Catalytically Generating and Utilizing Hydrogen to Reduce NOx Emissions in Automobile Applications

  • Nawaf AlGhamdi

Student thesis: Master's Thesis

Abstract

Heterogeneous catalysis is a powerful chemical technology because it can enhance the conversion of reactants, promote selectivity to a desired product, and lower the reaction temperature requirements. The breaking and forming of chemical bonds in heterogeneous catalysis is facilitated on a solid surface where adsorbed gas-phase species react and form products. This study is concerned with utilizing heterogeneous catalysis in the automobile industry via the generation and utilization of hydrogen to reduce NOx emissions. In spark ignition engines, the three-way-catalyst technology is ineffective at the more efficient, lean-burn conditions. In compression-ignition engines, an ammonia-based technology is implemented but has associated high cost and ammonia slip challenges. This motivates providing an alternative technology, such as hydrogen selective catalytic reduction (H2-SCR). In this study, four catalysts were investigated for the lean-burn selective catalytic reduction of NO using hydrogen. The catalysts were platinum (Pt) and palladium (Pd) noble metals supported on cerium oxide (CeO2) and magnesium oxide (MgO). Additionally, finding a source of hydrogen for H2-SCR on board a vehicle is a challenge due to the issues associated with hydrogen storage. A numerical study was performed to investigate the utilization of the partial oxidation of natural gas on a rhodium surface to synthesis gas, CO and H2. A kinetic understanding of natural gas demands an understanding of its components. While methane and ethane have been extensively studied, propane partial oxidation on rhodium has only been kinetically examined at low temperatures. The aim of the numerical study was to obtain an improved understanding of propane partial oxidation kinetics by extending the surface reactions mechanism to high temperatures and developing a gas phase mechanism to capture the effects of gas-phase reactions. Moreover, the optimal temperature and pressure for H2 generation were determined, and the kinetic simulation results were analyzed by temperature sensitivity, chemical path flux and hydrogen production sensitivity analyses.
Date of AwardNov 2018
Original languageEnglish
Awarding Institution
  • Physical Science and Engineering
SupervisorMani Sarathy (Supervisor)

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