Effect of pretreatment and various types of catalysts on liquefaction of lignite and biomass

Today, fossil fuels are still being used intensively to meet the growing energy demand. Direct combustion of coal leads to an increase in greenhouse gases and global average temperature. Direct liquefaction technology is an important modern clean coal technology for the efficient and clean use of coal resources. Conversion of low-quality coals with high ash and sulfur content into new liquid fuels and chemical raw meterials by direct liquefaction is an effective method for such coals. In this work, the desulphurization of high sulfur Muğla-Yatağan (MY) and Tunçbilek (TB) lignites and the potential of liquefaction of lignite and pine cones under catalytic and non-catalytic conditions to produce a new liquid fuel and valuable basic chemical raw materials were investigated. Liquefaction experiments were carried out at 325-375 ºC, 1/1-1/4 solid/solvent ratio, 20 bar initial pressure, 1-9%catalyst concentration, 15-90 min, 1/1-1/4 lignite/biomass ratio. The zero valence nano-iron catalyst (SDN/CK) used in the catalytic liquefaction experiments was synthesized under laboratory conditions. To determine the effect of mineral matter in the coal on the liquefaction efficiency, liquefaction experiments were carried out using both raw lignite samples and lignite samples subjected to a desulfurization process. According to the desulfurization results obtained, the total desulfurization was 32%and 48%for MY and TB lignite at 30oC, 30%H2O2 and 60 min process conditions, respectively. The highest total conversion (85%) and oil yield (62%) were obtained at 400oC and 3%SDN/SC catalyst concentration of pine cones with Muğla-Yatağan lignite under catalytic conditions. The SDN/CK catalyst partially outperformed the commercially used catalysts. The liquid products obtained from the liquefaction of lignite alone under non-catalytic conditions at 375ºC for 60 min consisted mainly of compounds with carbon numbers C6-C26, whereas the liquid products obtained from the liquefaction of lignite and biomass together under catalytic conditions (SDN/SC catalyst) at 375ºC for 60 min consisted of compounds with carbon numbers C6-C14. It was observed that total conversion and oil yields decreased in the liquefaction of lignite after desulfurization.