Unravelling the Role of Zr–Laponite Supports in Enhancing the Activity of a MnNi Catalyst for the Low-Temperature NH₃-Selective Catalytic Reduction Reaction

Novel catalysts must be developed for the low-temperature NH3-selective catalytic reduction (SCR) of nitrogen oxides (NOx) produced in power plants, factories, and automobiles, because NOx emissions are harmful to human health and the environment. In this study, Mn and Ni oxides are impregnated on Zr–Laponite clay supports containing different amounts (1, 3, 5, and 7 wt %) of Tergitol surfactant. The NOx removal (deNOx) efficiencies of these catalysts during NH3-SCR were evaluated at 100–340 °C with different O2 concentrations. Zr pillaring in the Zr–Laponites improved their textural properties and morphology, as evidenced by X-ray diffraction, N2 sorption isotherms, high-resolution scanning and transmission electron microscopy, H2-temperature-programmed reduction, NH3-temperature-programmed desorption, and X-ray photoelectron spectroscopy. MnNi/Zr–Laponite(3 wt %) demonstrated the highest deNOx activity (90%), highest turnover frequency (19 × 10–2 s–1), and lowest activation energy (22.4 kJ/mol) among the MnNi/Zr–Laponites and MnNi/ZrO2 at 220 °C with good recyclability for 6 cycles and time-on-stream stability. These novel bimetallic Laponite catalysts have practical applications for NOx removal via NH3-SCR.