Abstract: A catalyst and process for hydrotreating and/or hydroconverting heavy metal-containing hydrocarbon feeds, said catalyst comprising a support in the form of beads based on alumina, at least one catalytic metal or a compound of a catalytic metal from group VIB (column 6 in the new periodic table notation), optionally at least one catalytic metal or compound of a catalytic metal from group VIII (columns 8, 9 and 10 of the new periodic table notation), with a pore structure composed of a plurality of juxtaposed agglomerates, each formed by a plurality of acicular platelets, the platelets of each agglomerate being generally radially orientated with respect to each other and with respect to the center of the agglomerate. The catalyst also comprises at least one doping element selected from the group constituted by phosphorus, boron, silicon (or silica which does not belong to that which could be contained in the selected support) and halogens.

Abstract: A spherical activated carbon is produced from a starting pitch obtainable from a heavy hydrocarbon oil, such as petroleum tar, coal tar or ethylene, through a moderate process. The starting pitch has a softening point of at least 150° C., a toluene-insoluble content of at least 40% and a property of retaining optical isotropy even after being heated at 430° C. for 1 hour. The starting pitch is converted into a porous spherical pitch, which is then infusibilized, carbonized and activated to provide a spherical activated carbon.

Abstract: A porous wall hollow glass microsphere is provided having a diameter range of between 1 to 200 microns, a density of between 1.0 to 2.0 gm/cc, a porous-wall structure having wall openings defining an average pore size of between 10 to 1000 angstroms, and which contains therein a hydrogen storage material. The porous-wall structure facilitates the introduction of a hydrogen storage material into the interior of the porous wall hollow glass microsphere. In this manner, the resulting hollow glass microsphere can provide a membrane for the selective transport of hydrogen through the porous walls of the microsphere, the small pore size preventing gaseous or liquid contaminants from entering the interior of the hollow glass microsphere.

Abstract: A precursor to a catalytic structure comprising zinc oxide and copper oxide. The zinc oxide has a sheet-like morphology or a spherical morphology and the copper oxide comprises particles of copper oxide. The copper oxide is reduced to copper, producing the catalytic structure. The catalytic structure is fabricated by a hydrothermal process. A reaction mixture comprising a zinc salt, a copper salt, a hydroxyl ion source, and a structure-directing agent is formed. The reaction mixture is heated under confined volume conditions to produce the precursor. The copper oxide in the precursor is reduced to copper. A method of hydrogenating a carbon oxide using the catalytic structure is also disclosed, as is a system that includes the catalytic structure.

Abstract: The invention relates to spherical active carbon having the following pore size distribution: a) 1.2 1.7 nm: 20-50%, b) 1.7 2.1 nm: 20-50%, c) 2.1 2.5 nm: 10-25%, d) 2.5 2.9 nm: 3-15%, e) 2.9 3.3 nm: 1-10%. The sum of a) to e) is at least 88%. The difference between the sum of a) to e) in relation to 100% corresponds to a proportion of pores having a diameter of <1,2 nm and/or >3,3 nm. The fractal dimension of the open porosity is at least 2.30.

Abstract: A process for producing inorganic spheres, which comprises injecting an aqueous liquid containing an inorganic compound into a laminar flow of an organic liquid which runs at a flow rate of from 0.001 to 2 m/s in a flow path compartmentalized by a partition wall through a plurality of inlet holes formed in one partition wall to form a W/O type emulsion containing the organic liquid as a dispersion medium and the aqueous liquid containing the inorganic compound as a dispersed phase, and solidifying the aqueous liquid containing an inorganic compound in the W/O type emulsion, wherein the partition wall having a plurality of inlet holes is made of a metal sheet having a surface subjected to water repellent treatment.

Abstract: A process for introducing annular coated catalysts K into a reaction tube of a tube bundle reactor, in which adhering pairs of annular coated catalysts K formed in the preparation of the annular coated catalysts K, before the introduction thereof into the reaction tube, are removed at least partly from the annular coated catalysts K.

Abstract: A process for preparing beads of various compositions has been developed. The process involves preparing a reaction mixture of sources of framework elements of a molecular sieve. The reaction mixture can optionally contain molecular sieve seeds. Additional sources of the framework elements are added to give a concentration above the critical supersaturation limit thereby forming beads. Depending on the composition of the reaction mixture and the reaction conditions one can obtain beads which are substantially amorphous, to beads that are substantially crystalline molecular sieve. These beads in turn can be further processed to deposit a molecular sieve layer onto the beads.

