Method for the heterogenically catalysed partial gas phase oxidation of propene to form acrylic acid

摘要

Heterogeneous catalyzed gas phase partial oxidation of propene to acrylic acid comprises processing a reaction mixture using a fixed catalyst bed comprising two separate reaction zones in series, A and B maintained at 290-380[deg]C and where active mass comprises a multimetal oxide of Mo, Fe and Bi followed by a second fixed catalyst bed separated into 2 reaction zones C and D at 230-320[deg]C comprising a multimetal oxide of Mo and V. A process for the heterogeneous catalyzed partial oxidation of propene to acrylic acid in the gas phase comprises processing a reaction mixture comprising propene, molecular oxygen and at least one inert gas having a molar ratio of O 2 to C 3H 6 of at least 1 in a first reaction stage using a fixed catalyst bed. The fixed bed comprises two separate reaction zones in series, A and B maintained at 290-380[deg]C. The catalyst active mass comprises a multimetal oxide of Mo, Fe and Bi such that zone A results in a propene conversion of 40-80 mol.% and a single pass through the total catalyst bed results in a greater than 90 mol.% propene conversion with a selectivity to acrolein of greater than 90 mol.%. The process features optional cooling of the mixture leaving the first reaction stage and optional addition of molecular oxygen and/or inert gas. The product mixture comprises acrolein, molecular oxygen and at least one inert gas to form a second reaction mixture having a molar ratio of O 2:C 3H 4O of at least 0.5 that is fed to a second fixed catalyst bed. The second fixed catalyst bed is separated into two reaction zones C and D at 230-320[deg]C comprising a multimetal oxide of Mo and V. The conversion of acrolein in zone C is 45-85 mol.% and the acrolein conversion over the second bed is at least 90 mol.% with a selectivity (propene to acrylic acid) of greater than 80 mol.%. The reaction mixture passes through the zones corresponding to their alphabetical order and is characterized by in the first fixed bed: (i) a reaction gas loading of 90-160 Nl propene per liter of fixed catalyst bed per hour; (ii) the volume specific activity of the fixed catalyst bed in the flow direction of the reaction mixture is either constant or increases at least once; and (iii) the difference between the maximum temperatures in zone A and B is at least 0[deg]C The second fixed bed features: a reaction gas feed of 70-145 Nl acrolein per liter of bed per hour; at least one increase in the volume specific activity of the second catalyst bed in the direction of flow; and a difference between the maximum temperature in C and D of at least 0[deg]C.