Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C21/00—Acyclic unsaturated compounds containing halogen atoms
  • C07C21/02—Acyclic unsaturated compounds containing halogen atoms containing carbon-to-carbon double bonds
  • C07C21/04—Chloro-alkenes
  • C07C21/06—Vinyl chloride
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J38/00—Regeneration or reactivation of catalysts, in general
  • B01J38/02—Heat treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • B01J21/08—Silica
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/90—Regeneration or reactivation
  • B01J23/96—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J38/00—Regeneration or reactivation of catalysts, in general
  • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
  • B01J38/12—Treating with free oxygen-containing gas
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/01—Chlorine; Hydrogen chloride
  • C01B7/03—Preparation from chlorides
  • C01B7/035—Preparation of hydrogen chloride from chlorides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/01—Chlorine; Hydrogen chloride
  • C01B7/07—Purification ; Separation
  • C01B7/0706—Purification ; Separation of hydrogen chloride
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/013—Preparation of halogenated hydrocarbons by addition of halogens
  • C07C17/02—Preparation of halogenated hydrocarbons by addition of halogens to unsaturated hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
  • C07C17/15—Preparation of halogenated hydrocarbons by replacement by halogens with oxygen as auxiliary reagent, e.g. oxychlorination
  • C07C17/152—Preparation of halogenated hydrocarbons by replacement by halogens with oxygen as auxiliary reagent, e.g. oxychlorination of hydrocarbons
  • C07C17/156—Preparation of halogenated hydrocarbons by replacement by halogens with oxygen as auxiliary reagent, e.g. oxychlorination of hydrocarbons of unsaturated hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/25—Preparation of halogenated hydrocarbons by splitting-off hydrogen halides from halogenated hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/44—Palladium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/61—Surface area
  • B01J35/612—Surface area less than 10 m2/g
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/584—Recycling of catalysts

