Effect of O2 on Selective Catalytic Reduction of NO by C3H6 over Fe Catalysts Supported on Porous Clay Heterostructures (Fe-PCH)

Abstract

K10 montmorillonite was used as the raw clay to prepare porous clay heterostructures (PCH) by organic template intercalation and tetraethylorthosilicate (TEOS) was used as silicone source. Fe was load on the PCH support by impregnation method to prepare Fe-PCH catalysts. The catalytic activity tests were carried out in a fixed bed micro-reactor in the atmosphere of 0.1% C3 H6 , 0.1%NO, 0~10%O2 in N2 balance. The total flow rate was 100ml/min and corresponding gas hourly space velocity (GHSV) was 15000h-1. The mircro-reaction pathways were studied by Diffuse Reflection Infrared Fourier Transform Spectrometer (DRIFTS). The influence of O2 on the SCR-C3 H6 reactivity over Fe-PCH was analyzed. The results showed that FePCH catalyst exhibited the best catalytic performance without oxygen, which reached the maximum NO conversion of 100% at 4000 C. When the concentration of O2 is below a critical value, [O2 ]crit, the catalytic activity gradually decreased with the increasing concentration of O2 . When the concentration of O2 is above [O2 ]crit, the NO conversion was only 20%~30%. Fe-PCH catalysts were characterized by transmission electron microscope (TEM), N2 adsorption/desorption and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that Fe-PCH had supermicroporous and mesoporous structures. The active components on Fe-PCH catalyst were mainly α-Fe2 O3 nanorods, exposing (024) and (104) planes. The in situ DRIFTS technique was used to detect the reactive intermediates over the surface of Fe-PCH catalyst, which could help analyze the mechanism of the influence of oxygen on catalytic activity. The results presented that oxygen could inhibit the formation of isocyanate species over Fe-PCH catalyst during C3 H6 -SCR, which might be the reason for the decrease of NO conversion. Finally, a reasonable reaction path of C3 H6 -SCR over Fe-PCH catalyst was proposed.