenching), compression and drying of the gases as well as elimination of carbon dioxide and sulfur compounds (for example example by means of an alkaline washing), hydrogenation of the undesirable derivatives generated during the first pyrolysis step such as, for example, acetylene and the elimination of part of the hydrogen, for example via a PSA process ( pressure swing adsorption) or via a membrane process.

  Advantageously, in the process according to the invention, the mixture of products containing ethylene and other constituents from step a) comprises, as important compounds, hydrogen, carbon monoxide, methane and compounds comprising from 2 to 7 carbon atoms. By important compounds is meant those compounds which are present in an amount of at least 200 ppm by volume.

  For the purposes of the present invention, the term "simplified process" is intended to mean that after the above-mentioned step a) of cracking, the mixture of products containing ethylene and other constituents is subjected to step b ) which advantageously comprises at most four, preferably at most three, separation steps to obtain at least one fraction containing ethylene. The simplified process therefore does not require many complex and expensive separation steps in order to isolate ethylene from other cracking products and to obtain a product of very high purity.

  In step b), the product mixture is separated into at least one fraction containing ethylene and a heavy fraction (fraction C). Fraction C contains, advantageously, ethane and compounds comprising at least 3 carbon atoms. Among the compounds comprising at least 3 carbon atoms, mention may be made of propane, propene, butanes and their unsaturated derivatives and all heavier saturated or unsaturated compounds.

  According to a first variant of the process according to the invention, fraction C is sent to cracking, preferably to the first stage of cracking which is a pyrolysis step.

  Prior to this step of sending to cracking, according to a first preferred subvariant, fraction C is preferably subjected to a hydrogenation step.

  According to a first particularly preferred embodiment, the hydrogenation step is followed by the sending of the entire fraction C to the first stage of cracking.

  According to a second particularly preferred embodiment, the hydrogenation step is followed by at least one, most preferably a separation step, preferably by distillation, in two different fractions respectively containing compounds comprising less of 5 carbon atoms, for one of them, and compounds comprising at least 5 carbon atoms for the other. Compounds containing less than 5 carbon atoms are then very particularly preferably sent to cracking while compounds comprising at least 5 carbon atoms are burned to provide energy or recovered in any form whatsoever.

  Prior to this step of sending to cracking, according to a second preferred subvariant, the fraction C is preferably firstly subjected to at least one, particularly preferably to a separation step consisting of the separation of the fraction C, with preferably by distillation, in two different fractions respectively containing compounds comprising less than 5 carbon atoms, for one of them, and compounds comprising at least 5 carbon atoms for the other. The resulting fraction containing the compounds comprising less than 5 carbon atoms is then very particularly preferably subjected to a hydrogenation step before being sent to cracking. As for the compounds comprising at least 5 carbon atoms, they are very particularly preferably burned to provide energy or recovered in any form whatsoever.

  The fraction that is sent to the cracking can be sent directly to the cracking furnace of the first pyrolysis step or be first mixed with the hydrocarbon source.

  The first sub-variant explained above is particularly preferred, with a very particular preference for the second embodiment.

  The above-mentioned hydrogenation step can be carried out using any known hydrogenation catalyst such as, for example, catalysts based on palladium, platinum, rhodium, ruthenium or iridium deposited on a support such as alumina. , silica, silica alumina, carbon, calcium carbonate or barium sulfate. Preferably, the hydrogenation step is carried out by means of a palladium or platinum-based catalyst deposited on alumina or carbon. In a particularly preferred manner, it is carried out using a palladium catalyst deposited on carbon.

  The amount of palladium in the catalyst is advantageously of the order of 1% by weight.

  The temperature at which the hydrogenation step is carried out is advantageously at least 5, preferably at least 20, particularly preferably at least 50 C. It is advantageously at most 150, preferably at most 100 C. As for the pressure, it is advantageously greater than or equal to 1, preferably greater than or equal to 3 bar. It is advantageously less than or equal to 20, preferably less than or equal to 10 bar.

  Preferably, this hydrogenation step is carried out using quantities of hydrogen such that it is complete, that is to say preferably at least 99%. The excess of non-consumed hydrogen may be separated from the hydrogenated fraction or may optionally be sent to the first pyrolysis step therewith when this is the case.

