Patent ID: 6403829
Filing Date: 2002-06-11
Classification: B01J,C07C

Abstract:
A process for the catalytic gas-phase oxidation of acrolein to acrylic acid, in which a reaction gas starting mixture comprising acrolein, molecular oxygen and at least one inert gas, at least 20% by volume of which consists of molecular nitrogen, and containing the molecular oxygen and the acrolein in a molar ratio O2:C3H4O&gE;0.5 is passed, at elevated temperatures, over a fixed-bed catalyst, whose active material is at least one molybdenum- and vanadium-containing multimetal oxide, in such a way that the acrolein conversion in a single pass is &gE;90 mol % and the associated selectivity of the acrylic acid formation is &gE;90 mol %, whereina) the loading of the fixed-bed catalyst where the acrolein contained in the reaction gas starting mixture is &gE;150 l (s.t.p.) of acrolein per l of catalyst bed per h, b) the fixed-bed catalyst consists of a catalyst bed arranged in two spatially successive reaction zones A, B, the temperature of the reaction zone A being from 230 to 270Â° C. and the temperature of the reaction zone B being from 250 to 300Â° C. and at the same time being at least 5Â° C. above the temperature of the reaction zone A, c) the reaction gas starting mixture flows first through the reaction zone A and then through the reaction zone B and d) the reaction zone A extends to an acrolein conversion of from 55 to 85 mol %.