Abstract: A process for preparing shaped catalyst bodies whose active composition is a multielement oxide, in which a finely divided precursor mixture with addition of graphite having a specific particle size is shaped to the desired geometry and then treated thermally.

Abstract: A precursor to a catalytic structure comprising zinc oxide and copper oxide. The zinc oxide has a sheet-like morphology or a spherical morphology and the copper oxide comprises particles of copper oxide. The copper oxide is reduced to copper, producing the catalytic structure. The catalytic structure is fabricated by a hydrothermal process. A reaction mixture comprising a zinc salt, a copper salt, a hydroxyl ion source, and a structure-directing agent is formed. The reaction mixture is heated under confined volume conditions to produce the precursor. The copper oxide in the precursor is reduced to copper. A method of hydrogenating a carbon oxide using the catalytic structure is also disclosed, as is a system that includes the catalytic structure.

Abstract: Novel catalyst beds comprising a physical mixture of catalytically active and catalytically inactive shaped bodies, in which the catalytically inactive shaped bodies have rounded edges on the external rubbing surfaces.

Abstract: A method of preparing spherical pellets from a slurry comprising a ceramic powder, a solvent, and any desired additives, by means of a drop-generating orifice to which said slurry is fed is described, wherein the drops are released from said orifice by means of a relative flow of a liquid medium which is a poor solvent for the solvent of the slurry, formed into spherical bodies in said liquid medium by means of the action of surface tension, and thereafter treated for consolidation. More specifically, the present invention relates to the preparation of pellets of a catalyst or catalyst support material, suitable for use in high temperature conditions.

Abstract: The present invention relates to a process for the preparation of catalyst particles with a particle diameter in the range 20–2000 microns involving the steps of agitating at least two dry catalyst ingredients, spraying a liquid binding agent on the catalyst ingredients while continuing the agitation, and isolating formed catalyst particles with the desired particle diameter and comprising the catalyst ingredients. In contrast to the conventional way of preparing such particles, spray-drying, the present process allows the formation of small particles from slurries with a high solids content. Hence, smaller amounts of liquid have to be evaporated, which makes the process energy efficient.

Abstract: A method for manufacturing of an attrition resistant vanadium/phosphorous oxide catalyst involving forming an aqueous slurry comprising; vanadium/phosphorous oxide catalyst or vanadium/phosphorous oxide catalyst precursor particles, an aqueous solution of H3PO4, and optionally an aqueous colloidal silica sol, an aqueous polysilicic acid solution or mixture thereof and then spray drying the slurry to form attrition resistant catalyst precursor followed by calcining/activating the spray dried precursor. Such a catalyst is particularly useful in oxidation processes such as the catalytic air oxidation of butane to maleic anhydride.

Abstract: A process for producing inorganic spheres, which comprises injecting an aqueous liquid containing an inorganic compound through an inlet hole into an organic liquid which flows at a flow rate of from 0.001 to 2 m/s in a laminar flow state in a flow path to form a W/O type emulsion, and solidifying the aqueous liquid containing an inorganic compound in the W/O type emulsion.

Abstract: A process for producing inorganic spheres, which comprises injecting an aqueous liquid containing an inorganic compound into a laminar flow of an organic liquid which runs at a flow rate of from 0.001 to 2 m/s in a flow path compartmentalized by a partition wall through a plurality of inlet holes formed in one partition wall to form a W/O type emulsion containing the organic liquid as a dispersion medium and the aqueous liquid containing the inorganic compound as a dispersed phase, and solidifying the aqueous liquid containing an inorganic compound in the W/O type emulsion, wherein the partition wall having a plurality of inlet holes is made of a metal sheet having a surface subjected to water repellent treatment.

Abstract: Metal catalysts comprising hollow forms or spheres are made of metal alloy and optionally activated. The metal catalysts can be used for the hydrogenation, dehydrogenation, isomerization reductive alkylation, reductive amination, and/or hydration reaction of organic compounds.

Abstract: Metal catalysts comprising hollow forms or spheres are made of metal alloy and optionally activated. The metal catalysts can be used for the hydrogenation, dehydrogenation, isomerization reductive alkylation, reductive amination, and/or hydration reaction of organic compounds.