  The hydrogenation of acetylene during cracking can also be carried out using the catalysts mentioned above with the same preferences. The temperature at which the acetylene hydrogenation step is then carried out is advantageously at least 5, preferably at least 20 C. It is advantageously at most 80, preferably at most 50 C. As for the pressure, it is advantageously greater than or equal to 1, preferably greater than or equal to 3 bar. It is advantageously less than or equal to 20, preferably less than or equal to 10 bar. Preferably, the hydrogenation of acetylene is carried out using quantities of hydrogen such that its hydrogenation is complete, that is to say preferably at least 99%, even if this is accompanied by hydrogenation of part of the ethylene to ethane. The latter is then advantageously returned to the first stage of cracking.

  According to a second variant of the process according to the invention, the fraction C is sent to the pyrolysis furnace of the DCE, in VC, as a fuel.

  Another source of energy that can be used to ensure, at least partially, the operation of the DCE pyrolysis furnace in VC can advantageously be found by burning unconverted products to the chlorination of ethylene to DCE, particularly the hydrogen and methane. These unconverted products are preferably separated prior to the chlorination, for example via a PSA process or a membrane method.

  The heat generated in the cracking furnace, which consists of a heat recovery on hot gases (also called sensible heat), can advantageously also be a source of energy, at least partial, to ensure the operation of the pyrolysis furnace of the DCE. in VC.

  The separation of the product mixture containing ethylene and other constituents in step b) leads to the formation of at least one fraction containing ethylene, preferably two fractions containing ethylene, particularly preferably an ethylene-containing fraction which is enriched in compounds lighter than ethylene, referred to below as fraction A, and a second fraction containing ethylene advantageously enriched in ethylene, called fraction B below.

  Advantageously, the content of lighter compounds than ethylene, in particular methane, hydrogen and carbon monoxide, in fraction A is greater than or equal to 2% by volume, preferably greater than or equal to 3% by weight. volume and particularly preferably greater than or equal to 5% by volume. Advantageously, the content of lighter compounds than ethylene in fraction A is less than or equal to 90% by volume, preferably less than or equal to 85% by volume and particularly preferably less than or equal to 80% by volume.

  Fraction A is characterized by a content of compounds comprising at least 3 carbon atoms, advantageously less than or equal to 0.01% by volume, preferably less than or equal to 0.005% by volume and particularly preferably less than or equal to 0.001% by weight. % in volume.

  Fraction A advantageously contains from 10% to 60% by volume of ethylene. The fraction A advantageously contains at least 10% by volume, preferably at least 15% by volume and particularly preferably at least 20% by volume of ethylene. The fraction A advantageously contains at most 60% by volume, preferably at most 40% by volume and particularly preferably at most 30% by volume of ethylene.

  In the preferred case where the hydrocarbon source is ethane, fraction A advantageously contains at least 15% by volume, preferably at least 20% by volume and particularly preferably at least 25% by volume of ethylene. The fraction A advantageously contains at most 60% by volume, preferably at most 40% by volume and particularly preferably at most 30% by volume of ethylene.

  In the preferred case where the hydrocarbon source is a propane / butane mixture, fraction A advantageously contains at least 10% by volume, preferably at least 15% by volume and particularly preferably at least 20% by volume of ethylene. . The fraction A advantageously contains at most 60% by volume, preferably at most 30% by volume and particularly preferably at most 25% by volume of ethylene.

  The fraction A is further characterized by an acetylene content advantageously less than or equal to 0.01% by volume, preferably less than or equal to 0.005% by volume and particularly preferably less than or equal to 0.001% by volume.

  Fraction B is advantageously characterized by a hydrogen content of less than or equal to 2% by volume, preferably less than or equal to 0.5% by volume and particularly preferably less than or equal to 0.1% by volume.

  Fraction B is characterized by a content of compounds comprising at least 3 carbon atoms, advantageously less than or equal to 0.01% by volume, preferably less than or equal to 0.005% by volume and particularly preferably less than or equal to 0.001% by weight. % in volume.

  Fraction B advantageously contains from 40% to 99.5% by volume of ethylene. Fraction B advantageously contains at least 40% by volume, preferably at least 50% by volume and particularly preferably at least 60% by volume of ethylene. Fraction B advantageously contains at most 99.5% by volume, preferably at most 99.2% by volume and particularly preferably at most 99% by volume of ethylene.

