Effects of added transition metals and two-stage heating on reactions of sodium-aluminate-treated coals in water with CO, H₂ and CO-H₂ mixtures

A small suite of well-characterized Australian and N. American coals ranging in rank from brown to high-volatile bituminous and in H/C atomic ratio from 0.73 to 1 was reacted at 365 and 400°O0C with CO, H₂ and CO-H₂ mixtures in water. The effect of acid-washing was negligible, except for one coal of high Mg and Ca content. Impregnation of the coals with sodium aluminate (NaAlO₂) and Fe, Co, Ni, Cu and Ni-Mo led to modest increases in conversion compared with coals impregnated with NaAlO₂ alone for reaction at 365°C. Impregnation with Sn gave no increase in conversion. Greater effects were observed on addition of transition metals for reaction at 400°C. Nickel and nickel-molybdenum were the most effective additives. There were no consistent effects of coal rank or H/C atomic ratio. Reactions in which the alkali and transition metals were added as the carbonylates NaHFe(CO)₄ and NaCo(CO)₄ gave similar results to those obtained by the impregnation method of catalyst addition. Reactions with two-stage heating (first stage 365°C; second stage 400°C) using CO or CO-H₂ gave little benefit for brown (Loy Yang) and subbituminous (Taiheiyo) coals but modest increases in conversion and asphaltene yields for high-volatile bituminous (Surat Basin) coal. However, two-stage reactions of Loy Yang brown coal with CO-H₂O-NaAlO₂ in which CO was recharged before the second stage (first stage 330, 365 or 400°C; second stage 400°C) gave large increases in both total conversion and oil yield compared with reactions for the same duration at 400°C with only a single charge of CO.