UCLA

The growing demand for aromatic compounds and the desire to produce them in an environmentally sustainable way has encouraged research efforts to tap into renewable sources for their production. Bio-oil, a free-flowing dark brown liquid derived from the depolymerization and fragmentation of cellulose, hemicellulose, and lignin, is considered to be one of the most valuable resources with the potential to replace fossil oils. However, inherent properties of bio-oils such as high-water content, high viscosity, and high process corrosiveness caused by acidic compounds are limiting their industrial applications. These unfavorable properties are mostly caused by the high oxygen content which is the main property that distinguishes bio-oils from fossil oils. As the main constituent of bio-oils, oxygenated hydrocarbons such as organic acids, alcohol, aldehydes, and ketones have been extensively explored for their conversion into valuable products with efforts focusing on developing highly selective and stable catalysts. Zeolites modified with transition metals stand as some of the most selective and highly stable catalysts for the production of aromatics from oxygenated hydrocarbons thanks to their acid-metal bifunctional nature. In addition, the co-feeding of light alkanes with oxygenates has been regarded as an effective strategy to mitigate prolonged catalyst deactivation due to the active participation of the alkane in the conversion cycle over the bifunctional catalyst. In this dissertation, we aim at exploring the conversion of butanal (as a model compound representing bio-oils) with isobutane co-feed over H-BEA zeolite modified with Zn2+ ions. We first assess the conversion of butanal on Zn/H-BEA catalysts with different metal loadings to note the contribution of different Zn2+ acid sites in catalyzing various reaction products. Then, we develop a detailed kinetic model, which accounts for catalyst deactivation, for the reaction of butanal over the Zn/H-BEA catalysts to elucidate the effect of Zn2+ species on the activation energies of different reactions and the binding energies of reactive surface species. Finally, we investigate the deoxygenation and aromatization of butanal with isobutane co-feed over Zn/H-BEA catalysts to identify the proper loading and proportions of Zn2+ sites to boost the deoxygenation rates, increase the selectivity to aromatics, and improve the catalyst stability.