Abstract: The present invention relates to a petroleum resin having the content of a volatile organic compound component of less than 100 wt ppm; and a hydrogenated petroleum resin having the content of a volatile organic compound component of less than 100 wt ppm.

Abstract: The present invention relates to a petroleum resin having the content of a volatile organic compound component of less than 100 wt ppm; and a hydrogenated petroleum resin having the content of a volatile organic compound component of less than 100 wt ppm.

Abstract: System and method for producing 1-butene are disclosed. The method includes dehydrogenating butane to form a mixture comprising butene isomers. 1-butene is separated from the mixture using a system that includes a membrane. The system also includes an isomerizing unit for isomerizing cis-2-butene and trans-2-butene to form additional 1-butene.

Abstract: The present invention relates to a process for oligomerization of C2- to C8-olefins in at least two reaction stages, wherein in the last distillation column the reaction mixture is fractionated such that only very small amounts of the oligomers formed remain in the distillate.

Abstract: Provided are a fouling inhibitor and a method of oligomerizing an olefin using the same. More particularly, in the method of oligomerizing an olefin, it is possible to minimize a total amount of polymers produced during a reaction and basically inhibit fouling of the polymers produced during the reaction onto an inner wall of a reactor by injecting a predetermined fouling inhibitor.

Abstract: The invention relates to a catalyst system for oligomerizing olefins over a catalyst comprising nickel, to the use of this catalyst and to a method for dimerizing olefins.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to a process stream having aromatic compounds. The acetylene stream can be reacted to generate larger hydrocarbon compounds, which are passed to a cyclization and aromatization reactor to generate aromatics. The method according to certain aspects includes controlling the level of carbon oxides in the hydrocarbon stream.

Abstract: Disclosed is a method of recovering 1,3-butadiene from a C4 stream containing butane, isobutane, 2-butene, 1-butene, isobutene, butadiene and acetylene. The process of recovering highly pure 1,3-butadiene includes acetylene conversion for selectively converting acetylene through liquid-phase hydrogenation, so that the acetylene content is decreased to 70 wt ppm or less, and 1,3-butadiene extraction using an extractive distillation column, a pre-separator, a solvent stripping column, a solvent recovery column, and a purification column. Through the acetylene conversion, the concentration of vinylacetylene is decreased to 70 wt ppm or less, after which 1,3-butadiene is recovered using only one extractive distillation column, thereby considerably decreasing the degree of utility and the loss of streams in the course of extraction. The number of units necessary for the process is decreased, thus remarkably reducing the time during which impurities can accumulate in a processing unit.

Abstract: Processes for the production of olefins are disclosed, which may include: contacting a hydrocarbon mixture comprising linear butenes with an isomerization catalyst to form an isomerization product comprising 2-butenes and 1-butenes; contacting the isomerization product with a first metathesis catalyst to form a first metathesis product comprising 2-pentene and propylene, as well as any unreacted C4 olefins, and byproducts ethylene and 3-hexene; and fractionating the first metathesis product to form a C3? fraction and a C5 fraction comprising 2-pentene. The 2-pentene may then be advantageously used to produce high purity 1-butene, 3-hexene, 1-hexene, propylene, or other desired products.

Abstract: An object of the present invention is to provide a method for production of a high purity conjugated diolefin. The method for production of a conjugated diolefin of the present invention comprises steps of supplying a source gas containing a C4 or higher monoolefin and an oxygen-containing gas into a reactor, bringing a catalyst into contact with the gas mixture, compressing a gas containing a conjugated diolefin produced by an oxidative dehydrogenation reaction to obtain a liquefied gas and rinsing the liquefied gas with water.

