Patent ID: 7884235

Claim:
A method for gas-phase catalytic oxidation in a fixed bed reactor including a gas-phase oxidation catalyst layer, wherein a treating agent for removing organic substance and/or carbides is disposed on the upstream side of the gas-phase oxidation catalyst layer in respect of the direction of the gas flow, the adsorption capacity of the treating agent being at least 0.05% by mass, as measured by crotonaldehyde as an indicator of organic substance, in which the gas phase catalytic oxidation reaction is that for producing (meth)acrylic acid through two-stage reaction of propylene, isobutylene, t-butyl alcohol or methyl-t-butyl ether, including a catalyst for the first stage reaction and a catalyst for the second stage reaction, and wherein said treating agent is selected from the group consisting of silica-alumina, silica-titania, silica-zinc oxide, silica-zirconia, alumina-titania, alumina-zinc oxide, alumina-zirconia, titania-zirconia, zinc oxide-zirconia, zeolite, magnesium carbonate and calcium carbonate.