Study on catalytic thermal dissolution of lignite and hydro-liquefaction of its soluble fraction for potential jet fuel

Abstract

This work proposes a promising means for jet fuel production using lignite as feedstock, which is of great significance for resource utilization of low rank coals (LRCs). Thermal dissolution soluble fractions (TDSFs) were prepared and the ensuing hydro-liquefaction of the TDSFs was performed to obtain liquefied oil, which can be upgraded and refined into jet fuels. The effects of different catalysts on the catalytic thermal dissolution (TD) properties of Xilinguole (XLGL) lignite were studied. The structure of the TDSFs was analyzed and characterized. The results suggested that the catalytic TD could notably enhance TDSFs yield compared to non-catalytic TD, and the activity of the four catalysts used was in order of BF3/SBA-15＞FeS + S＞SO42-/ZrO2＞Fe2O3. The oil yield and composition, especially cyclanes content, varied with the hydro-liquefaction conditions, i.e., technical parameters including temperature, catalyst, solvent and TDSF type significantly changed the oil yield and cyclanes content, thus affecting the potential for jet fuel production. The Ni-Mo-S/γ-Al2O3 catalyst effectively promoted TDSFs hydro-liquefaction, and both conversion and oil yield increased with rising temperatures during catalytic and non-catalytic hydro-liquefaction. On the other hand, the cyclanes content in liquefied oil decreased with rising hydro-liquefaction temperatures. The TDSFs prepared at low temperatures are more suitable for jet fuel production due to its higher cyclanes content through hydro-liquefaction.