Effects of Ionic Liquid-Assisted Pretreatment of Heavy Metal-Contaminated Biomass on the Yield and Composition of Syngas Production Using Noncatalytic and Catalytic Pyrolysis and Gasification Processes

In this research, noncatalytic and catalytic pyrolysis and gasification of heavy metal-contaminated biomass (HMCB)-untreated and pretreated using a low-cost ionic liquid (IL, triethylammonium hydrogen sulfate)-are investigated. To explore the effects of the pretreatment on the yield and composition of the produced syngases, both untreated and IL-pretreated HMCB were exposed to pyrolysis and gasification processes to highest temperatures of 700 and 900 degrees C with heating rates of 30 and 5 degrees C/min without and with zeolite, tincal, and potassium carbonate catalysts, respectively. Pyrolysis results show the negative effects of IL-based pretreatment of HMCB on syngas yield and its composition. In absolute terms, tincal and zeolite play positive roles in enhancing the syngas yield and H-2 concentration obtained from catalytic pyrolysis of the IL-pretreated HMCB, but not in comparison with the pyrolysis of the raw biomass. On the contrary, the results demonstrate the synergetic effects of IL-based pretreatment of HMCB and its catalytic gasification toward higher syngas yield and H-2/CO ratio with 32 and 153% increment, respectively, compared to noncatalytic gasification of the raw HMCB. The catalytic gasification of the IL-pretreated HMCB revealed five times higher syngas yield (an H-2-enriched syngas with lower CO2 content), compared to catalytic pyrolysis using tincal.