An oxide catalyst to be used for gas-phase catalytic ammoxidation reaction of propane or isobutane, the oxide catalyst comprising a composite oxide, wherein the composite oxide comprises a catalytically active species to be isolated from the composite oxide using a hydrogen peroxide solution, and the catalytically active species has an average composition represented by the following formula (1) in STEM-EDX measurements;

Formula:

Mo.sub.1V.sub.aSb.sub.bNb.sub.cW.sub.dX.sub.eO.sub.n   (1) wherein X represents at least one selected from the group consisting of Te, Ce, Ti, and Ta; a, b, c, and d satisfy relations represented by a formulae of 0.050≤a≤0.200, 0.050≤b≤0.200, 0.100≤c≤0.300, 0≤d≤0.100, 0≤e≤0.100, and a≤c; and n represents a number determined by valences of the other elements.

The present invention relates to catalyst compositions containing a mixed oxide catalyst of formula (I) or formula (II) as described herein, their preparation, and their use in a process for ammoxidation of various organic compounds to their corresponding nitriles and to the selective catalytic oxidation of excess NH.sub.3 present in effluent gas streams to N.sub.2 and/or NO.sub.x.

The present invention relates to catalyst compositions containing a mixed oxide catalyst of formula (I) or formula (II) as described herein, their preparation, and their use in a process for ammoxidation of various organic compounds to their corresponding nitriles and to the selective catalytic oxidation of excess NH.sub.3 present in effluent gas streams to N.sub.2 and/or NO.sub.x.

The present invention clarifies the characteristic of the hygroscopicity of the catalyst for producing acrylic acid and finds out a relationship between the water amount of the catalyst and the catalytic performance as the catalyst for producing acrylic acid, and provides an excellent catalyst. Provided is a catalyst for producing acrylic acid, which contains molybdenum and vanadium as essential active components, in which the amount of water contained in the catalyst is 0.01 mass % or more and 0.53 mass % or less.

The present invention clarifies the characteristic of the hygroscopicity of the catalyst for producing acrylic acid and finds out a relationship between the water amount of the catalyst and the catalytic performance as the catalyst for producing acrylic acid, and provides an excellent catalyst. Provided is a catalyst for producing acrylic acid, which contains molybdenum and vanadium as essential active components, in which the amount of water contained in the catalyst is 0.01 mass % or more and 0.53 mass % or less.

Provided is a catalyst for producing an unsaturated carboxylic acid, in which a ratio of a diffraction line intensity of 2=19.10.3 with respect to a diffraction line intensity of 2=10.70.3 in X-ray diffraction measurement is 0.20 or more and less than 0.58, and the catalyst having an active component represented by formula (A) shown below:

Mo.sub.10V.sub.aP.sub.bCu.sub.cAs.sub.dX.sub.eO.sub.g(A)

Provided is a catalyst for producing an unsaturated carboxylic acid, in which a ratio of a diffraction line intensity of 2=19.10.3 with respect to a diffraction line intensity of 2=10.70.3 in X-ray diffraction measurement is 0.20 or more and less than 0.58, and the catalyst having an active component represented by formula (A) shown below:

Mo.sub.10V.sub.aP.sub.bCu.sub.cAs.sub.dX.sub.eO.sub.g(A)

A method for producing an oxide catalyst containing Mo, V, Sb, and Nb, the method including: a raw material preparation step including sub-step (I) of preparing an aqueous mixed liquid (A) containing Mo, V, and Sb, sub-step (II) of adding hydrogen peroxide to the aqueous mixed liquid (A), thereby facilitating oxidation of the aqueous mixed liquid (A) and obtaining an aqueous mixed liquid (A), and sub-step (III) of mixing the aqueous mixed liquid (A) and a Nb raw material liquid (B), thereby obtaining an aqueous mixed liquid (C); a drying step of drying the aqueous mixed liquid (C), thereby obtaining a dried powder; and a calcination step of calcining the dried powder under an inert gas atmosphere, wherein a time elapsed from addition of the hydrogen peroxide to the aqueous mixed liquid (A) to mixing the Nb raw material liquid (B) therewith is less than 5 minutes and the aqueous mixed liquid (A) before being subjected to the sub-step (III) has an oxidation-reduction potential of 150 to 350 mV.

A method for producing an oxide catalyst containing Mo, V, Sb, and Nb, the method including: a raw material preparation step including sub-step (I) of preparing an aqueous mixed liquid (A) containing Mo, V, and Sb, sub-step (II) of adding hydrogen peroxide to the aqueous mixed liquid (A), thereby facilitating oxidation of the aqueous mixed liquid (A) and obtaining an aqueous mixed liquid (A), and sub-step (III) of mixing the aqueous mixed liquid (A) and a Nb raw material liquid (B), thereby obtaining an aqueous mixed liquid (C); a drying step of drying the aqueous mixed liquid (C), thereby obtaining a dried powder; and a calcination step of calcining the dried powder under an inert gas atmosphere, wherein a time elapsed from addition of the hydrogen peroxide to the aqueous mixed liquid (A) to mixing the Nb raw material liquid (B) therewith is less than 5 minutes and the aqueous mixed liquid (A) before being subjected to the sub-step (III) has an oxidation-reduction potential of 150 to 350 mV.

The present invention disclose catalyst compositions for the selective catalytic reduction of nitrogen oxides, consisting of at least one oxide of vanadium in an amount of 2.0 to 4.0 wt.-%, calculated as V.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of tungsten in an amount of 2.5 to 7.2 wt.-%, calculated as WO.sub.3 and based on the total weight of the catalyst composition, at least one oxide of antimony in an amount of 0.6 to 3.4 wt.-%, calculated as Sb.sub.2O.sub.5 and based on the total weight of the catalyst composition, at least one oxide of zirconium in an amount of 0 to 1.0 wt.-%, calculated as ZrO.sub.2 and based on the total weight of the catalyst, and at least one oxide of titanium in an amount of 84.6 to 94.9 wt.-% calculated as TiO.sub.2 and based on the total weight of the catalyst, wherein the weight ratio of the oxides of vanadium, tungsten, antimony, titanium and optionally zirconium, calculated as V.sub.2O.sub.5, WO.sub.3, Sb.sub.2O.sub.5, TiO.sub.2 and optionally ZrC.sub.2, respectively, add up to 100 wt.-%. Furthermore, SCR catalytic articles are disclosed wherein an SCR catalyst composition according to the invention is affixed in the form of a coating. Suitable catalyst carriers are corrugated substrates and cordierite monoliths. The SCR catalytic articles can be used in a method for the reduction of nitrogen oxides in exhaust gases of lean-burn internal combustion engines, and they can furthermore be comprised in an exhaust gas purification system for the treatment of diesel exhaust gas.