Abstract: According to a method for producing acetic acid by carbonylation of methanol characterized in that an acid having an acid dissociation constant (pKa) smaller than the constant of acetic acid is allowed to be present in the reaction system, acetic acid can be produced by the reaction of methanol and carbon monoxide in a reaction liquid in the presence of a solid catalyst containing rhodium and alkyl iodide, to achieve an enhanced reaction rate of carbonylation of methanol in producing acetic acid in the region at a high carbonylation degree (Ca>0.8 mol/mol) for more efficient production of acetic acid.

Abstract: An improved hydroprocessing slurry catalyst is provided for the upgrade of heavy oil feedstock. The catalyst comprises dispersed particles in a hydrocarbon medium with the dispersed particles have an average particle size ranging from 1 to 300 ?m. The catalyst has a total pore volume of at least 0.5 cc/g and a polymodal pore distribution with at least 80% of pore sizes in the range of 5 to 2,000 Angstroms in diameter. The catalyst is prepared from sulfiding and dispersing a metal precursor solution in a hydrocarbon diluent, the metal precursor comprising at least a Primary metal precursor and optionally a Promoter metal precursor, the metal precursor solution having a pH of at least 4 and a concentration of less than 10 wt. % of Primary metal in solution.

Abstract: A layered catalyst including a surface axis including a catalyst material layer, and a substrate material layer contacting the catalyst material layer. The catalyst material layer includes a compressed atomic distance between two adjacent catalyst atoms along the surface axis relative to an atomic distance of the same catalyst material as in bulk. The substrate material has a higher surface energy than the catalyst material. In certain instances, at least 70 percent of total atoms of the catalyst material are in a film growth mode. In certain other instances, a surface free energy of the substrate material is 1 to 50 percent greater than a surface free energy of the catalyst material. In yet certain other instances, the catalyst material layer has a d-band center in a range of ?2.1 eV to ?2.25 eV.

Abstract: A catalyst for purification of exhaust gas, in which a noble metal is supported on a metal oxide support, has a basic site content of 1 mmol/L-cat or less, as determined on the basis of an amount of CO2 desorbed per liter of the catalyst as measured by a CO2 temperature-programmed desorption method.

Abstract: A denitration catalyst composition to efficiently and reductively remove nitrogen oxides from exhaust gas of a boiler or an internal combustion engine operated in lean-combustion, such as a gasoline engine, a diesel engine, by carbon monoxide and hydrocarbons; and a denitration method using the catalyst composition. In the denitration catalyst composition, a precious metal element having Rh as an essential component is supported on a zirconium oxide-based carrier formed by condensing or mixing primary particles having a zirconium oxide as a main component, and further a cerium-containing oxide (B) is present at the surface of the zirconium oxide-based carrier and at the gap of the secondary particles; and a denitration method characterized in that exhaust gas containing NO, CO and O2 is contacted with the denitration catalyst composition, under oxidative atmosphere having an air/fuel ratio of 14.7 or higher, at a temperature of 400 to 800° C.

Abstract: The present invention provides an electrocatalytic material and a method for making an electrocatalytic material. There is also provided an electrocatalytic material comprising amorphous metal or mixed metal oxides. There is also provided methods of forming an electrocatalyst, comprising an amorphous metal oxide film.

Abstract: A method of producing a Fischer-Tropsch catalyst by preparing a nitrate solution, wherein preparing comprises forming at least one metal slurry and combining the at least one metal slurry with a nitric acid solution; combining the nitrate solution with a basic solution to form a precipitate; promoting the precipitate to form a promoted mixture, wherein promoting comprises combining the precipitate with (a) silicic acid and one or more selected from the group consisting of non-crystalline silicas, crystalline silicas, and sources of kaolin or (b) at least one selected from non-crystalline silicas and sources of kaolin, in the absence of silicic acid; and spray drying the promoted mixture to produce catalyst having a desired particle size. Catalyst produced by the disclosed method is also described.

Abstract: A platinum alloy catalyst PtXY, wherein X is nickel, cobalt, chromium, copper, titanium or manganese and Y is tantalum or niobium, characterised in that in the alloy the atomic percentage of platinum is 46-75 at %, of X is 1-49 at % and of Y is 1-35 at %; provided that the alloy is not 66 at % Pt 20 at % Cr14 at % Ta or 50 at % Pt, 25 at % Co, 25 at % Ta is disclosed. The catalyst has particular use as an oxygen reduction catalyst in fuel cells, and in particular in phosphoric acid fuel cells.

