Process for continuously separating phthalic anhydride from the reaction gases of the catalytic oxidation of o-xylene and/or naphthalene

In the process for the continuous separation of phthalic anhydride from the reaction gas of the catalytic oxidation of o-xylene and/or naphthalene whereby said reaction gas is treated with an organic absorbent in an absorption zone, the absorbent, which is loaded with phthalic anhydride is withdrawn from the absorption zone, the absorbent is separated from said phthalic anhydride, and the separated absorbent is returned to the absorption zone, the improvement which comprises treating the reaction gas with a maleic anhydride-based absorbent containing from 0 to about 85% by weight phthalic anhydride.