FeSO4, Fe-2(SO4)(3), and Fe(NH4)(SO4)(2) were calcined in air at 500-800 degreesC and examined in hydrocracking of model compounds of coal, diphenyl ether, and diphenylmethane under pressurized hydrogen, 5 kg/cm(2). Highly active and stable catalysts were obtained by calcination at 800 degreesC while the heat-treatment at temperatures below 700 degreesC was of no effect. Main products from diphenyl ether were benzene and phenol in a ratio of 4:1; those from diphenylmethane were toluene and benzene in a 5:4 ratio. The catalysts showed satisfactory activities for hydrocracking of benzyl phenyl ether forming toluene and phenol as main products. TG and XRD analyses showed that all of the sulfates completely decomposed from Fe-2(SO4)(3) to Fe2O3 at temperatures between 600 and 700 degreesC. Three Fe2O3 samples were prepared by hydrolysis of iron nitrate, chloride, and sulfate followed by calcination and tested for the hydrocrackings, but all of them were inactive. XRD measurements of the sulfate materials heat-treated at 700 and 800 C showed that Fe2O3 totally transformed to Fe3O4 and alpha -Fe species by reduction and that the reduction of Fe3O4 to alpha -Fe was suppressed when prepared by treating at 800 degreesC.