(516f) Investigating C-C Coupling Pathways for the Sustainable Production of Liquid Fuels

The search for renewable alternatives to current industrial products, processes, and technologies has been a priority for the field of catalysis during the past decades. In particular, research efforts have focused on utilizing abundant, renewable resources available in the United States, such as biomass, and transforming them into fuels and value-added products in a sustainable manner. C­rude oil, a non-renewable unrefined petroleum feedstock subject to depletion, has served as the principal energy source for processing and refinement into transportation fuels. Thus, both environmental and economic reasons have driven the development of biological, catalytic, and thermochemical pathways for deconstruction, conversion, and further upgrading of biomass into advanced materials. The thermochemical pathway for conversion typically involves hydrogenation, dehydration, hydrodeoxygenation, isomerization, and carbon-carbon coupling reactions. Carbon-carbon coupling reactions are key in the catalytic conversion step of the process, as they enable the construction of complex organic molecules by forming new carbon-carbon bonds and can be rate limiting under a variety of conditions. In this work, propionaldehyde and ethylene were studied as model compounds representative of cellulosic-derived biomass deconstruction products. Conversion of these compounds into longer carbon-chain structures over aluminosilicate materials via three coupling routes, including aldol condensation, Prins reaction, and oligomerization was studied. The effects of ethylene : propionaldehyde feed ratio, reaction temperature, and catalyst type (H-Al-MCM-41, H-ZSM-5, SiO₂-Al₂O₃) were investigated. Our findings suggest that propionaldehyde self-aldol condensation to form 2-methyl-2-pentenal is the predominant pathway, followed by the acid-catalyzed Prins reaction between ethylene and propionaldehyde to form 1,3-pentadiene.