PhD Oral Exam - Azam Movasati, Chemical and Materials Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Diesel engine emissions including CO, unburned hydrocarbons and NOX remain a major concern for the environment and health. Despite growing electrification, heavy-duty vehicles continue to rely on diesel engines, particularly in remote regiones because of insufficient charging infrastructure. This thesis investigated Pt-Pd catalysts supported on Al2O3 and Ce-Zr-Al mixed oxides for oxidizing diesel and bio-based diesel fuel emissions at low temperature.

In the first part, the Pt-Pd catalysts supported on ceria-zirconia-alumina with varying Ce/Zr/Al contents were investigated for CO and C3H6 oxidation. Pt-Pd/C(0.78)Z-71A and Pt-Pd/C(0.1)Z-50A reached T50 of 109 °C for CO and 198 °C for C3H6, respectively, with high Pt0 and Pd2+ fractions, more Ce3+ and labile surface oxygen, showing that support compositions controlled the catalysts redox properties and performance.

The second part focused on oxidation of ethanol and acetaldehyde, unregulated emissions from (bio)ethanol/DEE blends, over Pt, Pd and Pt-Pd/Al2O3 as well as Pt-Pd supported on the optimized Ce-Zr-Al supports. Pt-Pd/Al2O3 showed the highest activity, while Pd-containing catalysts released more byproducts. The Ce/Zr ratio directed the oxidation pathway toward either acetic acid or formate/carbonate routes.

Finally, CO, NO and H2O were added to ethanol-acetaldehyde feed. NO inhibited ethanol oxidation, CO lowered the acetaldehyde light-off temperature and promoted methane formation on Ce-Zr-Al supports, and NO with H2O increased acetic acid release only on Al2O3. DRIFTS identified a shared ethoxide-acetaldehyde-acetyl sequence branching into CO oxidation and acetate routes, controlled by the support. These findings provide guidance for designing oxidation catalysts for diesel and bio-based diesel fuels emissions.