Patent ID: 7157597
Filing Date: 2007-01-02
Classification: C07C

Abstract:
1. A process for partially oxidizing acrolein to acrylic acid in the gas phase under heterogeneous catalysis by conducting a starting reaction gas mixture comprising acrolein, molecular oxygen and at least one inert gas, and contains the molecular oxygen and the acrolein in a molar O 2 :C 3 H 4 O ratio of ≧0.5 in a reaction stage over a fixed catalyst bed whose active composition is at least one multimetal oxide comprising the elements Mo and V, in such a way that the fixed catalyst bed is arranged in two spatially successive temperature zones A, B, both the temperature of temperature zone A and the temperature of temperature zone B are a temperature in the range from 230 to 320° C., the fixed catalyst bed consists of at least two spatially successive fixed catalyst bed zones, and the volume-specific activity within one fixed catalyst bed zone is substantially constant and increases sharply in the flow direction of the reaction gas mixture at the transition from one fixed catalyst bed zone to another fixed catalyst bed zone, the temperature zone A extends up to a conversion of the acrolein of from 45 to 85 mol %, on single pass of the starting reaction gas mixture through the entire fixed catalyst bed, the acrolein conversion is ≧90 mol % and the selectivity of acrylic acid formation based on converted acrolein is ≧90 mol %, the sequence in time in which the reaction gas mixture flows through the temperature zones A, B corresponds to the alphabetic sequence of the temperature zones, the hourly space velocity of the acrolein contained in the starting reaction gas mixture on the fixed catalyst bed is ≧70 l (STP) of acrolein/l of fixed bed catalyst ·h, and the difference T wherein the transition from temperature zone A to temperature zone B in fixed catalyst bed does not coincide with a transition from one fixed catalyst bed zone to another fixed catalyst bed zone.