Abstract: The present invention relates to a nitrogen oxide storage catalyst comprising: a substrate; a first washcoat layer disposed on the substrate, the first washcoat layer comprising metal oxide support particles and a nitrogen oxide storage material comprising at least one metal compound selected from the group consisting of alkaline earth metal compounds, alkali metal compounds, rare earth metal compounds, and mixtures thereof, at least a portion of said at least one metal compound being supported on the metal oxide support particles; and a second washcoat layer disposed over the first washcoat layer, said second washcoat layer comprising Rh, wherein the first washcoat layer contains substantially no Rh, and wherein the second washcoat layer is disposed on 100-x % of the surface of the first washcoat layer, x ranging from 20 to 80.

Abstract: The present invention is directed to a catalyst suitable for catalyzing a Fischer-Tropsch reaction, said catalyst comprising cobalt metal supported on zinc-oxide and having the following particle size distribution by volume: <10% having a particle size below 1 micron, 70-99% having a particle size between 1 and 5 micron, and <20% having a particle size above 5 micron.

Abstract: A process for preparing a slurry catalyst for the upgrade of heavy oil feedstock is provided. The process employs a pressure leach solution obtained from a metal recovery process as part of the metal precursor feed. In one embodiment, the process comprises: sulfiding a pressure leach solution having at least a Group VIB metal precursor compound in solution forming a catalyst precursor, and mixing the sulfided catalyst precursor with a hydrocarbon diluent to form the slurry catalyst. In another embodiment, the pressure leach solution is mixed with a hydrocarbon diluent under high shear mixing conditions to form an emulsion, which emulsion can be sulfided in-situ upon contact with a heavy oil feedstock in the heavy oil upgrade process.

Abstract: Electrooxidative materials and various method for preparing electrooxidative materials formed from an alloy of oxophilic and electrooxidative metals. The alloy may be formed using methods such as spray pyrolysis or mechanosynthesis and may or may not include a supporting material which may or may not be sacrificial as well as the materials.

Abstract: An Object of the patent is to remove highly reducing hydrocarbon exhausted during acceleration period, and to remove efficiently hydrocarbon even after contacting with highly reducing hydrocarbon. By using a catalyst having a higher proportion of palladium having surface charge of 2-valence or 4-valence supported than that of 0-valence by supporting palladium together with magnesium oxide, hydrocarbon exhausted from an internal combustion engine especially during acceleration period can be efficiently removed.

Abstract: In one embodiment, the invention is to a process for producing a catalyst composition for converting ethanol to higher alcohols, such as butanol. The process comprises contacting magnesium carbonate with one or more metal precursors to form a catalyst intermediate and calcining the catalyst intermediate to form the catalyst composition that comprises the one or more metals and magnesium oxide. The one or more metal precursors comprises one or more metal selected from the group consists of nickel, palladium, platinum, germanium, copper, ruthenium, gallium, tin, iridium, and mixtures thereof.

Abstract: A process for handling an active catalyst includes introducing a mixture of active catalyst particles and a molten organic substance, which is at a temperature Ti, and which sets at a lower temperature T2 so that T2<T1, into a mould. The mould is submerged in a cooling liquid, so as to cool the organic substance down to a temperature T3, where T3?T2. In this fashion, a casting comprising an organic substance matrix in which the active catalyst particles are dispersed, is obtained.

Abstract: The present invention is directed to hollow catalyst particles comprising a layered shell structure and to a method of their manufacture. The catalyst particles have the general formula Hcore/PMinner shell/IL/PMouter shell in which Hcore is the hollow core, PMinner shell is a precious metal forming the innermost layer of the shell, IL is an intermediate layer comprising a base metal/precious metal alloy, and PMouter shell is a precious metal forming the outermost layer of the shell. The precious metal is selected from Pt, Ir and Pd and mixtures or alloys thereof, and IL is an intermediate layer comprising a base metal/precious metal alloy wherein the concentration of the base metal changes from the periphery of the hollow core to the outer surface of the intermediate layer. The base metal is selected from Co, Ni, and Cu and mixtures thereof.

