Superacid coal chemistry. 2. Model compound studies under conditions of HF:BF 3:H 2 catalysed mild coal liquefaction

Abstract

Selected model compounds representing coal structural entities were studied under the conditions of HF-BF 3-H 2 catalysed mild coal liquefaction. Bibenzyl and diphenylmethane gave near quantitative conversion at room temperature without added hydrogen. Biphenyl, however, required hydrogen pressure at 150 °C and gave a conversion of only ≈30%. Among the model compounds containing ether linkages, dibenzyl ether and benzyl phenyl ether gave quantitative conversion at room temperature without added hydrogen. Diphenyl ether in contrast was converted (≈70% yield) only under hydrogen pressure at 155 °C. Sulphur- and nitrogen-containing model compounds were also studied. At 95 °C in the absence of hydrogen, benzyl phenyl sulphide and dibenzyl sulphide gave over 95% conversion. On the other hand diphenyl sulphide and diphenyl disulphide required hydrogen pressure at 150 °C to give conversions of ≈95%. Quinoline gave a conversion of ≈20% under hydrogen pressure at 150 °C. The formation of condensation products in these conversion processes could be suppressed by the use of a good hydrogen donor, such as isopentane.