Influences of chemical structure and physical properties of coal macerals on coal liquefaction by quantum chemistry calculation

Abstract

Significant progress has been made in the simulation of coal liquefaction by the quantum chemistry calculation among similar rank coals. Three Chinese bituminous coals from Lingwu, Shendong and Pingshuo were chosen as samples and evaluated. By means of density gradient centrifugation, six kinds of coal macerals with greater than 95% purity were obtained. Using Materials Studio 4.0 quantum chemistry software the hydro-liquefaction activity differences were analyzed by the bond orders of six maceral model structures. Calculation results were compared with specific surface area and average pore size data from nitrogen physical adsorption. It showed that the specific surface area of macerals had no direct relation with their liquefaction yield, while their average pore size and liquefaction yield were shown to be positively correlated. Also, chemical bond cleavage activity of coal structure units influenced liquefaction yield. Under the solvent cycle condition, the capacity of coal liquefaction is potentially decided by the efficiency of hydrogenation to stabilize the free radicals, and also by coal pore size. The rapid cycle of solvent increases the liquefaction yield due to more additional fresh solvent added. The chemical structure and physical properties of Shendong coal displayed much better liquefaction capability than other coals examined.