Process for the hydrohalogenation of an unsaturated hydrocarbon

This application claims priority to European application No. 12198097.3 filed December 19, 2012, the whole content of this application being incorporated herein by reference for all purposes.

The present invention relates to a process for the hydrohalogenation of an unsaturated hydrocarbon, preferably for the hydrochlorination of acetylene in order to produce vinyl chloride (VC).

The manufacture of VC by reaction between acetylene and hydrogen chloride is conventionally carried out in the gas phase, in a fixed-bed reactor, in the presence of a heterogeneous solid catalyst based on mercury chloride on a support. Mainly for reasons of toxicity, there is currently an increasing interest in catalytic systems with decreased mercury content or which are free of mercury compounds.

Various catalysts intended to replace the current catalysts in gas-phase processes have been developed.

For example, unexamined Japanese Patent Application 52/136104 describes a process of hydrochlorinating acetylene in the gas phase in the presence of a fixed catalyst bed composed of noble metal halides deposited on active carbon. To date however, the lifetime of such alternative catalysts intended for gas-phase processes remains much shorter than that of catalysts based on mercury compounds.

Furthermore, in the literature there are some examples of hydrochlorinating acetylene in the presence of a liquid catalytic medium.

German Patent 709.000 describes a process for preparing vinyl halides by bringing acetylene into contact, at high temperatures, with a molten mass of hydrohalide salts of organic bases containing a standard catalyst. Aliphatic, aromatic or heterocyclic amines and mixtures thereof are envisaged as organic bases.

Inventor's certificate SU 237116 describes the use of an aqueous acid solution containing 46 wt % of cuprous chloride and from 14 to 16 wt % of a methylamine, dimethylamine or trimethylamine hydrochloride.

European Patent Application EP-A-0 340 416 discloses a process for preparing VC by reaction of acetylene with hydrogen chloride in the presence of a palladium compound as catalyst in a solvent composed of an aliphatic or cycloaliphatic amide, at a temperature above room temperature. Although it allows high yields to be obtained, this process has, however, some significant drawbacks: it has emerged that, under the reaction conditions, the liquid catalyst system gradually degrades, forming blackish products of carbonaceous appearance. In addition, in the presence of hydrogen chloride, the amide is converted to a hydrochloride, the melting point of which is generally much higher than room temperature. N-Methylpyrrolidone hydrochloride, for example, is only liquid above 80°C. In practice, this may cause serious implementation problems, problems linked to agglomeration of the catalytic medium during reactor shutdowns or blocking of the lines at the coldest points of the installation. The entire reactor and also the lines in which the reaction medium flows must then be continuously kept at a temperature above the melting point of the hydrochloride.

These various problems seemed to have been solved thanks to the catalytic hydrochlorination systems described in European Patent Applications

EP 0 519 548-A1 and EP 0 525 843-A1 and which comprise at least one group VIII metal compound and either an amine hydrochloride, the melting point of which is less than or equal to 25 °C, or a fatty amine hydrochloride comprising more that 8 carbon atoms, the melting point of which is above 25°C and an organic solvent chosen from aliphatic, cycloaliphatic and aromatic hydrocarbons and mixtures thereof. Nevertheless, the catalyst systems that are described therein, especially those of which the group VIII metal compound is

platinum (II) chloride or palladium (II) chloride, are not completely satisfactory when considering the performances that they enable to be achieved in terms of productivity of the VC produced by hydrochlorination of acetylene and in terms of long term stability.

WO 2008/77868 discloses a catalytic hydrochlorination system comprising at least one amine hydrochloride and at least one group VIII metal compound selected from the group composed of mixtures of a platinum (IV) compound with Sn(II) chloride, mixtures of a platinum (II) compound with

triphenylphosphine oxide and mixtures of a palladium (II) compound with triphenylphosphine. These catalytic systems show an improved productivity compared to the systems as described in European patent applications

EP-A 0519548 and EP-A 0525843. Another example of disclosure in relation with liquid catalytic medium for the hydrochlorination of acetylene into VC is patent application CN 102671701 which discloses catalysts avoiding the draining of mercury by being constituted by a specific carrier loaded with a mercury-fixed ionic liquid, the ionic liquid being chemically bound with the surface of the carrier through silane coupling agent-silicate ester and the mercury chloride being connected to the imidazole ring of the ionic liquid through a coordinate bond. The catalytic

hydrochlorination of acetylene is said to be performed on the ionic liquid layer fixed on the carrier surface and allowing reaching high conversion ratio of acetylene.

Finally, patent application CN 101716528 (citing Zhiyong Yu as inventor) discloses catalytic systems for production of VC by the hydrochlorination of acetylene comprising an imidazolium (which is a non-protonated cation)-based ionic liquid (IL) with chloride, bromide, hexafluorophosphate or

tetrafluorophosphate ion as anion and one or more of gold, platinum, palladium, tin, mercury, copper or rhodium chlorides.

The last above-mentioned catalytic system seems to lead to relatively high selectivity and conversion rates at least when it is used in lab apparatus made of chemically inert material (like glass or Pyrex). In that regard, publication Green Chem., 2011, 13, 1495 having Zhiyong Yu as one of the authors, explicitly describes a glass reactor without mentioning any corrosion problem. In fact, glass was not chosen on purpose for corrosion problems but was merely the fall back material used for general purpose lab apparatus.

However, the Applicant noticed that surprisingly, the materials used in the industrial facilities handling the processes of the above mentioned patent using an amine hydrochloride, were rapidly and severely corroded if submitted to the above described imidazolium containing hydrochlorination medium. And from some testing, the Applicant noticed that this problem seems to be generalized at least to ILs comprising at least one non-protonated cation and HC1.

