Abstract

Catalytic oxidation of ethanol provides a valuable platform for understanding how catalyst structure influences activity and selectivity in oxidation chemistry. In this dissertation, ethanol oxidation was investigated over Au/TiO₂, Au/SrTiO₃, and Au/ZnO catalysts (1 wt% Au, ~5 nm particles) using a downflow fixed-bed reactor with online gas chromatography. Under differential conditions (513 K, 1 kPa ethanol, 1.5 kPa O₂, 101 kPa total pressure), Au/TiO₂ exhibited the highest activity, followed by Au/SrTiO₃ and Au/ZnO. Acetaldehyde was the dominant product (80–99% carbon selectivity), while acetate species (acetic acid and ethyl acetate) appeared only in minor amounts (<4%), confirming their role as secondary products. Apparent activation energy analysis, supported by catalyst dilution experiments, demonstrated the absence of internal diffusion limitations, validating the intrinsic kinetic measurements.

Reaction rate and selectivity trends revealed that acetaldehyde formation increased with temperature before leveling off near 500 K, while acetate formation increased only slightly for the most active catalyst. Kinetic modeling focused on acetaldehyde formation (selectivity >96%) showed that the best-fitting Langmuir–Hinshelwood model required ethanol dissociation on two types of active sites and exhibited minimal oxygen dependence, consistent with a mechanism involving surface ethoxy intermediates reacting with activated atomic oxygen. Spectrokinetic analysis using Charge-Transfer Spectrokinetic Analysis (CT-SKAn) identified O*, HO*, and HOO* as the reactive oxygen species, while ruling out molecular O₂*. Gold Maximum Plasmon Peak Shift (Au-MAPS) analysis further highlighted the role of undercoordinated perimeter sites at the gold–support interface, which preferentially adsorb oxygen species regardless of support identity.

Together, these catalytic, kinetic, and spectroscopic studies demonstrate the superior performance of Au/TiO₂ and provide fundamental insights into how support identity and surface chemistry govern ethanol oxidation pathways. The findings advance mechanistic understanding of alcohol oxidation and offer guidance for the rational design of catalysts for selective and sustainable oxidation processes.