FR2880019A1 - Manufacturing 1,2-dichloroethane, comprises cracking core hydrocarbonated source, separating into fractions, sending into chlorination reaction chamber and oxychlorination reaction chamber and separating from chambers - Google Patents

Abstract

Preparation of 1,2-dichloroethane (I), comprises cracking a core hydrocarbonated source (Ia) to form a gas mixture (II) (ethylene and other components), separating (II) in a light fraction comprising fractions of ethylene (F1), enriched ethylene (F2) and an optional heavy fraction (F3), passing (F1) in a chlorination reaction chamber (R1) and (F2) in a oxychloration reaction chamber (R2) to form (I) and separating (I) from (R1) and (R2). Independent claims are also included for: (1) a manufacturing process of vinyl chloride comprising pyrolosing (I); and (2) a manufacturing process of poly (vinyl chloride) by polymerization of vinyl chloride.

Description

Process for the manufacture of 1,2-dichloroethane

  The present invention relates to a process for the manufacture of 1,2-dichloroethane, a process for the manufacture of vinyl chloride and a process for the manufacture of polyvinyl chloride.

  To date, more than 99.99% pure ethylene is usually used for the manufacture of 1,2-dichloroethane. 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.

  In view of the high cost of obtaining ethylene of such high purity, various processes for producing 1,2-dichloroethane using ethylene of purity lower than 99.99% have been developed. These methods have the advantage of reducing the cost of a cracker by giving up complex separations and of no interest for the manufacture of 1,2-dichloroethane.

  For example, patent application WO 00/26164 describes a process for the manufacture of 1,2-dichloroethane by simplified cracking of ethane coupled with a chlorination of ethylene. For this purpose, a chlorination step of the ethylene takes place in the presence of the impurities obtained during the cracking of ethane.

  The patent application WO 03/48088 describes a process for the manufacture of 1,2-dichloroethane by dehydrogenation of ethane giving rise to the formation of a fraction comprising ethane, ethylene and impurities of which the hydrogen, then subjected to chlorination and / or oxychlorination.

  The described processes nevertheless have the disadvantage that the ethylene obtained can not be used for a chlorination / oxychlorination process of ethylene, since ethylene contains impurities whose presence during the oxychlorination reaction could cause operating problems namely a poisoning of the catalyst by heavy products and a non-economic conversion of the hydrogen present. This conversion of hydrogen would consume oxygen and release a significant heat of reaction. This would then limit the capacity of the oxychlorination reactor, generally related to the heat exchange capacity. An abnormally high investment should therefore be made to guarantee the heat exchange surface, and thereby the reactor volume, induced by the presence of hydrogen in the mixture.

  The present invention aims to provide a simplified process that has the advantage of reducing the cost of a cracker by giving up complex separations and without interest for the manufacture of 1,2-dichloroethane and which has the advantage to avoid problems related to the presence of the aforementioned impurities.

  To this end, the invention relates to a simplified process for producing 1,2-dichloroethane from a hydrocarbon source according to which: a) the hydrocarbon source is subjected to cracking producing a mixture of gases containing ethylene and other constituents; b) separating the gas mixture into a light fraction containing part of the ethylene (fraction A), into a fraction enriched in ethylene (fraction B) and, optionally, a heavy fraction (fraction C); c) fraction A is sent to a chlorination reactor and fraction B to an oxychlorination reactor, reactors in which most of the ethylene present in fractions A and B is converted to 1,2-dichloroethane; d) the 1,2-dichloroethane obtained is separated from the product streams from the chlorination and oxychlorination reactors.

  The hydrocarbon source considered may be any known hydrocarbon source. Preferably, the hydrocarbon source subjected to simplified cracking is selected from the group consisting of naphtha, gas oil, natural gas liquid, ethane, propane, butane, isobutane and mixtures thereof. 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.

  By cracking is meant for the purposes of the present invention, all stages of treatment of the hydrocarbon source which lead to the formation of a gas mixture containing ethylene and other constituents.

  Such cracking can be carried out according to any known technique provided that it allows to obtain a mixture of gases containing ethylene and other constituents. For example, the cracking may comprise 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, at least one sulfur derivative and / or at least one catalyst. This first stage is advantageously 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 by means of an alkaline washing) and hydrogenation of undesirable derivatives such as, for example, acetylene.

  For the purposes of the present invention, the term "simplified process" is intended to mean that, after the cracking defined above, the mixture of gases containing ethylene and other constituents is advantageously subjected to a maximum of two separation steps. 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. Preferably, the simplified method according to the invention comprises only a separation step (called step S) of the gas mixture resulting from cracking.

