The invention is for a method for making a heteropoly acid compound catalyst from compounds containing molybdenum, vanadium, phosphorus, cesium, copper, bismuth, antimony and boron in which molybdenum, vanadium, phosphorus, cesium, copper, bismuth and boron are at their highest oxidation states and antimony has a 3+ oxidation state. The catalyst contains oxides of molybdenum, vanadium, phosphorus, cesium, copper, bismuth, antimony, boron and, optionally, other metals. The catalyst has the formula:
Mo.sub.12V.sub.aP.sub.bCs.sub.cCu.sub.dBi.sub.eSb.sub.fB.sub.gO.sub.x
where Mo is molybdenum, V is vanadium, P is phosphorus, Cs is cesium, Cu is copper, Bi is bismuth, Sb is antimony, B is boron, O is oxygen, a is 0.01 to 5.0, b is 0.5 to 3.5, c is 0.01 to 2.0, d is 0.0-1.5, e is 0.0-2.0, f is 0.01-3.0, g is 0.0-4.0 and x satisfies the valences. Molybdenum is reduced by antimony and reoxidized during catalyst synthesis.

The invention is for a method for making a heteropoly acid compound catalyst from compounds containing molybdenum, vanadium, phosphorus, cesium, copper, bismuth, antimony and boron in which molybdenum, vanadium, phosphorus, cesium, copper, bismuth and boron are at their highest oxidation states and antimony has a 3+ oxidation state. The catalyst contains oxides of molybdenum, vanadium, phosphorus, cesium, copper, bismuth, antimony, boron and, optionally, other metals. The catalyst has the formula:
Mo.sub.12V.sub.aP.sub.bCs.sub.cCu.sub.dBi.sub.eSb.sub.fB.sub.gO.sub.x
where Mo is molybdenum, V is vanadium, P is phosphorus, Cs is cesium, Cu is copper, Bi is bismuth, Sb is antimony, B is boron, O is oxygen, a is 0.01 to 5.0, b is 0.5 to 3.5, c is 0.01 to 2.0, d is 0.0-1.5, e is 0.0-2.0, f is 0.01-3.0, g is 0.0-4.0 and x satisfies the valences. Molybdenum is reduced by antimony and reoxidized during catalyst synthesis.

Homogeneous water oxidation catalysts (WOCs) for the oxidation of water to produce hydrogen ions and oxygen, and methods of making and using thereof are described herein. In a preferred embodiment, the WOC is a polyoxometalate WOC which is hydrolytically stable, oxidatively stable, and thermally stable. The WOC oxidized waters in the presence of an oxidant. The oxidant can be generated photochemically, using light, such as sunlight, or electrochemically using a positively biased electrode. The hydrogen ions are subsequently reduced to form hydrogen gas, for example, using a hydrogen evolution catalyst (HEC). The hydrogen gas can be used as a fuel in combustion reactions and/or in hydrogen fuel cells. The catalysts described herein exhibit higher turn over numbers, faster turn over frequencies, and/or higher oxygen yields than prior art catalysts.

To provide a catalyst having excellent performance and durability by improving a NOx reduction ratio at 350 C. or higher without deteriorating excellent durability of a TiVMoP catalyst in view of problems of conventional art. A NOx reduction catalyst for exhaust gas, which is composed of a catalyst composition that comprises titanium (Ti), an oxide of phosphorous, molybdenum (Mo) and/or tungsten (W), oxide of vanadium (V), and high-silica zeolite that has an SiO.sub.2/Al.sub.2O.sub.3 ratio of not less than 20 is obtained by kneading in the presence of water, drying and calcining (1) titanium oxide, and phosphoric acid or an ammonium salt of phosphoric acid in an amount of more than 1% by weight and not more than 15% by weight relative to the titanium oxide in terms of H.sub.3PO.sub.4, (2) an oxo acid or oxo acid salt of molybdenum (Mo) and/or tungsten (W) and an oxo acid salt of vanadium (V) or vanadyl salt respectively in an amount of more than 0% by atom and not more than 8% by atom relative to the titanium oxide and (3) high-silica zeolite in an amount of more than 0% by weight and not more than 20% by weight relative to the titanium oxide.

