Method for the catalytic gas-phase oxidation of propene to acrylic acid
AssigneeBASF SE
InventorsSigne Unverricht, Heiko Arnold, Andreas Tenten, Ulrich Hammon, Hans-Peter Neumann, Klaus Harth
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Abstract
A process for the catalytic gas-phase oxidation of propene to acrylic acid, in which the reaction gas starting mixture is oxidized, with an increased propene loading, in a first reaction stage, over a first fixed-bed catalyst and then the acrolein-containing product gas mixture of the first reaction stage is oxidized, in a second reaction stage, with an increased acrolein loading, over a second fixed-bed catalyst, the catalyst moldings in both reaction stages having an annular geometry.
Claims57
A process for the catalytic gas-phase oxidation of propene to acrylic acid, in which a reaction gas starting mixture 1 which comprises propene, molecular oxygen and at least one inert gas and contains the molecular oxygen and the propene in a molar O2:C3H6 ratio of ≧1 is first passed, in a first reaction stage at elevated temperatures, over a first fixed-bed catalyst whose active material is at least one multimetal oxide containing (1) at least one of molybdenum and tungsten, and (2) at least one of bismuth, tellurium, antimony, tin and copper, in such a way that the propene conversion in a single pass is ≧90 mol % and the associated selectivity of the acrolein formation and of the acrylic acid byproduct formation together is ≧90 mol %, the temperature of the product gas mixture leaving the first reaction stage is, if required, reduced by direct, indirect, or direct and indirect, cooling and, if required, molecular oxygen, inert gas, or molecular oxygen and inert gas, are added to the product gas mixture, and the product gas mixture, as reaction gas starting mixture 2 which comprises acrolein, molecular oxygen and at least one inert gas and contains the molecular oxygen and the acrolein in a molar O2:C3H4O ratio of ≧0.5, is then passed, in a second reaction stage at elevated temperatures, over a second fixed-bed catalyst whose active material is at least one multimetal oxide containing molybdenum and vanadium, in such a way that the acrolein conversion in a single pass is ≧90 mol % and the selectivity of the acrylic acid formation balanced over both reaction stages is ≧80 mol %, based on propene converted, wherein
- a) the loading of the first fixed-bed catalyst with the propene contained in the reaction gas starting mixture 1 is ≧160 l (S.T.P.) of propene/l of catalyst bed·h,
- b) the loading of the second fixed-bed catalyst with the acrolein contained in the reaction gas starting mixture 2 is ≧140 l (S.T.P.) of acrolein/l of catalyst bed·h and
- c) both the geometry of the catalyst moldings of the first fixed-bed catalyst and the geometry of the catalyst moldings of the second fixed-bed catalyst are annular, with the proviso that
- the external ring diameter is from 2 to 11 mm,
- the ring length is from 2 to 11 mm and
- the wall thickness of the ring is from 1 to 5 mm.
A process for the catalytic gas-phase oxidation of propene to acrolein, acrylic acid, or acrolein and acrylic acid, in which a reaction gas starting mixture 1 which comprises propene, molecular oxygen and at least one inert gas and contains the molecular oxygen and the propene in a molar O2:C3H6 ratio of ≧1 is passed, in a reaction stage at elevated temperatures, over a first fixed-bed catalyst whose active material is at least one multimetal oxide containing (1) at least one of molybdenum and tungsten, and (2) at least one of bismuth, tellurium, antimony, tin and copper, in such a way that the propene conversion in a single pass is ≧90 mol % and the associated selectivity of the acrolein formation and of the acrylic acid byproduct formation together is ≧90 mol %, wherein
- a) the loading of the fixed-bed catalyst with the propene contained in the reaction gas starting mixture 1 is ≧160 l (S.T.P.) of propene/l of the catalyst bed·h and
- b) the geometry of the catalyst moldings of the fixed-bed catalyst is annular, with the proviso that
- the external diameter of the ring is from 2 to 11 mm,
- the ring length is from 2 to 11 mm and
- the wall thickness of the ring is from 1 to 5 mm.
The process according to claim 56, wherein the molar O2:acrolein ratio in the reaction gas starting mixture 2 is ≧1 and ≦2.
Dependencies are inferred from the claim text.