Abstract: Metal catalysts comprising hollow forms or spheres are made of metal alloy and optionally activated. The metal catalysts can be used for the hydrogenation, dehydrogenation, isomerization reductive alkylation, reductive amination, and/or hydration reaction of organic compounds.

Abstract: The present invention provides a process for producing spherical catalyst carrier of silica, silica-alumina composition, zirconia-alumina composition, titania-alumina composition, boria-alumina composition, or boria-silica-alumina composition which has almost the same pore characteristics as alumina hydrate gel, silica-alumina hydrate gel, zirconia-alumina hydrate gel, or titania-alumina hydrate gel (or alumina hydrate paste, boria-alumina hydrate paste, or boria-silica-alumina hydrate paste) as the major raw material, has uniform sphericity and smooth surface and homogeneity, and has a macropore volume that can be controlled.

Abstract: A method for producing small spherical particles that are especially useful as catalysts and catalyst supports employed in chemical processes is disclosed. According to some embodiments, the method includes impregnating a porous support with a metal or metal oxide and dissolving the support to release spherical particles. In certain embodiments the support that is employed in the method comprises a number of spherical voids which determine the size of the spherical particles, and preferably have micrometer range diameters. One embodiment of an attrition resistant Fischer-Tropsch catalyst comprises a plurality of micrometer size spherical metal and/or metal oxide particles that are prepared according to the above-described method.

Abstract: The present invention relates to spherical solid catalyst components for the polymerization of olefins, comprising a titanium compound, supported on a magnesium halide, containing more than one Ti-halogen link and optionally containing groups different from halogen in an amount lower than 0.5 mole per mole of Ti. Spherical solid compounds of the invention are characterized by having a surface area, measured by the BET method, of lower than 70 m2/g, a total porosity, measured by the mercurium method, higher than 0.5 cm3/g and a pore radius such that at least 50% have values higher than 800 Å.

Abstract: A process for removing hydrogen sulfide from a fluid stream by contacting a hydrogen sulfide-containing stream with a sorbent composition wherein said sorbent composition is produced by mixing at least one zinc component which is zinc oxide or a compound convertible to zinc oxide, at least one silica component where the silica component comprises silica or a compound convertible to silica, at least one colloidal metal oxide, and optionally at least one pore generator component so as to form a mixture, extruding the mixture, sphering the resulting extrudate to form spherical particles having a size of form about 0.5 to about 15 millimeters drying the resulting spherical particles, calcining the dried particles, steaming the resulting calcined particles, sulfiding the steamed particles by contacting them with sulfides or sulfur at a temperature of about 200° C. to 1400° C.

Abstract: The present invention provides a process for producing spherical catalyst carrier of silica, silica-alumina composition, zirconia-alumina composition, titania-alumina composition, boria-alumina composition, or boria-silica-alumina composition which has almost the same pore characteristics as alumina hydrate gel, silica-alumina hydrate gel, zirconia-alumina hydrate gel, or titania-alumina hydrate gel (or alumina hydrate paste, boria-alumina hydrate paste, or boria-silica-alumina hydrate paste) as the major raw material, has uniform sphericity and smooth surface and homogeneity, and has a macropore volume that can be controlled.

Abstract: The present invention relates to spherical solid catalyst components for the polymerization of olefins, comprising a titanium compound, supported on a magnesium halide, containing more than one Ti-halogen link and optionally containing groups different from halogen in an amount lower than 0.5 mole per mole of Ti.

Abstract: A solid catalyst component for olefin polymerization superior in shatter resistance and narrowness of particle size distribution, is provided, which component is prepared by spraying a mixture of Mg compound with an alcohol in a molten state, in a column; cooling the inside of the column; to obtain a component (B); partly removing the alcohol from (B), to obtain a solid component (C); contacting a halogen-containing Ti compound and an electron donor with (C); to obtain (D); contacting (D) with a halogen-containing Ti compound; in the above process, specifying the composition formulas of (A), (B) and (C); specifying the X-ray diffraction spector of (C) in comparison of that of (B); and contacting (C) with a halogen-containing Ti compound and an electron donor using an aliphatic hydrocarbon of a specified b.p., in a specified temperature.