Hence, a patent application to the Applicant (WO 2012/113778) aims at protecting a process for the hydrohalogenation of an unsaturated hydrocarbon (preferably acetylene) using an IL as catalyst and which is at least partly carried out in apparatus made from or covered with materials which are resistant to halogenated acids in dissociated form. The Applicant has now found that surprisingly, the catalysts according to the invention reduce significantly the above mentioned corrosion problem during the hydrohalogenation of an unsaturated hydrocarbon using an IL catalyst.

Therefore, the present invention relates to a process for the

hydrohalogenation of an unsaturated hydrocarbon using a catalyst comprising at least one ionic liquid (IL) and at least one metal, according to which said IL and metal are encapsulated inside a porous solid carrier.

Any unsaturated hydrocarbon may be used in the process according to the invention. Preferably, it is gaseous at the hydrohalogenation reaction temperature.

By unsaturated hydrocarbon is meant a component made of carbon and hydrogen and having at least one double and/or triple bond between two C atoms; examples are acetylene, ethylene, and the like.

Acetylene gives good results within the frame of the invention and is particularly preferred.

In a preferred embodiment of the invention, the hydrohalogenation reaction is hydrochlorination. This embodiment is particularly interesting when the unsaturated hydrocarbon is acetylene.

The process according to the invention is therefore preferably a process for the hydrochlorination of acetylene in order to produce VC.

In the present description, the term "acetylene" has to be understood as a source of acetylene which may either be "pure" acetylene (as available commercially) or mixtures comprising acetylene which can, in addition to acetylene, comprise other components.

Such other components may be by-products of acetylene synthesis, e.g. ethylene or other unsaturated hydrocarbons, gases like N ₂ , CO ₂ , H ₂ , CO, H ₂ O....

Acetylene is manufactured by the partial combustion of methane, by oxidative cracking of hydrocarbon source, by electric arc coal furnace, by plasma coal furnace or appears as a side product in the ethylene stream from cracking of hydrocarbons.

Another method for the manufacture of acetylene is the hydrolysis of calcium carbide

CaC ₂ + 2H ₂ 0→ Ca (OH) ₂ + C ₂ H ₂

The manufacture of CaC ₂ from CaO or CaC(¾ and C requires extremely high temperatures of approximately 2000°C, necessitating the use of an electric furnace or the like. When mixtures comprising acetylene and ethylene are used, they may be used directly as such, i.e. without the necessity to separate the components as the reactivity of acetylene vs. ethylene should enable the hydrochlorination of acetylene to be carried out first with separation of the VC obtained and the subsequent use of ethylene. This ethylene could be chlorinated to produce 1 ,2- dichloroethane (DCE) for a combined process for the manufacture of VC. The pyrolysis of the DCE can produce the hydrogen chloride for the first reaction with acetylene.

Alternatively, as such hydrogen chloride resulting from pyrolysis of DCE usually contains small amount of acetylene which is usually hydrogenated before hydrogen chloride is recycled to the process, such acetylene can be submitted to the process according to the present invention.

Therefore, according to one variant according to the invention, the preferred process of hydrochlorination according to the present invention is carried out after the pyrolysis of DCE in a process to produce DCE and VC from ethylene, as an alternative to the hydrogenation of acetylene sometimes used in such a process.

In a first sub-variant, the catalyst of the invention is put within or downstream of a quenching device used to quench the pyrolysis gases.

In a second sub- variant, the catalyst of the invention is put in the column used to separate HC1 from VC and the other constituents of the quenched gases.

In a third sub-variant, the catalyst of the invention is put on a side-stream taken on the column used to separate HC1 from VC and the other constituents of the quenched gases. The side-stream is taken from any location of the column under or over the feed point, preferably over the feed point. The side-stream could be taken from the vapor phase or from the liquid phase or from both phases circulating in the column. Preferably the side-stream is taken from the vapor phase. The reacted gas (i.e. the gas from which the acetylene has been converted to VC) is recycled downstream of the pyrolysis in any suitable place. Suitable recirculation place are for instance the quench, the feed of the column or the column itself.

In a fourth sub-variant, the catalyst of the invention is put on the stream separated at the top of the column, preferably after suitable thermal treatment and/or pressure treatment of said stream.

In these variants, the catalyst is preferably of the honeycomb type and preferably has large channels so as to avoid clogging of said channels by tars. The expression "encapsulated inside a porous solid carrier" has to be understood in the context of the present invention as meaning that the ionic liquid and the metal are both physically confined mainly in the porous solid carrier; in other words they are mainly in the cage constituted by the porous solid carrier/they are mainly confined/trapped into the porous solid carrier-gel nanopores relatively firmly but advantageously without any chemical link.

By the word "mainly", it is meant according to the present invention, that essentially all the ionic liquid and metal are in the porous solid carrier but that it is not excluded that a small part of them can be present on the outer surface of the porous solid carrier but in any case advantageously without any chemical link.

The porous solid carrier preferably comprises silica or alumina. More preferably, the porous solid carrier comprises silica and even more preferably: it consists essentially of silica.

The catalyst used in the process according to the invention is

advantageously prepared by

• mixing a precursor of the porous solid carrier with an alcohol and obtaining a mixture thereof;

• heating such mixture and then adding to it said IL and metal, preferably previously mixed;

• once a clear and homogenous liquid mixture is obtained, adding an acid to such mixture and let it coagulated; and

• aging the coagulated mixture in order to obtain the catalyst, preferably in the form of a powder.

This process can be qualified as a sol-gel process considering that it allows the ionic liquid and the metal to be physically confined/encapsulated in the porous solid carrier-gel matrix.

