Patent ID: 7258766

Claim:
A method for collecting acrylic acid comprising: (1) providing a collection column to which a first, second, third, fourth and fifth lines are respectively connected, wherein a first line is connected at the bottom of the collection column; a second line is connected to the collection column at a higher position than the bottom; a third line is connected to the first line and to the collection column at a higher position than the position where the second line is connected, and has a heat-removing device; a fourth line is connected to the collection column at a higher position than the position where the third line is connected; and, a fifth line is connected at the top of the collection column, which is a higher position than the position where the fourth line is connected; (2) introducing a reaction gas from the second line into the collection column at a temperature of 140 to 250° C., the reaction gas comprising acrylic acid obtained by catalytic vapor-phase oxidation of propane, propylene, and/or acrolein; (3) introducing an aqueous medium from the fourth line into the collection column at a temperature of 20 to 50° C. whereby the acrylic acid in the reaction gas is collected in the aqueous medium to produce an acrylic acid aqueous solution; (4) causing the acrylic acid aqueous solution as bottoms to flow out from the bottom of the collection column through the first line; (5) causing the reaction gas remaining after the collection step to flow out from the top of the collection column through the fifth line; (6) introducing the acrylic acid aqueous solution of the first line into the collecting column through the third line; and (7) performing heat removal in the collection column by using the heat-removing device to maintain the following condition: 0.8<(B/A)<1.25, wherein A represents a weight fraction of acrylic acid to all condensable ingredients in the reaction gas before collecting acrylic acid and B represents a weight fraction of acrylic acid in the bottoms.