Preparing acrylic acid comprises supplying propane gas to a zone to give a gas containing e.g. propylene, supplying molecular oxygen, feeding oxidation reactor with another gas containing e.g. propylene and subjecting the gas to oxidation

摘要

Preparing acrolein and/or acrylic acid from propane comprises supplying two gaseous, propane-containing current to a first reaction zone A, under the formation of a reaction gas A; introducing the reaction gas A to a reaction zone A, supplying molecular oxygen and removing the product gas containing propylene, propane and water vapor; separating water vapor from the product gas A; feeding oxidation reactor with a reaction gas B containing propane, propylene and molecular oxygen and subjecting propylene to heterogeneously catalyzed, partial gas-phase oxidation. Preparation of acrolein and/or acrylic acid from propane comprises: (a) supplying at least two gaseous, propane-containing current (where one contains at least a fresh propane) to a first reaction zone A, under the formation of a reaction gas A; introducing the reaction gas A in the reaction zone A, formed through at least a catalyst bed by means of partial heterogeneous catalytic dehydrogenation of propane, molecular hydrogen and propylene, supplying molecular oxygen to the reaction zone A, where the molecular oxygen oxidizes a partial quantity of molecular hydrogen contained in the reaction gas A to form water vapor in the reaction zone A, and removing the product gas containing propylene, propane and water vapor, from the reaction zone A; (b) partially or completely separating, optionally in a first separation zone I, the water vapor contained in the product gas A by means of condensation incorporating indirect and/or direct cooling of the product gas A, while leaving behind a product gas Aa; (c) using the product gas A or Aa along with the supply of molecular oxygen, in a reaction zone B, for feeding at least an oxidation reactor with a reaction gas B containing propane, propylene and molecular oxygen, and subjecting the propylene contained in the reactor to heterogeneously catalyzed, partial gas-phase oxidation to form acrolein and/or acrylic acid as end product, and product gas B containing non-converted propane; (d) discharging the product gas B from the reaction zone B and separating the end product in a second separation zone II, while leaving behind a residual gas containing propane; (e) optionally reintroducing the partial quantity of the residual gas exhibiting the same composition of the residual gas as a propane-containing feed stream into the reaction zone A; (f) partially or completely separating the water vapor and/or the molecular hydrogen, in a separation zone III, which are possibly contained previously in the residual gas that is not fedback into the reaction zone A, by means of condensation and membrane separation processes respectively, and taking up the contained propane from the residual gas by absorption in an organic solvent under the formation of an absorbed substance that contains propane; and (g) separating the propane, in a separation zone IV, from the absorbed substance and reintroducing as propane-containing feed stream into the reaction zone A, where in the reaction zone A, at least lot of molecular hydrogen is oxidized to form water vapor, so that the hydrogen quantity that is oxidized in the reaction zone A to form water vapor amounts to at least 20 mol.% of the quantity of molecular hydrogen that is formed in the reaction zone A.