In another embodiment, the catalyst may also be prepared by:

• preparing a catalyst (A) according to the procedure disclosed in patent application EP2617698 in the name of the Applicant, the content of which is incorporated by reference in the present application, said catalyst comprising a solid carrier, a metal and an ionic liquid;

• mixing catalyst (A) with a solution (B) in which the ionic liquid is preferably not soluble, said solution (B) comprising a precursor of a porous solid carrier and an alcohol, in order to obtain a slurry (C);

• adding an acid to this slurry (C) and letting it coagulate; and • aging the coagulated mixture in order to obtain the catalyst, preferably in the form of a powder.

The precursor of the porous solid carrier can be chosen among the available precursors.

When the porous solid carrier is silica, the precursor is advantageously selected from the compounds responding to formula Si(0-Ri)(0-R2)(0-R ₃ )(0- R4) wherein Ri, R2, R ₃ and R4 are alkyl chains, identical or different, preferably saturated, comprising from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms and more preferably from 1 to 3 carbon atoms. Preferably when the porous solid carrier is silica, the precursor is selected from the compounds responding to formula Si(0-Ri)(0-R ₂ )(0-R ₃ )(0-R ₄ ) wherein Rj, R ₂ , R ₃ and R* are all an ethyl group (tetraethoxyorthosilicate).

When the porous solid carrier is alumina, the precursor is preferably selected from aluminium alkoxides of formula Al(OR)3 with R being three alkyl groups identical or different, preferably identical.

Any alcohol can be chosen for preparing the catalysts used in the process according to the invention. Preferred alcohols are alcohols containing from 1 to 8 carbon atoms, preferably saturated. More preferred alcohols are the ones containing from 1 to 6 carbon atoms, preferably saturated. Most preferred alcohols are the ones containing from 1 to 4 carbon atoms, preferably saturated. Ethanol gives very good results.

The heating of the mixture of the precursor of the porous solid carrier with the alcohol can be made at any temperature suitable for the components in presence. Advantageously, the heating is made at a temperature comprised between 40 and 75 °C, preferably between 50 and 70°C and more preferably at 60°C.

The acid to be added can be selected among any compound considered as an Bronsted acid. Examples of acids that can be cited are HF, HBr, HI, HC1, H2SO3, H ₂ S0 ₄ , HNO2, HNO3, H2CO3, H3PO3, H ₃ P0 ₄ and their corresponding ammonium salts as well as acetic acid. Preferably, the acid is HC1 or NH ₄ F.

The aging of the coagulated mixture can be made at any temperature required to obtain the catalyst in a suitable form. Advantageously, this aging is made at a temperature comprised between 40 and 80°C, preferably between 50 and 70°C and more preferably at 60°C.

Depending on the unsaturated hydrocarbon, preferably acetylene, content of the unsaturated hydrocarbon, preferably acetylene, source, the hydrohalogenation, preferably hydrochlorination, reaction can advantageously be carried out at a temperature in the range of from -30°C to 230°C. Higher temperatures are not recommended since the catalytic system has a tendency to degrade.

In the process according to the present invention,

- when the unsaturated hydrocarbon, preferably acetylene, source has an unsaturated hydrocarbon, preferably acetylene, content equal to or above 10%, the hydrohalogenation, preferably hydrochlorination, reaction is advantageously carried out at a temperature of 40°C to 200°C;

- when the unsaturated hydrocarbon, preferably acetylene, content of the unsaturated hydrocarbon, preferably acetylene, source is below 10 %, the hydrohalogenation, preferably hydrochlorination, reaction is advantageously carried out at a temperature between -30°C and 200°C.

When the unsaturated hydrocarbon, preferably acetylene, source has an unsaturated hydrocarbon, preferably acetylene, content equal to or above 10%, advantageous reaction temperature, that is to say that offering the best compromise between productivity, yield and stability of the catalytic medium, is greater than or equal to 40°C. The best results are then obtained at temperatures greater than or equal to 50°C with a more particular preference for temperatures greater than or equal to 80°C and a most particular preference for temperatures greater than or equal to 110°C. Advantageously, the reaction temperature does not exceed 200°C. In certain cases, a reaction temperature not exceeding 170°C has proven advantageous or even not exceeding 130°C. Lower corrosion rates and coke formation are observed at lower temperatures, however, higher conversion rates may be observed at higher temperature.

In the process according to the invention,

- when the unsaturated hydrocarbon, preferably acetylene, source has an unsaturated hydrocarbon, preferably acetylene, content equal to or above 10%, the hydrohalogenation, preferably hydrochlorination, reaction is advantageously carried out at a pressure below 10 MPa, preferably below 5 MPa, more preferably below 2.5 MPa;

- when the unsaturated hydrocarbon, preferably acetylene, content of the unsaturated hydrocarbon, preferably acetylene, source is below 10 %, the hydrohalogenation, preferably hydrochlorination, reaction is advantageously carried out at a pressure below 5 MPa, preferably below 2.5 and more preferably below 1 MPa. The pressure is however advantageously higher than 5 Pa, preferably higher than 8 Pa and more preferably higher than 10 Pa.

The hydrohalogenation, preferably hydrochlorination, of unsaturated hydrocarbon, preferably acetylene, could be carried out in the gaseous or in the liquid phase, preferably in the gaseous phase. The hydrohalogenation, preferably hydrochlorination, of unsaturated hydrocarbon, preferably acetylene, is advantageously carried out by bringing the gaseous reactants - preferably acetylene and hydrogen chloride - into contact with the catalyst, in any suitable reactor.

