As the effects of global climate change become more apparent every year, renewable and environmental-friendly fuels are needed to replace fossil fuels. Biomass fast pyrolysis (BFP) produces a key intermediate, bio-oil, that can be upgraded to provide a needed alternative. BFP combined with catalysis, known as catalytic fast pyrolysis (CFP), is a method for green synthesis of valuable aromatic chemicals, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), which are very important petrochemicals. BFP and CFP offer potential solutions to replace the current petroleum-based infrastructure and reduce the effects of climate change. However, the complex structure of biomass leads to multi-route reactions during pyrolysis that are not well defined. To better understand the reaction pathways, this study develops and deploys a methodology using isotopically labeled Arabidopsis thaliana cells as surrogate substrates. In this approach, plant cells are heterotrophically grown and preferentially labeled using 13C-containing biosynthetic precursors (glucose for carbohydrate and phenylalanine for lignin). The harvested cells, containing different levels of 13C-label, were subjected to pyroprobe-gas chromatography/mass spectrometry (py-GC/MS) to identify the products for both BFP and CFP. By tracking the 13C from substrates to products, recognizing that either holocellulose or lignin are preferentially labeled in the plant cells, reaction pathways are revealed. Furthermore, HZSM-5 catalyst modified with several types of metals were tested during CFP for BTEX yield performance. Spent coffee was the selected feedstock as BTEX yields were highest amongst various biomass varieties. Chromium modified HZSM-5 exhibited the highest aromatic yields of the catalysts evaluated, with 1 wt.% Cr/HZSM-5 leading to the highest monoaromatic hydrocarbon yield.
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