Contrasting coking behaviour in ZSM-11 and ZSM-5 for biomass transformations

Catalyst lifetime is a vital metric for improving the efficiency of industrial processes, both from a financial and sustainable viewpoint. In microporous materials (with pore sizes < 2 nm), such as zeolites, the formation of bulky aromatic molecules (coke) is a common occurrence in many high-temperature (> 300 oC) catalytic hydrocarbon transformations. One such transformation is catalytic fast pyrolysis (CFP), which enables conversion of lignocellulosic biomass to valuable benzene, toluene, xylene (BTX) monomers in a single step, and is likely to form part of any future UK biorefinery scenario. This proposal investigates the use of two Fe modified zeolites with different frameworks, Fe/ZSM-5 (zig-zag channels) and Fe/ZSM-11 (straight channels) for CFP of a biomass model compound. Coke formation is the primary mechanism for deactivation during CFP, and this experiment aims to investigate how the choice of framework affects its formation.
The two systems have very similar size pores; ~ 5.3 – 5.5 Å, but with subtly different framework topologies. Whilst ZSM-5 is constructed from sinusoidal channels that intersect one another, the channels in ZSM-11 are straight. We believe that this plays a significant role in varying the catalysts lifetime.