Abstract: The present invention relates to a method for preparing a supported metal catalyst for the selective hydrogenation of unsaturated hydrocarbons, characterized in that it comprises the following steps: a) electroplating a layer of nickel on a metallic support, and then b) electroplating a top layer of platinum and/or palladium. The present invention also relates to the supported metal catalyst obtained by this process, and the use thereof in hydrogenation reactions of unsaturated hydrocarbons, in particular for the selective hydrogenation of light olefins.

Abstract: Provided is a substrate for carbon nanotube growth in which no metal particles as a catalyst aggregates and a method for manufacturing the substrate. A substrate for carbon nanotube growth 1 includes a base plate 2, a noble metal alloy catalyst 3 having an alloy of a noble metal and a transition metal, and a form-defining material layer 4 which allows the noble metal alloy catalyst 3 to be dispersed and arranged. A method for manufacturing a substrate for carbon nanotube growth 1 includes a step of sputtering a noble metal alloy on a base plate 2, a step of sputtering a form-defining material on the base plate 2, and a step of further sputtering the noble metal alloy on the form-defining material.

Abstract: Embodiments of the invention provide catalysts for hydrocarbon oxidation. One embodiment of the invention provides a catalyst for hydrocarbon oxidation comprising: a liquid medium including aromatic hydrocarbon 150; bis(2,4-pentanedionato)platinum; bis(2,4-pentanedionato)palladium; ferrocene; magnesium 2-ethylhexanoate; and cerium (III) 2-ethylhexanoate, rhenium in an organo-metallic compound, or both.

Abstract: Platinum (Pt)-based alloys are effective catalysts for oxygen reduction reaction (ORR) or fuel oxidation in proton exchange membrane fuel cells (PEMFCs). A wet-chemical approach for preparing monodisperse Pt3Ni, Pt3Co and Pt3Fe nanocubes and Pt3Ni nanoctahedra which are terminated with {100} and {111} facets, respectively, were developed. Such nanoscaled electrocatalysts supported on carbon black with controlled shape, e.g., octahedral configuration, is provided. ORR activity on the Pt3Ni nanoctahedra is ˜5.1 fold higher than that of nanocubes with a similar size, and their C-supported samples are highly active with respect to commercial Pt/C.

Abstract: A NOx storage component comprises caesium silicate (Cs2SiO3) and at least one platinum group metal. The invention also includes a NOx absorber catalyst comprising a NOx storage component according to the invention disposed on a substrate monolith; a method of treating exhaust gas containing NOx from a lean burn internal combustion engine comprising the steps of contacting a NOx storage component comprising caesium silicate (Cs2SiO3) and at least one platinum group metal with lean exhaust gas containing NOx to adsorb NOx thereon; and periodically desorbing adsorbed NOx by contacting the NOx storage component with stoichiometric or rich exhaust gas; and a method of making a NOx storage component according to the invention comprising the steps of combining and reacting an aqueous salt of at least one platinum group metal, an aqueous caesium salt and a source of silica.

Abstract: A solid catalyst having a close-packed structure has basic structural units present in the surface of the solid catalyst, the basic structural units including (i) a triangular lattice constituted of atoms of platinum, ruthenium, and at least one additional element which are disposed at the vertexes in the triangular lattice so that each atom of one of the elements adjoins atoms of the other elements or (ii) a rhombic lattice constituted of atoms of platinum, ruthenium, and at least one additional element which are disposed at the vertexes in the rhombic lattice in an atomic ratio of 1:2:1 so that each ruthenium atom directly adjoins a platinum atom and an atom of the additional element; and a fuel cell includes either of the solid catalyst as an anode-side electrode catalyst.

Abstract: Described is a nitrogen oxide storage catalyst comprising: a substrate; a first washcoat layer provided on the substrate, the first washcoat layer comprising a nitrogen oxide storage material, a second washcoat layer provided on the first washcoat layer, the second washcoat layer comprising a hydrocarbon trap material, wherein the hydrocarbon trap material comprises substantially no element or compound in a state in which it is capable of catalyzing selective catalytic reduction, preferably wherein the hydrocarbon trap material comprises substantially no element or compound in a state in which it is capable of catalyzing a reaction wherein nitrogen oxide is reduced to N2, said catalyst further comprising a nitrogen oxide conversion material which is either comprised in the second washcoat layer and/or in a washcoat layer provided between the first washcoat layer and the second washcoat layer.

