One of the largest contributors to global warming and the destruction of the Earth’s protective ozone layer is nitrous oxide (𝑵𝟐𝑶). It has a Global Warming Potential approximately 300 times larger than carbon dioxide when measured on a 100-year time scale. Although Nitrous Oxide concentrations in the atmosphere are very low, it is generated in large quantities in many different types of industries including production of nitric acid via catalytic oxidation of ammonia and in waste treatment systems. The difficulty in controlling these emission sources and the high costs associated with developing new and effective methods for reducing Nitrous Oxide emissions have made finding a cost-effective solution an imperative necessity. This thesis provides a method for addressing the challenge by a detailed investigation of the direct catalytic decomposition of nitrous oxide to produce nitrogen and oxygen, which are both environmentally benign compounds, over copper modified zeolite catalysts. The focus of the research is on the catalytic activities of Cu-modified ZSM-5, SAPO-34 and SAPO-41 zeolite catalysts. A major component of the research involves identifying the effects of oxygen concentration and hydrothermal reaction conditions on catalytic activity, intrinsic efficiency and long-term stability of the zeolite catalysts. To achieve this goal, the research combines several areas of study; namely, catalyst synthesis, advanced physicochemical characterization and catalytic evaluation under relevant industrial conditions to determine the limitations that affect the performance of the catalysts and to develop strategies to overcome them. Results obtained during the research demonstrated that Cu-H-ZSM-5 exhibited much higher 𝑵𝟐𝑶 conversion rates and turnover frequencies than Cu-SAPO based catalysts, and thus, achieved nearly 100% conversion at temperatures larger than 400°C. Oxygen was shown to decrease the rate of 𝑵𝟐𝑶 decomposition due to kinetic limitations resulting from the accumulation of surface oxygen rather than the degradation of the zeolite catalyst structure. Furthermore, the research indicated that Cu-ZSM-5 has a better ability to withstand exposure to oxygen rich feedstocks than did Cu-SAPO-34 and Cu-SAPO-41, suggesting that the type of zeolite framework and the stabilization of the copper sites played significant roles in maintaining the catalytic activity. Finally, the research demonstrated that Cu-ZSM-5 is able to maintain a significant fraction of its activity in the presence of high steam concentrations and therefore exhibits a high degree of resistance to sintering and zeolite framework structure collapse.
By elucidating the relationships between the zeolite structure, copper nanoparticle size distributions, dispersion, oxygen inhibition, and hydrothermal stability, this study advances the understanding of 𝑵𝟐𝑶 decomposition under realistic operating conditions. The findings contribute to the rational design of durable and efficient Cu-based zeolite catalysts and represent a meaningful step toward the development of practical catalytic technologies for long-term industrial 𝑵𝟐𝑶 emission control.