ES2364357T3 - PROCEDURE FOR THE MANUFACTURE OF 1,2-DICHLOROETHANE. - Google Patents

Abstract

Process for the manufacture of 1,2-dichloroethane from a hydrocarbon source, according to which: a) the hydrocarbon source is subjected to cracking, which produces a mixture of products containing ethylene and other constituents; b) the aforementioned mixture of products is separated into a fraction enriched in compounds that are lighter than ethylene, which contains part of ethylene (fraction A), in a fraction enriched in ethylene (fraction B), and in a heavy fraction (fraction C); c) fraction A is transported to a chlorination reactor, and fraction B to an oxychlorination reactor, reactors in which the majority of 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 derived from the chlorination and oxychlorination reactors.

Description

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 the manufacture of polyvinyl chloride (PVC).

To date, ethylene that is more than 99.8% pure is normally used for the manufacture of DCE. This ethylene of very high purity is obtained via the cracking of various petroleum products, followed by numerous complex and expensive separation operations, in order to isolate the ethylene from the other cracking products and obtain a very high purity product.

Given the high cost linked to the production of ethylene of such high purity, various processes have been developed for the manufacture of DCE using ethylene having a purity of less than 99.8%. These procedures have the advantage of reducing costs by simplifying the course of separating the products resulting from cracking, and thus abandoning complex separations that are not beneficial for the manufacture of DCE.

For example, patent application WO 00/26164 describes a process for the manufacture of DCE by simplified cracking of ethane, coupled to the chlorination of ethylene. For this, an ethylene chlorination stage takes place in the presence of impurities obtained during ethane cracking.

Patent application WO 03/48088 describes, for its part, a process for the manufacture of DCE by dehydrogenation of ethane, resulting in the formation of a fraction comprising ethane, ethylene and impurities that include hydrogen, a fraction to which it is subjected. then to chlorination and / or oxychlorination.

The processes described have, however, the disadvantage that the ethylene obtained cannot be used for a chlorination / oxychlorination process of ethylene, since ethylene contains impurities whose presence during the oxychlorination reaction could cause exploitation problems, namely a Catalyst poisoning with heavy products and a non-economical conversion of hydrogen present. This hydrogen conversion would consume oxygen, and release a great deal of heat of reaction. This would then limit the capacity of the oxychlorination reactor, which is generally linked to the heat exchange capacity. Therefore, an unusually high inversion must be made, in order to ensure the specific heat exchange surface, and thereby the reactor volume, induced by the presence of hydrogen in the mixture. The option adopted to burn hydrogen in a separating reactor does not solve the difficulty, because it requires a large amount of oxygen because it is stoichiometric with respect to hydrogen, and a large specific surface for exchange, in order to eliminate this heat of combustion, being its consequence a significant consumption of ethylene and may have problems related to safety. Finally, the elimination of water formed causes an increase in production costs.

The objective of the present invention, meanwhile, is to provide a process using ethylene with a purity of less than 99.8%, which has the advantage of reducing costs by abandoning complex separations to isolate ethylene from other cracking products that They are not beneficial for the manufacture of DCE, and it has the advantage of avoiding the problems mentioned above.

For this, the invention relates to a process for the manufacture of DCE from a source of hydrocarbons, according to which:

a) the source of hydrocarbons is subjected to cracking, which produces a mixture of products containing ethylene and other constituents;

b) the aforementioned mixture of products is separated into a fraction enriched in compounds that are lighter than ethylene, which contains part of ethylene (fraction A), in a fraction enriched in ethylene (fraction B), and in a heavy fraction (fraction C);

c) fraction A is transported 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 DCE;

d) the DCE obtained is separated from the product streams derived from the chlorination and oxychlorination reactors.

The source of hydrocarbons considered may be any known source of hydrocarbons. Preferably, the cracked hydrocarbon source (step a)) is chosen from the group consisting of naphtha, diesel, liquid natural gas, ethane, propane, butane, isobutane, and mixtures thereof. Particularly preferably, the hydrocarbon source is chosen from the group consisting of ethane, propane, and propane / butane mixtures. Good results were obtained with a hydrocarbon source chosen from the group consisting of propane and propane / butane mixtures. Propane / butane mixtures may exist as such, or they may consist of propane and butane mixtures.

The term ethane, propane, butane, and propane / butane mixtures is understood to mean, for the purposes of the present invention, products that are commercially available, namely, which consist primarily of the pure product (ethane, propane, butane, or propane / butane as a mixture), and secondly in other saturated or unsaturated hydrocarbons, which are lighter or heavier than the pure product itself.

The term "cracking" (step a)) is understood to mean, for the purposes of the present invention, all the steps for treating the source of hydrocarbons that lead to the formation of a mixture of products containing ethylene and other constituents that will be separated in fractions A, B and C in step b) of the process according to the invention.

Such cracking can be carried out according to any known technique, as long as it allows the production of a mixture of products containing ethylene and other constituents. Advantageously, the cracking comprises a first stage of pyrolysis (that is, a conversion under the action of heat) of the hydrocarbon source in the presence or absence of third compounds such as water, oxygen, a sulfur derivative and / or a catalyst. This first stage is preferably followed by steps for thermal recovery of heat from cracked gases, to separate heavy products (for example, via organic cooling and aqueous cooling), to compress and dry the gases, and to remove most of the dioxide of carbon and most of the sulfur compounds present or added (for example by means of an alkaline wash), optionally to hydrogenate the undesirable derivatives such as, for example, acetylene, and optionally remove part of the hydrogen and / or methane, for example via a PSA process (pressure change adsorption) or via a membrane process. The steps to hydrogenate the undesirable derivatives and to remove part of the hydrogen and / or methane can be carried out during stage b) below (for example during the first stage to separate the product mixture derived from stage a) or in fraction A). Preferably, these steps are carried out during stage a) for cracking.

Advantageously, in the process according to the invention, the mixture of products containing ethylene and other constituents derived from step a) comprises hydrogen, methane, compounds comprising from 2 to 7 carbon atoms, carbon monoxide, nitrogen and oxygen. Hydrogen, methane and compounds comprising 2 to 7 carbon atoms other than acetylene are preferably present in an amount of at least 200 ppm by volume relative to the total volume of said product mixture. Carbon monoxide, nitrogen, oxygen and acetylene may be present in an amount less than 200 ppm by volume, or in an amount of at least 200 ppm by volume, relative to the total volume of said product mix. Compounds containing more than 7 carbon atoms, carbon dioxide, hydrogen sulfide and other sulfur compounds and water may also be present in the aforementioned product mixture in an amount less than 200 ppm by volume, relative to the total volume of the aforementioned product mix.

After step a) for the cracking defined above, the mixture of products containing ethylene and other constituents is subjected to step b), which advantageously comprises a maximum of four, preferably a maximum of three separation stages, in order to obtain the two fractions containing ethylene, namely fraction A and fraction B.

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

According to the process of the invention, the amounts defined below to characterize fraction B and fraction A are those before their respective entry into oxychlorination and chlorination.

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

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

Fraction B advantageously contains 40% to 99.5% by volume of ethylene, relative to the total volume of fraction B. Fraction B advantageously contains at least 40%, preferably at least 50%, and particularly preferably at least 60% by volume of ethylene, relative to the total volume of fraction B. Fraction B advantageously contains at most 99.5%, preferably at most 99.2%, and particularly preferably at most 99% by volume of ethylene , in relation to the total volume of fraction B.

