Method for preparing an acrylic acid

A method for preparing acrylic acid, comprising the steps of:

• a first step of supplying an aqueous lactic acid solution to a reactor using a carrier gas;
• a second step of vaporizing the aqueous lactic acid solution to obtain vaporized lactic acid;
• a third step of bringing the vaporized lactic acid into contact with a dehydration catalyst;
• and
• a fourth step of obtaining acrylic acid,
• wherein;
• the first to the fourth steps are performed using a reactor equipped with a single reaction tube and a heating unit;
• the single reaction tube comprises a supply unit to which the aqueous lactic acid solution is supplied, a vaporization unit that vaporizes the aqueous lactic acid solution, a catalyst unit that brings the vaporized lactic acid into contact with the dehydration catalyst;
• and a discharge unit that discharges the acrylic acid;
• a heating unit comprises a first heating unit that heats the vaporization unit in a shape wrapping the single reaction tube, a second heating unit that is discontinuous with the first heating unit and heats a boundary portion between the vaporization unit and the catalyst unit and a front end of the catalyst unit, and a third heating unit which is discontinuous with the second heating unit and heats the rear end of the catalyst unit;
• and
• temperatures of the second to the fourth steps are each independently adjusted by the heating unit;
• and
• a set temperature of the second heating unit is higher than a set temperature of the third heating unit.