Date of Award

2017

Document Type

Open Access Dissertation

Department

Chemical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

John R. Regalbuto

Abstract

With climate change due to global warming, the production of hydrocarbon fuels and chemicals from renewable biomass resource has become more pressing in recent decades. The biggest challenge in biomass conversion is to develop active, selective and stable catalysts for particular applications. The objective of this research is to optimize catalytic performance for hydrodeoxygenation (HDO) and hydrogenation reactions by enhancing the stability of the support, tuning metal particle size, and controlling surface composition.

The high content of water in bio-oil and the aqueous environment of the upgrading process requires a hydrothermally stable catalyst. The hydrothermal stability has been effectively improved at 220oC by various means: the introduction of Zr, carbon coating on silica, and the development of mesoporous alumina. Monometallic and bimetallic catalysts were prepared on these stable supports by strong electrostatic adsorption (SEA) and ultra-small nanoparticles (<2 nm) were synthesized. Stability tests at the bio-oil HDO reaction temperature of 300oC revealed that the mesoporous alumina outperformed the other supports in terms surface area and pore structure maintenance, and metal particle stability. Mesoporous alumina-supported Pt/Ru and Cu/Ni were tested for HDO of bio-oil at USDA. Two methods were applied to control metal particle sizes. In the first, SEA-derived Ru and Pt nanoparticles (<2 nm) supported on mesoporous silica were treated at elevated

temperatures (800oC and 900oC) in humidified hydrogen to achieve series of catalysts with particle sizes ranging from 1 to 5 nm. This treatment, however, significantly deteriorated the support. A milder method was demonstrated via charge enhanced dry impregnation (CEDI): Pt particles were grown from about 1 to 10 nm on a variety of common supports by adding excess chloride to the impregnating solution. Particle size sensitivity to chloride was compared on various supports.

The effect on furfural hydrogenation of controlling of surface composition of bimetallic nanoparticles was demonstrated with silica supported PdCu and PdCo catalysts prepared by co-SEA, SEA followed by Electroless Deposition (SEA-ED), and dry impregnation (co-DI). SEA and co-SEA preparations yielded ultra-small (about 1 nm) single metal Pd, Cu, and Co and homogeneously alloyed PdCu and PdCo nanoparticles. Cu could be added as partial monolayer shells via ED to the SEA-synthesized Pd cores. The reaction pathway and product yield were seen to be a sensitive function of the synthesis method and corresponding surface composition.

Rights

© 2017, Qiuli Liu

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