Patent ID: 6995282

Claim:
A process for the purification of acrylic acid obtained by catalytic or redox oxidation of a propylene and/or acrolein gas substrate, from a gas mixture ( 1 ) resulting from said oxidation comprising mainly propylene, when the substrate comprises propylene, ultimate oxidation products, acrylic acid, acrolein, steam, acetic acid and heavy products from side reactions, wherein: the reaction gas mixture ( 1 ) is sent to the bottom of an absorption column (C 1 ), which column is fed countercurrentwise at the top with at least one heavy hydrophobic absorption solvent, in order to obtain: at the top of said column (C 1 ), a gas flow ( 7 ) composed of propylene and ultimate oxidation products of the mixture ( 1 ), major amounts of water and of acetic acid, and acrolein; and at the bottom of said column (C 1 ), a flow ( 4 ) composed of acrylic acid, the heavy absorption solvent, heavy products from side reactions, and minor amounts of acetic acid and of water; the gas flow from the top ( 7 ) of said absorption column (C 1 ) is sent to a heat exchanger (C 3 ), where it is brought into intimate contact with a descending liquid stream ( 8 ), fed at the top of the said heat exchanger (C 3 ), comprising a previously cooled flow ( 9 ), recycled from the bottom of the heat exchanger (C 3 ), in order to obtain, at the top of the heat exchanger (C 3 ), a gas flow ( 10 ) comprising the compounds present in gas ( 7 ) to said heat exchanger (C 3 ), in which most of the water and all the acetic acid are removed in flow ( 9 ) from the bottom of the heat exchanger (C 3 ), the flow ( 10 ) which contains acrolein is at least partially recycled to catalytic or redox oxidation.