The hydrohalogenation, preferably hydrochlorination, reaction may be carried out conventionally in any equipment promoting gas or liquid contact on solid materials. Such equipments are entrained bed, pneumatic transportation, cyclone, fluidized bed, vibrating bed, fixed bed, moving bed, bubbling bed, spouted bed or any combination.

In a first embodiment, the reaction is carried out in a fixed bed and/or in pre-assembled structures wherein the external surface to volume ratio (S/V) of the catalyst is advantageoulsy lower than or equal to 6 10 ⁴ m ¹ , preferably lower than or equal to 3 10 ⁴ , more preferably lower than or equal to 2 10 ⁴ m ^_1 and advantageously higher than or equal to 10 m ^"1 , preferably higher than or equal to 20 and more preferably higher than or equal to 25 m ^"1 , said process comprising feeding continuously a reaction zone comprising the catalyst with at least the unsaturated hydrocarbon, preferably acetylene, and the hydrohalogenation, preferably hydrochlorination, reactive, both in gaseous form, at a total linear velocity advantageously higher than or equal to 0.005 m/s, preferably higher than or equal to 0.008 m/s, 0.01, more preferably higher than or equal to 0.02 m/s and advantageously lower than or equal to 20 m/s, preferably lower than or equal to 15 m/s, more preferably lower than or equal to 12 m/s, and with a pressure drop across the reaction zone which is advantageously lower than or equal to 50 kPa/m, preferably lower than or equal to 40 kPa/m and more preferably lower than or equal to 35 kPa/m.

Equipment for such first embodiment can be random fixed bed, structured fixed bed, catalytic structured packing, honeycomb structure and the like or any combination of these equipments.

In a second embodiment, the reaction is carried out in a fluidized flow wherein the external surface to volume ratio (S/V) of the catalyst is

advantageoulsy lower than or equal to 10 ⁵ m ^"1 , preferably lower than or equal to 8 10 ⁴ , more preferably lower than or equal to 5 10 ⁴ m ^"1 and higher than or equal to 100 m ^"1 , preferably higher than or equal to 200 m ^"1 and more preferably higher than or equal to 250 m ^"1 , said process comprising feeding continuously a reaction zone comprising the catalyst with at least the unsaturated hydrocarbon, preferably acetylene, and the hydrohalogenation, preferably hydrochlorination, reactive, both in gaseous form at a total linear velocity advantageously higher than or equal to 0.15 m/s, preferably higher than or equal to 0.25 m/s, more preferably higher than or equal to 0.4 m/s and advantageously lower than or equal to 6 m/s, preferably lower than or equal 4 m/s, more preferably lower than or equal than 3 m/s and with a pressure drop across the reaction zone which is advantageously lower than or equal to 100 kPa/m, more preferably lower than or equal to 60 kPa/m.

Equipment allowing carrying out a fluidized flow can be fluidized bed, moving bed, vibrating bed, spouted bed, bubbling bed, and the like or any combination of these equipments.

In a third embodiment, the reaction is carried out in an entrained flow wherein the external surface to volume ratio (S/V) of the catalyst is

advantageoulsy lower than or equal to 2 10 ⁶ m ¹ , preferably lower than or equal to 1.2 10 ⁶ , more preferably lower than or equal to 6 10 ⁵ m ^"1 and advantageously higher than or equal to 100 m ^"1 , preferably higher than or equal to 200 more preferably higher than or equal to 250 m ^"1 , said process comprising feeding continuously a reaction zone comprising the catalyst with at least the unsaturated hydrocarbon, preferably acetylene, and the hydrohalogenation, preferably hydrochlorination, reactive, both in gaseous form at a total linear velocity which is advantageously higher than or equal to 0.25 m/s, preferably higher than or equal to 0.4 m/s, more preferably higher than or equal to 0.5 m/s and

advantageouly lower than or equal to 20 m/s, preferably lower than or equal to 15 m/s, more preferably lower than or equal to 12 m/s, wherein a pressure drop across the reaction zone is advantageously lower than or equal to 50 kPa/m, preferably lower than or equal to 20 kPa/m and more preferably lower than or equal to 5 kPa/m.

Equipment allowing carrying out an entrained flow can be pneumatic transportation, entrained bed, circulating bed, cyclone and the like or any combination of these equipments.

In the present invention, fixed bed and fluid bed are preferred, the fixed bed being most preferred. Catalyst particles are intended to mean solid element of catalyst such as powders, extrudates, pellets, etc., honeycomb structures, catalytic micro-reactors and structured packings like Katapack ^® , Melapack ^® , etc. The catalyst can be a bulk catalyst or a supported catalyst.

The catalyst particles could be assembled in sub- structures such as honeycomb structures, catalytic micro-reactors, structured packing elements and the like ; individual particles could also be assembled in an ordered way such as in bed ; or individual particles could be manipulated as a whole in a fluidised bed, entrained bed, vibrating bed, moving bed, spouted bed, bubbling bed or the like.

When the catalyst particles are assembled in sub-structures, the external volume of the catalyst can be calculated from the average geometric outer dimensions of the catalyst sub-structures, using classical surface and volume formulas. The catalyst surface can be calculated from the average geometric dimensions of the outer and inner dimensions of the macroscopic element. If no shape can be defined for the catalyst particles, they are considered as spheres and the geometric outer dimension is the diameter of the equivalent sphere.

When the catalyst particles are assembled in an ordered way such as in fixed bed of various geometrical forms, the external volume can be calculated from the average geometric outer dimensions of the catalyst bed, using classical surface and volume formulas. The catalyst surface can be calculated from the average geometric dimensions of the outer and inner dimensions of the particles. If no shape can be defined for the catalyst particles, they are considered as spheres and the geometric outer dimension is the diameter of the equivalent sphere.