Abstract: Vanadium oxide nanoparticles were produced with vanadium in a variety of oxidation states and with different crystalline lattice structures. These particles preferably have an average diameter of 150 nm or less with a narrow distribution of diameters. The particles manifest unique properties that result from the small particle size and correspondingly large surface area. A variety of the vanadium oxide nanoparticles can be produced by a versatile laser pyrolysis arrangement. These nanoparticles can be further processed to change the properties of the particles without destroying the nanoscale size of the particles.

Abstract: A method for manufacturing of an improved attrition resistant catalyst having an oxide-rich surface layer involving forming a slurry comprising; catalyst, catalyst precursor or catalyst support particles (e.g., transition metal oxides), a colloidal oxide sol (e.g., colloidal silica), and a solution of a solvent and solute wherein the solute consist essentially of a precursor of said oxide-rich surface with particle size no greater than 5 nm (e.g., aqueous silicic acid or polysilicic acid) and then spray drying the slurry to form porous microspheres of attrition resistant catalyst; and, calcining the spray dried microspheres. Such a catalyst is particularly useful in oxidation processes wherein the oxidation is performed by an oxidized form of the catalyst and the resulting reduced form of the catalyst is separately regenerated (e.g., two-step vapor phase processes carried out in recirculating solids reactors, transport bed reactors or circulating fluidized bed reactors and the like).

Abstract: The invention is directed to an unsintered spherical adsorbent particle composition having high mechanical strength and controlled pore size distribution, comprising finely divided silica hydrogel particles bonded together with a silica or metal oxide sol.

Abstract: A solid catalyst component for olefin polymerization superior in shatter resistance and narrowness of particle size distribution, is provided,which component is prepared byspraying a mixture of Mg compound with an alcohol in a molten state, in a column; cooling the inside of the column; to obtain a component (B); partly removing the alcohol from (B), to obtain a solid component (C); contacting a halogen-containing Ti compound and an electron donor with (C); to obtain (D); contacting (D) with a halogen-containing Ti compound;in the above process,specifying the composition formulas of (A), (B) and (C); specifying the X-ray diffraction spector of (C) in comparison of that of (B); and contacting (C) with a halogen-containing Ti compound and an electron donor using an aliphatic hydrocarbon of a specified b.p., in a specified temperature.

Abstract: The invention is directed to an unsintered spherical adsorbent particle composition having high mechanical strength and controlled pore size distribution, comprising finely divided silica hydrogel particles bonded together with a silica or metal oxide sol.

Abstract: The present invention relates to silica/zeolite composite materials in spherical form and the process for their preparation which occurs by the dispersion of submicronic particles of titanium silicalite, beta zeolite, or mixtures of beta zeolite with titanium silicalite, in a silica sol synthesized by acid hydrolysis of silicon alkoxides; the hybrid sol thus obtained, subjected to emulsification and gelation techniques in organic mediums, produces these materials in a spherical form with an average diameter of between 20 and 150 .mu.m and containing up to 70% by weight of titanium silicalite, beta zeolite or mixtures of titanium silicalite/beta zeolite.The materials of the invention, having a high mechanical resistance and characterized by a surface area of between 300 and 800 m.sup.2 /g, are applied as catalysts; in particular, those consisting of titanium silicalite or mixtures of titanium silicalite/beta zeolite are advantageously used in oxidation reactions of organic compounds with hydrogen peroxide.

Abstract: Catalysts and catalyst carriers, in the form of granules having a definite geometric form, characterized by porosity values such that at least 70% of the volume of the pores have a radius corresponding to the peak values of the porosity distribution curve. The catalysts and catalyst carriers are obtained by compression shaping, wherein the lubricant employed is applied to the molding of the chamber (external lubrication).

Abstract: Catalyst particles are prepared by coating a core particle, which is usually catalytically inert with respect to the intended chemical reaction, in a fluidized bed coating apparatus. The coating technique involves repeatedly applying and drying small quantities of an atomized slurry containing the coating material in the form of a colloidal dispersion or in the form of very fine, non-colloidal particles preferably mixed with colloidal particles. In this way, incremental layers are formed to produce a final thin shell which has a highly uniform thickness, which is formed on the surface of the core and which does not penetrate porous cores. Various methods are disclosed for converting the coated particles to the desired catalyst form.

