A Study on Direct Coal Liquefaction Behaviors in CO/H2O and H2/THN Systems

Abstract

In the CO/H2O and H2/tetralin conditions, the liquefaction behaviors of two brown coals (Xiaolongtan and Shengli coal) and three bituminous coals (Huainan, Shenhua, and Yanzhou coal) were investigated. The results show that the lower rank coals have higher total conversion and oil + gas yield, lower asphaltene yield in H2/tetralin system. The total conversion of Shengli brown coal is the highest, getting to 84.4%, oil + gas yield is 72.3%, and asphaltene yield is 12.1%. The liquefaction process in CO atmosphere using water as a solvent was preliminarily probed with those coals. Shengli brown coal also shows good liquefaction property in a CO/H2O system; the total conversion is the highest among the five coals in the same condition, getting to 66.1%, oil + gas yield is 46.5%, and asphaltene yield is 19.6%. The liquefaction property decreases with the increase in coal rank. Although the total conversion and oil + gas yield in the CO/H2O system is lower than in the H2/tetralin system because of the excellent H donor ability of tetralin, the liquefaction in the CO/H2O system is still feasible and this might be a direct liquefaction process well fitting for lower rank coal, especially brown coal containing a certain amount of water. The oil from the liquefaction in the two processes was analyzed by proton nuclear magnetic resonance (1H-NMR). The results show that there is more Hali than Har in the oil from the liquefaction both in CO/H2O and H2/tetralin systems, and the Hali content of the oil from liquefaction in CO/H2O system is much higher than that in the H2/THN system. The existence of the hydroxide in the oil from the liquefaction in CO/H2O process indicates a significant difference from the H2/tetralin process.