The effects of ZSM-5 mesoporosity and morphology on the catalytic fast pyrolysis of furan

Abstract

ZSM-5 catalysts with different morphologies were synthesized and evaluated for the catalytic conversion of furan in a fixed bed reactor to provide insights into the rational design of zeolite catalysts for catalytic fast pyrolysis (CFP). The effects of mesoporosity and morphology of ZSM-5 catalysts on the production of aromatics and olefins as well as catalyst deactivation were investigated. The results suggest that increasing mesoporosity and decreasing crystallite size can increase furan conversion and affect selectivity to products. Improved selectivities to benzene, toluene, xylene and olefins were achieved with mesoporous ZSM-5 and 100 nm ZSM-5 compared to 800 nm ZSM-5. Coke formation on zeolite catalysts during the reaction of furan was also largely reduced (up to 65%) by introducing mesoporosity. It was observed that coke is mainly formed and accumulated inside the micropores of ZSM-5 catalysts rather than on the external surface or within the mesopores. Characterization of mass transport in the coked zeolite samples using cyclohexane as a probe molecule suggested that coke blocks micropores, leading to a decrease in micropore volume during the catalyst deactivation process. However, due to the three-dimensional pore structure of ZSM-5, the mass transport properties of mesoporous ZSM-5 do not exhibit an apparent change. Catalyst deactivation was mainly due to the coverage of active sites by coke, rather than the blockage of the transport pathways by coke.