Method for producing acrylic acid

A method d for producing acrylic acid, comprising 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,

• wherein the reaction tube is packed with catalysts having different activities in such a way that two or more catalyst layers are formed in a tube axis direction of the reaction tube;
• 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 of all the catalyst layers;
• a layer length of a catalyst layer including the catalyst X is 3 to 30% of the length of all the catalyst layers;
• a catalytically active component x in the catalyst X has Mo, V, and optionally Cu, and when Cu is included, an amount thereof is 0.8 mol or less per 12 mol of Mo;
• and
• a specific surface area of the catalytically active component x is 15 m2/g to 40 m2/g.