Selective Ammonia Oxidation over Hybrid Catalysts Composed of Hydrotalcite-derived Alloy and Micro-/Mesoporous Zeolite

• Applicant: Dr.-Ing. Magdalena Jablonska, Ph.D.
• Subject Area: Technical Chemistry ; Solid State and Surface Chemistry, Material Synthesis
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 466310768

Euro VI emission standards for heavy-duty vehicles (HDVs), e.g., trucks, buses or tractors, etc., introduced for the first time limits for NH3 emission up to 10 ppm. The selective catalytic oxidation of ammonia into nitrogen and water vapor (NH3-SCO) is the most promising method for the elimination of NH3 from diesel cars – AdBlue system (the selective catalytic reduction of NOx by on-board generated NH3 from a urea solution). Currently applied, Pt-based catalysts provide high activity, however also low selectivity to N2. The activity and N2 selectivity strongly depend on the loading of noble metal and furthermore can be steered into the desired direction by the combination of noble and transition metals. Thus, bifunctional catalysts mainly consist of Pt-based component (active in NH3 oxidation into NOx) and Cu- and/or Fe-based component (active in the selective catalytic reduction of NOx with NH3, NH3-SCR). Furthermore, NH3 on Brønsted acid sites of zeolites form stable NH4+, which does not participate in the NH3-SCO reaction pathway directly but serves as NH3 reservoir in the high-temperature range, ensuring enhanced selectivity to N2. Moreover, the preliminary studies indicated that micro-/mesoporous zeolite-based catalysts enhanced activity and N2 selectivity in NH3-SCO. In view of the above challenges, this project aims to obtain a deeper understanding of property/activity relationships over a wide range of bifunctional hybrid catalysts composed of the hydrotalcite-derived alloy (Pt-Cu/MgAlOx, Au-Cu/MgAlOx, a single noble metal atom dispersed on Cu nanoclusters) and micro-/mesoporous zeolite (H-SSZ-13, H-UZM-12, H-ZSM-5) in NH3-SCO under application-relevant reaction conditions (up to 873 K in the presence of H2O, COx and SOx). Herein, the wide range of methods used for physico-chemical characterization of such hybrid catalysts enables to describe their structure, texture and acid/redox properties and determine active species involved in NH3-SCO. Catalytic tests coupled with temperature-programmed, steady-state state isotopic transient kinetic analysis and IR studies (including time-resolved rapid-scan IR) is a combination that allows an understanding of the role of the catalysts components in NH3-SCO and its reaction mechanism.

• DFG Programme: Research Grants
• International Connection: Croatia, Poland, United Kingdom
• Cooperation Partners: Dr. Andrew Beale; Professorin Dr. Kinga Góra-Marek; Dr. Ana Palcic