Abstract: The present invention a catalyst that includes a metallic or ceramic foam catalyst support having surfaces within the foam for the placement of a catalytic material, and an active catalyst material which is applied by washcoating or dipping.

Abstract: A natural gas reforming catalyst includes a metal core and rhodium deposited on the metal core. A natural gas reformer includes a hydrocarbon inlet, a reforming catalyst for generating hydrogen from a hydrocarbon and water and a hydrogen outlet. The reforming catalyst includes a metal core and a rhodium layer deposited on the metal core. A method for preparing a natural gas reforming catalyst includes adding a rhodium compound and a metal core to a reaction vessel and depositing the rhodium compound on the metal core.

Abstract: The present invention provides a catalyst comprising a catalytic metal, preferably cobalt, rhenium or mixtures thereof. The catalytic metal is supported on a support comprising a major amount of titania and a minor amount of cobalt aluminate derived from anatase titania. The support also includes a minor amount of titania derived from a titanium chelate.

Abstract: A method for providing a catalyst on a substrate is disclosed comprising providing a first washcoat comprising a soluble washcoat salt species, a polar organic solvent, and an insoluble particulate material, contacting the first washcoat with a substrate to form a coated substrate, and then contacting the coated substrate with a second washcoat comprising an oxide or an oxide-supported catalyst to physisorb, chemisorb, bond, or otherwise adhere the oxide or the oxide-supported catalyst to the coated substrate. Also disclosed is a catalyst on a substrate comprising: a substrate; an anchor layer comprising a soluble washcoat salt species, a polar organic solvent, and an insoluble particulate material; and a second layer comprises an oxide or an oxide-supported catalyst. The catalyst on a substrate can be in either green or fired form.

Abstract: RuCore—Ptshell nanocatalysts with 1˜3 atomic layers of Pt-shell were developed for enhancing the catalytic activities. Uniform atomic layers of Pt were successfully deposited on the core nanoparticles with high precision. Using such nanocatalysts as the cathode of the dye-sensitized solar cell (DSSC), the efficiency of DSSC can be significantly increased. For direct methanol fuel cell (DMFC) applications, much higher performance can also be achieved by using such RuCore—Ptshell nanocatalysts and the DMFC can be operated at room temperature without the need to raise the cell temperature to above room temperature (such as 80° C.).

Abstract: Catalysts comprising porous metal nanoparticles, which are individually encapsulated with a reaction-enhancing material, and their use in fuel cell catalysis are provided.

Abstract: An improved process to make a slurry catalyst for the upgrade of heavy oil feedstock is provided. In the process, at least a metal precursor feedstock is portioned and fed in any of the stages: the promotion stage; the sulfidation stage; or the transformation stage of a water-based catalyst precursor to a slurry catalyst. In one embodiment, the promoter metal precursor feedstock is split into portions, the first portion is for the sulfiding step, the second portion is for the promotion step; and optionally the third portion is to be added to the transformation step in the mixing of the sulfided promoted catalyst precursor with a hydrocarbon diluent to form the slurry catalyst. In another embodiment, the Primary metal precursor feedstock is split into portions.

Abstract: The invention discloses a preparation method of nano-scale platinum (Pt) using an open-loop reduction system. The preparation method comprises the steps of: utilizing carbon nanotubes (CNTs) as a catalyst support; mixing platinum salt with a reducing agent and deionized water to form a precursor solution in a flask; heating the precursor solution in the flask at a predetermined temperature range to reduce nano-scale platinum nanoparticles on the carbon nanotubes by the process of water evaporation; allowing the water vapor to flow through a connection tube to a condenser; filling a cooling substance into the condenser via the first opening and draining the cooling substance from the condenser via the second opening to lower the temperature of the water vapor in the inner tube by the cooling substance and condense the water vapor into liquid water, which is collected with a beaker placed under the condenser.

Abstract: A single metal slurry catalyst for the upgrade of heavy oil feedstock is provided. The slurry catalyst is prepared by sulfiding a Primary metal precursor, then mixing the sulfided metal precursor with a hydrocarbon diluent to form the slurry catalyst. The single-metal slurry catalyst has the formula (Mt)a(Sv)d(Cw)e(Hx)f(Oy)g(Nz)h, wherein M is at least one of a non-noble Group VIII metal, a Group VIB metal, a Group IVB metal, and a Group IIB metal; 0.5a<=d<=4a; 0<=e<=11a; 0<=f<=18a; 0<=g<=2a; 0<=h<=3a; t, v, w, x, y, z, each representing total charge for each of: M, S, C, H, O, and N; and ta+vd+we+xf+yg+zh=0. The slurry catalyst has a particle size ranging from 1 to 300 ?m.