Definitions

• the present invention relates to a process for regenerating a specific hydrogenation catalyst and to an industrial process using such a regenerated catalyst.
• Numerous industrial processes employ a catalytic hydrogenation step.
• Catalysts highly suitable for this purpose are those comprising a metal from group VIII of the Periodic Table, selected from the elements Ru, Rh, Pd, Os, Ir and Pt, on an inert support (silica, alumina, etc.).
• VCM vinyl chloride monomer
• DCEa 1,2-dichloroethane
• a small amount of acetylene (C 2 H 2 ) of the order of approximately 2000 ppm (by volume relative to the volume of HC1), is co -produced, but cannot easily be separated from the HC1, owing to their very similar volatilities.
• the pyrolysis HC1 is then recycled to the oxychlorination, in the course of which the C H 2 reacts to give various worthless by-products, which are detrimental to the profitability of the process.
• One known method, an elegant one, for removing this C 2 H 2 consists in converting it into ethylene (C 2 H 4 ) by hydrogenation, using an appropriate catalyst.
• One such catalyst is described in patent application DE 24 38 153, which illustrates in particular a catalyst based on Pd supported on non-porous silica.
• this catalyst undergoes gradual deactivation and, although the abovementioned application records the possibility in theory of regenerating it, in practice such regeneration has proved to be fruitless, owing in particular to the contamination of this catalyst with heavy metals (H. MuUer et al., Chem.-Ing.-Tech. 59 (1987) No. 8, pp. 645-7).
• the applicant has surprisingly found that if such a contaminated catalyst is treated in the presence of oxygen, at a temperature sufficient to remove the contaminations but not too high, so as not to impair the catalyst, the said catalyst can nevertheless be regenerated satisfactorily.
• the present invention accordingly provides a process for regenerating a hydrogenation catalyst comprising at least one catalytic metal selected from the group consisting of Ru, Rh, Pd, Os, Ir and Pt on an inert support, the said regeneration process consisting essentially of a thennal treatment in the presence of oxygen at a temperature between 300 and 700°C.
• a catalytic metal selected from the group consisting of Ru, Rh, Pd, Os, Ir and Pt on an inert support
• Pt and Pd preference is given to Pt and Pd.
• Pd is particularly preferred on account of its high hydrogen adsorption capacity.
• the concentration of the catalytic metal in the catalyst is generally greater than or equal to 0.01% by weight (relative to the total weight of the catalyst), preferably greater than or equal to 0.05%, or even greater than or equal to 0.1%.
• the inert support of the catalyst which is regenerable by the process according to the present invention is preferably selected from porous and non- porous silica, alumina and silica-alumina. Supports based primarily on silica (in other words composed of more than 50%, preferably of more than 95%, of SiO ) give good results.
• the support is preferably non-porous or of low porosity, in other words having a specific surface area (measured in accordance with the
• the BET method with nitrogen of less than 5 m 2 /g, and preferably less than 3 m 2 /g, or even less than 1 m 2 /g.
• the average pore volume of this support is advantageously less than 0.01 ml/g.
• Its particle size is advantageously between 1 and 20 mm, or even between 2 and 10 mm, and preferably between 3 and 7 mm.
• the catalytic metal is generally present in a layer of less than or equal to a micron. It is generally in the form of crystallites having a size of between 0.1 and 0.5 ⁇ m.
• the non-porous silica as described in the aforementioned references (DE 24 38 153 and the article by M ⁇ ller) gives good results.
• the process according to the invention “essentially consists of a thermal treatment” is meant that the major part of the regeneration of the catalyst (in other words at least 50% of the gain in selectivity and/or in degree of conversion) is realized by the thermal treatment.
• at least 75% of the regeneration is the outcome of the thermal treatment, or even at least 90%, and with particular preference the entirety of the regeneration is the outcome thereof, implying that according to this version of the invention the process takes place in the absence of any regenerative treatment (with steam or H 2 , for example) preceding or following the said thermal treatment, and therefore that the catalyst obtained from the thermal treatment is reused as it is in a hydrogenation reaction.
• the thermal treatment in question consists in a residence at a high temperature (of between 300 and 700°C) in the presence of oxygen.
• the temperature during the thermal treatment is preferably greater than or equal to 400°C, or even greater than or equal to 500°C, in order to increase the efficiency of the regeneration.
• the thermal treatment may take place in the presence of pure oxygen.
• the oxygen is diluted, with an inert gas for example. Accordingly air gives good results.
• the treatment in question therefore in fact typically involves what is generally referred to as an oxidizing atmosphere, which may be either static or moving (which is to say that a gaseous stream containing oxygen is passed over the catalyst to be regenerated).
• a moving oxidizing atmosphere gives good results.
• Another way which gives good results consists in passing the oxidizing atmosphere through the bed of catalyst, in situ for example, in the hydrogenation reactor.
• Better results are generally obtained when the catalyst is dispersed during the treatment: that is, when it presents a maximum surface area to the oxidizing atmosphere.
• the catalyst will advantageously be spread in a layer, ranging from a monolayer of catalyst (whose thickness depends on the particle size of the catalyst) to a layer of approximately 20 cm, although, preferably, the thickness of this layer does not exceed 10 cm, or even 5 cm.
• the duration of the said treatment is readily determined by the skilled person and will be adapted to the desired degree of regeneration. It is generally greater than or equal to 1 h, or even to 5 h. This duration is, however, generally less than or equal to 48 h, or even to 24 h.
• the catalyst that it is intended should be regenerated by the process according to the invention is a "spent" catalyst, (i.e.
• a catalyst which has served in a hydrogenation reaction subsequent to which its catalytic activity (in terms of selectivity and/or degree of conversion) has dropped.
• Such a drop in catalytic activity is generally ascribed to the deposition of carbonaceous substances and/or to contamination with chlorine compounds and/or traces of at least one heavy metal.
• the te ⁇ n "heavy metal" is intended to denote one of the following metals: Al, As, Cd, Cr, Ni, Cu, Sn, Fe, Mn, Hg, Pb, Zn and Ti (although the latter is not generally considered to be a heavy metal, it nevertheless constitutes a disruptive contamination for hydrogenation catalysts and, as such, is considered to be a heavy metal in the context of the present invention).
• traces of heavy metals are particularly disruptive and, among them, Fe and Ti in particular, since they are commonly present in industrial fluids, owing to the nature of the equipment used to convey/treat them.
• traces of Hg which may be encountered in certain sources of H 2 , are also disruptive.
• traces are meant amounts of the order of ppm, or even tens of ppm. It is not uncommon for the starting catalyst already to include traces of certain heavy metals (Fe in particular, but generally less than 50 ppm), but in the course of use an increase in the amount thereof (for example to an amount greater than or equal to 50 ppm in the case of Fe) generally contributes to a drop in the catalytic activity.
• the hydrogenation reaction in which the catalyst has been used is preferably an acetylene hydrogenation reaction. It applies preferably to traces of acetylene (C 2 H 2 ) which are present in a fluid and, preferably, in a gas mixture consisting essentially of HC1 and obtained from the pyrolysis of DCEa, as described above. Such a mixture generally contains between 1500 and 2500 ppm of acetylene. It often also contains of the order of tens to hundreds of ppm of chlorinated organic products such as VCM and methyl or ethyl chloride, and/or non-chlorinated organic products such as ethylene ( H 4 ), methane and butadiene.
• catalysts based on Pd on a non-porous silica support give good results and are readily regenerable by the process according to the invention.
• the catalyst regenerated by the process according to the invention may be used in any hydrogenation reaction for which it has a catalytic activity. Preferably it is reused in a process similar to that in which it was used beforehand.
• the present invention likewise provides a process for synthesizing VCM by coupling of a direct chlorination and an oxychlorination of ethylene to form DCEa, which is primarily converted into VCM and into HCl by pyrolysis, the said HCl containing traces of acetylene and being recycled to the oxychlorination following hydrogenation of these traces of acetylene in the presence of a catalyst regenerated by a process as described above.
• Catalyst E39H (beads of silica 3 to 5 mm in diameter with 0.15% of Pd supported at the surface and with a specific surface area of less than 1 m 2 /g), sold by Degussa and as described in the aforementioned article by MuUer, was used for four and a half years (54 months) in contact with HCl containing approximately 2000 ppm of C 2 H 2 under 10 bars and at a temperature of between 120 and 180°C.
• the residence time (ratio between the number of m 3 (s.t.p.) of HCl/h and the volume of the catalyst bed in m 3 ) was 1680 h "1 .
• the quantity of H 2 employed was 3.8 mol per mole of C 2 H 2 .
• the thus-spent catalyst was analyzed and compared with the virgin catalyst. The results of these analyses are given in the table below:

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