  In the preferred case where the hydrocarbon source is ethane, the fraction B advantageously comprises at least 60% by volume, preferably at least 70% by volume and particularly preferably at least 75% by volume of ethylene. Fraction B advantageously comprises at most 99.5% by volume, preferably at most 99.2% by volume and particularly preferably at most 99% by volume of ethylene.

  In the preferred case where the hydrocarbon source is a propane / butane mixture, fraction B advantageously comprises at least 40% by volume, preferably at least 50% by volume and particularly preferably at least 60% by volume of ethylene. . Fraction B advantageously comprises at most 99.5% by volume, preferably at most 99.2% by volume and particularly preferably at most 99% by volume of ethylene.

  Fraction B is further characterized by an acetylene content advantageously less than or equal to 0.01% by volume, preferably less than or equal to 0.005% by volume and particularly preferably less than or equal to 0.001% by volume.

  Any separation process may be used to separate said ethylene-containing product mixture into fraction A, fraction B and fraction C as long as it advantageously comprises at most four, preferably at most three, separation steps for obtain the two fractions A and B. According to a first preferred embodiment, the product mixture containing ethylene from step a) is subjected to a first separation step to extract the fraction C and the resulting mixture is then subjected to a second separation step in fraction A and fraction B. According to a second preferred embodiment, the mixture of products containing ethylene from step a) is subjected to a first separation step allowing extracting fraction A and the resulting mixture is then subjected to a second separation step in fraction B and fraction C. The first preferred mode is particularly preferred re. Many variants can make it possible to achieve this first preferred mode of separation of the mixture of ethylene-containing products from step a). A preferred variant consists in subjecting said mixture to a first separation step for extracting fraction C and then subjecting the resulting mixture to a second separation step in fraction A and fraction B, both of which are distillation steps carried out. by means of a distillation column provided with associated ancillary equipment such as at least one boiler and at least one condenser.

  According to this preferred variant, the fraction C preferably leaves at the bottom of the first distillation column, fraction A at the head of the second distillation column and fraction B at the bottom of the second distillation column.

  According to the process according to the invention, fraction A is advantageously sent to the chlorination reactor and fraction B to the oxychlorination reactor, preferably after expansion with energy recovery.

  The chlorination reaction is advantageously carried out in a liquid phase (preferably substantially DCE) containing a dissolved catalyst such as FeCl 3 or another Lewis acid. This catalyst can advantageously be combined with co-catalysts such as alkaline chlorides. A couple that has given good results is the complex of FeCl 3 with LiCl (lithium tetrachloroferrate as described in patent application NL 6901398).

  The amounts of FeCl 3 advantageously used are of the order of 1 to 10 g of FeCl 3 per kg of liquid foot. The molar ratio of FeCl 3 to LiCl is advantageously in the range of 0.5 to 2.

  The chlorination process according to the invention is advantageously carried out at temperatures of between 30 and 150 ° C. Good results have been obtained regardless of the pressure at a temperature below the boiling point (sub-cooled chlorination). at the boiling point itself (boiling chlorination).

  When the chlorination process according to the invention is a sub-cooled chlorination process, it has given good results by working at a temperature advantageously greater than or equal to 50 ° C. and preferably greater than or equal to 60 ° C., but advantageously less than or equal to 60 ° C. equal to 80 C and preferably less than or equal to 70 C; with a pressure in the gaseous phase advantageously greater than or equal to 1.5 and preferably greater than or equal to 2 bar absolute but advantageously less than or equal to 20, preferably less than or equal to 10 and particularly preferably less than or equal to 6 absolute bar.

  Particularly preferred is a boiling chlorination process which, if necessary, can usefully recover the heat of reaction. In this case, the reaction advantageously takes place at a temperature greater than or equal to 60 ° C., preferably greater than or equal to 90 ° C. and particularly preferably greater than or equal to 95 ° C., but advantageously less than or equal to 150 ° C. and preferably lower. or 135 C; with a pressure in the gaseous phase advantageously greater than or equal to 0.2, preferably greater than or equal to 0.5, particularly preferably greater than or equal to 1.2, and very particularly preferably greater than or equal to 1.5 absolute bar but advantageously less than or equal to 10 and preferably less than or equal to 6 bar absolute. - 10-

  The chlorination process may also be a mixed shuttle boiling chlorination process. By mixed process boiling chlorination cooled by shuttle means a process in which a cooling of the reaction medium is carried out, for example by means of an exchanger immersed in the reaction medium or by a shuttle circulating in an exchanger, while producing in the gas phase at least the amount of DCE formed. Advantageously, the temperature and the reaction pressure are adjusted to release the product DCE in the gas phase and remove the remaining calories by commuting the reaction medium on an exchanger.

