CATALYTIC EFFECTS OF ZINC-CHLORIDE IN THE PYROLYSIS OF SPANISH HIGH SULFUR COALS

Study of the catalytic effects of zinc chloride (ZnCl2) in the slow pyrolysis of two Spanish high sulphur coals showed that the behaviour of ZnCl2 was modified by the presence of organic sulphur and minerals such as calcite and pyrite in the coals. The desulphurization of chars from impregnated coals was lower due to the formation of ZnS from the H2S evolved during pyrolysis. ZnCl2 produced a specific dehydrogenation of coal structure from aliphatic structures. This reaction took place at temperatures below 400-degrees-C and produced a loss of tar-forming structures and an increase of cross-linking. This implies a reduction of tar yield for impregnated coals.