Investigating the synergistic driving action of microwave and char-based multi-catalysts on biomass catalytic pyrolysis into value-added bio-products

A method for preparing value-added bio-products dominated by aromatic hydrocarbon bio-oil with high selectivity by fast pyrolysis of biomass under the synergistic effect of microwave and char-based multi-catalysts (CMCs) was proposed. Various CMCs were prepared, and their structural characteristics were compared in detail. Microwave pyrolysis (MWP) experiment shows that the synergistic of microwave and biochar (hot spot effect) activates the active sites of molecular sieve catalysts, which can improve the diffusion of heavy components, thus regulating the pyrolytic products. Two non-noble metal active sites were introduced into CMCs, and their pyrolysis characteristics were compared. The Zn-modified CMCs showed good selectivity to monocyclic aromatic hydrocarbons. The yield of monocyclic aromatic hydrocarbons (MAHs) increased to 28.49 %, and the content of C-6 similar to C-8 aromatic hydrocarbons was obviously increased, especially in the decarbonylation reaction. The Zrmodified CMCs could inhibit the transition condensation and cyclization of aromatic hydrocarbons. The ratio of MAHs to polycyclic aromatic hydrocarbons (PAHs) reached 1.31-1.42, which optimized the distribution of liquid products, and the yield of MAHs was between 22.99-28.61 %. CMCs have the characteristics of microwave absorption and catalytic conversion of aromatic hydrocarbons with high activity.