Method for purifying (meth)acrylic acid obtained by oxidizing a gaseous substrate

A process for the purification of (meth)acrylic acid from reaction gas mixture obtained by catalytic or redox oxidation of a gas selected from the group consisting of propane, propylene, acrolein, isobutane, isobutene, tertbutyl alcohol, (meth)acrolein and mixture thereof, characterized in that:

• said purification takes place in the presence of at least one polymerization inhibitor;
• said reaction gas mixture (1) is sent to the bottom of an absorption column (Cl) which is supplied at the top and in countercurrent flow with at least one heavy hydrophobic absorption solvent or solvents, to obtain:
• at the top of the column (Cl) a gas stream (7) consisting of propane, propylene, isobutane, isobutene, the products of the final oxidation of the reaction gas mixture (1), major quantities of water, acetic acid, acrylic acid, acrolein and mixtures thereof;
• at the bottom of said column (C1), a stream (4) consisting of (meth)acrylic acid, said at least one heavy absorption solvent or solvents, minor quantities of acetic acid, water, acrylic acid and mixtures thereof;
• the stream (4) issuing from the bottom of column (Cl) is sent to a separation column (C2) in which a separation is carried out to obtain:
• at the top of column (C2), a stream (5) consisting of light impurities which are sent to the bottom of absorption column (Cl);
• and
• at the bottom, a stream (6) consisting of components selected from the group consisting of (meth)acrylic acid in solution in the at least one heavy absorption solvent or solvents, a small proportion of acetic acid, acrylic acid, polymerization inhibitor or inhibitors and mixtures thereof
• characterized in that column (Cl) is operated with flow rate of said at least one heavy hydrophobic absorption solvent or solvents that is 3 to 5.6 times the flow rate of (meth)acrylic acid in the reaction gas mixture, and in that, as a separation column (C2), a rectification column is used, which is operated with a top feed and without reflux and without the introduction of external inert gas.