PREPARATION OF ACRYLIC ACID

PURPOSE:To prepare the titled compound economically, without environmental pollution, by concentrating the process waste water of the catalytic vapor- phase propylene-oxidation process using a double effect evaporator, and reusing the obtained condensed liquid as the absorbent water for collecting acrylic acid. CONSTITUTION:Acrylic acid is prepared by the catalytic vapor-phase oxidation of propylene using steam and an O2-containing gas. In the above process, acrylic acid produced by the reactors 101 and 102 is cooled and absorbed in water in the collector 103 to obtain an aqueous solution. A part of the waste gas left after the collection is recycled to the oxidation reaction process through the pipe 10, and the aqueous solution of acrylic acid is sent to the acrylic acid separation steps 104-107. The waste water discharged from the separation step is concentrated by a double effect evaporator. That is, the waste water is introduced through the pipe 24 to the first evaporator 109, the vapor generated therefrom is recycled to the reactor 101, and the vapor generated from the second evaporator 110 is used as the heat source of the evaporator 109. The obtained condensed water is recycled through the pipe 9 and reused as the absorbent water for collecting acrylic acid.