Catalytic upgrading of Quercus Mongolica under methane environment to obtain high yield of bioaromatics

Abstract

This work investigated the impact of pyrolysis medium and catalyst on the production of bio-BTX (benzene, toluene, and xylene) from Quercus Mongolica (Q. Mongolica) via catalytic pyrolysis. Two different pyrolysis media (N-2 and CH4) and five different zeolite catalysts (HY, HBeta, HZSM-5, 1 wt% Ni/HZSM-5, and 1 wt% Ga/HZSM-5) were considered for the Q. Mongolica pyrolysis. The HZSM-5 yielded more BTX than the HY and HBeta due to its strong acidity. The employment of CH4 as the pyrolysis medium improved the BTX yield (e.g., 2.7 times higher total BTX yield in CH4 than in N-2) and resulted in low coke yield (e.g., 5.27% for N-2-pyrolysis and 2.57% for CH4-pyrolysis) because the CH4-drived hydrogen simulated a hydropyrolysis condition and facilitated dehydroaromatization reaction. CH4 also led to direct coupling, Diels-Alder, and co-aromatization reactions during the pyrolysis, contributing to enhancing the BTX yield. The addition of Ga to the HZSM-5 could further increase the BTX yield by means of facilitating hydrocracking/demethylation and methyl radical formation from CH4 assisting the generation of >C2 alkenes that could be further converted into BTX on acid sites of the HZSM-5.