Selective catalytic reduction of NO with NH3 over high purity palygorskite-supported MnO2 with different crystal structures

Abstract

In order to find efficient catalysts for low-temperature selective catalytic reduction with ammonia (NH3-SCR), several MnO2 with different crystal structure have been supported on high-purity palygorskite (Pal) by a hydrothermal method. The effect of MnO2 crystal structures on the NH3-SCR performance of the catalysts was investigated. All catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Raman spectrum, Thermo gravimetric analysis/Differential thermo gravimetric (TG/DTG), ammonia-temperature programmed desorption (NH3-TPD), hydrogen-temperature programmed reduction (H2-TPR), Transmission electron microscope (TEM) and X-ray energy dispersive spectroscopy (EDS) and X-ray photoelectron spectrometer (XPS). The presented results suggested that α-MnO2/Pal catalyst exhibit the highest catalytic activity among four type MnO2/Pal catalysts in the temperature range of 50–400°C, own promising stability during a 24 h continuous denitration experiment. Furthermore, the crystal structure affords α-MnO2/Pal with the highest specific surface area and more acidic sites, which is beneficial for the SCR reaction. It has improved the NH3 adsorption ability and catalytic activity of the catalyst.