Patent ID: 6960684

Claim:
A production process for an unsaturated aldehyde and an unsaturated carboxylic acid, which comprises the step of carrying out catalytic gas phase oxidation of at least one compound selected from the group consisting of propylene, isobutylene, t-butyl alcohol, and methyl t-butyl ether as a raw material with molecular oxygen or a molecular-oxygen-containing gas by using a fixed bed multitubular reactor which is packed with catalysts, thereby producing the unsaturated aldehyde and the unsaturated carboxylic acid which correspond to the raw material; wherein an oxide and/or complex oxide including molybdenum, bismuth, and iron as essential components are used as the catalysts, and further with the production process further comprising the steps of: dividing the inside of each reaction tube of the fixed-bed multitubular reactor in a tubular axial direction to thus arrange at least two reaction zones; and then packing these reaction zones with the catalysts in such a manner that the ratio R of the apparent density of the catalyst to the true density of the catalyst (apparent density of catalyst/true density of catalyst) in each reaction zone differs from that in another reaction zone.