PURPOSE: To obtain the titled compound useful as a raw material for dye, etc. by common reaction operations in high conversion directly, by reacting phthalic anhydride or phthalic anhyride with benzene using a catalyst consisting of silica-alumina-iron oxide at high temperature in gaseous phase.

CONSTITUTION: Phthalic anhydride or phthalic anhydride and benzene are subjected to catalytic reaction in the presence of a catalyst consisting substantially of silica-alumina-iron oxide at 300W500°C for 0.5W10sec to give anthrquinone. In the composition of the catalyst, a weight ratio of SiO2: Al2O3 is 95:5W50:50, and a weight ratio of iron oxide to SiO2-Al2O3 is 100:0.1W100:20. The catalyst is prepared by blending silica gel with Al(OH)3 and iron oxide in the above-mentioned ratio, adding water to the blend, mixing well the blend, drying the blend at 100W 150°C, and calcining at 500W600°C.

EFFECT: The activity of the catalyst lasts for a long time, a time required for reproduction operation is short.

USE: An additive for pulp production, etc.