Abstract: The invention provides a method and apparatus for creating plasma particles and applying the plasma particles to a liquid. Liquid feedstock (e.g., water and/or hydrocarbons mixed with biomass) is pumped through a pipeline; the single-phase stream is then transformed into a biphasic liquid-and-gas stream inside a chamber. The transformation is achieved by transitioning the stream from a high pressure zone to a lower-pressure zone. The pressure drop may occur when the stream further passes through a device for atomizing liquid. Inside the chamber, an electric field is generated with an intensity level that exceeds the threshold of breakdown voltage of the biphasic medium leading to a generation of a plasma state. Furthermore, the invention provides an energy-efficient highly adaptable and versatile method and apparatus for sanitizing water using plasma particles to inactivate biological agents contaminating water.

Abstract: A process for producing a base for a fuel from a C2 ethanol feedstock, by a first stage for oligomerization of the feedstock into a hydrocarbon effluent that contains a mixture of olefins for the most part having between 4 and 30 carbons, and contains a C10-C24 fraction that has a mean linearity that is greater than 60%, in the presence of a homogeneous catalytic system that contains a metal precursor of titanium, zirconium, hafnium, nickel and/or iron, a second stage for oligomerization of a portion of the effluent that is obtained from stage a), into a hydrocarbon effluent that contains a mixture of olefins for the most part having between 4 and 30 carbon atoms, and containing a C10-C24 fraction that has a mean linearity that is less than 50%, in the presence of a homogeneous catalytic system.

Abstract: Hydrodesulphurization of a gasoline cut containing hydrocarbons containing at least 2 carbon atoms per molecule and having an end point of 250° C. or less, by contacting the gasoline cut with at least one catalyst having an active phase of at least one metal from group VIII and at least one metal from group VIB deposited on a support, said catalyst being prepared using a process of: i) contacting support with precursors of group VIII and group VIB metals; ii) contacting support with at least one organic compound formed from at least one cyclic oligosaccharide composed of at least 6?-(1,4)-bonded glucopyranose subunits; iii) drying to obtain at least said metal from group VIII and at least said metal from group VIB in the oxide form; then iv) sulphurization such that said active phase is in the sulphide form; i) and ii) being carried out separately, in any order, or simultaneously.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of acids from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of acids in the hydrocarbon stream by use of adsorbents or basic solutions.

Abstract: A method of producing butadiene includes: (1) dimerizing ethylene to butene followed by (2) oxidatively dehydrogenating the butene to butadiene and (3) recovering the butadiene by (i) absorbing the product with a hydrocarbon absorber oil and (ii) stripping a crude product stream from the absorber oil. The absorber oil is selected so as to be effective to sequester ethylene dimerization-derived impurities from the system.

Abstract: The present invention is a mixture comprising by weight 0.01 to 28% of at least one medium or large pore crystalline silicoaluminate, silicoaluminophosphate materials or silicoaluminate mesoporous molecular sieves (co-catalyst) (A) for respectively 99.99 to 72% of at least a MeAPO molecular sieve. Preferably the proportion of (A) is 1 to 15% for respectively 99 to 85% of MeAPO molecular sieves. MeAPO molecular sieves having CHA (SAPO-34) or AEI (SAPO-18) structure or mixture thereof are the most preferable. Si is the most desirable metal in MeAPO. The present invention also relates to catalysts consisting of the above mixture or comprising the above mixture.

Abstract: Oils from plants and animal fats are hydrolyzed to fatty acids for a Kolbe reaction. The invention relates to a high productivity Kolbe reaction process for electrochemically decarboxylating C4-C28 fatty acids using small amounts of acetic acid to lower anodic passivation voltage and synthesizing C6-C54 hydrocarbons. The C6-C54 undergo olefin metathesis and/or hydroisomerization reaction process to synthesize heavy fuel oil, diesel fuel, kerosene fuel, lubricant base oil, and linear alpha olefin products useful as precursors for polymers, detergents, and other fine chemicals.

Abstract: A process is presented for the purification of 1,3 butadiene. The process is for treating a butadiene stream from an oxidative dehydrogenation unit, where a butane stream is dehydrogenated, generating a butadiene rich stream. The butadiene rich stream is fractionated and passed through a butadiene recovery unit. Additional C4 compounds recovered from the fractionation bottoms stream are further processed for increasing yields of butadiene.