  Advantageously, in the process according to the invention, the mixture of gases containing ethylene and other constituents derived from cracking comprises, as major components, hydrogen, carbon monoxide, methane and compounds comprising 2 to 7 carbon atoms. By major compounds is meant those compounds which are present at a rate of at least 200 ppm by volume.

  Preferably, the gas mixture resulting from cracking comprises as major compounds hydrogen, carbon monoxide, methane and compounds comprising from 2 to 7 carbon atoms and said mixture is separated into the 3 fractions A, B and C, the fraction C containing mainly ethane and compounds comprising at least 3 carbon atoms.

  In the process according to the invention, the separation step S advantageously decomposes into a first separation step (called step S1) and into a second separation step (called step S2).

  Step S1 advantageously consists in separating the gas mixture resulting from cracking in a main column (called column C1) into 3 different fractions, namely the fraction, A which leaves at the top of column C1, the fraction C which leaves at the bottom of the column Cl and a fraction (called fraction F) which is withdrawn laterally from the column Cl.

  Step S2 advantageously consists in separating fraction F withdrawn laterally from column C1 into 2 different fractions, including fraction B. In the process according to the invention, separation into the 3 fractions A, B and C is preferably carried out by means of a main column (column C1), the fraction A being obtained at the top of the column C1, the fraction C at the bottom of the column C1 and the fraction B consisting of all or part of a fraction F which is withdrawn laterally from column Cl.

  Prior to its introduction into the column Cl, the gas mixture resulting from cracking can be subjected to a thermal conditioning step. By thermal conditioning step is meant a succession of heat exchanges optimizing the use of energy for example the gradual cooling of the gas mixture in a train of exchangers first cooled with raw water, then with ice-cold water and then with increasingly cold fluids plus cross-exchangers recovering the sensible heat of the flows produced.

  The gas mixture can be introduced to the column C1 during step S1 in a single fraction or in several sub-fractions. It is preferably introduced in a single fraction.

  The main column C1 is advantageously a column comprising a depletion section and a rectification section. The rectification section preferably overcomes the depletion section.

  The column Cl is advantageously chosen from distillation columns, rectification columns and exhaustion columns. Preferably, the Cl column is a distillation column.

  Column Cl is advantageously provided with associated auxiliary equipment such as for example at least one boiler and at least one condenser. Devices for intermediate withdrawal and intermediate heat exchange may be added to the main column.

  Fraction A enriched in the most volatile compounds is advantageously at the top of column C1 while fraction C enriched in the less volatile compounds is advantageously at the bottom of column Cl.

  As for the fraction F, it is advantageously withdrawn laterally from the column Cl by sampling liquid or vapor circulating in the column.

  The withdrawal is preferably carried out on the liquid.

  Advantageously, the withdrawal takes place in the rectification section of the column. A draw in the central third of the rectification section is preferred. The withdrawal of liquid in the central third of the grinding section is particularly preferred.

  The fraction F withdrawn laterally from the column C1 is advantageously subjected to the separation step S2.

  The fraction F can be withdrawn from the column C1 in the liquid state or in the gaseous state.

  If the fraction F is withdrawn in the liquid state, it can be sent to an evaporator or to an auxiliary column C2 '.

  In the case where the fraction F is sent to an evaporator, part of the fraction F is advantageously evaporated and recycled to the column C1 while the other part is advantageously extracted from the evaporator thus constituting the fraction B. As a variant, the fraction F can also be partially vaporized to produce the fraction B, the balance being recycled to the column Cl.

  In the case where the fraction F is sent to an auxiliary column C2 ', the auxiliary column C2' is preferably a depletion column, namely a column which has only one exhaustion section. The auxiliary column C2 'is advantageously provided with associated auxiliary equipment, preferably a boiler. Fraction B is advantageously extracted and the balance of fraction F in the form of a concentrated stream of impurities more volatile than ethylene (H 2, CO, CH 4) is advantageously returned to column Cl.

  If the fraction F is withdrawn in the gaseous state, it can be sent to a condenser or an auxiliary column C2 ".

  In the case where the fraction F is sent to a condenser, part of the fraction F is condensed and recycled to the main column C1 while another part of the uncondensed fraction F is extracted to form the fraction B. As a variant , the fraction F can also be partially condensed to produce the fraction B, the uncondensed balance being recycled to the column Cl.

  In the case where the fraction F is sent to an auxiliary column C2 ", the auxiliary column C2" is preferably a rectification column, namely a column which comprises only one rectification section. The auxiliary column C2 "is advantageously provided with associated auxiliary equipment, preferably a condenser, fraction B is advantageously extracted and the balance of the fraction F in the form of a flux concentrated in less volatile impurities than ethylene. (Ethane, compounds having at least 3 carbon atoms) is advantageously returned to the Cl column.

