Self-assembled biomineralized MnOx for low temperature selective catalytic reduction of NOx

A self-assembled biomineralized MnOx materials was prepared by a simple liquid phase co-precipitation method for selective catalytic reduction (SCR) of nitrogen oxides (NOx). Biomineralized MnOx exhibited great SCR performance (achieve > 99% NOx conversion at 100 °C) and high N2 selectivity (exceed 70% at 75–200 °C). The effects of biomineralized materials on physiochemical properties of catalyst were investigated by various characterization methods. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the crystal structure and the morphologies of MnOx and biomineralized MnOx are remained the same. In order to eliminate the effect of specific surface area, the rate of specific reaction for biomineralized MnOx was calculated to be about twice than that of MnOx. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analyze intermediates during SCR, and speculated that biomineralized MnOx catalyst may mainly follow the Langmuir-Hinshelwood(L-H) mechanism below 200 ℃. The above excellent N2 selectivity can be attributed to the fast NOx specific reaction rate, form Mn-O-C and Mn-C-N structure, provide abundant oxygen vacancies, and high Mn3+/Mn atomic ratio on the catalyst surface. Moreover, biomineralized MnOx possessed a better catalytic cycle performance due to the synergistic effect between biomass and Mn species. Therefore, a reasonable preparation method is proposed to realize the industrial application of biomineralized manganese oxide.