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

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

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

Fraction A is enriched in compounds that are lighter than ethylene. These compounds are generally methane, nitrogen, oxygen, hydrogen and carbon monoxide. Advantageously, fraction A contains at least 70%, preferably at least 80%, and particularly preferably at least 85% of compounds lighter than ethylene, which are contained in the product mixture subjected to step b). Advantageously, fraction A contains a maximum of 99.99%, preferably a maximum of 99.97%, and particularly preferably a maximum of 99.95% of compounds lighter than ethylene, which are contained in the mixture of products subjected to the stage b).

In the preferred case where the hydrocarbon source is ethane, fraction A contains at least 90%, preferably at least 95%, and particularly preferably at least 98% of compounds lighter than ethylene, which are contained in the product mix submitted to stage b). Advantageously, fraction A contains at most 99.99%, preferably at most 99.98%, and particularly preferably at most 99.97% of compounds lighter than ethylene, which are contained in the mixture of products subjected to the stage b).

In the preferred case where the hydrocarbon source is a propane / butane mixture, fraction A contains at least 70%, preferably at least 80%, and particularly preferably at least 85% compounds lighter than ethylene, which are contained in the product mix submitted to stage b). Advantageously, fraction A contains a maximum of 99.99%, preferably a maximum of 99.95%, and particularly preferably a maximum of 99.9% of compounds lighter than ethylene, which are contained in the mixture of products subjected to the stage b).

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

Fraction A advantageously contains an ethylene volume content so that it represents from 10% to 90% of the ethylene volume content of fraction B. Fraction A advantageously contains an ethylene volume content so that it is less than or equal to at 90%, preferably less than or equal to 85%, and particularly preferably less than or equal to 80% of the ethylene volume content of fraction B. Fraction A advantageously contains an ethylene volume content so that it is at at least 10%, preferably at least 15%, and in a particularly preferred manner at least 20% of the ethylene volume content of fraction B.

In the preferred case where the hydrocarbon source is ethane, fraction A advantageously contains a volume content of ethylene so that it is less than or equal to 90%, preferably less than or equal to 85%, and particularly preferably less or equal to 80% of the ethylene volume content of fraction B. Fraction A advantageously contains a volume content of ethylene so that it is at least 15%, preferably at least 20%, and particularly preferably at least 22 % of the ethylene volume content of fraction B.

In the preferred case where the hydrocarbon source is a propane / butane mixture, fraction A advantageously contains a volume content of ethylene so that it is less than or equal to 80%, preferably less

or equal to 75%, and particularly preferably less than or equal to 70% of the ethylene volume content of fraction B. Fraction A advantageously contains a volume content of ethylene so that it is at least 10%, preferably at at least 15%, and particularly preferably at least 20% of the ethylene volume content of fraction B.

Fraction A is further characterized by an acetylene content that is advantageously less than or equal to 0.01%, preferably less than or equal to 0.005%, and particularly preferably less than or equal to 0.001% by volume, relative to the total volume of fraction A.

According to a first variant of the process according to the invention, considering that the process for the manufacture of DCE is advantageously balanced (ie, that the manufacturing process by chlorination and oxychlorination of ethylene and pyrolysis of 1,2-dichloroethane (DCE) formed makes possible to generate the amount of HCl necessary for the process), the fraction by weight of ethylene production in each of fractions A and B is advantageously between 45 and 55% of the total amount of ethylene produced (fraction A + fraction B ). Preferably, the weight fraction of ethylene production in fraction A is of the order of 55%, and the weight fraction of ethylene production in fraction B is of the order of 45% of the total amount produced. Particularly preferably, the weight fraction of ethylene production in fraction A is of the order of 52.5%, and the weight fraction of ethylene production in fraction B is of the order of 47.5% of The total amount produced.

According to a second variant of the process according to the invention, considering that the process for the manufacture of DCE is advantageously unbalanced (i.e., for example, that an external source of HCl makes it possible to provide part of the supply of HCl for oxychlorination, or that a fraction of the produced DCE is not subjected to pyrolysis), the fraction by weight of ethylene production in each of fractions A and B is advantageously between 20 and 80% of the total amount of ethylene produced (fraction A + fraction B ). Preferably, the weight fraction of ethylene production in fraction A is between 25 and 75% of the total amount of ethylene produced (fraction A + fraction B).

According to a first embodiment of the second variant of the process according to the invention, considering that the process for the manufacture of DCE is advantageously unbalanced by an external source of HCl, the mole fraction of ethylene production in fraction A is advantageously between 45 and 55%, preferably between 50 and 54%, and particularly preferably on the order of 52.5% of the difference between the total molar amount of ethylene contained in the product mixture subjected to step b) and the molar amount of HCl from the external source.

According to a second embodiment of the second variant of the process according to the invention, considering that the process for the manufacture of DCE is advantageously unbalanced by a co-production of DCE (part of the DCE is therefore not subjected to pyrolysis), the mole fraction of the production of ethylene in fraction B is advantageously between 45 and 55%, preferably between 46 and 50%, and particularly preferably on the order of 47.5% of the difference between the total molar amount of ethylene contained in the mixture of products submitted to stage b) and the molar amount of co-produced DCE.

According to the process of the invention, during step b), the product mixture is separated into a fraction enriched in compounds lighter than ethylene, which contains part of ethylene (fraction A), in a fraction enriched in ethylene (fraction B ), and in a heavy fraction (fraction C). Fraction C advantageously contains ethane and compounds comprising at least 3 carbon atoms. Advantageously, these compounds comprising at least 3 carbon atoms result from the mixture of products containing ethylene and other constituents derived from stage a), or are generated by side reactions during stage b). Among the compounds comprising at least 3 carbon atoms, there may be mentioned propane, propene, butanes and their unsaturated derivatives, as well as all heavier saturated or unsaturated compounds.

After production during stage b), according to a first case, fraction C is advantageously subjected to a hydrogenation stage, preferably followed by a separation stage, for example by distillation, in two different fractions containing respectively compounds comprising less than 5 carbon atoms, for one of them, and compounds comprising at least 5 carbon atoms, for the other. This separation step is particularly preferably followed by the recycling of compounds comprising less than 5 carbon atoms to the cracking stage. Compounds comprising at least 5 carbon atoms are, in turn, very particularly preferred, burned in order to provide energy, or are improved in any way.

According to a second case, advantageously a separation step is carried out consisting of the separation of the fraction C, for example by distillation, into two different fractions containing respectively 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 compounds comprising less than 5 carbon atoms is then preferably subjected to a hydrogenation stage before recycling to the cracking stage. As for the compounds comprising at least 5 carbon atoms, they are, particularly preferably, burned in order to provide energy, or improved in any form.

The first case described above is preferred.

According to a first embodiment of the process according to the invention, the product mixture derived from step a) is advantageously subjected to a first separation stage, called step S1, and a second separation stage, called step S1 ', in order to obtain the two fractions containing ethylene, namely fraction A and fraction B.

Step S1 advantageously consists of separating the product mixture derived from step a) into a main column (called column C1) into three different fractions, namely fraction A, which exits the top of the column C1, fraction C, which comes out from the bottom of column C1, and a fraction (called fraction F1) that is extracted from the side of column C1.

Step S1 ’consists advantageously in separating the fraction F1 into two different fractions, namely a fraction F1’, which is transported to column C1, and a fraction B.

