Regulating light olefins or aromatics production in ex-situ catalytic pyrolysis of biomass by engineering the structure of tin modified ZSM-5 catalyst

Valorization of biomass to olefin or aromatics harbours tremendous practical value due to growing concerns about sustainable production of chemicals. Herein, the olefin or aromatics yields of ex-situ catalytic pyrolysis of pine can be regulated by impregnating Sn on hollow-structured ZSM-5 (M-ZSM-5) and microporous ZSM-5 catalysts in fixed-bed reactor, respectively. Results showed that Sn/ZSM-5 catalyst simultaneously increased medium acidic sites and maintained strong acidic sites, which obtained the maximum carbon yield of aromatics (33.77%) due to enhanced cracking and deoxygenation reactions. In addition, Sn boosted alkylation between olefin and aromatics, generating more alkylbenzene. In contrast, Sn/M-ZSM-5 catalyst produced the highest olefins carbon yield (12.39%) because the reduction of strong acidic sites and microporous volume inhibited the olefin aromatization. Moreover, olefins were easier to desorb from Sn/M-ZSM-5 due to the enhanced mass transfer ability, which weakened the alkylation reactions. The synergistic effect harbours great significance to manipulate the distribution of products.