When the catalyst particles are manipulated as a whole such as in fluidised bed, entrained bed, vibrating bed, moving bed, spouted bed, bubbling bed or the like, the external volume can be calculated from the average geometric outer dimensions of the catalyst hope at rest, using classical surface and volume formulas. The catalyst surface can be calculated from the average geometric dimensions of the outer and inner dimensions of the individual catalyst particles of the hope. If no shape can be defined for the catalyst particles, they are considered as spheres and the geometric outer dimension is the diameter of the equivalent sphere.

In the process according to the invention, the catalyst particles can exhibit any form. The catalyst particle is generally in a form selected from the group consisting of rings, beads, pellets, tablets, extrudates, granules, crushed, saddled, flakes, honeycomb structures, impregnated structured packings and any mixture thereof.

When the catalyst is in the form of beads, the beads are considered as spheres and the geometric outer dimension is the diameter of the equivalent sphere.

When the catalyst is in the form of cylindrical particles (e.g. pellets, extrudates), the catalyst particles are considered as cylinders and the geometrical outer dimensions are the average particle diameter and the average particle length. The average can be geometric, arithmetic or logarithmic. The arithmetic average is for instance particularly convenient.

When the catalyst particles do not have simple geometrical form like for instance, crushed, flakes, saddles, extrudates of various forms (stars, etc.), they are considered as spheres and the geometrical outer dimensions is the diameter of the equivalent sphere.

When the catalyst particles are in the form of cylindrical rings, the catalyst particles are considered as hollow cylinders and the geometrical dimensions are the average diameters (internal and external) of the cylinders, and the average length of the cylinders.

When the catalyst is the form of a honeycomb structure with cylindrical channels, the geometrical dimensions are the average length and diameter of the channels.

Those are only a few examples on how the geometrical outer dimensions of the catalyst particles needed for calculating the external surface to volume ratio of the catalyst can be defined. The man of ordinary skill in the art will easily understand how to obtain those dimensions for any catalyst form, including the forms not disclosed here above.

The value of the characteristical outer dimensions of catalyst particles can be obtained by any means, for instance, by visual or microscopic measurements on individual catalyst particles followed by averaging the measure on a sufficiently large number of particles (e.g. more than 100) to be statistically reliable or from particle size distribution via sifting, sedimentation (natural or forced) methods or light scattering methods for instance.

In the embodiments above, the total linear velocity is understood to mean the linear velocity of the total gas feed of the reaction zone containing the catalyst. The total linear velocity is obtained by dividing the flow of the total gas feed of the reaction zone containing the catalyst by the section of said zone.

The total gas feed can be measured by any means like for instance via orifices, venturies, nozzles, rotameters, Pitot tubes, calorimetrics, turbine, vortex, electromagnetic, Doppler, ultrasonic, thermal or Coriolis flow meters.

The section of the said reaction zone is understood to mean the average section along the length of the said reaction zone. Said reaction zone can be horizontal or vertical.

The pressure drop across the reaction zone containing the catalyst is understood to mean the dynamic pressure drop including the pressure drop corresponding to the fluid devices connected to the zone.

The pressure drop can be measured by any means like for instance differential pressure (Dp) cells, manometers such as U tube manometer, cup manometer, bourdon manometer, Piranni manometer, ionisation manometer, membrane manometer, piezo electric manometer, and any combination thereof Preferred means are selected from the group consisting of Dp cells, U tube manometer, bourdon manometer, membrane manometer, piezo electric manometer, and any combination thereof. More preferred means are selected from the group consisting of Dp cells, membrane manometer, piezo electric manometer, and any combination thereof.

The embodiments described above, which may be combined, generally allow to obtain a residence time such that a high conversion may be obtained and also, to ensure a good dispersion of the reactives inside the catalyst.

In the process according to the invention,

- when the unsaturated hydrocarbon, preferably acetylene, source has an unsaturated hydrocarbon, preferably acetylene, content equal to or above 10 %, the molar ratio of the hydrohalogenation reactive, preferably hydrogen chloride, to the unsaturated hydrocarbon, preferably acetylene, is advantageously greater than or equal to 0.5, preferably greater than or equal to 0.8 and advantageously less than or equal to 3, preferably less than or equal to 1.5;

- when the unsaturated hydrocarbon, preferably acetylene, content of the unsaturated hydrocarbon, preferably acetylene, source is below 10 %, the molar ratio of the hydrohalogenation reactive, preferably hydrogen chloride, to the unsaturated hydrocarbon, preferably acetylene, is advantageously greater than or equal to 1000, preferably greater than or equal to 5000 and less than or equal to 100000, preferably less than or equal to 50000 and more preferably less than or equal to 20000.

The unsaturated hydrocarbon, preferably acetylene, and the

hydrohalogenation reactive, preferably hydrogen chloride, may be brought into contact in the reactor or, preferably, mixed prior to being introduced into the reactor.

The catalyst used according to the instant invention comprises at least one ionic liquid (a liquid which shows ionic properties at least during the process of the invention i.e. during the hydrohalogenation of the unsaturated hydrocarbon) hence comprising at least one cation and at least one anion and in one embodiment, comprising at least one non-protonated cation and at least one anion.

Ionic liquids are in principle salts in the liquid state while ordinary liquids, such as e.g. water and gasoline are predominantly made of electronically neutral molecules. Ionic liquids are advantageously made of ions. It worth noting that within the frame of the invention, imidazoles are not ionic liquids per se but in the process of the invention involving the hydrohalogenation of the unsaturated hydrocarbon, they may become ionic liquids by reaction with the

hydrohalogenation reactive (HC1 for instance).

