Short contact-time pyrolytic liquefaction of Wandoan subbituminous coal and catalytic upgrading of the SCT-SRC

In the two stage liquefaction of Wandoan subbituminous coal it was found that the coal was effectively converted into THF-soluble products with high conversion and low hydrogen consumption by pyrolytic procedures in a N₂-tetralin system, using relatively low heating rates, high temperature and short-contact-time conditions. Runs carried out at 440 °C (with 2.5 MPa N₂) showed better efficiency as regards higher conversions and SRC yields, and lower consumption of hydrogen from tetralin. Comparative examination of these short contact-time runs with other runs under different conditions suggested that coal pyrolysis and transferable hydrogen within the coal itself effectively contributed to the liquefaction of the coal in the N₂-tetralin system. The so derived SCTSRC from the first stage was upgraded in a H₂-tetralin system in the presence of MoCl₃- and NiCl₂LiClKCl salt catalysts. The yields of oil (hexane-solubles) including light distillates (C₅-250 °C) were as high as in the range 69-79 wt % of SRC and gas yields were < 2.9 wt % of SRC with hydrogen consumptions of < 1.4 wt % of SRC. The use of the MoCl₃ and the NiCl₂ salt catalysts appeared to decrease the heteroatom content and improved the quality of the oil products. The results are discussed on the basis of a generalized reaction model for coal liquefaction.