A method includes supplying a gas containing acrolein to a fixed bed reactor including a reaction tube to produce acrylic acid by vapor phase catalytic oxidation of acrolein. The reaction tube is packed with catalysts having different activities in such a way that catalyst layers are formed in a tube axis direction. A catalyst X having the highest activity among the catalysts contained in all the catalyst layers is placed in the whole or a part of a section up to 30% of a length of all the catalyst layers from a rearmost portion on a gas outlet side toward a gas inlet side. A catalytically active component x in the catalyst X has Mo, V, and optionally Cu. When Cu is included, its amount is 0.8 mol or less per 12 mol of Mo. A specific surface area of the catalytically active component x is 15-40 m.sup.2/g.

Embodiments of the present invention include a filter element for decomposing contaminants including a substrate, and a photocatalytic composition comprising at least a photocatalyst and a co-catalyst. The embodiments of the present invention also includes a system for decomposing contaminants including a substrate, and a photocatalytic composition comprising at least a photocatalyst and a co-catalyst; and a method using the system.

Embodiments of the present invention include a filter element for decomposing contaminants including a substrate, and a photocatalytic composition comprising at least a photocatalyst and a co-catalyst. The embodiments of the present invention also includes a system for decomposing contaminants including a substrate, and a photocatalytic composition comprising at least a photocatalyst and a co-catalyst; and a method using the system.

A method of converting one or more alkanes to one or more alkenes that includes a) providing a first stream containing one or more alkanes and oxygen to an oxidative dehydrogenation reactor; b) converting at least a portion of the one or more alkanes to one or more alkenes in the oxidative dehydrogenation reactor to provide a second stream exiting the oxidative dehydrogenation reactor containing one or more alkanes, one or more alkenes, oxygen, carbon monoxide and optionally acetylene; and c) providing the second stream to a second reactor containing a catalyst that includes a group 11 metal to convert a least a portion of the carbon monoxide to carbon dioxide and reacting the acetylene.

A method of converting one or more alkanes to one or more alkenes that includes a) providing a first stream containing one or more alkanes and oxygen to an oxidative dehydrogenation reactor; b) converting at least a portion of the one or more alkanes to one or more alkenes in the oxidative dehydrogenation reactor to provide a second stream exiting the oxidative dehydrogenation reactor containing one or more alkanes, one or more alkenes, oxygen, carbon monoxide and optionally acetylene; and c) providing the second stream to a second reactor containing a catalyst that includes a group 11 metal to convert a least a portion of the carbon monoxide to carbon dioxide and reacting the acetylene.

Provided is a composition for catalyst production which is used in the production of a catalyst for gas phase catalytic oxidation reaction or a catalyst for gas phase catalytic ammoxidation reaction, wherein the composition for catalyst production is an aqueous solution containing a niobium compound and hydrogen peroxide and optionally containing an organic acid, a molar ratio (organic acid/Nb) of a concentration of the organic acid to a Nb concentration is 0.00 or more and 2.00 or less, and a molar ratio (hydrogen peroxide/Nb) of a concentration of the hydrogen peroxide to a Nb concentration is 0.01 or more and 50 or less.

Provided is a composition for catalyst production which is used in the production of a catalyst for gas phase catalytic oxidation reaction or a catalyst for gas phase catalytic ammoxidation reaction, wherein the composition for catalyst production is an aqueous solution containing a niobium compound and hydrogen peroxide and optionally containing an organic acid, a molar ratio (organic acid/Nb) of a concentration of the organic acid to a Nb concentration is 0.00 or more and 2.00 or less, and a molar ratio (hydrogen peroxide/Nb) of a concentration of the hydrogen peroxide to a Nb concentration is 0.01 or more and 50 or less.

Provided is a method of preparing a pure M1 phase MoVTeNb-oxide catalyst with a high specific surface area, including S1) mixing and dissolving a molybdenum-containing compound, a vanadium-containing compound, a tellurium-containing compound, a niobium-containing compound and a protective agent to obtain a precursor-protective agent mixed solution, in which the protective agent is a surfactant or a small molecule organic acid and a salt thereof; S2) subjecting the precursor-protective agent mixed solution to a hydrothermal reaction to separate out a solid; S3) calcining the solid in an air atmosphere, followed by calcining the same in an inert gas, and then performing a hydrogen peroxide purification treatment to obtain a pure M1 phase MoVTeNb-oxide catalyst. This catalyst exhibits an excellent conversion rate, selectivity, space time yield and stability in the oxidative dehydrogenation reaction of ethane for preparing ethylene.

Provided is a method of preparing a pure M1 phase MoVTeNb-oxide catalyst with a high specific surface area, including S1) mixing and dissolving a molybdenum-containing compound, a vanadium-containing compound, a tellurium-containing compound, a niobium-containing compound and a protective agent to obtain a precursor-protective agent mixed solution, in which the protective agent is a surfactant or a small molecule organic acid and a salt thereof; S2) subjecting the precursor-protective agent mixed solution to a hydrothermal reaction to separate out a solid; S3) calcining the solid in an air atmosphere, followed by calcining the same in an inert gas, and then performing a hydrogen peroxide purification treatment to obtain a pure M1 phase MoVTeNb-oxide catalyst. This catalyst exhibits an excellent conversion rate, selectivity, space time yield and stability in the oxidative dehydrogenation reaction of ethane for preparing ethylene.

The present invention relates to a catalyst comprising at least one oxide of vanadium, at least one oxide of tungsten, at least one oxide of cerium, at least one oxide of titanium and at least one oxide of niobium, and an exhaust system containing said oxides.