process for the production of acrolein or methacrolein by catalytic oxidation of propylene and isobutylene or tertiary butanol in oxygenated gaseous mixtures

摘要

A process is disclosed for preparing acrolein from propylene and methacrolein from isobutylene or tertiary butanol, by oxidation in oxygen-containing gas mixtures on specially prepared coated catalysts comprised of an inert support and a coating, enclosing this support, of an oxidic catalyst material containing the elements nickel, cobalt, iron, bismuth, phosphorus, molybdenum and tantalum or samarium and, if appropriate, also alkali metal or alkaline earth metal in certain atomic ratios. This coated catalyst is obtained by spraying a suspension of the starting material for the coating, which suspension contains a binder and, if appropriate, a pore-former, from above in an increasing amount onto a bed of the support, which bed is mechanically agitated and loosened up by a gas stream blow in from below, the ratio between suspending medium sprayed on and removed again by the gas stream remaining approximately constant. The thermal expansion coefficient of the precursor as a dry powder must not deviate by more than 15% from the coefficient of the support. The coating is densified by further agitation, and the material is dried in the continuing gas stream and heat-treated, if appropriate after decomposition of an added pore-former.