Abstract: An improvement is proposed in the so-called urea method for the preparation of fine particles of yttrium oxide, according to which, while an aqueous reaction mixture containing a water-soluble yttrium salt, e.g., nitrate, and urea dissolved therein in specified concentrations is heated at 90.degree. to 100.degree. C. to effect precipitation of yttrium carbonate hydroxide particles followed by calcination of the carbonate hydroxide in air into yttrium oxide, the aqueous reaction mixture is diluted with addition of a specified volume of preheated water within a critical period between incipient appearance of turbidity in the reaction mixture by the precipitation of the carbonate hydroxide and a moment 30 minutes thereafter. In this way, the yttrium oxide particles obtained have a globular particle configuration with a very small average particle diameter D.sub.50 in the range from 0.1 to 0.3 .mu.m and are suitable for use in various fine applications.

Abstract: The present invention are methods for preparing hydrous titanium oxide spherules, hydrous titanium oxide gels such as gel slabs, films, capillary and electrophoresis gels, titanium monohydrogen phosphate spherules, hydrous titanium oxide spherules having suspendible particles homogeneously embedded within to form a composite sorbent, titanium monohydrogen phosphate spherules having suspendible particles of at least one different sorbent homogeneously embedded within to form a composite sorbent having a desired crystallinity, titanium oxide spherules in the form of anatase, brookite or rutile, titanium oxide spherules having suspendible particles homogeneously embedded within to form a composite, hydrous titanium oxide fiber materials, titanium oxide fiber materials, hydrous titanium oxide fiber materials having suspendible particles homogeneously embedded within to form a composite, titanium oxide fiber materials having suspendible particles homogeneously embedded within to form a composite and spherules of b

Abstract: Process for preparing a poly-1-olefinBy means of a highly active spherical Ziegler catalyst based on a dialkylmagnesium, spherical polymers can be obtained in the polymerization of alpha-olefins. A further advantage of the catalyst of the invention lies in the high catalyst activity, so that only very small amounts of the catalyst are required for the polymerization. The residual titanium and/or zirconium content in the polymers prepared according to the invention is less than 10 ppm. Owing to its good responsiveness to hydrogen, the catalyst is particularly suited to two-stage processes for preparing polymers having a broad bimodal molecular weight distribution. The replacement of sulfur-containing electron donors such as diethyl sulfite by alcohols such as ethanol leads to less odor problems and broadened opportunities for use of the polymer.

Abstract: This invention relates to a process for obtaining pure or mixed oxide zirconia spheres, microspheres or washcoats consisting of:preparing a zirconium solution in water at a concentration, formally expressed as ZrO.sub.2, equal or lower than 400 g/l, starting from a basic zirconium carbonate additioned of conc. nitric acid up to a molar ratio ?NO.sub.3.sup.- !/?Zr.sup.4+ ! between 0.8 and 1.1, and eventually preparing one or more solutions of the other oxides when necessary;preparing a sol of zirconium, eventually mixed to other metals, by a thickening agent and, in the case of spheres and microspheres, of a surface active agent too;dripping the sol into an alkaline gelation bath for obtaining gel spheres or microspheres, or sucking the sol into the honeycomb channels in order to obtain the washcoats, with subsequent gelation with gaseous ammonia;ageing the so obtained gel;rinsing with water down to pH=9-10, only in the case of gel spheres or microspheres;drying and calcining.

Abstract: The present invention relates to a process for the preparation of mixed porous oxides with a spherical morphology and the oxides themselves thus obtained.This process consists in emulsifying, in an acid environment, a mixed sol with a dispersing medium, gelifying the microemulsion thus formed by contact with an alkaline solution and subjecting the gel obtained to thermal aging in the presence of the emulsifying liquid and gelation base of the sol or in a water medium, under controlled conditions of pH and temperature.The above mixed oxides can be widely applied as carriers for catalysts or as precursors of ceramic materials.

Abstract: Magnesium chloride, titanium chloride and at least an electron donor are introduced in a plasma torch. These chlorides being in solution or in suspension in a liquid that can be an electron donor. A very fine granulometry powder is collected after cooling. The powder is very fine, it has a controlled morphology and it can be used as catalyst for alpha-olefins polymerization.

Abstract: The present invention is directed to a supported metallocene catalyst useful in the polymerization of .alpha.-olefins which is obtained by tethering a metallocene catalyst component to the surface of a particulate, functionalized copolymeric support material.