Abstract: The present invention provides a process for preparing ethylene and/or propylene, comprising the steps of contacting a stream comprising C4+ olefins with a zeolite-comprising catalyst at a temperature in the range of from 350 to 1000° C. and retrieving an olefinic product stream comprising: ethylene and/or propylene, and a C4+ hydrocarbon fraction, comprising paraffins, normal olefins and iso-olefins; The C4+ hydrocarbon fraction is recycled while part of the fraction is purged. The part of the C4+ hydrocarbon with is purged is treated to extract C4+ isoolefins as tert-alkyl ethers. At least part of tert-alkyl ethers are converted to further ethylene and propylene.

Abstract: The invention relates to a process for preparing butadiene from n-butenes, which comprises the following steps: A) provision of a feed gas stream a comprising n-butenes; B) introduction of the feed gas stream a comprising n-butenes and an oxygen-comprising gas into at least one dehydrogenation zone and oxidative dehydrogenation of n-butenes to butadiene, giving a product gas stream b comprising butadiene, unreacted n-butenes, water vapor, oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases; C) cooling and compression of the product gas stream b in at least one compression stage, giving at least one condensate stream c1 comprising water and a gas stream c2 comprising butadiene, n-butenes, water vapor, oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases; D) separation of incondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases as gas stream d2 from the gas stream c2 b

Abstract: The present invention provides a process for preparing ethylene and/or propylene, comprising the steps of: a) providing an oxygenate-comprising feedstock; b) contacting the oxygenate-comprising feedstock with a molecular sieve-comprising catalyst at a temperature in the range of from 450 to 700° C. and converting at least part of the oxygenate into an olefinic product comprising ethylene and/or propylene; and c) retrieving the olefinic product, wherein the oxygenate-comprising feedstock comprises in the range of from 1 to 97 wt % of at least one tert-alkyl ether selected from the group MTBE, ETBE, TAME and TAEE, based on the weight of the oxygenates in the oxygenate-comprising feedstock, and further comprises methanol and/or DME.

Abstract: A process for converting feedstock triglycerides to lube basestocks. The process has the steps of (a) metathesizing the feedstock triglycerides with ethylene in the presence of a metathesis catalyst to form alpha olefins and medium-chain triglycerides and (b) hydroisomerizing the medium-chain triglycerides in the presence of a hydroisomerization catalyst and hydrogen to form methyl-branched triglycerides. The alpha olefins may be oligomerized in the presence of an oligomerization catalyst to form poly(alpha olefins).

Abstract: The present invention provides a process for preparing ethylene and/or propylene, comprising the steps of providing a hydrocarbon stream, comprising C4+ normal olefins and C4+ iso-olefins; converting C4+ isoolefins to tert-alkyl ether and separating the ethers from the hydrocarbon stream; isomersing the C4+ normal olefins to iso-olefins and converting C4+ isoolefins to tert-alkyl ether and separating the ethers from the hydrocarbon stream; converting the obtained tert-alkyl ether to ethylene and propylene by contacting the tert-alkyl ether with a molecular sieve-comprising catalyst and retrieving an olefinic product.

Abstract: The present invention provides a method for start-up of an Oxygenate-to-Olefins process, which process comprises the steps: a) providing an oxygenate-comprising feedstock to an Oxygenate-to-Olefins reaction zone and contacting the feedstock with a zeolite-comprising catalyst at a temperature in the range of from 450 to 700° C. ° C., to obtain an reaction product containing olefins; b) separating the reaction product obtained in step a) in at least a product fraction containing ethylene and/or propylene and a product fraction containing C4+ olefins; c) recycling at least part of the C4+ olefins in the product fraction containing C4+ olefins to the Oxygenate-to-Olefins reaction zone in step (a), characterized in that upon start-up the oxygenate-comprising feedstock initially comprises a first amount of externally supplied tert-alkyl ether and subsequently the amount of externally supplied tert-alkyl ether in the oxygenate-comprising feedstock is reduced.

