The present invention relates to a catalyst in which a ratio (B/A) of a cumulative pore volume (B) in a pore diameter of 0.35 m to 4.0 m to a cumulative pore volume (A) in a pore diameter of 4.0 m to 10.0 m measured by mercury porosimetry is 2.5 to 15.0, and a cumulative specific surface area is less than 5 m.sup.2/g.

Mixed metal oxide catalysts having an amorphous content of not less than 40 wt. % are prepared by calcining the catalyst precursor fully or partially enclosed by a porous material having a melting temperature greater than 600 C. in an inert container including heating the catalyst precursor at a rate from 0.5 to 10 C. per minute from room temperature to a temperature from 370 C. to 540 C. under a stream of pre heated gas chosen from steam and inert gas and mixtures thereof at a pressure of greater than or equal to 1 psig having a temperature from 300 C. to 540 C. and holding the catalyst precursor at that temperature for at least 2 hours and cooling the catalyst precursor to room temperature.

Mixed metal oxide catalysts having an amorphous content of not less than 40 wt. % are prepared by calcining the catalyst precursor fully or partially enclosed by a porous material having a melting temperature greater than 600 C. in an inert container including heating the catalyst precursor at a rate from 0.5 to 10 C. per minute from room temperature to a temperature from 370 C. to 540 C. under a stream of pre heated gas chosen from steam and inert gas and mixtures thereof at a pressure of greater than or equal to 1 psig having a temperature from 300 C. to 540 C. and holding the catalyst precursor at that temperature for at least 2 hours and cooling the catalyst precursor to room temperature.

The present invention provides a catalyst precursor and a catalyst suitable for preparing multi-wall carbon nanotubes. The resulting multi-wall carbon nanotubes have a narrow distribution as to the number of walls forming the tubes and a narrow distribution in the range of diameters for the tubes. Additionally, the present invention provides methods for producing multi-wall carbon nanotubes having narrow distributions in the number of walls and diameters. Further, the present invention provides a composition of spent catalyst carrying multi-wall nanotubes having narrow distribution ranges of walls and diameters.

The present invention provides a catalyst precursor and a catalyst suitable for preparing multi-wall carbon nanotubes. The resulting multi-wall carbon nanotubes have a narrow distribution as to the number of walls forming the tubes and a narrow distribution in the range of diameters for the tubes. Additionally, the present invention provides methods for producing multi-wall carbon nanotubes having narrow distributions in the number of walls and diameters. Further, the present invention provides a composition of spent catalyst carrying multi-wall nanotubes having narrow distribution ranges of walls and diameters.

A method for producing a complex oxide catalyst containing a complex oxide represented by the formula:
Mo.sub.1V.sub.aSb.sub.bNb.sub.cW.sub.dZ.sub.eO.sub.n
(wherein a component Z represents an element such as La, Ce, Pr, Yb, Y, Sc, Sr, and Ba; a, b, c, d, e, and n each represent an atomic ratio of an element to one Mo atom; 0.1a0.4, 0.1b0.4, 0.01c0.3, 0d0.2, and 0e0.1; an atomic ratio a/b is 0.85a/b<1.0, and an atomic ratio a/c is 1.4<a/c<2.3.), the method including: a step of preparing a specific raw material-formulated solution containing Mo, V, Sb, Nb, W, and Z; a step of drying the raw material-formulated solution to obtain a dry powder; a step of pre-stage calcining the dry powder to obtain a pre-stage calcined product; a step of main-calcining the pre-stage calcined product to obtain a calcined product having a protrusion on the surface of the particle; and a step of removing the protrusion by an air stream, wherein the reduction rate of the pre-stage calcined product is 8 to 12%, and the specific surface area of the calcined product is 7 to 20 m.sup.2/g.

A method for producing a complex oxide catalyst containing a complex oxide represented by the formula:
Mo.sub.1V.sub.aSb.sub.bNb.sub.cW.sub.dZ.sub.eO.sub.n
(wherein a component Z represents an element such as La, Ce, Pr, Yb, Y, Sc, Sr, and Ba; a, b, c, d, e, and n each represent an atomic ratio of an element to one Mo atom; 0.1a0.4, 0.1b0.4, 0.01c0.3, 0d0.2, and 0e0.1; an atomic ratio a/b is 0.85a/b<1.0, and an atomic ratio a/c is 1.4<a/c<2.3.), the method including: a step of preparing a specific raw material-formulated solution containing Mo, V, Sb, Nb, W, and Z; a step of drying the raw material-formulated solution to obtain a dry powder; a step of pre-stage calcining the dry powder to obtain a pre-stage calcined product; a step of main-calcining the pre-stage calcined product to obtain a calcined product having a protrusion on the surface of the particle; and a step of removing the protrusion by an air stream, wherein the reduction rate of the pre-stage calcined product is 8 to 12%, and the specific surface area of the calcined product is 7 to 20 m.sup.2/g.

The present disclosures and inventions relate to a supported catalyst composition for the catalytic oxidation of a hydrocarbon such as propane with oxygen or air, in the presence of a catalyst composition comprising a support material and a mixed metal composition comprising metals in the molar ratios described by the formula Mo.sub.aV.sub.bGa.sub.cPd.sub.dNb.sub.eZ.sub.f, wherein the support material is neutral or oxidative.

The present disclosures and inventions relate to a supported catalyst composition for the catalytic oxidation of a hydrocarbon such as propane with oxygen or air, in the presence of a catalyst composition comprising a support material and a mixed metal composition comprising metals in the molar ratios described by the formula Mo.sub.aV.sub.bGa.sub.cPd.sub.dNb.sub.eZ.sub.f, wherein the support material is neutral or oxidative.

An exhaust gas-purifying catalyst includes a support and a catalytic metal as one or more precious metals supported by the support. The support includes a composite oxide having a composition represented by a general formula AB.sub.C.sub.O.sub.3, wherein A represents one or more elements selected from the group consisting of lanthanum, neodymium, and yttrium, B represents iron or a combination of iron and aluminum, C represents one or more elements selected from the group consisting of iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, and each represents a numerical value within a range of more than 0 and less than 1, and and satisfy relational formulae of > and +1.