Optimum catalyst design plays a pivotal role in maximizing catalytic fast pyrolysis (CFP) bio-oil yield and quality. This work investigates the use of mordenite framework inverted (MFI) zeolites with hierarchical pore structures as potential catalysts to address the aforementioned challenges. Mesoporous MFI catalysts were created using both top-down and bottom-up approaches, were characterized and evaluated as CFP catalysts. CFP with mesoporous catalysts resulted in higher yields to aromatics and lower coke and char yields. The results of this study indicate that there is a maximum amount of mesopore volume required for optimal acid site accessibility leading to increased bio-oil production. After this maximum, intermediate aromatic hydrocarbons continue to polymerize to form bulky poly-cyclic aromatic hydrocarbons (PAHs) and coke.

The objective of the present work is to explore the particularities of a micro-scale experimental apparatus with regards to the study of catalytic fast pyrolysis (CFP) of biomass. In situ and ex situ CFP of miscanthus × giganteus were performed with ZSM-5 catalyst. Higher permanent gas yields and higher selectivity to aromatics in the bio-oil were observed from ex situ CFP, but higher bio-oil yields were recorded during in situ CFP. Solid yields were comparable across both configurations. The results from in situ and ex situ PyGC were also compared with the product yields and selectivities obtained using a bench-scale, spouted-bed reactor. The bio-oil composition and overall product distribution for the PyGC ex situ configuration more closely resembled that of the spouted-bed reactor. The coke/char from in situ CFP in the PyGC was very similar in nature to that obtained from the spouted-bed reactor.

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Formation of coke during biomass catalytic pyrolysis deteriorates the selectivity to valuable liquid products and deactivates the catalyst, due to pore blocking and active site poisoning. In this work we investigate reaction mechanisms of coke formation and the structure of coke, formed from model compounds of relevance to biomass catalytic pyrolysis. Specifically, toluene, propylene, tolualdehyde and furan are catalytically pyrolyzed over ZSM-5, focusing on their yields to catalytic coke. Pyrolysis over inert silica is also performed, in order to understand the extent of thermal reactions. The pyrolysis product distribution of each model compound is presented and discussed in comparison with coke formation mechanisms proposed in the literature. It is shown that coke is mainly formed via oligomerization and polymerization of aromatic hydrocarbons and olefins. Catalytic reactions enhance the production of coke with higher crystallinity, less condensed structure and higher H/C ratio. Catalytic pyrolysis of toluene and tolualdehyde produces coke of similar structure, containing significant amounts of aliphatic carbons. Among the model compounds studied, furan produces the most condensed form of coke with no aliphatic carbons.

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In this work, we explore pyrolysis options, namely, high pressure, H2, and metal‐loaded ZSM‐5 catalysts, to improve the limited deoxygenation capacity and reduce the excessive production of solids in biomass catalytic fast pyrolysis (CFP). Specifically, we explore the product selectivity of Miscanthus x giganteus CFP in inert or H2‐rich environments, pressures up to 450 psig, and over ZSM‐5 and Ni‐ZSM‐5. We show that higher pressures promote decarboxylation reactions, reduce the yields to liquids, and enhance the formation of solid products. Ni‐ZSM‐5 promotes decarboxylation, dehydration, and methanation reactions. The cofeeding of H2 at high pressures increases the selectivity to monoaromatic hydrocarbons with a parallel enhancement of the yield to saturated products. Solid products are reduced drastically in H2‐rich, high‐pressure experiments, and the CH4 selectivity increases. Based on these experimental findings, we present a reaction scheme that describes the impact of pressure, H2, and Ni on the product selectivity of biomass CFP.