Synthesis of biomass-mediated hierarchical Zeolite socony Mobil–5 and their selectivity for lignin conversion to bio-oils: Review and perspective

Conversion of lignin biomass to bio-oil is currently a very industrially attractive strategy due to energy shortages and resource scarcity. Combining the advantages of mesoporous structure and strong acidity, hierarchical zeolites are considered the promising catalytic materials that have attracted great attention in the field of crude oil cracking. This work reviewed the effect of biomass-derived compounds as templates on the pore structure and acidity of the molecular sieves, and evaluated the bio-oil quality of these biomass-mediated hierarchical molecular sieves acting on lignin or lignin derivatives and their selectivity. The morphology, particle size, and properties of biomass templates are intimately tied to the secondary porosity of hierarchical zeolites, enabling the creation of unprecedented structural features and properties within the hierarchical zeolite. The resulting hierarchical zeolite exhibits exceptional crystallinity and superior mesoporous connectivity. In addition, hierarchical zeolites synthesized from biomass templates are competitive in improving the catalytic performance of lignin degradation. When the acid content is high enough, the mesopore content and pore size become key parameters in determining the catalytic efficiency to selectively improve the bio-oil quality of lignin and its derivatives. Finally, a systematic and comprehensive outlook on the opportunities and challenges of biomass-mediated hierarchical zeolites in the synthesis and conversion of lignin to bio-oil was presented from several perspectives. This review intends to provide theoretical guidance for green synthesis of hierarchical zeolites and to propose a feasible strategy for the conversion of lignin into bio-oil.