Comparison of coal hydroliquefaction catalysed by ZnCl 2- MCl n (CuCl, CrCl 3 and MoCl 5) and ZnCl 2 melts

Abstract

Hydrogenation of four bituminous coals impregnated with 5 wt% of either mixtures of ZnCl 2- MCl n (CuCl, CrCl 3 and MoCl 5) systems or ZnCl 2 was carried out using a batch autoclave system at 400° for 3 h at 9.8 MPa of initial hydrogen pressure. The ZnCl 2-MoCl 5 system showed the highest yield of the hexane-soluble (HS) fraction compared with the other systems irrespective of the coal used. The difference between the yields of HS fractions using the ZnCl 2-MoCl 5 and other systems was most marked for coals of fairly low volatile matter content, though the conversion was relatively low (47–66%), whilst for coals of high volatile matter content HS yields with the binary melt systems were high (86–91% conversion). Elemental analyses of the HS fractions indicated that the ZnCl 2-MoCl 5 system is most favourable in decreasing the average molecular weight and the heteroatom content of HS, this characteristic trend being confirmed also with five HS fractions separated by Chromatographic techniques. Both elemental analyses and molecular weights of asphaltene (benzene-soluble materials, BS) indicated that the ZnCl 2-MoCl 5 system is also most effective in cracking coal structure.