It may be generally said that any salt melting without decomposition will usually yield an ionic liquid. Many salts, however, melt at high temperatures, much higher than the temperatures used in catalytic processes. For the purposes of the instant invention the term ionic liquid shall refer to a system being liquid at temperature used in the process in which the catalytic system is used.

Preferred ionic liquids for the purposes of the instant invention are those which are liquid at temperatures of 150°C or less, more preferably at temperatures of 100°C or less even more preferably at temperatures of 80°C or less. Furthermore, preferred ionic liquids are those which have a very low vapor pressure and a very low flammability and which show a good electrical conductivity.

The ionic liquid, which advantageously functions as reaction medium, has preferably a solvent capability for the reagents (unsaturated hydrocarbon and hydrohalogenation reactive like acetylene and HC1 for instance) but preferably, the products (and eventually the intermediates) formed in the reaction (like VC) are not soluble in the ionic liquid. In the present description, the expression "at least one ionic liquid" is understood to mean one or more than one ionic liquid.

Preferably, the catalyst comprises only one ionic liquid as defined above.

In the remainder of the text, the expression "ionic liquid" used in the singular or plural should be understood as denoting one or more than one ionic liquid, except where denoted otherwise.

In the present description, the expression "at least one non-protonated cation" is understood to mean one or more than one non-protonated cation.

Preferably, the ionic liquid comprises one non-protonated cation.

In the remainder of the text, the expression "non-protonated cation" used in the singular or plural should be understood as denoting one or more than one non-protonated cation, except where denoted otherwise.

The term non-protonated cations as used herein for the purpose of the instant invention shall mean cations which do not carry free hydrogen atom(s) at the atom(s) to which the positive charge of the cation is allocated.

Advantageoulsy, the non-protonated cation is selected from

- quaternary ammonium cations which can be represented by the general formula

- phosphonium cations which can be represented by the general formula

[PR ¹ R ² R ³ R] ⁺ , and

- cations comprising five or six-membered heterocycles which have at least one nitrogen atom, advantageously one or two nitrogen atoms.

Preferred cations comprising five or six membered heterocycles are

imidazolium cations of the general formula (I)

eral formula (II), and

- pyrrolidinium cations of the general formula (III)

wherein radicals R and R ¹ to R ⁹ may, independently from one another, with the proviso that the radical carried by the atom(s) to which the positive charge of the cation is allocated is not hydrogen, each be hydrogen, an optionally substituted saturated or unsaturated Ci-Ci ₈ alkyl group (preferably an optionally substituted saturated or unsaturated C1-C16 alkyl group and more preferably an optionally substituted saturated or unsaturated Ci-Ci ₄ alkyl group), an optionally substituted saturated or unsaturated C2-C18 alkyl group with the carbon chain interrupted by one oxygen atom or an optionally substituted C ₆ -Ci2 aryl group.

Preferably, the non-protonated cation is selected from quaternary ammonium cations, phosphonium cations, imidazolium cations, pyridinium cations and pyrrolidinium cations.

More preferably, the non-protonated cation is selected from phosphonium cations, imidazolium cations, pyridinium cations and pyrrolidinium cations.

Most preferably, the non-protonated cation is selected from phosphonium cations and imidazolium cations. Especially the latter are preferred, and more specifically: dialkyl imidazolium cations, and even more preferably : 1,3 dialkyl imidazolium cations.

Examples of quaternary ammonium cations are tributylmethylammonium, butyltrimethylammonium, octyltrimethylammonium, tetramethylammonium, tetraethylammonium, tetrabutylammonium, methyltrioctylammonium,

2-hydroxyethyltrimethylammonium and diethylmethyl(2- methoxyethyl)ammonium.

Examples of phosphonium cations are triisobutylmethylphosphonium, tributylmethylphosphonium, ethyltributylphosphonium, tetrabutylphosphonium, tetraoctylphosphonium, tributyltetradecylphosphonium,

trihexyltetradecylphosphonium and benzyltriphenylphosphonium.

Examples of imidazolium cations are 1,3-dimethylimidazolium, l-ethyl-3- methylimidazolium, l-butyl-3-methylimidazolium, l-pentyl-3- methylimidazolium, l-hexyl-3-methylimidazolium, l-decyl-3- methylimidazolium, 1 -dodecyl-3-methylimidazolium, 1 -tetradecyl-3- methylimidazolium, l-hexadecyl-3-methylimidazolium, l-(2-hydroxyethyl)-3- methylimidazolium, l-Allyl-3-methylimidazolium, l-benzyl-3- methylimidazolium, l-phenylpropyl-3-methylimidazolium, 1,3- diethylimidazolium, l-butyl-3-ethylimidazolium, l-methyl-3- propylimidazolium, l-methyl-3-octylimidazolium, l-methyl-3- octadecylimidazolium, 1 ,3-dibutyl-2-methylimidazolium, 1 ,3-didecyl-2- methylimidazolium, 1 -(2-hydroxyethyl)-3-methylimidazolium, 1 -ethyl-2,3- dimethylimidazolium, l-propyl-2,3-dimethylimidazolium, l-butyl-2,3- dimethylimidazolium, 1 -butyl-3 ,4-dimethylimidazolium, 1 -hexyl-2, 3- dimethylimidazolium, l-hexadecyl-2,3-dimethylimidazolium,

1 ,2,3-trimethylimidazolium, 1,3,4-trimethylimidazolium, l-butyl-3- ethylimidazolium, 1 ,3-dibutylimidazolium, 1 -methyl-3-octylimidazolium, 1 -butyl-3, 4,5-trimethylimidazolium and 1 ,3,4,5-tetramethylimidazolium.

