Abstract
Selective catalytic reduction of NOx by ammonia (NH3-SCR) was the most efficient and economic technology for De-NOx applications. Therefore, a series of MnOx/vermiculite (VMT) and MnOx-Fe2O3/VMT catalysts were prepared by an impregnation method for the selective catalytic reduction (SCR) of nitrogen oxides (NOx). The MnOx-Fe2O3/VMT catalysts provided an excellent NO conversion of 96.5% at 200 °C with a gas hourly space velocity (GHSV) of 30,000 h−1 and an NO concentration of 500 ppm. X-ray photoelectron spectroscopy results indicated that the Mn and Fe oxides of the MnOx-Fe2O3/VMT catalyst were mainly composed of MnO2 and Fe2O3. However, the MnO2 and Fe2O3 components were well dispersed because no discernible MnO2 and Fe2O3 phases were observed in X-ray powder diffraction spectra. Corresponding MnOx-Fe2O3/VMT monolithic honeycomb catalysts (MHCs) were prepared by an extrusion method, and the MHCs achieved excellent SCR activity at low temperature, with an NO conversion greater than 98.6% at 150 °C and a GHSV of 4000 h−1. In particular, the MnOx-Fe2O3/VMT MHCs provided a good SCR activity at room temperature (20 °C), with an NO conversion of 62.2% (GHSV = 1000 h−1). In addition, the NO reduction performance of the MnOx-Fe2O3/VMT MHCs also demonstrated an excellent SO2 resistance.
Highlights
Nitrogen oxides (NOx ) in stationary stack source emissions are strong contributing factors of acid rain, photochemical smog, and ozone depletion and are, detrimental to the natural environment and human health [1,2,3]
It is well known that the key component affecting the selective catalytic reduction (SCR) and economic performance of NH3 -SCR technology is the catalyst employed in the process, which should be low in cost, and provide high SCR activity at low temperatures
The SCR activity of pure MnOx catalysts is profoundly deteriorated by SO2 and H2 O, and emissions with high concentrations of SO2 and H2 O can lead to poisoning and the eventual deactivation of pure MnOx catalysts
Summary
Nitrogen oxides (NOx ) in stationary stack source emissions are strong contributing factors of acid rain, photochemical smog, and ozone depletion and are, detrimental to the natural environment and human health [1,2,3]. Numerous types of supports have been employed for Mn-based catalysts, such as molecular sieves, carbon materials, and metal oxides. Molecular sieves modified with Mn-based catalyst materials have shown excellent SCR activity because of their regular pore structures, high strength, and high specific surface areas [9]. Metal oxide supports provide high catalyst surface areas, high thermal stability, and surface acid-base properties [14,15]. To improve the low temperature performance, corresponding MnOx -Fe2 O3 /VMT monolithic honeycomb catalysts (MHCs) were prepared by an extrusion method, and the MHCs achieve an NO conversion greater than 98.6% at 150 ◦ C and GHSV = 4000 h−1.
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