  In addition, the chlorination process is advantageously carried out in a chlorinated organic liquid medium. Preferably this chlorinated organic liquid medium, also called liquid foot, consists essentially of DCE.

  Fraction A containing ethylene as well as chlorine (itself pure or diluted) may be introduced by any known device into the reaction medium together or separately. A separate introduction of fraction A can be used to increase its partial pressure and to facilitate its dissolution, which is often a limiting step in the process.

  Chlorine is added in sufficient quantity to convert most of the ethylene and without the addition of excess unconverted chlorine. The chlorine / ethylene ratio used is preferably between 1.2 and 0.8 and particularly preferably between 1.05 and 0.95 mol / mol.

  The chlorinated products obtained essentially contain DCE as well as small amounts of by-products such as 1,1,2-trichloroethane or small amounts of chlorination products of ethane or methane. The separation of the DCE obtained from the stream of products from the chlorination reactor operates according to known modes and generally makes it possible to exploit the heat of the chlorination reaction.

  The unconverted products (methane, carbon monoxide and hydrogen) are then separated more easily than would have been necessary to separate pure ethylene from the initial mixture.

  The oxychlorination reaction is advantageously carried out in the presence of a catalyst comprising active elements including copper deposited on an inert support. The inert support is advantageously chosen from alumina, silica gels, mixed oxides, clays and other supports of natural origin. Alumina is a preferred inert carrier.

  Catalysts comprising advantageously at least two active elements, one of which is copper, are preferred. Among the active elements other than copper, mention may be made of alkali metals, alkaline earth metals, rare earth metals and metals of the group consisting of ruthenium, rhodium, palladium, osmium and iridium. , platinum and gold. The catalysts containing the following active elements are particularly interesting: copper / magnesium / potassium, copper / magnesium / sodium; copper / magnesium / lithium, copper / magnesium / cesium, copper / magnesium / sodium / lithium, copper / magnesium / potassium / lithium and copper / magnesium / cesium / lithium, copper / magnesium / sodium / potassium, copper / magnesium / sodium / cesium and copper / magnesium / potassium / cesium. The catalysts described in patent applications EP-A 255 156, EP-A 494 474, EP-A-657 212 and EP-A 657 213, incorporated by reference, are very particularly preferred.

  The copper content, calculated in metallic form, is advantageously between 30 and 90 g / kg, preferably between 40 and 80 g / kg and particularly preferably between 50 and 70 g / kg of the catalyst.

  The magnesium content, calculated in metallic form, is advantageously between 10 and 30 g / kg, preferably between 12 and 25 g / kg and particularly preferably between 15 and 20 g / kg of the catalyst.

  The content of alkali metal (s), calculated in metallic form, is advantageously between 0.1 and 30 g / kg, preferably between 0.5 and g / kg and particularly preferably between 1 and 15 g. / kg of the catalyst.

  The atomic ratios Cu: Mg: alkali metal (s) are advantageously 1: 0.1-2: 0.05-2, preferably 1: 0.2-1.5: 0.1-1, And particularly preferably 1: 0.5-1: 0.15-1.

  Catalysts having a specific surface area measured according to the B.E.T. Nitrogen advantageously between 25 m2 / g and 300 m2 / g, preferably between 50 and 200 m2 / g and particularly preferably between 75 and 175 m2 / g, are particularly interesting.

  The catalyst can be used in a fixed bed or in a fluid bed. This second option is preferred. The oxychlorination process is operated within the range of conditions usually recommended for this reaction. The temperature is advantageously between 150 and 300 ° C., preferably between 200 ° and 275 ° C. and most preferably between 215 ° and 255 ° C. The pressure is advantageously greater than atmospheric pressure. Values between 2 and 10 bar absolute gave good results. The range between 4 and 7 bar absolute is preferred. This pressure can usefully be modulated to achieve an optimum residence time in the reactor and to maintain a constant rate of passage for various gait speeds. The usual residence times are from 1 to 60 seconds and preferably from 10 to 40 seconds.