Examples of pyridinium cations are 1 -methylpyridinium,

1 -ethylpyridinium, 1 -propylpyndinium, 1-butylpyridinium, 1 -hexylpyndinium, 1 -octylpyridinium, 1 ,2-dimethylpyridinium, 2-ethyl- 1 -methylpyridinium, 1 -butyl-2-methylpyridinium, 1 -butyl- 3 -methylpyridinium, 1 -butyl-4- methylpyridinium, 1 -hexyl-3-methylpyridinium, 1 -hexyl-4-methylpyridinium, 1 -butyl-2-ethylpyridinium, 1 -butyl-3 -ethylpyridinium, 4-methyl- 1 - octylpyridinium, l-butyl-2-ethyl-6-methylpyridinium, 2-ethyl- 1 ,6- dimethylpyridinium, 1 -butyl-3, 4-dimethylpyridinium and 1 -butyl-3, 5- dimethylpyridinium.

Examples of pyrrolidinium cations are 1 , 1 -dimethylpynolidinium, 1-ethyl- 1 -methylpyrrolidinium, l-ethyl-3-methylpynolidinium, 1 -butyl- 1- methylpyrrolidinium, 1-hexyl-l -methylpyrrolidinium, 1-octyl-l- methylpyrrolidinium, 1 -butyl- 1 -ethylpyrrolidinium and 1 -methyl- 1- propylpyrrolidinium.

In another embodiment, the cation may be a protonated cation like an imidazole cation, preferably an N-alkylated imidazole cation. Preferably, the N-alkylated imidazole is defined by the formula (IV)

(IV)

wherein radicals R ¹ , R ² , R ³ and R ⁴ may, independently from one another, each be hydrogen or an optionally substituted saturated or unsaturated Ci-Ci ₈ alkyl group. More preferably, the N-alkylated imidazole is selected from

1 -methylimidazole, 1 -ethylimidazole, 1 -butylimidazole, 1-hexylimidazole, 1-octylimidazole, 1 -decylimidazole, l-methyl-2-octylimidazole, l-ethyl-2- methylimidazole, 1 -butyl-2-methylimidazole, 1 -hexyl-2-methylimidazole and l-decyl-2-methylimidazole. N-alkylated imidazoles selected from

1 -methylimidazole, 1 -ethylimidazole and 1 -butylimidazole are even more preferred.

In the present description, the expression "at least one anion" is understood to mean one or more than one anion.

Preferably, the ionic liquid comprises one anion.

In the remainder of the text, the expression "anion" used in the singular or plural should be understood as denoting one or more than one anion, except where denoted otherwise.

As anions, it is in principle possible to use all anions. The anion is preferably selected from :

the group consisting of halides and halogen-containing anions and so called pseudo-halides,

the group consisting of sulfates, sulfites and sulfonates,

the group consisting of phosphates,

the group consisting of phosphonates and phosphinates,

the group consisting of phosphites,

the group consisting of phosphonites and phosphinites,

the group consisting of carboxylic acids,

the group consisting of borates,

the group consisting of boronates,

the group consisting of carbonates and carbonic esters,

the group consisting of silicates and silicic esters,

the group consisting of alkylsilane and arylsilane salts,

the group consisting of carboximides, bis(sulfonyl)imides and sulfonylimides, the group consisting of alkoxides and aryloxides.

The anion(s) are preferably chosen among the following ones : chloride, bromide, iodide, triflate (trifluoromethanesulfonate), tosylate,

tetrafluoroethylsulfonate, bis-trifluoromethylsulfonylimide, tetrachloroferrate, tetrafluoroborate, tetrafluorophosphate and hexafluorophosphate. The most preferred IL are imidazolium halogenated salts and more specifically chlorides. Particularly preferred is l-Butyl-3-methylimidazolium chloride (BMIMC1) because readily available commercially.

Methods for the manufacture of suitable ionic liquids are known to the skilled man and thus a detailed description is not necessary here, especially since some of them and especially BMIMC1 are commercially available.

The catalyst use according to the invention also comprises at least one metal.

In the present description, the expression "al least one metal" is understood to mean one or more than one metal. Preferably, the catalyst comprises only one metal.

The metal can be any metal. The metal is advantageously chosen from Pd, Pt, Au, Hg, Ru, Os, Ru, Rh and Ir. Preferably, the metal is chosen from Pd, Pt, Au, Hg, Ru and Os.

While good results have been obtained when the metal is chosen among the ones cited above, very good results have been obtained when the metal is chosen from Pd, Ru, Au and Os, particularly very good results have been obtained when the metal is chosen from Pd, Ru and Au and more particularly very good results have been obtained when the metal is chosen from Pd and Ru. The most interesting results have been obtained when metal is Pd.

The metal content of the catalyst according to the invention, is preferably equal to or higher than 0.25 wt % (based on the total weight of catalyst), preferably than 0.5 wt %. It is generally equal to or lower than 10 wt %, preferably than 5 wt %.

The expression "metal" as used herein includes metal compound i.e. single metal compounds of one metal as well as mixtures of different compounds of the same metal or mixtures of compounds of different metals or compounds comprising two metals as defined hereinbefore.

Preferably, the catalyst is obtained from one compound of at least one metal and more preferably from one compound of one metal.

The metal compound may be of any nature ; however, it is generally a salt, more preferably a halide and even more preferably, a chloride.

Among the chloride-based compounds of palladium (II), mention may be made of palladium (II) chloride and the palladochlorides of alkali metals or of alkaline-earth metals, such as for example Na2(PdCl ₄ ), K^PdC ), Li ₂ (PdCL and (NH ₄ )2(PdCl ₄ ). Palladium (II) chloride gives good results. All the embodiments described above allow getting very low corrosion rates on materials which can be used for industrial apparatus during a normal industrial life time (several years, typically at least 10 years) at the design pressure either in massive form or as a protective layer allowing the apparatus to resist to the corrosivity of the reaction medium. The protective layer could be made of the same material as the one providing the mechanical resistance of the apparatus or from another material.