  Another variant of the process according to the invention could be to carry out the separation step S2 by means of a column C2 identical to the main column C1, the two columns possibly being thermally integrated and working at different pressures; the condenser of one serving as boiler to another.

  In the process according to the invention, the amount by weight of ethylene in each of the fractions A and B is advantageously between 45 and 55% of the total amount of ethylene produced (fraction A + fraction B). Preferably, the amount by weight of ethylene in fraction A is of the order of 55% and the amount by weight of ethylene in fraction B is of the order of 45% of the total amount produced. In a particularly preferred manner, the amount by weight of ethylene in the fraction A is of the order of 52.5% and the amount by weight of ethylene in the fraction B is of the order of 47.5% of the total amount produced.

  Fraction A is advantageously enriched in lighter compounds than ethylene, in particular methane, hydrogen and carbon monoxide.

  Advantageously, the content of lighter compounds than ethylene in fraction A is greater than or equal to 2% by volume, preferably greater than or equal to 5% by volume and particularly preferably greater than or equal to 10% 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 advantageously contains from 10% to 60% by volume of ethylene. Fraction A advantageously contains at least 10% by volume, preferably at least 15% by volume of ethylene and particularly preferably at least 20% by volume of ethylene. Fraction A advantageously contains at most 60% by volume, preferably at most 40% by volume of ethylene and particularly preferably at most 30% by volume of ethylene.

  In the process according to the invention, the. fraction A is sent to the chlorination reactor, preferably after expansion with energy recovery.

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

  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.

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

  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 advantageously contains from 40% to 95% by volume of ethylene.

  The fraction B advantageously contains at least 40% by volume, preferably at least 50% by volume of ethylene and particularly preferably at least 60% by volume. The fraction B advantageously contains at most 95% by volume, preferably at most 85% by volume of ethylene and particularly preferably at most 80% by volume of ethylene.

  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.

  In the process according to the invention, the fraction B is sent to the oxychlorination reactor, preferably after evaporation if the fraction F is withdrawn in the liquid state or after expansion if the fraction F is withdrawn in the gaseous state, in both cases advantageously with energy recovery. Particularly preferably, the fraction B is sent to the oxychlorination reactor after evaporation and expansion in the case where the fraction F is withdrawn in the liquid state, advantageously with energy recovery.

  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. Fraction B advantageously comprises at most 95% by volume, preferably at most 90% by volume and particularly preferably at most 85% by volume.

  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. Fraction B advantageously comprises at most 95% by volume, preferably at most 85% by volume and particularly preferably at most 80% by volume.

  With regard to fraction C, according to a first preferred variant, it is advantageously subjected to a hydrogenation step, preferably after a separation step, for example by distillation, followed by the recycling of compounds comprising 3 and 4 carbon atoms to cracking. Compounds comprising at least 5 carbon atoms are in turn advantageously burned to provide energy or recovered in any form whatsoever.

  According to a second preferred variant, a separation step S3 consisting in separating the fraction C leaving at the bottom of column C1 into two different fractions respectively containing compounds comprising 3 and 4 carbon atoms, for one of them, and compounds comprising at least 5 carbon atoms for each other can be advantageously effected. The resulting fraction containing the compounds comprising 3 and 4 carbon atoms is then preferably subjected to a hydrogenation step before recycling to cracking. As for the compounds comprising at least 5 carbon atoms, they are advantageously burned to provide energy or recovered in any form whatsoever.

  The chlorination reaction is advantageously carried out in a liquid phase (preferably 1,2-dichloroethane essentially) 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 pair having given good results is the complex of FeC13 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., preferably greater than or equal to 60 ° C., but advantageously lower than or equal to 80 C, preferably less than or equal to 70 C and with a pressure in the gas 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 bar absolute and particularly preferably less than or equal to 6 bar absolute.

  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 at 90 ° C., particularly preferably at 95 ° C., but advantageously less than or equal to 150 ° C., preferably at 135 ° C. and with pressure. in the gaseous phase advantageously greater than or equal to 0.2, preferably 0.5, particularly preferably 1.2, very particularly preferably 1.5 bar absolute but advantageously less than or equal to 10, preferably at 6 bar absolute.

  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 1,2-dichloroethane formed. Advantageously, the temperature and the reaction pressure are adjusted to release 1,2-dichloroethane produced in the gas phase and remove the rest of 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 1,2-dichloroethane.

  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 1,2-dichloroethane as well as small quantities of by-products such as 1,1,2-trichloroethane or small amounts of chlorination products of ethane or methane. The purification of 1,2-dichloroethane takes place 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: metal: (to) alkali (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 bars 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.

- 12

  The oxygen source of this oxychlorination may be air or pure oxygen, 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 invention also relates to a process for the manufacture of vinyl chloride. For this purpose, the invention relates to a process for the manufacture of vinyl chloride, characterized in that the 1,2-dichloroethane obtained by the process according to the invention is subjected to pyrolysis.

