Production process for unsaturated aldehyde

#A. TECHNICAL FIELD

#The present invention relates to a production process for an unsaturated aldehyde and/or an unsaturated carboxylic acid. More particularly, the present invention relates to a process comprising 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 an unsaturated aldehyde and/or an unsaturated carboxylic acid.

#B. BACKGROUND ART

#While 10 L of pure water was heat-stirred, 1,500 g of ammonium molybdate was dissolved thereinto, and 425 g of 20 mass % silica sol was further added thereto. To this mixed liquid, a liquid as obtained by dissolving 1,236 g of cobalt nitrate, 412 g of nickel nitrate, 372 g of iron nitrate, and 5.7 g of potassium nitrate into 1,000 ml of pure water was dropwise added under vigorously stirred conditions. Subsequently, a liquid as obtained by dissolving 446 g of bismuth nitrate into an aqueous solution was dropwise added thereto under vigorously stirred conditions, wherein the aqueous solution was obtained by adding 250 ml of concentrated nitric acid to 500 ml of pure water. Then, the suspension as produced was heat-stirred, and thereby the major part of the water was evaporated, thus obtaining a cake solid. The cake solid as obtained was heat-treated with a box-type dryer (temperature of heated gas: 170° C., linear velocity of heated gas: 1.2 m/sec, and heat-treatment time: 12 hours), thus obtaining a blockish catalyst precursor. This catalyst precursor was pulverized, and thereafter its ignition loss ratio was measured. As a result, it was 18.9 mass %. Next, 50 mass % aqueous ammonium nitrate solution was added to the resultant catalyst precursor powder in a ratio of 260 g of the solution to 1 kg of the catalyst precursor powder, and the resultant mixture was kneaded for 1 hour, and thereafter the mixture was extrusion-molded into a ring shape of 6.0 mm in outer diameter, 2.0 mm in inner diameter, and 6.0 mm in height. Next, the resultant molded structure was calcined under a stream of air at 480° C. for 5 hours, thus obtaining a catalyst (1). The composition of metal elements in this catalyst except for oxygen was as follows:

#catalyst (1): Mo12Co6Ni2Bi1.3Fe1.3Si2K0.08.

#The catalyst (1) had a ratio R of its apparent density to its true density (apparent density of catalyst/true density of catalyst) of 0.35.