FIELD: chemistry.
SUBSTANCE: according to the method: A) at least two initial gas streams containing propane, which form the reaction gas A, are fed into a reaction zone A, where one of said gas streams contains fresh propane; the reaction gas A is passed through at least one catalyst layer in reaction zone A in which partial heterogeneously catalysed dehydrogenation of propane results in formation of molecular hydrogen and propylene; molecular oxygen is fed into reaction zone A and oxidises molecular hydrogen in the reaction gas A to water vapour, and a gaseous product A is collected from reaction zone A, said product containing molecular hydrogen, water vapour, propylene and propane; B) the gaseous product A collected from the reaction zone A, while feeding molecular oxygen, is used in reaction zone B to supply at least one oxidation reactor with reaction gas B which contains molecular hydrogen, water vapour, propane, propylene and molecular oxygen, and propylene contained in reaction gas B undergoes two-step heterogeneously catalysed partial gas-phase oxidation in reaction zone B to obtain a gaseous product B containing acrylic acid as the end product, unconverted propane, molecular hydrogen, water vapour and carbon dioxide as by-products, as well as other secondary components with boiling point lower or higher the boiling point of water; C) gaseous product B is output from the reaction zone B and acrylic acid, water and secondary components with boiling point higher than that of water contained therein are separated in a first separation zone I through fractional condensation or absorption, wherein the residual gas I contains unconverted propane, carbon dioxide, molecular hydrogen, secondary components with boiling point lower than that of water, as well as, if necessary, propylene and molecular oxygen not converted in reaction zone B; D) residual gas I undergoes further treatment by washing carbon dioxide contained therein, separation of a partial amount of residual gas I, as well as, if necessary, separation of molecular hydrogen contained in the residual gas I using a separating membrane; E) after further treatment, unconverted propane-containing residual gas I is returned to reaction zone A as at least one of at least two propane-containing initial streams, where in reaction zone A, a certain amount (M) of molecular hydrogen is oxidised to water vapour, which makes up at least 35 mol % but not more than 65 mol % of the total amount of molecular hydrogen produced in reaction zone A and, if necessary, fed into said reaction zone A.
EFFECT: improved method of producing acrylic acid from propane.
22 cl, 1 ex