  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 1,2-dichloroethane is advantageously limited to 45 to 75% to limit the formation of by-product and fouling of the furnace tubes. The following steps make it possible, by any known device, to harvest the purified vinyl chloride and the hydrogen chloride to be valorised in preference to the oxychlorination. For purification, unconverted 1,2-dichloroethane is conveniently returned to the pyrolysis furnace.

  In addition, the invention also relates to a method of manufacturing polyvinyl chloride. For this purpose, the invention relates to a process for the manufacture of polyvinyl chloride by polymerization of vinyl chloride obtained by the process according to the invention. - 13

  The process for producing the polyvinyl chloride may 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 process for producing 1,2-dichloroethane according to the invention has the advantage of using two different ethylene fractions which are well adapted to the chlorination reaction and the oxychlorination reaction, respectively. In particular, the process according to the invention has the advantage of using a fraction of ethylene slightly contaminated with hydrogen for the oxychlorination reaction and this for a low cost.

  Another advantage of this process is that it makes it possible to separate the compounds comprising at least 3 carbon atoms via fraction C, compounds generally responsible for a certain inhibition during the pyrolysis of 1,2-dichloroethane. This inhibition is due to the formation of derivatives such as 1,2-dichloropropane and monochloroprapenes. These derivatives are difficult to completely separate from 1,2-dichloroethane. Their ease of formation of stable allyl radicals explains their powerful inhibitory effect of the pyrolysis of 1,2-dichloroethane, which takes place by a radical route. The formation of these by-products containing three carbon atoms and heavier would also constitute an unnecessary consumption of reagents and generate destruction costs.

- 14 -.

  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 final advantage of the process according to the invention is that it would make it possible, by modifying the separation conditions of the fractions as defined below, to cope with situations where it is advantageous to upgrade an external source of chlorine. hydrogen, from another manufacture such as an isocyanate production unit. Conversely, we can know the situation of an interesting market of hydrogen chloride which leads to a decrease in the share of oxychlorination compared to chlorination.

  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 simplified process for the manufacture of 1,2-dichloroethane according to the invention.

  The gas mixture 1 containing ethylene and other constituents resulting from the cracking of the hydrocarbon source is introduced into the main column 2 which is a distillation column where it is separated into 3 different fractions, namely the fraction 3 which at the top of column 2 and which is sent to the chlorination, the fraction 4 coming out at the bottom of column 2 and the fraction 5 which is withdrawn laterally from column 2. Fraction 5 is then sent to an auxiliary column 6 of which is extracted fraction 7 which is sent to the oxychlorination. The balance of fraction 5 in the form of a concentrated stream of more volatile impurities than ethylene 8 is returned to column 2. -15-E

Claims (4)

  A simplified process for the manufacture of 1,2-dichloroethane from a hydrocarbon source according to which: a) the hydrocarbon source is subjected to cracking producing a mixture of gases containing ethylene and other constituents; b) separating the gas mixture into a light fraction containing part of the ethylene (fraction A), into a fraction enriched in ethylene (fraction B) and, optionally, a heavy fraction (fraction C); c) fraction A is sent to a chlorination reactor and fraction B to an oxychlorination reactor, reactors in which most of the ethylene present in fractions A and B is converted to 1,2-dichloroethane; d) the 1,2-dichloroethane obtained is separated from the product streams from the chlorination and oxychlorination reactors.   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 hydrocarbon source is selected from the group consisting of ethane, propane, butane and propane mixtures. butane.   4 - Process for the manufacture of 1,2-dichloroethane according to any one of claims 1 to 3, characterized in that the mixture of gas from the cracking comprises as major components of hydrogen, carbon monoxide, methane and compounds comprising from 2 to 7 carbon atoms, and in that said mixture is separated into fractions A, B and C, fraction C containing mainly ethane and compounds comprising at least 3 carbon atoms.   Process according to Claim 4, in which the separation into the 3 fractions A, B and C is carried out by means of a main column (column C1), the fraction A being obtained at the top of the column C1, the fraction C at the bottom of the column Cl and the fraction B consisting of all or part of a fraction F which is withdrawn laterally from the column C1.   Process for the production of 1,2-dichloroethane according to any one of Claims 1 to 5, characterized in that fraction A contains from 10% to 60% by volume of ethylene.   7 - Process for the manufacture of 1,2-dichloroethane according to any one of claims 1 to 6, characterized in that aa fraction B contains from 40% to 95% by volume of ethylene.   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 7 is subjected to pyrolysis.   Process for the production of polyvinyl chloride by polymerization of vinyl chloride obtained by the process according to claim 8.