Examples of materials which are resistant to halogenated acids, preferably to HC1, in dissociated form, that can be used either in massive form or as protective layer are metals, fluorinated polymers, ceramics, (impregnated) graphite, enamel and silicon carbide.

Examples of materials that may be used as protective layer (made of a different material than the one providing the mechanical resistance) are metals such as Nb, Ta, metal alloys such as Hastelloy ^® C276, Hastelloy ^® HB2, Monel ^® , Inconnel ^® , Incoloy ^® , enamels such as Pfaudler ^® email WWG, Pfaudler ^® email 4300, Pfaudler ^® email ASG, fluorinated polymers like PTFE, PFA, MFA, PVDF...

For metals, the corrosion allowance (or amount of corrosion allowed before having to replace the concerned piece) is usually less than 5 mm, a corrosion allowance of less than 3 mm being preferable, a corrosion allowance of less than 2 mm being more preferable and a corrosion allowance of less than 1.8 mm being particularly preferred. Corrosion allowance for metals is usually higher than 0.01 mm, preferably higher than 0.03 mm and more preferably higher than 0.05 mm.

For non-metallic protective layers, the thickness of the layer is usually greater than 0.1 mm, preferably greater than 0.3 mm, more preferably greater than 0.5 mm. Usually the thickness of the protective layer is lower than 20 mm, preferably lower than 15 mm and more preferably lower than 10 mm.

The apparatus could be made in a single material or be bimaterial. When the apparatus is bimaterial, generally the support material is not in contact with the reaction medium and provides the mechanical resistance. The support material could be metallic or plastic. Example of support materials are carbon steel, stainless steel, fiber glass reinforced polyester, polyethylene,

polypropylene, PVC... Carbon steel is preferred. The support material providing the mechanical resistance is usually subjected to the corrosivity of the external atmosphere. Preferably the support material also has a protective layer versus the external corrosion. External protective layers could be an extra thickness of the same material, or a paint layer. When the protective layer is an extra thickness it is usually higher than 0.1 mm, preferably higher than 0.3, and more preferably higher than 0.5 mm, while it usually is lower than 5 mm, preferably lower than 3 mm, more preferably lower than 2.5 mm.

The examples hereafter are intended to illustrate the invention without however limiting the scope thereof.

Exemple 1 (according to the invention)

BMIMC1 (1.4 g) was melted during 5 min at 100°C. Then, PdCl ₂ (0.097 g) was added under stirring during 45 min.

A mixture of tetraethoxyorthosilicate (TEOS, 10 mL) and ethanol (7 mL) was heated to 60°C and then BMIMCl-containing-PdCl ₂ -mixture was immediately transferred into the TEOS containing solution.

After the formation of a clear and homogeneous liquid mixture, hydrochloric acid (5M, 5 mL) was added and the mixture gradually coagulated.

After aging at 60°C for 12h, the resultant solid material was dried in vacuum at 150°C for 3h and then grinded to obtain a fine powder.

Hydrochlorination reaction was performed in a glass reactor having a diameter of 10 mm equipped at the bottom with a sintered glass disk to obtain a good dispersion of the gaseous reactants composed of acetylene and hydrochloric acid.

The catalyst particles were arranged as a fixed bed lying on the bottom of the reactor.

The thermal control of the system was obtained by a double wall reactor with a thermal oil regulation to maintain the desired temperature controlled by a thermowell placed in the reactor itself.

Hydrochlorination at 150°C with 1.543 g of catalyst and with a gaseous flow rate of 5 NL/hour for C ₂ H ₂ and 6 NL/hour for HCl led to a C ₂ H ₂ conversion of 24.6 %, and a selectivity above 99.8 %, leading to a productivity (expressed in g VC/g catalyst/h) of 2.036 after 22 hours.

Exemple 2 (according to the invention)

Example 1 was repeated with 2.0 g of BMIMC1 and 0.024 g of PdC12 for the preparation of the catalyst.

Hydrochlorination was performed in the same condition except that the quantity of catalyst which was 2.7 g. The C ₂ H ₂ conversion was 17.10 %, and the selectivity above 99.8 %, leading to a productivity (expressed in g VC/g catalyst/h) of 0.809 after 167 hours.

Example 3 (according to the invention)

BMIMC1 (5.7 g) was melted during 5 min at 100°C. Then, PdCl ₂ (0.39 g) was added under stirring during 45 min.

A mixture of tetraethoxyorthosilicate (TEOS, 40 mL) and ethanol (28 mL) was heated to 60°C and then BMIMCl-containing-PdCl ₂ -mixture was immediately transferred into the TEOS containing solution.

After the formation of a clear and homogeneous liquid mixture, hydrochloric acid (5M, 20 mL) was added and the mixture gradually coagulated.

After aging at 60°C for 12h, the resultant solid material was dried in vacuum at 150°C for 3h and then grinded to obtain a fine powder.

A corrosion experiment was performed as described here after using an amount of fresh catalyst. First, a plate of 1.5+/- 0.2 mm of zirconium was inserted inside a reactor. The catalyst was then added in a way that allowed the coverage of at least 75 % of the total surface of the plate. The reaction was then started under 5 NL/h of C ₂ H ₂ and 6 NL/h of HCl flow rates at 150°C and stopped after 2 hours. The plate was recovered and then sent for analysis. These results where obtained according to ASTM Gl, 1999 version. The measured corrosion was 330 μιη/year.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.