Abstract: The process and apparatus converts ethylene in a dilute ethylene stream that may be derived from an FCC product to heavier hydrocarbons. The catalyst may be an amorphous silica-alumina base with a Group VIII and/or VIB metal. The catalyst is resistant to feed impurities such as hydrogen sulfide, carbon oxides, hydrogen and ammonia. At least 40 wt-% of the ethylene in the dilute ethylene stream can be converted to heavier hydrocarbons.

Abstract: The process and apparatus converts ethylene in a dilute ethylene stream that may be derived from an FCC product to heavier hydrocarbons. The catalyst may be an amorphous silica-alumina base with a Group VIII and/or VIB metal. The catalyst is resistant to feed impurities such as hydrogen sulfide, carbon oxides, hydrogen and ammonia. At least 40 wt-% of the ethylene in the dilute ethylene stream can be converted to heavier hydrocarbons.

Abstract: The present invention provides a process for preparing ethylene and/or propylene and an iso-olefin-depleted olefinic product, comprising the steps of: a) providing a C5 hydrocarbon-comprising stream, comprising C5 cyclopentene and C5 iso-olefins; b) subjecting the C5 hydrocarbon-comprising stream to an etherification process with methanol and/or ethanol wherein at least part of the C5 iso-olefins are converted with methanol and/or ethanol to an tert-alkyl ether, and retrieving an etherification product stream; c) separating at least part of the etherification product stream into at least an ether-enriched stream and a first iso-olefin-depleted olefinic product; d) converting at least part of the tert-alkyl ether in the ether-enriched stream to ethylene and/or propylene by contacting at least part of the ether-enriched stream with a molecular sieve-comprising catalyst at a temperature in the range of from 350 to 1000° C. and retrieving a second olefinic product comprising ethylene and/or propylene.

Abstract: In a process for oligomerizing an olefinic hydrocarbon feedstock comprising at least 65 wt % olefins and/or sulfur-containing molecules, the feedstock is contacted under oligomerization conditions with (a) a first unidimensional 10-ring molecular sieve catalyst and (b) a second multidimensional crystalline molecular sieve catalyst. The first and second catalysts may be contained in separate reactors or as separate beds in a single reactor.

Abstract: The present invention provides a process for preparing ethylene and/or propylene, comprising the steps of contacting a stream comprising C4+ olefins with a zeolite-comprising catalyst to retrieve an olefinic product stream comprising ethylene and/or propylene, and a C4+ hydrocarbon fraction, comprising paraffins, normal olefins and iso-olefins. The C4+ hydrocarbon fraction is subjected to an etherification process with wherein at least part of the iso-olefins are converted with methanol and/or ethanol to an tert-alkyl ether and an etherification product stream is retrieved and separated into an ether-enriched stream and an iso-olefin-depleted C4+ hydrocarbon stream. Part of the iso-olefin-depleted C4+ hydrocarbon stream from the process to purge part of the paraffinic C4+ hydrocarbons while another part of the iso-olefin-depleted C4+ hydrocarbon stream is recycled.

Abstract: The present invention provides a process for preparing ethylene and propylene, comprising the step of: a) contacting a feed comprising methanol, ethanol and C4+ olefins with a catalyst, comprising ZSM-5 having a silica to alumina ratio in the range of from 40 to 100, at a temperature in the range of from 350 to 1000° C. to obtain a olefinic product comprising ethylene and propylene.

Abstract: The present invention provides a process for preparing ethylene and propylene and a butadiene-enriched product, comprising the steps of: a) providing a C4 hydrocarbon stream, comprising iso-olefins and butadiene. b) subjecting the C4 hydrocarbon stream to an etherification process, wherein the iso-olefins are converted with methanol and/or ethanol to an tert-alkyl ether in the presence of a catalyst, wherein the molar ratio of alcohol to iso-olefin is maintained above 1, and retrieving an etherification product stream; c) separating the etherification product stream into an ether-enriched stream and a butadiene-enriched product; d) converting the tert-alkyl ether in the ether-enriched stream to ethylene and/or propylene by contacting least part of the ether-enriched stream with a molecular sieve-comprising catalyst at a temperature in the range of from 350 to 1000° C. and retrieving an olefinic product comprising ethylene and/or propylene.

