Comparison of dry and solvent mediated liquefaction of high sulfur Turkish coals

摘要

Two high-sulfur Turkish coals (Gcdiz 11.1 % daf; Cayirhan 7.5 % daf) were liquefied via catalytic and non-catalytic reactions in microautoclave tubing bombs in the temperature range 300-450°C, under 1000 psi H_2 for 30 min., in the presence and absence of the H-donor solvent, tetralin. Ammonium heptamolybdate was utilised as the catalyst precursor in the catalytic runs. In terms of total conversion to THF-solubles and oil and gas formation, optimum conditions were found to be 450 °C in the presence of tetralin. Indeed, the presence of tetralin promoted higher total conversions and oil formation at all temperatures. However, both coals demonstrated their highest overall conversion at 400 °C in the absence of solvent; 90% for Gediz coal and 75% for Cayirhan, although the product slate shifted to higher molecular weight products in this case. Conversion of sulfur to H_2S increased with temperature; approximately half the sulfur content of both coals converted to H_2S at 450 °C. However tetralin was found to retard H_2S formation; the amount of H_2S formed was ca. 1/3-1/2 of that without solvent. Primary sulfur structures determined in the oil fraction were dibenzothiophene and various alkyl substituted benzothiophenes. Catalyst was slightly effective in removing sulfur in the absence of solvent, but only a negligible effect was observed in the presence of tetralin.