Provided is a process for preparing acrolein by catalytic gas phase oxidation comprising (a) providing a reaction gas comprising (i) 5 to 10 mol % propylene, (ii) 0.02 to 0.75 mol % propane, and (iii) 0.25 to 1.9 mol % of a fuel mixture comprising at least one of methane and ethane, wherein the molar ratio of the total amount of propane, methane, and ethane to the total amount of propylene is from 0.01:1 to 0.25:1, and (b) contacting the reaction gas with a mixed metal oxide catalyst comprising one or more of molybdenum, bismuth, cobalt, and iron.

Provided is a process for preparing acrolein by catalytic gas phase oxidation comprising (a) providing a reaction gas comprising (i) 5 to 10 mol % propylene, (ii) 0.02 to 0.75 mol % propane, and (iii) 0.25 to 1.9 mol % of a fuel mixture comprising at least one of methane and ethane, wherein the molar ratio of the total amount of propane, methane, and ethane to the total amount of propylene is from 0.01:1 to 0.25:1, and (b) contacting the reaction gas with a mixed metal oxide catalyst comprising one or more of molybdenum, bismuth, cobalt, and iron.

Provided is a method for producing at least one of an unsaturated aldehyde and an unsaturated carboxylic acid from an alkene by an oxidation reaction, in which a n-layered catalyst layer (n≥2) is provided in a gas flow direction in a reaction tube, two or more kinds of catalysts having different activities are used; and the catalysts are packed in such a manner that dT≤20° C. is satisfied, when a difference between a temperature PT.sub.n of an exothermic peak in a n-th layer as counted from a gas inlet and a minimum value mT.sub.n-1 of a temperature of a catalyst layer which appears between an exothermic peak in a (n−1)th layer and an exothermic peak in a n-th layer from the gas inlet is represented as dT (=PT.sub.n−mT.sub.n-1), and the change rate of dT is 2.5 or less at a reaction bath temperature within a range of ±6° C. of a reaction bath temperature at which the highest yield is obtained.

Provided is a method for producing at least one of an unsaturated aldehyde and an unsaturated carboxylic acid from an alkene by an oxidation reaction, in which a n-layered catalyst layer (n≥2) is provided in a gas flow direction in a reaction tube, two or more kinds of catalysts having different activities are used; and the catalysts are packed in such a manner that dT≤20° C. is satisfied, when a difference between a temperature PT.sub.n of an exothermic peak in a n-th layer as counted from a gas inlet and a minimum value mT.sub.n-1 of a temperature of a catalyst layer which appears between an exothermic peak in a (n−1)th layer and an exothermic peak in a n-th layer from the gas inlet is represented as dT (=PT.sub.n−mT.sub.n-1), and the change rate of dT is 2.5 or less at a reaction bath temperature within a range of ±6° C. of a reaction bath temperature at which the highest yield is obtained.

Provided is a method for producing at least one of an unsaturated aldehyde and an unsaturated carboxylic acid from an alkene by an oxidation reaction, in which a n-layered catalyst layer (n≥2) is provided in a gas flow direction in a reaction tube, two or more kinds of catalysts having different activities are used; and the catalysts are packed in such a manner that dT≤20° C. is satisfied, when a difference between a temperature PT.sub.n of an exothermic peak in a n-th layer as counted from a gas inlet and a minimum value mT.sub.n-1 of a temperature of a catalyst layer which appears between an exothermic peak in a (n−1)th layer and an exothermic peak in a n-th layer from the gas inlet is represented as dT (=PT.sub.n−mT.sub.n-1), and the change rate of dT is 2.5 or less at a reaction bath temperature within a range of ±6° C. of a reaction bath temperature at which the highest yield is obtained.

The present invention relates to a process for producing mixed oxide catalysts on the basis of molybdenum and bismuth oxides in which the precursor compounds of the components of mixed oxide catalysts provided in the form of a solution and/or suspension are subjected to a spray-drying with a specific temperature regime and the spray particles obtained in this way are then calcined to yield a catalytic active mass, and to the mixed oxide catalysts obtainable by this process and to the use of these catalysts in the partial oxidation of olefins, in particular in the partial gas phase oxidation of propene to acrolein and acrylic acid. The spray drying of the precursor compounds containing solution or suspension is performed in concurrent with a gas stream having a specific entrance temperature. Alternatively, when the main gas stream has a higher entrance temperature, an additional colder gas stream can be fed in downstream. The thus obtained mixed oxide catalysts give lower a maximum temperature in the hot spot of catalyst fixed bed when they are used in the partial gas phase oxidation of olefins.

The present invention relates to a process for producing mixed oxide catalysts on the basis of molybdenum and bismuth oxides in which the precursor compounds of the components of mixed oxide catalysts provided in the form of a solution and/or suspension are subjected to a spray-drying with a specific temperature regime and the spray particles obtained in this way are then calcined to yield a catalytic active mass, and to the mixed oxide catalysts obtainable by this process and to the use of these catalysts in the partial oxidation of olefins, in particular in the partial gas phase oxidation of propene to acrolein and acrylic acid. The spray drying of the precursor compounds containing solution or suspension is performed in concurrent with a gas stream having a specific entrance temperature. Alternatively, when the main gas stream has a higher entrance temperature, an additional colder gas stream can be fed in downstream. The thus obtained mixed oxide catalysts give lower a maximum temperature in the hot spot of catalyst fixed bed when they are used in the partial gas phase oxidation of olefins.

The present invention relates to a process for producing mixed oxide catalysts on the basis of molybdenum and bismuth oxides in which the precursor compounds of the components of mixed oxide catalysts provided in the form of a solution and/or suspension are subjected to a spray-drying with a specific temperature regime and the spray particles obtained in this way are then calcined to yield a catalytic active mass, and to the mixed oxide catalysts obtainable by this process and to the use of these catalysts in the partial oxidation of olefins, in particular in the partial gas phase oxidation of propene to acrolein and acrylic acid. The spray drying of the precursor compounds containing solution or suspension is performed in concurrent with a gas stream having a specific entrance temperature. Alternatively, when the main gas stream has a higher entrance temperature, an additional colder gas stream can be fed in downstream. The thus obtained mixed oxide catalysts give lower a maximum temperature in the hot spot of catalyst fixed bed when they are used in the partial gas phase oxidation of olefins.

A method of determining the inertness of a material regarding the formation of heavy by-products during the reaction of propylene to acrolein and acrylic acid.

A method of determining the inertness of a material regarding the formation of heavy by-products during the reaction of propylene to acrolein and acrylic acid.