Mechanistic Insights from Isotopic Studies of Glucose Conversion to Aromatics Over ZSM-5

摘要

Due to its low cost and large availability, lignocellulosic bio-mass is being studied worldwide as a feedstock for renewable liquid biofuels.There are currently several routes being studied to convert solid biomass to a liquid fuel, which involve multiple steps, thus greatly increasing the cost of biomass con-version. We have recently shown that aromatics can be directly produced from solid biomass in a single step by catalytic fast pyrolysis (CFP) with ZSM-5 catalysts.The advantages of this approach are that aromatics can be directly produced from biomass in a single low-cost step with inexpensive zeolite-based catalysts. The desired reactions all occur inside the zeolite catalyst. Other researchers have used zeolite catalysts for conversion of biomass-derived feedstocks into aromatics, including the early work in the 1980s by Chen et al. and Dao et al. on the conversion of aqueous sugar solutions and more recently pyrolysis oilsand lignocellulosic feedstocks. The main challenge when using zeolite catalysts is controlling the complicated chemistry that occurs inside the catalyst pores. The objective of this study is to elucidate the reaction mechanism for conversion of biomass-derived oxygenates inside zeolite catalysts by performing isotopic studies. These findings give us insight into how we might control zeolite chemistry for the conversion of biomass into aromatics. Glucose is used as a model compound for cellulosic biomass in this study. We have previously shown that both glucose and cellulose yield similar product distributions when pyrolized in the presence of ZSM-5 catalyst. These previous findings suggest that both cellulose and glucose decompose to common intermediates. Therefore the mechanistic conclusions from this paper can be extended to more complicated cellulosic-type feedstocks.