Properties and liquefaction activities of ferrous sulfate based catalyst impregnated on two Chinese bituminous coals

Activities of ferrous sulfate based catalysts impregnated on two Chinese coals were studied in coal liquefaction, and compared with an impregnated iron sulfide catalyst. Chemical forms and particle size distribution of the impregnated ferrous sulfate based catalysts were determined using EXAFS, XRD and SAXS techniques. The impregnated ferrous sulfate shows significant activity in the liquefaction of bituminous coals, but is less active than the impregnated iron sulfide catalyst. Addition of Na2S or urea to the ferrous sulfate in the impregnation process increases the coal conversion to the level of the impregnated iron sulfide catalyst. Addition of Na2S does not significantly promote the formation of iron sulfide on coal surface as usually believed. The iron impregnated on the coal surface existed mainly in the form of γ-FeOOH regardless of the forms of iron and the promoters. The most probable diameter of the impregnated ferrous sulfate based catalyst determined by SAXS is around 40–50 Å.