Direct liquefaction performance of sub-bituminous coal from Hefeng by solid super acids and pyrolysis kinetic analysis of the corresponding residue

摘要

Highly active, recyclable, and reusable supported super-acid catalyst is of great significance for improving coal liquefaction performance and liquefaction conditions and realizing comprehensive utilization of coal resources. Solid super-acid catalysts were prepared by impregnation method with trifluoromethanesulfonic acid (TFMSA) supported on different carriers (ZrO2, Al2O3, SiO2, and ZSM-5). Hefeng sub-bituminous coal (HFSB) was used as raw material to investigate the liquefaction effect of the catalysts. Composition, structure, acidity property of the catalysts were analyzed by EDS, XRD, and NH3-TPD methods, and direct coal liquefaction performance of the catalysts was performed, and TG-DTG characterization was used to evaluate the pyrolysis behavior of the liquefaction residue. Results showed that activity of the four supported solid super-acid catalysts was followed by TFMSA/ZrO2, TFMSA/ZSM-5, TFMSA/Al2O3, and TFMSA/SiO2, with coal conversions of 84.20 %, 78.40 %, 76.67 % and 73.23 %, and oil yields of 67.16 %, 62.53 %, 61.15 %, and 58.41 %, respectively. The Coast-Redfern method was used to analyze the pyrolysis kinetics of the four coal liquefaction residues (R-ZrO2, R-ZSM-5, R-Al2O3, and R-SiO2). Results presented that, in low temperature range (200-530 degrees C), except R-SiO2, the pyrolysis process of residues conforms to the third-order reaction. And in high temperature range (530-850 degrees C), the four-order reaction is more suitable for the four residues. The pyrolysis activation energy of R-ZrO2 is lower at low temperature region (16.822 kJ/mol), while R-Al2O3 presents lower activation energy at high temperature range (45.494 kJ/mol).