According to the first embodiment of the process according to the invention, step b) therefore preferably comprises:

-a first stage of separation S1, which consists in the separation of said product mix

within a main column C1 in fraction A at the top of column C1, in fraction C in the

lower part of column C1, and in fraction F1 extracted from the side of column C1, and

-a second stage of separation S1 ’, which consists of the separation of fraction F1 into a fraction F1’, which is transported to column C1, and in fraction B.

Particularly preferably, step b) comprises only the two stages mentioned above.

Prior to its introduction in column C1, the product mixture derived from step a) can be subjected to a thermal conditioning stage. The term "thermal conditioning stage" is understood to mean a succession of heat exchanges that optimizes the use of energy, for example the gradual cooling of the product mixture in a train of exchangers cooled first with untreated water, and then with cooled water. with ice, and then with increasingly cold fluids, more cross exchangers that recover the sensible heat of the currents produced.

The mentioned product mixture can be introduced in column C1 during step S1 as a single fraction, or as several subfractions. Preferably it is introduced as several subfractions.

The main column C1 is advantageously a column comprising a steam entrainment section, and / or a rectification section. If both sections are present, the rectification section is preferably above the steam entrainment section.

Column C1 is advantageously chosen from distillation columns comprising the two sections mentioned above, and columns containing only one of the two sections. Preferably, column C1 is a distillation column.

Therefore, step S1 is preferably a distillation stage.

Column C1 is advantageously provided with the associated auxiliary equipment, such as, for example, at least one evaporator, and at least one condenser. Devices that allow intermediate extraction and intermediate heat exchange can be added to the main column.

Fraction A, enriched in the most volatile compounds, advantageously exits the top of column C1, while fraction C, enriched in less volatile compounds, advantageously exits the bottom of column C1.

As for fraction F1, it is advantageously extracted from the side of column C1, collecting liquid or vapor circulating in the column. The extraction is preferably carried out on the liquid.

Extraction can be carried out in the steam drag extraction section, or in the rectification section of the column. Preferably it is carried out in the rectification section. An extraction in the central third of the rectification section is particularly preferred. The extraction of the liquid in the central third of the rectification section is very particularly preferred.

The step S1 mentioned above is advantageously carried out at a pressure of at least 15, preferably of at least 20, and particularly preferably of at least 25 bars. Step S1 is advantageously carried out at a pressure of at most 45, preferably at most 40, and particularly preferably at most 38 bars.

The temperature at which step S1 is carried out is advantageously at least -70, preferably at least -65, and particularly preferably at least -60 ° C at the top of column C1. Advantageously it is at most -30, preferably at most -40, and particularly preferably at most -50 ° C at the top of column C1.

In the case where the hydrocarbon source is ethane, the temperature at the bottom of column C1 is advantageously at least -10, preferably at least 0, and particularly preferably at least 5 ° C.

It is advantageously at most 40, preferably at most 30, and particularly preferably at most 25 ° C.

In the case where the hydrocarbon source is a propane / butane mixture, the temperature at the bottom of column C1 is advantageously at least 30, preferably at least 40, and particularly preferably at least 50 ° C. Advantageously it is at most 100, preferably at most 90, and particularly preferably at most 80 ° C.

The fraction F1 extracted from the side of column C1 is advantageously subjected to the separation step S1 ’to be separated into two different fractions, namely a fraction F1’, which is transported to column C1, and a fraction B.

The fraction F1 can be extracted from column C1 in a liquid state or in a gaseous state.

If fraction F1 is extracted in a liquid state, it can be transported to an evaporator or an auxiliary column C1 ’.

In the case where the fraction F1 is transported to an evaporator, part of the fraction F1, in the form of a fraction F1 ', is evaporated and recycled advantageously to the main column C1, while the other part is advantageously removed from the evaporator, thus constituting fraction B. As a variant, fraction F1 can also be partially vaporized in order to produce fraction B, the remainder being recycled, in the form of a fraction of F1 ', to column C1.

In the case where fraction F1 is transported to an auxiliary column C1 ', the auxiliary column C1' is preferably a steam entrainment column, namely a column comprising only a steam entrainment section . The auxiliary column C1 ′ is advantageously provided with the associated auxiliary equipment, preferably an evaporator. Fraction B is advantageously extracted from it, and the rest of fraction F1, in the form of a fraction F1 'which is then a stream concentrated in impurities more volatile than ethylene (H2, CO, N2, O2 and CH4), is transported advantageously to column C1.

If fraction F1 is extracted in the liquid state, it is preferably transported to an auxiliary column C1 ’, which is preferably a steam entrainment column. In this case, step S1 ’is then preferably a steam entrainment stage.

If fraction F1 is extracted in the gaseous state, it can be transported to a condenser or an auxiliary column C1 ’.

In the case where the fraction F1 is transported to a condenser, part of the fraction F1, in the form of a fraction F1 ', is condensed and recycled advantageously to the main column C1, while the other part is advantageously removed from the condenser, thus constituting fraction B. As a variant, fraction F1 can also be partially condensed in order to produce fraction B, the remainder being recycled, in the form of a fraction F1 ', to column C1.

In the case where fraction F1 is transported to an auxiliary column C1 ’, the auxiliary column C1’ is preferably a rectification column, namely a column comprising only a rectification section. The auxiliary column C1 ′ is advantageously provided with associated auxiliary equipment, preferably a condenser. Fraction B is advantageously extracted from it, and the rest of fraction F1, in the form of a fraction F1 'which is then a stream concentrated in impurities less volatile than ethylene (ethane, compounds containing at least 3 carbon atoms), it is advantageously transported to column C1.

If fraction F1 is extracted in the gaseous state, it is preferably transported to an auxiliary column C1 ’, which is preferably a rectification column. In this case, step S1 ’is then preferably a rectification stage.

According to the first embodiment of the process according to the invention, very particular preference is given to the case in which fraction F1 is transported to an auxiliary column C1 ’.

According to this very particular preference, step b) therefore comprises, particularly preferably:

-a first stage of separation S1, which consists in the separation of said product mix

within a main column C1 in a fraction A at the top of column C1, in fraction C in

the bottom of column C1, and in fraction F1 taken from the side of column C1, and

-a second stage of separation S1 ’, which consists of the separation of the fraction F1 within a column

C1 ’in a fraction F1’ at the top of column C1 ’, which is transported to column C1, and in a

fraction B at the bottom of column C1 ’.

According to the first embodiment of the process according to the invention, very particular preference is given to the case in which fraction F1 is extracted from column C1 in the liquid state, and is transported to an auxiliary column C1 ', which is a column of steam extraction.

The step S1 ′ mentioned above is then advantageously carried out at a pressure of at least 15, preferably at least 25, and particularly preferably at least 30 bar. Step S1 'is advantageously carried out at a pressure of at most 45, preferably at most 40, and in a particularly preferred manner of at most 38 bars.

The temperature at which step S1 'is carried out is advantageously at least -40, preferably at least -30, and particularly preferably at least -25 ° C at the top of the steam entrainment column C1' . Advantageously it is at most 0, preferably at most -10, and particularly preferably at most -15 ° C at the top of column C1 '.

The temperature at the bottom of the C1 ’steam entrainment column is at least -30, preferably at least -20, and particularly preferably at least -15 ° C. Advantageously it is at most 20, preferably at most 15, and particularly preferably at most 10 ° C.

