Catalytic pyrolysis of lignin with metal-modified HZSM-5 as catalysts for monocyclic aromatic hydrocarbons production

This work aimed to investigate the feasibility of using metal-modified (Fe, Co, Ni, Cu, Zn, Ga) HZSM-5 zeolite as catalysts for high-value monocyclic aromatic hydrocarbons production via lignin catalytic pyrolysis in a two-stage fixed bed reactor. The structure-performance relationship of the catalysts was revealed based on the catalytic reaction testing results along with the acidity and textural properties obtained via systematic physicochemical characterization techniques, thus guiding the selection of the best modification metal and the optimal loading amount. As demonstrated, the 1 wt% Co modified HZSM-5 (1%Co-HZ) exhibited relatively slight coverage effect on the active sites, while increased the mesoporous surface area and average pore size of the parent HZSM-5 zeolite. Consequently, enhanced mass-transfer efficiency was attained by the 1%Co-HZ catalyst, which achieved the highest monocyclic aromatic hydrocarbons content (29.3%) among all the investigated metal-modified HZSM-5 catalysts. In addition, the Co modified sample showed better resistance to carbon deposition than that of the unmodified one. Overall, 1%Co-HZ can be used as an effective catalyst for monocyclic aromatic hydrocarbons production in lignin catalytic pyrolysis.