Abstract: Embodiments of the present disclosure provide for NiPt nanoparticles, compositions and supports including NiPt nanoparticles, methods of making NiPt nanoparticles, methods of supporting NiPt nanoparticles, methods of using NiPt nanoparticles, and the like.

Abstract: A supported platinum catalyst comprising an open-pored support material and platinum of oxidation state 0, wherein an XRD spectrum of the catalyst is free of signals of elemental platinum.

Abstract: A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

Abstract: A metal oxide-supported nickel catalyst includes a matrix containing a metal oxide and catalytic sites distributed throughout the matrix and having an intricate interface with the matrix, in which the catalytic sites are selected from the group consisting of nano-nickel(0) domains and nano-nickel(0)-A(0) alloy domains. Also disclosed are a method for preparing this catalyst and a method for using it to produce carbon monoxide and hydrogen by partial oxidation of a C1-C5 hydrocarbon.

Abstract: The invention provides a catalyst for catalytically removing three components, which are carbon monoxide, hydrocarbons and nitrogen oxides, from combustion exhaust gas generated by combusting fuel at around the stoichiometric air to fuel ratio. The catalyst includes: (A) a first catalyst component including at least rhodium, platinum, or palladium in a content of 0.01 to 0.5% by weight; and (B) a second catalyst component, which is the remainder, including a composite oxide or a mixed oxide including (a) at least zirconium oxide or titanium oxide, and (b) an oxide of at least praseodymium, yttrium, neodymium, tungsten, niobium, silicon, or aluminum, wherein the content of the oxide (a) in the composite oxide or the mixed oxide is in a range of 70 to 95% by weight. The invention further provides a two-layer catalyst that includes a surface catalyst layer containing the above-mentioned catalyst.

Abstract: This invention concerns a procedure for the formation of a bimetallic composition by means of the subsequent depositing of Co(0) and Pd(0) on an inert support, a composition obtained by means of said procedure and the use of said bimetallic composition as a catalyst. Another aspect of this invention is a catalytic device that includes said bimetallic composition.

Abstract: The present subject matter provides a method of preparing a multicomponent metal-hybrid nanocomposite using co-gasification, in which a multicomponent metal-hybrid nanocomposite can be prepared by a one-step process without using a complicated process including the steps of supporting-drying-calcining-annealing and the like at the time of preparing a conventional alloy catalyst, and provides a multicomponent metal-hybrid nanocomposite prepared by the method. The method is advantageous in that a multicomponent metal-hybrid nanocomposite can be synthesized by a simple process of simultaneously gasifying two kinds of metal precursors, and in that an additional post-treatment process is not required.

Abstract: A process for hydrogenating highly unsaturated hydrocarbons to less unsaturated hydrocarbons wherein production of saturated hydrocarbons is minimized. The process utilizes catalyst including Ce2O3, MgO, and an inorganic support, and optionally palladium, optionally silver, and/or an optional alkali metal.

Abstract: A method for supporting a catalytic metal on the surface of a carrier by bringing an aqueous catalytic metal salt solution into contact a porous carrier. The method includes the steps of: impregnating the carrier with a liquid hydrophobic organic compound before bringing the aqueous catalytic metal salt solution into contact with the carrier, and drying the impregnated carrier to volatilize the hydrophobic organic compound on the surface of the carrier, followed by bringing the carrier into contact with the aqueous catalytic metal salt solution; and then bringing a reducing agent into contact with the catalytic metal salt on the surface of the carrier to reduce the catalytic metal salt to undergo insolubilization treatment. The catalytic component is supported in a region from the surface of the carrier to a depth of 50 ?m or more and 500 ?m or less.