According to the first embodiment of the process according to the invention, fraction B is advantageously transported to the oxychlorination reactor, preferably after evaporation and expansion if fraction F1 is extracted in the liquid state, or after expansion if fraction F1 is extracted in the gaseous state, in both cases advantageously with energy recovery. Particularly preferably, fraction B is transported to the oxychlorination reactor after evaporation and expansion in the case where fraction F1 is extracted in the liquid state, advantageously with energy recovery.

A preferred subvariant of the first embodiment of the process according to the invention is to carry out the separation step S1 'by means of an auxiliary column C1' identical to the main column C1, both columns being optionally thermally integrated and operating at different pressures; serving the condenser of one as the evaporator of the other.

According to a second embodiment of the process according to the invention, the product mixture derived from step a) is advantageously subjected to a first separation stage, called step S2, to a second separation stage, called step S2 ', and to a third stage of separation, called step S2 '', in order to obtain the two fractions containing ethylene, namely, fraction A and fraction B.

Step S2 advantageously consists of separating the product mixture derived from step a) into a main column (called column C2) into two different fractions, namely a fraction F2, which exits the top of column C2 , and a fraction C, which comes out from the bottom of column C2.

The step S2 'advantageously consists in the separation of the fraction F2 into two different fractions, namely, fraction A and an fraction F2'.

The S2 ’stage advantageously consists of the separation of the F2 fraction into two different fractions, namely, the B fraction and an F2 fraction.

According to the second embodiment of the process according to the invention, step b) therefore preferably comprises:

-a first stage of separation S2, which consists in the separation of said mixture of products in

a main column C2 in a fraction F2 at the bottom of column C2, and in a fraction C in the

bottom of column C2,

- a second stage of separation S2 ’, which consists of the separation of fraction F2 into a fraction A and a fraction F2’, and

-a third stage of separation S2 ’, which consists of the separation of fraction F2’ into fraction B and a fraction F2 ’.

Particularly preferably, step b) comprises only the three stages mentioned above.

Before being introduced into column C2, the product mixture derived from step a) can be subjected to a thermal conditioning stage. The term "thermal conditioning stage" is understood to mean a succession of heat exchanges that optimizes the use of energy, for example the gradual cooling of the product mixture in a train of exchangers cooled first with untreated water, then with water cooled with ice, and then with increasingly cold fluids, more cross exchangers that recover the sensible heat of the currents produced.

The aforementioned mixture of products can be introduced in column C2 during step S2 as a single fraction, or as several subfractions. Preferably it is introduced as several subfractions.

The main column C2 is advantageously a column comprising a steam entrainment section, and / or a rectification section. If both sections are present, the rectification section is preferably above the steam entrainment section.

Column C2 is advantageously chosen from distillation columns comprising the two sections mentioned above, and columns comprising only one of the two sections. Preferably, column C2 is a distillation column.

Therefore, step S2 is preferably a distillation stage.

Column C2 is advantageously provided with the associated auxiliary equipment, such as, for example, at least one evaporator, and at least one condenser.

Fraction F2, enriched in the most volatile compounds, advantageously exits the top of column C2, while fraction C, enriched in less volatile compounds, advantageously exits the bottom of column C2.

The step S2 mentioned above is advantageously carried out at a pressure of at least 15, preferably of at least 20, and particularly preferably of at least 25 bars. Step S2 is advantageously carried out at a pressure of at most 45, preferably at most 40, and particularly preferably at most 38 bars.

The temperature at which step S2 is carried out is advantageously at least -70, preferably at least -65, and particularly preferably at least -60 ° C at the top of column C2. Advantageously it is at most -20, preferably at most -30, and particularly preferably at most -40 ° C at the top of column C2.

In the case where the hydrocarbon source is ethane, the temperature at the bottom of the C2 column is advantageously at least -10, preferably at least 0, and particularly preferably at least 5 ° C. It is advantageously at most 40, preferably at most 30, and particularly preferably at most 25 ° C.

In the case where the hydrocarbon source is a propane / butane mixture, the temperature in the lower part of column C2 is advantageously at least 30, preferably at least 40, and particularly preferably at least 50 ° C. Advantageously it is at most 100, preferably at most 90, and particularly preferably at most 80 ° C.

Fraction F2, which exits at the top of column C2, is advantageously subjected to the separation stage S2 ’to be separated into two different fractions, namely, fraction A, and a fraction F2’.

The separation stage S2 ’is advantageously an absorption stage, in which the fraction F2 is contacted with a washing agent containing DCE.

In the present description, the term "washing agent containing DCE", or more simply "washing agent", is understood to mean a composition in which the DCE is present in a liquid state.

The washing agent that can be used according to the present invention therefore advantageously contains DCE in a liquid state. The presence, in said washing agent, of other compounds is not at all excluded from the scope of the invention. However, it is preferable that the washing agent contains at least 50% by volume of DCE, more particularly at least 80% by volume, and particularly preferably at least 95% by volume.

The washing agent used for step S2 'may consist of a recent washing agent of any origin, for example raw DCE leaving the oxychlorination unit and which has not been purified, said previously purified DCE, or recovered washing agent during step S2 "detailed below (fraction F2"), optionally supplemented with fresh washing agent.

Preferably, the washing agent used for step S2 ’consists of fraction F2’, optionally supplemented with fresh washing agent. Particularly preferred, the washing agent used for step S2 ’consists of the fraction F2’ supplemented with recent washing agent (to compensate for the loss of washing agent during steps S2 ’and S2’).

An important advantage of the second embodiment of the process according to the invention lies in the fact that the presence of this DCE is not at all problematic, since it is the compound formed mainly during oxychlorination or chlorination.

The relationship between the respective productions of washing agent and ethylene to be extracted from the F2 fraction is not critical, and can vary greatly. In practice, it is only limited by the cost of regeneration of the washing agent. In general, the production of washing agent is at least 1, preferably at least 5, and particularly preferably at least 10 tons per ton of ethylene to be extracted from fraction F2. In general, the production of washing agent is at most 100, preferably at most 50, and particularly preferably at most 25 tons per ton of ethylene to be extracted from fraction F2.

The step S2 'is advantageously carried out by means of an absorber, such as, for example, a descending or ascending film absorber, or an absorption column C2' chosen from dish columns, packed columns, columns with structured packaging, columns that combine one or more of the internal elements mentioned above, and spray columns. The step S2 ’is preferably carried out by means of an absorption column C2’, and particularly preferably by means of an absorption column of C2 ’plates.

Column C2 ’is advantageously provided with associated auxiliary equipment, such as, for example, at least one condenser and a cooler internal or external to the column.

The step S2 'mentioned above is advantageously carried out at a pressure of at least 15, preferably at least 20, and particularly preferably at least 25 bar. The step S2 ’is advantageously carried out at a pressure of at most 40, preferably at most 35, and particularly preferably at most 30 bars.

The temperature at which step S2 ’is carried out is advantageously at least -10, preferably at least 0, and particularly preferably at least 10 ° C at the top of the absorber or the C2 'column. Advantageously it is at most 60, preferably at most 50, and particularly preferably at most 40 ° C in the upper part of the absorber or of the C2 ’column.

The temperature at the bottom of the absorber or the C2 ’column is at least 0, preferably at least 10, and particularly preferably at least 20 ° C. Advantageously it is at most 70, preferably at most 60, and particularly preferably at most 50 ° C.

The F2 ’fraction is advantageously subjected to the S2’ ’separation stage to be separated into two different fractions, namely, the B fraction and an F2’ fraction.

