FIELD: chemistry.
SUBSTANCE: in a first reaction zone, a starting reaction gas mixture 1 which contains propylene, molecular oxygen and at least one inert diluent gas molar ratio O2:C3H6≥1, at a first reaction stage at high temperature is passed through at least one first catalyst bed whose active mass contains at least one polymetal oxide based on molybdenum, iron and bismuth, wherein conversion of propylene in a single passage through the first catalyst bed is ≥90 mol %, while the total selectivity (SAC) of formation of acrolein and acrylic acid by-product is ≥80 mol %; optionally the temperature of the product gas mixture 1 obtained at the first reaction stage is reduced by direct cooling or indirect cooling or direct and indirect cooling; optionally secondary gas in the form of molecular oxygen or inert gas or molecular oxygen and inert gas is added to product gas mixture 1, and as a starting reaction gas mixture 2 which contains acrolein, molecular oxygen and at least one inert diluent gas in molar ratio O2:C3H4O≥0.5 at a second reaction stage at high temperature is passed through at least one second catalyst bed whose active mass contains at least one polymetal oxide based on molybdenum and vanadium, wherein acrolein conversion in a single passage through the second catalyst bed is ≥90% mol %. Total selectivity (SAA) of formation of acrylic acid on both reaction stages with respect to converted propylene is ≥70 mol %, after which acrylic acid contained in the product gas mixture 2 obtained at the second reaction stage in a separation zone is converted to condensed from which it is separated in a second separation zone by at least one thermal separation technique, characterised by that the starting reaction gas mixture 1 contains from 100 mol ppm to 3 mol % cyclopropane based on the molar amount of propylene contained therein, and propylene, required as the starting substance for this method, is added to the starting reaction gas mixture 1 in form of crude propylene which, based on volume thereof, contains at least 90 vol. % propylene, wherein at least one thermal separation technique in the second separation zone includes at least one technique for crystallisation separation of acrylic acid from the condensation phase.
EFFECT: method enables to obtain the end product depleted of propionic acid.
16 cl, 1 ex