Abstract: The present invention describes a process for the production of 1,3-butadiene from ethylene by dimerizing ethylene into butenes using homogeneous catalysis and dehydrogenating the butenes obtained.

Abstract: This invention describes a process for the production of 1,3-butadiene from ethylene implementing a stage for oligomerization of ethylene into n-butenes and into oligomers with 6 carbon atoms and more by homogeneous catalysis, a stage for separation in such a way as to obtain an n-butene-enriched fraction, and then a stage for dehydrogenation of said n-butene-enriched fraction.

Abstract: A process for preparing butadiene from n-butane by two-step dehydrogenation and removal of the residual oxygen comprised in the gas stream by means of a catalytic combustion stage which is carried out in the presence of a catalyst which comprises a monolith which comprises a catalytically inert material having a low BET surface area and a catalyst layer which has been applied to the monolith and comprises an oxidic support material, at least one noble metal selected from the group consisting of the noble metals of group VIII of the Periodic Table of the Elements, optionally tin and/or rhenium, and optionally further metals, where the thickness of the catalyst layer is from 5 to 500 ?m, is described.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of solids from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of inorganic and organic solids in the hydrocarbon stream by use of adsorbent beds, filters, cyclone or gravity separators.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of mercury from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of mercury and mercury containing compounds in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of mercury containing compounds from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of organic, ionic or suspended mercury compounds by first converting these compounds to elemental mercury or to inorganic mercury compounds and then removing them by use of an adsorbent bed.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of glycols from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of glycols and in particular, dimethyl ethers of polyethylene glycol in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of hydrides of arsenic, phosphorus, antimony, silicon, and boron from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of hydrides of arsenic, phosphorus, antimony, silicon, and boron in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of carbon dioxide from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of oxygen in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of acids from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of acids in the hydrocarbon stream by use of adsorbents or basic solutions.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of sulfur containing compounds from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of sulfur containing compounds in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of water, carbon dioxide and other condensable contaminants in the hydrocarbon stream by use of a fluid separation assembly such as a supersonic inertia separator. In addition, one or more adsorbent beds may be used to remove remaining trace amounts of condensable contaminants. The fluid separation assembly has a cyclonic fluid separator with a tubular throat portion arranged between a converging fluid inlet section and a diverging fluid outlet section and a swirl creating device.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of water from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of water in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of carbon monoxide from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of carbon monoxide in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of heavy metals from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of heavy metals in the hydrocarbon stream.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of heavy hydrocarbon compounds including C2+ hydrocarbons from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level heavy hydrocarbons in the hydrocarbon stream by use of adsorbents, physical separators or cryogenic separation.

Abstract: Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of carbon dioxide from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of carbon dioxide in the hydrocarbon stream by contacting a stream with a physical or a chemical solvent.

Abstract: A reverse flow regenerative reactor having first and second zones, each having first and second ends, the first zone having a plurality of channels capable of separately conveying at least two components of a combustible gas mixture, a gas distributor configured for injecting the components of the combustible gas mixture into first zone, a combustion zone including a selective combustion catalyst disposed at or downstream of the second end of said channels for catalyzing combustion, wherein the second zone is positioned and situated to receive a combusted gas mixture. Processes usefully conducted in the reactor are also disclosed.

Abstract: A catalyst is described which comprises at least one IZM-2 zeolite, at least one matrix and at least one metal selected from metals from groups VIII, VIB and VIIB, said zeolite having a chemical composition expressed as the anhydrous base in terms of moles of oxides by the following general formula: XO2:aY2O3:bM2/nO, in which X represents at least one tetravalent element, Y represents at least one trivalent element and M is at least one alkali metal and/or alkaline-earth metal with valency n, a and b respectively representing the number of moles of Y2O3 and M2/nO; and a is in the range 0.001 to 0.5 and b is in the range 0 to 1.