Abstract: The invention relates to mass catalysts based on chromium and nickel oxides, obtained from a sol of chromium and nickel hydroxides.These catalysts, in which the Ni/Cr atomic ratio is between 0.05 and 5, may be used from the fluorination of halogenated hydrocarbons by HF in the gas phase.

Abstract: The description relates to an abrasion-resistant carrier catalyst for removing the nitrite and/or nitrate content of polluted water with selective nitrogen formation. The catalytically active metal component is palladium and/or rhodium or palladium and a metal from the copper group. The carrier consists of aluminum oxide in the "theta" and "kappa" modification and has either one maximum pore diameter in the 70 to 150 nm (700 to 1500 .ANG.) range or two maxima in the 10 to 150 nm (100 to 1500 .ANG.) range. The description also relates to a continuously operable process for the removal or reduction of the oxygen, nitrite and/or nitrate content of water by catalytic hydrogenation. The process is implemented using the novel carrier catalysts, the carriers being made of aluminum oxide of the theta and kappa modifications. Contamination of the catalyst is effectively prevented by the preferred use according to the fluidized bed process.

Abstract: A process to make a small, discrete, spherical magnesium dihalide alcohol adduct is provided. This process comprises: contacting a magnesium dihalide and an alcohol in a high-viscosity liquid that consists of hydrocarbons, to obtain a dispersion; heating and agitating the dispersion to obtain a molten dipersion; cooling the molten dispersion to form said small, discrete, spherical magnesium dihalide alcohol adduct.

Abstract: A process for preparing fracture-resistant sol/gel particles which contain silicon dioxide, in which a highly disperse filler is added to the aqueous alkali metal silicate solution and/or the aqueous acid solution used in the preparation process.

Abstract: A process for producing a spherical zeolite catalyst is disclosed, which comprises dropping a zeolite-containing alumina sol into a surfactant-containing oil phase from a dropping opening directly or through air to thereby form spherical droplets of the sol, and then allowing the droplets to gel in an aqueous alkaline solution phase underlying the oil phase and withdrawing the thus gelled droplets, said dropping of the sol being conducted while the dropping opening is being impulsed to thereby impart a spherical and uniform shape to the resulting zeolite particles containing alumina as a binder, and a novel apparatus therefor.

Abstract: Disclosed are amorphous silica or silica-alumina spherical particles composed of X-ray diffractometrically substantially amorphous silica or silica-alumina, wherein individual particles have a definite spherical shape and a notched surface, the circularity (A) represented by the following formula: ##EQU1## wherein r1 stands for the radius of the circumcircle of the profile of the particle in an electron microscope photo thereof and r2 stands for the radius of the inscribed circle of the profile of the particle in the electron microscope photo, is in the range of from 0.90 to 1, the notching degree (B) represented by the formula: ##EQU2## wherein .DELTA.t stands for the depth between the peak and trough in the radial direction of notches on the profile of the particle in the electron microscope photo and r1 is as defined above, is in the range of from 1 to 10%, and the primary particle size (2r1) determined by the electron microscope method is in the range of from 0.1 to 20 .mu.m.

Abstract: An initiator suspension for use in the suspension polymerization of ethylenically unsaturated monomers is prepared by (a) heating the initiator to its melting point; (b) finely dividing the initiator in water while it is in a molten state; and (c) rapidly cooling so that the initiator is in a molten state for a period of time which is less than about 5 minutes. The initiator suspension has very small particles and a narrow particle size distribution whereby at least 50% by weight of the particles are smaller than 5 .mu.m and at least 90% by weight of the particles are smaller than 10 .mu.m.

Abstract: A dehydrogenating catalyst for saturated hydrocarbons comprising platinum, tin, sodium and .tau.-alumina. The support of the catalyst is a large pore diameter .tau.-Al.sub.2 O.sub.3 with dual pore diameter distribution. At least 40% of the total pore volume is contributed by pores with pore diameter in the range of 1000-10000 .ANG.. Platinum, tin, and sodium are impregnated onto support by co-impregnation method, followed by drying, calcinating, and steam-treating, as well as reducing by hydrogen, to prepare a long life dehydrogenating catalyst.

Abstract: A process is described for preparing attrition resistant catalyst, particularly vanadium/phosphorus oxide catalyst, having an oxide rich surface layer. The oxide rich surface layer is obtained from a stable oxide-forming mixture which contains both colloidal oxide sol and a soluble oxide precursor.