In situ impregnated iron-based catalysts for direct coal liquefaction

Three methods of preparing catalysts for direct coal liquefaction (DCL) are presented, using ferric sulfide as a precursor. Of these, one involves the physical mixing of the coal and the supercritically dried catalyst, and the other two involve impregnation of the catalyst in the coal. In one of the latter two, the catalyst is prepared in situ as well. The in situ impregnated sample (IIS) of catalyst plus coal results in a high level of coal conversion. The nominal loading of the catalyst is 1.67 wt%, but even lower loadings, <0.5 wt%, show significant improvements in activity and oil yield relative to uncatalysed DCL. For DCL using the IIS catalyst, a solvent with negligible hydrogen-donating and shuttling abilities can be used; a more active solvent, with greater ability to donate and shuttle hydrogen from the gas phase to the coal, results in only a slight improvement in activity and oil yield. Hence the IIS approach appears to be an efficient method of catalyst introduction for carrying out catalytic DCL.