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

Abstract

Novel catalysts must be developed for the low-temperature NH 3 -selective catalytic reduction (SCR) of nitrogen oxides (NO x ) produced in power plants, factories, and automobiles, because NO x 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 NO x removal (deNO x ) efficiencies of these catalysts during NH 3 -SCR were evaluated at 100−340 °C with different O 2 concentrations. Zr pillaring in the Zr−Laponites improved their textural properties and morphology, as evidenced by X-ray diffraction, N 2 sorption isotherms, high-resolution scanning and transmission electron microscopy, H 2 -temperature-programmed reduction, NH 3 -temperature-programmed desorption, and X-ray photoelectron spectroscopy. MnNi/Zr−Laponite(3 wt %) demonstrated the highest deNO x 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/ZrO 2 at 220 °C with good recyclability for 6 cycles and time-on-stream stability. These novel bimetallic Laponite catalysts have practical applications for NO x removal via NH 3 -SCR.