Ultralow specific surface area vermiculite supporting Mn-Ce-Fe mixed oxides as “curling catalysts” for selective catalytic reduction of NO with NH3

Abstract

In this study, the ultralow specific surface area clay vermiculite (VMT) was selected to be a catalyst support for the NH3-SCR process, and the active components MnCeFeOx loaded on vermiculite was just like curling on ice from the TEM results. The de-NOx performance of Mn–Ce–Fe/VMT exhibited almost complete NO conversion with a gas hourly space velocity (GHSV) of 15,300 h−1 at 150 °C, which was 25% and 10% higher than that of Mn/VMT and Mn–Ce/VMT, respectively. Ce and Fe co-doping improved the BET surface area, the quantities of active Mn4+, the acid sites and NH3 adsorption energy of Mn/VMT, all of which contributed to the increase in low-temperature SCR activity. In situ DRIFT measurements suggested that NOx removal over Mn–Ce–Fe/VMT followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms at 150 °C, but the E-R mechanism played a dominant role. Corresponding Mn–Ce–Fe/VMT monolithic catalysts reached 90% NO conversion with a GHSV of 4000 h-1.