Hydrogenation reactions of iron/tin treated and acid-washed Morwell coal in a time-sampled autoclave

Liquefaction of iron/tin treated acid-washed Morwell coal has been studied in a time-sampled reactor which rapidly charges reactants into a preheated autoclave and samples its contents throughout the course of the reaction. A large increase in conversion at short residence times compared to that of untreated coal was observed, and almost 100% conversion was achieved for residence times greater than 30 min. The increased conversion was mainly to oil, whereas in conventional batch autoclaves the increase is mainly to asphaltenes. Strong evidence was obtained for the formation of a viscous product after 5 to 10 min of reaction; this viscous product made sampling unreliable and sometimes blocked the sampling lines completely. It decomposed after 10 to 20 min of reaction. The fate of the iron and tin additives was followed by ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectroscopy. Most of the iron was converted from Fe(III) oxyhydroxide to magnetite (Fe₃O₄) and troilite (FeS) during the residence time interval, 6 to 8 min, when the viscous product was present. The tin was reduced from its initial SnO₂.xH₂O form but the reaction was much slower than that of iron. Acid-washing the Morwell coal increased the conversion at short reaction times in the time-sampled autoclave, as was observed earlier in batch autoclave studies.