The separation stage S2 ’is advantageously a desorption stage, in which fraction B is extracted from the washing agent.

The washing agent recovered after step S2 ’which constitutes the fraction F2’ can be removed, transported completely or partially to the oxychlorination section, or transported to step S2 ’with optional addition of recent washing agent. Preferably, the F2 ’fraction is transported to step S2’ with optional addition of recent washing agent. Particularly preferably, the F2 ’fraction is transported to step S2’ with the addition of a recent lifting agent.

The step S2 "is advantageously carried out by means of a desorber, such as, for example, a descending or ascending film desorber, an evaporator or a desorption column C2" chosen from plates columns, packed columns, columns with structured packing, columns that combine one or more of the internal elements mentioned above, and spray columns. The step S2 "is preferably carried out by means of a desorption column C2", and particularly preferably by means of a desorption column of dishes C2 ".

The C2 ’column is advantageously provided with associated auxiliary equipment, such as, for example, at least one condenser and an internal or external column cooler, and at least one evaporator.

The step S2 ’mentioned above is advantageously carried out at a pressure of at least 1, preferably at least 2, and particularly preferably at least 3 bars. Step S2 'is advantageously carried out at a pressure of at most 20, preferably at most 15, and particularly preferably at most 10 bars.

The temperature at which step S2 '' is carried out is advantageously chosen so that more than 90%, preferably more than 95% of the ethylene contained in fraction F2 'is in fraction B. The temperature at which step S2 '' is carried out is advantageously at least -10, preferably at least 0, and particularly preferably at least 10 ° C at the top of the desorber or column C2 ''. Advantageously it is a maximum of 60, preferably a maximum of 50, and particularly preferably a maximum of 40 ° C at the top of the desorber or of the C2 ’column.

The temperature at the bottom of the desorber or the C2 ’column is at least 60, preferably at least 80, and particularly preferably at least 100 ° C. Advantageously it is at most 200, preferably at most 160, and particularly preferably at most 150 ° C.

According to the second embodiment of the process according to the invention, very particular preference is given to the case in which fraction F2 is transported to an absorption column C2 ’, and fraction F2’ is transported to a desorption column C2 ’.

According to this very particular preference, step b) therefore comprises, particularly preferably:

-a first stage of separation S2, which consists in the separation of said mixture of products in

a main column C2 in a fraction F2 at the top of column C2, and in fraction C in the part

bottom of column C2,

-a second stage of separation S2 ’, which consists of the separation of the fraction F2 in a column of

adsorption C2 ’in fraction A at the top of column C2’, and in a fraction F2 ’at the bottom of

column C2 ’, and

-a third stage of separation S2 ’, which consists of the separation of the fraction F2’ in a column of

desorption C2 ’’ in fraction B at the top of column C2 ’’, and in a fraction F2 ’’ at the bottom

from column C2 ’.

According to a third embodiment of the process according to the invention, the product mixture derived from step a) is advantageously subjected to a first separation stage called step S3, and a second separation stage called step S3 ', in order to obtain both fractions containing ethylene, namely fraction A and fraction B.

Step S3 advantageously consists of separating the product mixture derived from step a) into a main column (called column C3) into two different fractions, namely a fraction F3, which exits at the top of column C3 , and fraction C, which comes out from the bottom of column C3.

Step S3 'advantageously consists of the separation of fraction F3 in a column C3' into two different fractions, namely, fraction A, which exits the top of column C3 ', and fraction B, which leaves by the bottom of column C3 '.

According to the third embodiment of the process according to the invention, step b) therefore preferably comprises:

-a first stage of separation S3, which consists in the separation of said mixture of products in

a main column C3 in a fraction F3 at the top of column C3, and in fraction C in the part

bottom of column C3, and

- a second separation stage S3 ', which consists in the separation of fraction F3 in a column C3' in a fraction A in the upper part of column C3 ', and in fraction B in the lower part of column C3 '.

Particularly preferably, step b) comprises only the two stages mentioned above.

Prior to its introduction into column C3, the product mixture derived from step a) can be subjected to a thermal conditioning stage. The term "thermal conditioning stage" is understood to mean a succession of heat exchanges that optimizes the use of energy, for example the gradual cooling of the product mixture in a train of exchangers cooled first with untreated water, and then with cooled water. with ice, and then with increasingly cold fluids, more cross exchangers that recover the sensible heat of the currents produced.

The aforementioned mixture of products can be introduced in column C3 during step S3 as an individual fraction, or as several subfractions. Preferably it is introduced as several subfractions.

The main column C3 is advantageously a column comprising a steam entrainment section, and / or a rectification section. If both sections are present, the rectification section is preferably above the steam entrainment section.

Column C3 is advantageously chosen from distillation columns comprising the two sections mentioned above, and columns containing only one of the two sections. Preferably, column C3 is a distillation column.

Therefore, step S3 is preferably a distillation stage.

Column C3 is advantageously provided with the associated auxiliary equipment, such as, for example, at least one evaporator, and at least one condenser.

Fraction F3, enriched in the most volatile compounds, advantageously exits from the top of column C3, while fraction C, enriched in less volatile compounds, advantageously exits from the bottom of column C3.

The step S3 mentioned above is advantageously carried out at a pressure of at least 15, preferably at least 20, and particularly preferably at least 25 bars. Step S3 is advantageously carried out at a pressure of at most 45, preferably at most 40, and particularly preferably at most 38 bars.

The temperature at which step S3 is carried out is advantageously at least -70, preferably at least -65, and particularly preferably at least -60 ° C at the top of column C3. Advantageously it is at most -20, preferably at most -30, and particularly preferably at most -40 at the top of column C3.

In the case where the hydrocarbon source is ethane, the temperature at the bottom of column C3 is advantageously at least -10, preferably at least 0, and particularly preferably at least 5 ° C. Advantageously it is at most 40, preferably at most 30 and particularly preferably at most 25 ° C.

In the case where the hydrocarbon source is a propane / butane mixture, the temperature at the bottom of column C3 is advantageously at least 30, preferably at least 40, and particularly preferably at least 50 ° C. Advantageously it is at most 100, preferably at most 90, and particularly preferably at most 80 ° C.

The fraction F3 leaving the upper part of the column C3 is then advantageously subjected to the separation step S3 'in the column C3', to be separated into two different fractions, namely the fraction A at the top of the column C3 ', and fraction B at the bottom of column C3'.

Column C3 ’is advantageously a column comprising a steam entrainment section, and / or a rectification section. If both sections are present, the rectification section is preferably above the steam entrainment section.

Column C3 ’is advantageously chosen from distillation columns comprising the two sections mentioned above, and columns comprising only one of the two sections. Preferably, column C3 ’is a distillation column.

Therefore, step S3 ’is preferably a distillation stage.

The C3 ’column is advantageously provided with the associated auxiliary equipment, such as, for example, at least one evaporator, and at least one condenser.

The step S3 'mentioned above is advantageously carried out at a pressure of at least 15, preferably at least 20, and particularly preferably at least 25 bar. The step S3 'is advantageously carried out at a pressure of at most 40, preferably at most 37, and particularly at most 35 bars.

The temperature at which step S3 'is carried out is advantageously at least -70, preferably at least -67, and particularly preferably at least -65 ° C at the top of column C3'. Advantageously it is at most -40, preferably at most -45, and particularly preferably at most -50 ° C at the top of the C3 ’column.

