Patent ID: 6426433
Filing Date: 2002-07-30
Classification: C07C

Abstract:
A process for the preparation of acrolein, acrylic acid or the combination of acrolein and acrylic acid from propane, in which, in a first reaction zone, the propane is subjected to a partial oxydehydrogenation with molecular oxygen under homogeneous catalysis, heterogeneous catalysis or the combination of homogeneous and heterogeneous catalysis to give propene, and the propene-containing product gas mixture formed in the first reaction zone is fed, without separating off a component of the product gas mixture, into at least one further reaction zone and, in this at least one further reaction zone, the propene contained in the product gas mixture of the first reaction zone, together with all components of the product gas mixture of the first reaction zone, is subjected to a gas-phase catalytic oxidation to acrolein, acrylic acid or the combination of acrolein and acrylic acid, acrolein, acrylic acid or the combination of acrolein and acrylic acid and water contained in the product gas mixture of the gas-phase catalytic oxidation are separated from said mixture, and the unconverted propane contained in the remaining residual gas stream is recycled as a component of the residual gas stream to the first reaction zone, wherein the molecular oxygen required in the first reaction zone and differing from recycled oxygen is added as nitrogen-containing modified air to the reaction gas starting mixture fed to the first reaction zone, with the proviso that the nitrogen content of the modified air is less than, and the oxygen content of the modified air greater than, the corresponding contents of air, and, before the recycling of the residual gas stream to the first reaction zone, at least a part of the molecular nitrogen contained in the residual gas stream is separated from the residual gas stream.