Abstract: In some embodiments, the present disclosure provides a fuel cell catalyst having a catalyst surface bearing a non-occluding layer of iridium. In some embodiments, the present disclosure provides a fuel cell catalyst comprising a catalyst surface bearing a sub-monolayer of iridium. In some embodiments, the present disclosure provides a fuel cell catalyst comprising a catalyst surface bearing a layer of iridium having a planar equivalent thickness of between 1 and 100 Angstroms. In some embodiments, the fuel cell catalyst comprises nanostructured elements comprising microstructured support whiskers bearing a thin film of nanoscopic catalyst particles. The layer of iridium typically has a planar equivalent thickness of between 1 and 100 Angstroms and more typically between 5 and 60 Angstroms. The fuel cell catalyst typically comprises no electrically conductive carbon material and typically comprises at least a portion of the iridium in the zero oxidation state.

Abstract: A mesoporous oxide-catalyst complex including: a mesoporous metal oxide; and a catalyst metal supported on the mesoporous metal oxide, wherein the catalyst on the mesoporous metal oxide has a degree of dispersion of about 30 to about 90 percent.

Abstract: A composition comprising a supported hydrogenation catalyst comprising palladium and an organophosphorous compound, the supported hydrogenation catalyst being capable of selectively hydrogenating highly unsaturated hydrocarbons to unsaturated hydrocarbons. A method of making a selective hydrogenation catalyst comprising contacting a support with a palladium-containing compound to form a palladium supported composition, contacting the palladium supported composition with an organophosphorus compound to form a catalyst precursor, and reducing the catalyst precursor to form the catalyst.

Abstract: The present invention provides a method to produce olefins by the decarboxylation of organic carboxylic acids in the presence of an organopalladium catalyst.

Abstract: A method of using a hybrid oxidation catalyst system for remediating a lean emission from a vehicle includes the step of oxidizing the hydrocarbons and carbon monoxide in an engine emission comprising hydrocarbons, carbon monoxide, NOx including NO and NO2, and oxygen with a first catalyst. The first catalyst includes noble metal particles supported in a first ceramic layer. The method further includes oxidizing the NO with a second catalyst having base metal oxide particles supported in a second ceramic layer to form NO2. The first catalyst is disposed upstream of the second catalyst and the system is capable of converting at least 10% of the amount of NO to NO2 at a temperature ranging from 75° C. to 225° C.

Abstract: Process for isomerizing linear alpha-olefins having from 10 to 25 carbon atoms over a heterogeneous catalyst.

Abstract: The invention relates to a catalytic high-pressure process for the CO2 reforming of hydrocarbons, preferably methane, in the presence of iridium-comprising active compositions and also a preferred active composition in which Ir is present in finely dispersed form on zirconium dioxide-comprising support material. The predominant proportion of the zirconium dioxide preferably has a cubic and/or tetragonal structure and the zirconium dioxide is more preferably stabilized by means of at least one doping element. In the process of the invention, reforming gas is brought into contact at a pressure of greater than 5 bar, preferably greater than 10 bar and more preferably greater than 20 bar, and a temperature which is in the range from 600 to 1200° C., preferably in the range from 850 to 1100° C. and in particular in the range from 850 to 950° C., and converted into synthesis gas.

Abstract: A method is described for preparing a catalyst suitable for use in a steam reforming process, including the steps of: (i) spraying a slurry containing a particulate catalyst compound, including one or more catalytic metals selected from the group consisting of Ni, Cu, Pt, Pd, Rh, Ru and Au, on to the surface of a shaped support in a pan coater to form a coated shaped support material having the catalytic metal in a surface layer, (ii) drying and optionally calcining the coated shaped support material to form a catalyst precursor, and (iii) optionally reducing the metal or metals in the catalyst precursor to a lower oxidation state to form the catalyst. The egg-shell catalyst is useful for performing a steam reforming reaction.

Abstract: A cerium-zirconium composite metal oxide having improved durability at high temperature and a stable oxygen storage capacity is provided. The cerium-zirconium composite metal oxide is characterized in that the total mole number of Ce and Zr is at least 85% based on the total mole number of metal in the composite metal oxide, a molar ratio Ce/Zr is within a range from 1/9 to 9/1, and an isoelectric point of the composite metal oxide is more than 3.5. Preferably, the molar ratio Ce/Zr is within a range from 3/7 to 7/3 and the isoelectric point is within a range from 3.8 to 5.0, and the cerium-zirconium composite metal oxide contains a rare earth metal (excluding Ce) in a concentration of less than 15% by mole based on the total mole number of metal in the composite metal oxide. Also the present invention provides a cerium-zirconium composite metal oxide, characterized in that CeO2 forms a core surrounded by ZrO2.