The temperature at the bottom of the C3 'column is at least -30, preferably at least -25, and particularly preferably at least -20 ° C. Advantageously it is at most 20, preferably at most 15, and particularly preferably at most 10 ° C.

According to a fourth embodiment of the process according to the invention, the product mixture derived from step a) is advantageously subjected to a first separation stage, called S4, and a second separation stage, called step S4 ', in order to obtain the two fractions containing ethylene, namely fraction A and fraction B.

Step S4 advantageously consists of separating the product mixture derived from step a) into a main column (called column C4) into two different fractions, namely fraction A, which exits at the top of column C4 , and a fraction F4, which comes out from the bottom of column C4.

The step S4 'advantageously consists of the separation of the fraction F4 in a column C4' into two different fractions, namely, fraction B, which exits at the top of column C4 ', and fraction C, which leaves by the bottom of column C4 '.

According to the fourth embodiment of the process according to the invention, step b) therefore preferably comprises:

-a first stage of separation S4, which consists of the separation of said mixture of products in

a main column C4 in fraction A at the top of column C4, and in a fraction F4 in the part

bottom of column C4, and

- a second separation stage S4 ', which consists of the separation of fraction F4 in a column C4' in fraction B at the top of column C4 ', and in fraction C at the bottom of column C4 '.

Particularly preferably, step b) comprises only the two stages mentioned above.

Prior to its introduction in column C4, the product mixture derived from step a) can be subjected to a thermal conditioning stage. The term "thermal conditioning stage" is understood to mean a succession of heat exchanges that optimizes the use of energy, for example the gradual cooling of the product mixture in a train of exchangers cooled first with untreated water, then with water cooled with ice, and then with increasingly cold fluids, more cross exchangers that recover the sensible heat of the currents produced.

The aforementioned mixture of products can be introduced in column C4 during step S4 as a single fraction, or as several subfractions. Preferably it is introduced as several subfractions.

The main column C4 is advantageously a column comprising a steam entrainment section, and / or a rectification section. If both sections are present, the rectification section is preferably above the steam entrainment section.

Column C4 is advantageously chosen from distillation columns comprising the two sections mentioned above, and columns comprising only one of the two sections. Preferably, column C4 is a distillation column.

Therefore, step S4 is preferably a distillation stage.

Column C4 is advantageously provided with the associated auxiliary equipment, such as, for example, at least one evaporator, and at least one condenser.

Fraction A, enriched in the most volatile compounds, advantageously exits from the top of column C4, while fraction F4, enriched in less volatile compounds, advantageously exits from the bottom of column C4.

The step S4 mentioned above is advantageously carried out at a pressure of at least 15, preferably of at least 20, and particularly preferably of at least 25 bars. Step S4 is advantageously carried out at a pressure of at most 45, preferably at most 40, and particularly preferably at most 38 bars.

The temperature at which step S4 is carried out is advantageously at least -70, preferably at least -65, and particularly preferably at least -60 ° C at the top of column C4. Advantageously it is at most -20, preferably at most -30, and particularly preferably at most -40 ° C at the top of column C4.

In the case where the hydrocarbon source is ethane, the temperature at the bottom of column C4 is advantageously at least -10, and preferably at least -5 ° C. Advantageously it is at most 30, preferably at most 20, and particularly preferably at most 15 ° C.

In the case where the hydrocarbon source is a propane / butane mixture, the temperature at the bottom of column C4 is advantageously at least 20, preferably at least 30, and particularly preferably at least 40 ° C. Advantageously it is at most 80, preferably at most 70, and particularly preferably at most 60 ° C.

The fraction F4 leaving the lower part of the column C4 is then advantageously subjected to the separation step S4 'in the column C4', to be separated into two different fractions, namely the fraction B at the top of the column C4 ', and fraction C at the bottom of column C4'.

Column C4 ’is advantageously a column comprising a steam entrainment section, and / or a rectification section. If both sections are present, the rectification section is preferably above the steam entrainment section.

Column C4 ’is advantageously chosen from distillation columns comprising the two sections mentioned above, and columns comprising only one of the two sections. Preferably, column C4 ’is a distillation column.

Therefore, step S4 ’is preferably a distillation stage.

Column C4 ’is advantageously provided with the associated auxiliary equipment, such as, for example, at least one evaporator, and at least one condenser.

The step S4 'mentioned above is advantageously carried out at a pressure of at least 15, preferably at least 20, and particularly preferably at least 25 bar. Step S4 'is advantageously carried out at a pressure of at most 40, preferably at most 37, and particularly preferably at most 35 bars.

The temperature at which step S4 'is carried out is advantageously at least -50, preferably at least -40, and particularly preferably at least -30 ° C at the top of the C4' column. Advantageously it is at most 0, preferably at most -5, and particularly preferably at most -10 ° C at the top of the C4 ’column.

The temperature at the bottom of the C4 ’column is at least -20, preferably at least -15, and particularly preferably at least -10 ° C. Advantageously it is at most 20, preferably at most 15, and particularly preferably at most 10 ° C.

In the process according to the invention, each time the use of a distillation column is mentioned, it is possible to choose from dish distillation columns, packed distillation columns, distillation columns with structured packaging, and distillation columns combining two or more of the internal elements mentioned above.

In the process according to the invention, the first, third and fourth embodiments are preferred. Particularly preferred are the third and fourth embodiments, and the third preferred embodiment is particularly preferred.

The chlorination reaction is advantageously carried out in a liquid phase (preferably, mainly DCE) containing a dissolved catalyst, such as FeCl3 or another Lewis acid. It is possible to advantageously combine this catalyst with cocatalysts such as alkali metal chlorides. A pair that has given good results is the FeCl3 complex with LiCl (lithium tetrachloroferrate - as described in patent application NL 6901398).

The amounts of FeCl3 used advantageously are of the order of 1 to 10 g of FeCl3 per kilo of liquid batch. The molar ratio of FeCl3 to LiCl is advantageously of the order of 0.5 to 2.

The chlorination process according to the invention is advantageously carried out at temperatures between 30 and 150 ° C. Good results were obtained regardless of the pressure both at a temperature lower than the boiling temperature (subcooled chlorination) and at the boiling temperature itself (boiling chlorination).

When the chlorination process according to the invention is a subcooled chlorination, it gave good results operating at a temperature that is advantageously greater than or equal to 50 ° C, and preferably greater than or equal to 60 ° C, but advantageously less than or equal to 80 ° C, and preferably less than or equal at 70 ° C; with a gas phase pressure advantageously greater than or equal to 1.5, and preferably greater than or equal to 2 absolute bars, 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 bars.

A boiling chlorination process is particularly preferred, which makes it possible, when appropriate, to usefully recover the heat of reaction. In this case, the reaction takes place advantageously 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 less than or equal to 135 ° C; with a gas phase pressure 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 bars, but advantageously less than or equal to 10, and preferably less than or equal to 6 absolute bars.

The chlorination procedure may be a mixed chlorination procedure in subcooled boiling loop. The term "mixed chlorination process in subcooled boiling loop" is understood to mean a process in which the cooling of the reaction medium is carried out, for example, by means of an exchanger submerged in the reaction medium, or by a loop circulating in an exchanger, while at least the amount of DCE formed occurs in a gas phase. Advantageously, the reaction temperature and pressure are adjusted so that the produced DCE goes out in the gas phase, and to eliminate the rest of the calories from the reaction medium by means of the exchange surface.

