METHOD FOR PRODUCING PHTHALIC ANHYDRIDE THAT CONFORMS TO SPECIFICATIONS.

摘要

The invention relates to a method for producing phthalic anhydride that conforms to specifications in a purification of crude phthalic anhydride by distillation at a reduced pressure. According to said method, the crude phthalic anhydride is supplied to the distillation column above a lateral outlet, the low-boilers are drawn off at the head of the column or in the vicinity of the head of the column and the phthalic anhydride that conforms to specifications is removed from the lateral outlet. The method uses a distillation column with a number of theoretical separation stages situated above the supply of the crude phthalic anhydride to the distillation column that lies between 10 and 20 and the column operates with a reflux ratio of between 0.1 and 0.5.