Effects of oxidation of synthetic pyrite FeS_2 catalyst under air on the hydrogenation of 1-methylnaphthalene were investigated under coal hydroliquefaction condition. Catalytic activity of FeS_2 catalyst was decreased by the increasing of storage time under air at room temperature. The deactivation rate of FeS_2 was enhanced by the raising of atmospheric temperature. It was proved that the deactivated pyrite catalysts with air oxidation was reactivated by enough sulfur addition to the reaction system.