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

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

The chlorine is added in an amount sufficient to convert most of the ethylene and without the need for the addition of an excess of 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 mainly contain DCE and small amounts of by-products, such as 1,1,2-trichloroethane, or small amounts of ethane or methane chlorination products. The separation of the DCE obtained from the product stream derived from the chlorination reactor is carried out according to known ways, and in general makes it possible to take advantage of the heat of the chlorination reaction.

The unconverted products (methane, carbon monoxide, nitrogen, oxygen and hydrogen) are then advantageously subjected to an easier separation 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 constitutes a preferred inert support.

Catalysts comprising active elements that are advantageously at least two in number, one of which is copper, are preferred. Among the active elements other than copper, alkali metals, alkaline earth metals, rare earth metals, and group metals consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold may be mentioned. Catalysts containing the following active elements are particularly advantageous: 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 255156, EPA 494474, EP-A-657212 and EP-A 657213, are the most particularly preferred.

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

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

The alkali metal content, calculated in metallic form, is advantageously between 0.1 and 30 g / kg, preferably between 0.5 and 20 g / kg, and particularly preferably between 1 and 15 g / kg of catalyst.

The atomic ratios of Cu: Mg: metal or alkali metals are advantageously 1: 0.1-2: 0.05-2, preferably 1: 0.2-1.5: 0.1-1.5, and so Particularly preferred 1: 0.5-1: 0.15-1.

Particularly advantageous are catalysts having a specific surface, measured according to the method of

B.E.T. with 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.

The catalyst can be used in a fixed bed, or in a fluidized bed. This second option is preferred. The oxychlorination process is used in the range of conditions normally recommended for this reaction. The temperature is advantageously between 150 and 300 ° C, preferably between 200 and 275 ° C, and most preferably from 215 to 255 ° C. The pressure is advantageously greater than the atmospheric pressure. The values between 2 and 10 absolute bars give good results. The range between 4 and 7 absolute bars is preferred. This pressure can be usefully modulated in order to obtain an optimum residence time in the reactor, and to maintain a constant speed of passage for various operating speeds. The usual residence times range from 1 to 60 s, and preferably from 10 to 40 s.

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

Reagents can be introduced into the bed by any known device. For safety reasons, it is generally advantageous to introduce oxygen separately from the other reagents. This also requires keeping the gas mixture, which leaves the reactor or is recycled to it, out of the flammability limits at the pressures and temperatures considered. It is preferable to maintain a mixture called rich, that is, it contains too little oxygen, relative to the fuel, to start the ignition. In this regard, the abundant presence (> 2%, preferably> 5% by volume) of hydrogen would be a disadvantage, given the wide flammability range of this compound.

The hydrogen chloride / oxygen ratio used is advantageously between 3 and 6 mol / mol. The ethylene / hydrogen chloride ratio is advantageously between 0.4 and 0.6 mol / mol.

The chlorinated products obtained mainly contain DCE and small amounts of by-products, such as 1,1,2-trichloroethane. The separation of the DCE obtained from the product stream derived from the oxychlorination reactor is carried out according to known ways. The heat of the oxychlorination reaction is generally recovered in the form of steam, which can be used for separations or for any other purpose.

Unconverted products, such as methane and ethane, are then subjected to an easier separation than would have been necessary to separate pure ethylene from the initial mixture.

The DCE obtained by chlorination or by ethylene oxychlorination can then be converted into VC.

Therefore, the invention also relates to a process for the manufacture of VC. For this purpose, 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 subjected to pyrolysis.

The conditions under which pyrolysis can be carried out are known to persons skilled in the art. This pyrolysis is advantageously obtained by a gas phase reaction in a tubular oven. The usual pyrolysis temperatures are 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 interval of 5 to 25 seconds. The conversion rate of the DCE is advantageously limited to 45 to 75%, in order to limit the formation of by-products and fouling of the furnace tubes. The following steps make it possible, using any known device, to collect the purified VC and hydrogen chloride to preferably improve it upon oxychlorination. After purification, the unconverted DCE is advantageously transported to the pyrolysis furnace.

In addition, the invention also relates to a process for the manufacture of 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 process for manufacturing PVC can be a polymerization process in bulk, in solution or in aqueous dispersion, preferably it is a process of polymerization in aqueous dispersion.

The term "aqueous dispersion polymerization" is understood to mean polymerization by free radicals in aqueous suspension, as well as polymerization by free radicals in aqueous emulsion, and polymerization in aqueous microsuspension.

The term "free radical polymerization in aqueous suspension" is understood to mean any free radical polymerization process carried out in an aqueous medium, in the presence of oil-soluble free radical scattering and initiating agents.

The term "free radical polymerization in aqueous emulsion" is understood to mean any free radical polymerization process carried out in aqueous medium in the presence of water-soluble free radical emulsifying and initiating agents.

The term "aqueous microsuspension polymerization", also referred to as homogeneous aqueous dispersion polymerization, is understood to mean any free radical polymerization process in which oil soluble initiators are used, and an emulsion of droplets of monomers is prepared by stirring. powerful mechanics and in the presence of emulsifying agents.

The process for the manufacture of DCE according to the invention has the advantage of using two different ethylenic fractions, which are respectively very suitable for the chlorination reaction and for the oxychlorination reaction. In particular, the process according to the invention has the advantage of using an ethylenic fraction that is slightly contaminated with oxygen for the oxychlorination reaction, this being at a cost that is not very high.

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 which are generally responsible for some inhibition during the pyrolysis of the DCE. 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. Its ease of formation of stable allyl radicals explains its powerful inhibitory effect on the pyrolysis of DCE, which is produced by the free radical pathway. The formation of these by-products containing three carbon atoms, and which are heavier, would also constitute unnecessary reagent consumption during oxychlorination and during chlorination, or would result in destruction costs. In addition, these heavy compounds contribute to the fouling of columns and evaporators.

Another advantage of the process according to the invention is that it makes it possible to have, in the same industrial site, a completely integrated process from the source of hydrocarbons to the polymer obtained from the manufactured monomer.

A final advantage of the process according to the invention is that it would make it possible, by modification of the conditions to separate the fractions as defined below, to handle situations in which it is advantageous to improve an external source of hydrogen chloride, from another manufacturer, such as, for example, a unit for the manufacture of isocyanates. On the contrary, it is possible to find the situation of an advantageous market for hydrogen chloride, which leads to a decrease in the part of oxychlorination in relation to chlorination.

The first embodiment of the process according to the invention will now be described with reference to the drawing that accompanies the present description. This drawing consists of the attached Figure 1, which schematically represents an embodiment of the process for manufacturing DCE according to the invention.

The mixture of products 1 containing ethylene and other constituents resulting from the cracking of a hydrocarbon source is introduced into the main column 2, which is a distillation column equipped with an evaporator at the bottom and a condenser at the top, in which it is separated into three different fractions, namely fraction 3, which comes out from the top of column 2, which is enriched in compounds lighter than ethylene, in particular methane, hydrogen, nitrogen, oxygen and monoxide of carbon, and which is transported to chlorination, fraction 4, which comes out from the bottom of column 2, and fraction 5, which is extracted from the side of column 2. Fraction 5 is then transported to an auxiliary column 6, which is a steam entrainment column equipped with an evaporator, from which fraction 7 is extracted, characterized by a very low hydrogen content, which is transported to the oxychlorination. The remainder of fraction 5 in the form of a stream with a high concentration of more volatile impurities than ethylene 8 is transported to column 2.