  The oxygen source of this oxychlorination may be air, pure oxygen or their mixture, preferably pure oxygen. The last solution is preferred which allows easy recycling of unconverted reagents.

  The reagents can be introduced into the bed by any known device. It is generally advantageous to introduce oxygen separately from other reagents for safety reasons. These also require maintaining the gas mixture leaving the reactor or recycled to it outside the flammability limits at the pressures and temperatures considered. It is preferred to maintain a mixture said to be rich, ie containing too little oxygen with respect to the fuel to ignite. In this regard, the abundant presence (> 2%, preferably> 5% vol) of hydrogen would be a disadvantage given the broad flammability range of this compound.

  The hydrogen chloride / oxygen ratio used is advantageously between 2 and 4 mol / mol. The ethylene / hydrogen chloride ratio is advantageously between 0.4 and 0.6 mol / mol.

  The chlorinated products obtained essentially contain DCE as well as small amounts of by-products such as 1,1,2-trichloroethane. The separation of the DCE obtained from the flow of products from the oxychlorination reactor takes place according to known modes. The heat of the oxychlorination reaction is usually recovered as a vapor that can be used for separations or other uses.

  Unconverted products such as methane and ethane are then separated more easily than would have been necessary to separate pure ethylene from the initial mixture.

  The DCE obtained is then separated from the product streams from the chlorination and oxychlorination reactors and sent to the pyrolysis furnace to be advantageously converted into VC.

  The invention therefore also relates to a method of manufacturing VC. To this end, the invention relates to a process for the manufacture of VC, characterized in that the DCE obtained by the process according to the invention is converted into VC in the pyrolysis furnace.

  The conditions under which pyrolysis can be carried out are known to those skilled in the art. This pyrolysis is advantageously obtained by a reaction in the gas phase in a tubular furnace. The usual pyrolysis temperatures range between 400 and 600 ° C. with a preference for the range between 480 ° C. and 540 ° C. The residence time is advantageously between 1 and 60 seconds with a preference for the range of 5 to 25 seconds. . The degree of conversion of the DCE is advantageously limited to 45 to 75% to limit the formation of by-products and fouling of the furnace tubes. The following steps make it possible, by any known device, to harvest the purified VC and the hydrogen chloride to be valorised in preference to oxychlorination. For purification, the unconverted DCE is advantageously returned to the pyrolysis furnace.

  In addition, the invention also relates to a method of manufacturing PVC. For this purpose, the invention relates to a process for the manufacture of PVC by polymerization of the VC obtained by the process according to the invention.

  The PVC manufacturing process can be a mass, solution or aqueous dispersion polymerization process, preferably it is an aqueous dispersion polymerization process.

  The term "aqueous dispersion polymerization" is intended to denote radical polymerization in aqueous suspension as well as radical polymerization in aqueous emulsion and aqueous microsuspension polymerization.

  By radical polymerization in aqueous suspension is meant any radical polymerization process taking place in an aqueous medium in the presence of dispersing agents and oil-soluble radical initiators.

  By radical polymerization in aqueous emulsion is meant any radical polymerization process taking place in an aqueous medium in the presence of emulsifiers and water-soluble radical initiators.

  By polymerization in aqueous microsuspension, also called homogenized aqueous dispersion, is meant any radical polymerization process in which is implemented oil-soluble initiators and is carried out an emulsion of monomer droplets through a powerful mechanical stirring and the presence of emulsifiers.

  The method according to the invention therefore has the advantage, by the recovery of heavy compounds, substantially improve the economy of the DCE manufacturing process.

  Another advantage of this process is that, thanks to the separation of the compounds comprising at least 3 carbon atoms via the fraction C, it makes it possible to avoid the inhibition problems generally encountered during the pyrolysis of the DCE when these compounds are entrained with ethylene. This inhibition is due to the formation of derivatives such as 1,2-dichloropropane and monochloropropenes. These derivatives are difficult to separate completely from the DCE. Their ease of formation of stable allylic radicals explains their powerful inhibitory effect of the pyrolysis of DCE which takes place by a radical route.

  The presence of these products containing three or more carbon atoms would, moreover, constitute a useless consumption of oxychlorination and chlorination reagents or would generate destruction costs. In addition, these heavy compounds contribute to the dirtying of columns and evaporators.

