Optimizing the aromatic yield and distribution from catalytic fast pyrolysis of biomass over ZSM-5

The conversion of glucose, furan and maple wood has been investigated over different types of ZSM-5 catalyst in semi-batch and fixed-bed reactors. The aromatic yield from glucose conversion goes through a maximum as a function of the framework silica-to-alumina ratio (SAR) of ZSM-5 with an optimum at SAR = 30. This suggests that the concentration of acid sites inside the zeolite is critical for maximizing aromatic yield. Creating hierarchical mesopores within the zeolite slightly increased of coke formation and decreased the formation of the monocyclic aromatics. Mesoporous ZSM-5 was also observed to favor the production of larger alkylated monoaromatics. The selective removal of external acid sites from the ZSM-5 catalysts only slightly increased the catalyst activity but also decreased the selectivity to the desired aromatic products. (C) 2012 Elsevier B.V. All rights reserved.