The second embodiment of the process according to the invention will now be illustrated with reference to the drawing that accompanies the present description. This drawing consists of the attached Figure 2, which schematically represents an embodiment of the process for manufacturing DCE according to the invention.

The mixture of products 1 containing ethylene and other constituents resulting from the cracking of a hydrocarbon source is introduced into the main column 2, which is a distillation column equipped with an evaporator at the bottom and a condenser at the top, in which it is separated into two different fractions, namely, fraction 3 at the top of column 2, and fraction 4 at the bottom of column 2.

Fraction 3 is then transported to an adsorption column 5, equipped with a condenser. The washing agent from the desorption column 6 is introduced into the adsorption column 5 via the duct 7, after being cooled and placed under pressure in the exchangers 8 and the pump 9, respectively. The recent washing agent is added via conduit 10 to the washing agent from column 6.

After passing through column 5, fraction 3 separates into fraction 11, which exits at the top of column 5, and fraction 12, which leaves at the bottom of column 5. Fraction 11, enriched in compounds lighter than ethylene, in particular methane, hydrogen, nitrogen, oxygen and carbon monoxide, it is transported to the unit for the chlorination of ethylene.

Fraction 12, which comprises DCE enriched in ethylene, is introduced into desorption column 6 after being heated in exchanger 13.

After its passage in the desorption column 6, equipped with an evaporator at the bottom and a condenser at the top, the fraction 12 is separated into the fraction 14, which exits the top of the column 6, and in Fraction 15, which exits at the bottom of column 6. Fraction 14, characterized by a very low hydrogen content, is transported to the unit for ethylene oxychlorination. Fraction 15, which mainly contains DCE, is transported to column 5 via conduit 7 as explained above.

The exchangers 8 and 13 are coupled in an energy saving perspective.

The third embodiment of the process according to the invention will now be illustrated with reference to the drawing that accompanies the present description. This drawing consists of the attached Figure 3, which schematically represents an embodiment of the process for manufacturing DCE according to the invention.

The mixture of products 1 containing ethylene and other constituents resulting from the cracking of a hydrocarbon source is introduced into the main column 2, which is a distillation column equipped with an evaporator at the bottom and a condenser at the top, in which it is separated into two different fractions, namely, fraction 3 at the top of column 2, and fraction 4 at the bottom of column 2.

Fraction 3 is then transported to a distillation column 5, equipped with an evaporator at the bottom and a condenser at the top.

After its passage in column 5, fraction 3 separates into fraction 6, which exits at the top of column 5, and in fraction 7, which exits at the base of column 5.

Fraction 6, enriched in compounds lighter than ethylene, in particular methane, hydrogen, nitrogen, oxygen and carbon monoxide, is transported to the unit for the chlorination of ethylene.

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

The fourth embodiment of the process according to the invention will now be illustrated with reference to the drawing accompanying the present description. This drawing consists of the attached Figure 4, which schematically represents an embodiment of the process for manufacturing DCE according to the invention.

The mixture of products 1 containing ethylene and other constituents resulting from the cracking of a hydrocarbon source is introduced into the main column 2, which is a distillation column equipped with an evaporator at the bottom and a condenser at the top, in which it is separated into two different fractions, namely, fraction 3 at the top of column 2, and fraction 4 at the bottom of column 2.

Fraction 3, enriched in compounds lighter than ethylene, in particular methane, hydrogen, nitrogen, oxygen and carbon monoxide, is transported to the unit for the chlorination of ethylene.

Fraction 4 is then transported to a distillation column 5, equipped with an evaporator at the bottom and a condenser at the top.

After this step in column 5, fraction 4 is separated into fraction 6, which exits at the top of column 5, and at fraction 7, which exits at the bottom of column 5.

Fraction 6, characterized by a very low hydrogen content, is transported to the unit for ethylene oxychlorination.

Claims (12)

1. Procedure for the manufacture of 1,2-dichloroethane from a hydrocarbon source, according to which: a) the source of hydrocarbons is subjected to cracking, which produces a mixture of products containing ethylene and other constituents; b) the aforementioned mixture of products is separated into a fraction enriched in compounds that are lighter than ethylene, which contains part of ethylene (fraction A), in a fraction enriched in ethylene (fraction B), and in a heavy fraction (fraction C); c) fraction A is transported to a chlorination reactor, and fraction B to an oxychlorination reactor, reactors in which the majority of 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 derived from the chlorination and oxychlorination reactors.

2.

Methods according to claim 1, characterized in that the hydrocarbon source is selected from the group consisting of naphtha, diesel, liquid natural gas, ethane, butane, isobutane, and mixtures thereof.

3.

Process according to claims 1 and 2, characterized in that the hydrocarbon source is chosen from the group consisting of ethane, propane, butane, and propane / butane mixtures.

Four.

Process according to any one of claims 1 to 3, characterized in that the mixture of products containing ethylene and other constituents derived from step a) comprises hydrogen, methane, compounds comprising from 2 to 7 carbon atoms, carbon monoxide, nitrogen and oxygen

5.

Process according to any one of claims 1 to 4, characterized in that fraction B contains from 40% to 99.5% by volume of ethylene, relative to the total volume of fraction B.

6.

Process according to any one of claims 1 to 5, characterized in that fraction A contains a volume content of ethylene so that it represents 10% to 90% of the volume content of ethylene of fraction B.

7.

Method according to any one of claims 1 to 6, wherein step b) comprises:

-a first separation stage S1, which consists in the separation of said mixture of products within a main column C1 in fraction A at the top of column C1, at fraction C at the bottom of column C1 , and in fraction F1 extracted from the side of column C1, and -a second stage of separation S1 ’, which consists of the separation of fraction F1 into a fraction F1’, which is transported to column C1, and in fraction B. 8. The method according to any one of claims 1 to 6, wherein step b) comprises: -a first separation stage S2, which consists in the separation of said mixture of products in a main column C2 in a fraction F2 in the upper part of column C2, and in fraction C in the lower part of column C2 , - a second stage of separation S2 ’, which consists of the separation of fraction F2 into fraction A and a fraction F2’, and -a third stage of separation S2 ’, which consists of the separation of fraction F2’ into fraction B and a fraction F2 ’. 9. The method according to any one of claims 1 to 6, wherein step b) comprises: -a first separation stage S3, which consists of the separation of the said mixture of products in a main column C3 in a fraction F3 in the upper part of column C3, and in fraction C in the lower part of column C3 , Y - a second separation stage S3 ', which consists of the separation of fraction F3 in a column C3' in fraction A at the top of column C3 ', and in fraction B at the bottom of column C3 '. 10. The method according to any one of claims 1 to 6, wherein step b) comprises: -a first separation stage S4, which consists of the separation of said mixture of products in a main column C4 in fraction A at the top of column C4, and in a fraction F4 at the bottom of column C4 , Y - a second separation stage S4 ', which consists in the separation of fraction F4 in a column C4', and in fraction B in the upper part of column C4 ', and in fraction C in the lower part of the column 5 C4 '.

eleven.

Process for the manufacture of vinyl chloride, characterized in that the 1,2-dichloroethane obtained by the process according to any one of claims 1 to 10 is subjected to pyrolysis.

12.

Process for the manufacture of vinyl polychloride by polymerization of the vinyl chloride obtained by the process according to claim 11.