To provide a catalyst having excellent performance and durability by improving a NOx reduction ratio at 350 C. or higher without deteriorating excellent durability of a TiVMoP catalyst in view of problems of conventional art. A NOx reduction catalyst for exhaust gas, which is composed of a catalyst composition that comprises titanium (Ti), an oxide of phosphorous, molybdenum (Mo) and/or tungsten (W), oxide of vanadium (V), and high-silica zeolite that has an SiO.sub.2/Al.sub.2O.sub.3 ratio of not less than 20 is obtained by kneading in the presence of water, drying and calcining (1) titanium oxide, and phosphoric acid or an ammonium salt of phosphoric acid in an amount of more than 1% by weight and not more than 15% by weight relative to the titanium oxide in terms of H.sub.3PO.sub.4, (2) an oxo acid or oxo acid salt of molybdenum (Mo) and/or tungsten (W) and an oxo acid salt of vanadium (V) or vanadyl salt respectively in an amount of more than 0% by atom and not more than 8% by atom relative to the titanium oxide and (3) high-silica zeolite in an amount of more than 0% by weight and not more than 20% by weight relative to the titanium oxide.

A promoted VPO catalyst for the oxidation of n-butane to maleic anhydride wherein the catalyst comprises the mixed oxides of vanadium and phosphorus, niobium and at least one of antimony and bismuth, wherein the catalyst may be produced in a process comprising impregnating a VPO catalyst with a metal source compound of niobium and a metal source compound of at least one of antimony and bismuth, to form a metal impregnated VPO catalyst, and then drying the metal impregnated VPO catalyst to form the promoted VPO catalyst.

A promoted VPO catalyst for the oxidation of n-butane to maleic anhydride wherein the catalyst comprises the mixed oxides of vanadium and phosphorus, niobium and at least one of antimony and bismuth, wherein the catalyst may be produced in a process comprising impregnating a VPO catalyst with a metal source compound of niobium and a metal source compound of at least one of antimony and bismuth, to form a metal impregnated VPO catalyst, and then drying the metal impregnated VPO catalyst to form the promoted VPO catalyst.

A catalyst of Chemical Formula 1:

Mo.sub.aV.sub.bP.sub.cM.sup.1.sub.dM.sup.2.sub.eM.sup.3.sub.fM.sup.4.sub.gM.sup.5.sub.hM.sup.6.sub.iO.sub.j[Chemical Formula 1]

where Mo is molybdenum, V is vanadium, P is phosphorus, and O is oxygen, M.sup.1 is one or more selected from W, Sb, As, Sn, and Pb, M.sup.2 is one or more selected from Fe, Zn, Cr, Mn, and Cu, M.sup.3 is one or more selected from Se, Ga, Ti, Ge, Cd, Ta, and Ni, M.sup.4 is one or more selected from Al, Zr, Si, and Ce, M.sup.5 is one or more selected from Au, Pd, Pt, Ag, Ru, and Rh, M.sup.6 is one or more selected from Na, K, Li, Rb, Cs, Ca, Mg, Sr, and Ba, a, b, c, d, e, f, g, h, i, and j represent the atomic proportion of each element, for preparing (meth)acrylic acid; and a method for preparing the catalyst.

A catalyst of Chemical Formula 1:

Mo.sub.aV.sub.bP.sub.cM.sup.1.sub.dM.sup.2.sub.eM.sup.3.sub.fM.sup.4.sub.gM.sup.5.sub.hM.sup.6.sub.iO.sub.j[Chemical Formula 1]

where Mo is molybdenum, V is vanadium, P is phosphorus, and O is oxygen, M.sup.1 is one or more selected from W, Sb, As, Sn, and Pb, M.sup.2 is one or more selected from Fe, Zn, Cr, Mn, and Cu, M.sup.3 is one or more selected from Se, Ga, Ti, Ge, Cd, Ta, and Ni, M.sup.4 is one or more selected from Al, Zr, Si, and Ce, M.sup.5 is one or more selected from Au, Pd, Pt, Ag, Ru, and Rh, M.sup.6 is one or more selected from Na, K, Li, Rb, Cs, Ca, Mg, Sr, and Ba, a, b, c, d, e, f, g, h, i, and j represent the atomic proportion of each element, for preparing (meth)acrylic acid; and a method for preparing the catalyst.

The invention relates to a catalyst system for producing maleic anhydride by means of the catalytic oxidation of n-butane, comprising at least one reactor tube, which has two catalyst layers consisting of different catalyst particles, characterized in that the geometric surface area per catalyst particle is greater in the catalyst layer that is first in the gas flow direction than in the second catalyst layer. The invention further relates to a process for producing maleic anhydride by means of the catalytic oxidation of n-butane, wherein a mixture of oxygen and n-butane is fed through the catalyst system according to the invention and the at least one reactor tube is at elevated temperature.