  Another advantage of the process according to the invention is that it makes it possible to have on the same industrial site a completely integrated process ranging from the hydrocarbon source to the polymer obtained from the monomer produced.

  A particular embodiment of the method according to the invention will now be illustrated with reference to the drawing accompanying the present description. This drawing consists of the appended FIG. 1, schematically representing a typical embodiment of the first preferred variant of the simplified process for manufacturing DCE according to the invention.

  The mixture of products 1 containing ethylene and other constituents resulting from the cracking (not shown) of a hydrocarbon source which is ethane introduced to cracking with a flow rate of 19984 kg / h is introduced into the main column. 2 which is a distillation column equipped with a bottom boiler and a condenser at the head where it is separated into 2 different fractions, namely fraction 3 at the top of column 2 and fraction 4 at the bottom of column 2.

  Fraction 3 is then sent to a second distillation column 5 equipped with a bottom boiler and a condenser at the top.

  After passing through column 5, fraction 3 is separated into fraction 6 leaving the top of column 5 and fraction 7 exiting at the bottom of column 5.

  Fraction 6, enriched in compounds lighter than ethylene, in particular methane, hydrogen and carbon monoxide, is fed to the ethylene chlorination unit.

  Fraction 7, characterized by a very low content of hydrogen, is conveyed to the oxychlorination unit of ethylene.

  Fraction 4, consisting of ethane and compounds comprising at least 3 carbon atoms, is, for its part, either removed (case n 1) or sent as such to the first stage of cracking (case n 2), is subjected to a hydrogenation step followed by a distillation step to separate the compounds containing less than 5 carbon atoms from the compounds containing at least 5 carbon atoms and sending compounds containing less than 5 carbon atoms to the first step cracking (case 3).

  The yield of ethylene contained in the fractions 6 and 7 with respect to the ethane used for the 3 cases described above is 56, 83 and 89% respectively.

  These figures illustrate with advantage the economic interest represented by the valuation of fraction 4 (heavy fraction C).

Claims (4)

CLAIMS S   A simplified process for producing 1,2-dichloroethane from a hydrocarbon source wherein: a) the hydrocarbon source is cracked producing a mixture of products containing ethylene and other components; b) separating said product mixture into at least one fraction containing ethylene and a heavy fraction (fraction C); c) the ethylene-containing fraction (s) is fed into a chlorination reactor and / or an oxychlorination reactor, reactors in which most of the ethylene present is converted to 1,2-dichloroethane; d) the 1, 2-dichloroethane obtained is separated from the product streams from the chlorination and oxychlorination reactors and sent to the pyrolysis furnace; and e) fraction C is sent to the cracking or pyrolysis furnace of 1,2-dichloroethane as fuel.   2 - Process for the manufacture of 1,2-dichloroethane according to claim 1, characterized in that the hydrocarbon source is selected from the group consisting of naphtha, gas oil, natural gas liquid, ethane, propane, butane, isobutane and mixtures thereof.   3 - Process for the manufacture of 1,2-dichloroethane according to any one of claims 1 to 2, characterized in that the mixture of products containing ethylene and other components from step a) comprises as compounds hydrogen, carbon monoxide, methane and compounds comprising from 2 to 7 carbon atoms.   Process for the production of 1,2-dichloroethane according to any one of Claims 1 to 3, characterized in that fraction C contains ethane and compounds comprising at least 3 carbon atoms.   - Process for the manufacture of 1,2-dichloroethane according to any one of claims 1 to 4, characterized in that the fraction C is sent to cracking.   6 - Process for the manufacture of 1,2-dichloroethane according to claim 5, characterized in that the fraction C is sent to the first step of the cracking which is a pyrolysis step.   7 - Process for the manufacture of 1,2-dichloroethane according to any one of claims 5 to 6, characterized in that prior to its sending to cracking, fraction C is subjected to a hydrogenation step.   Process for the manufacture of 1,2-dichloroethane according to any one of Claims 1 to 4, characterized in that fraction C is sent to the pyrolysis furnace of 1,2-dichloroethane as fuel.   Process for the production of vinyl chloride, characterized in that the 1,2-dichloroethane obtained by the process according to any one of Claims 1 to 8 is converted into VC in the pyrolysis furnace.     Process for the production of polyvinyl chloride by polymerization of vinyl chloride obtained by the process according to claim 9.