Low temperature performance and sulfur resistance enhancement of Mn-Ce oxides supported on W-modified MWCNT for NH_3-SCR removal of NO_x

摘要

To eliminate nitrogen oxides (NO_X), composite carrier-supported catalysts (Mn-Ce/MWCNT-W) and traditional catalysts (Mn-Ce/MWCNT and W-Mn-Ce/MWCNT) were prepared using an ultrasonic impregnation method that preformed low-temperature ammonia-selective catalytic reduction (SCR) removal of NO_X. The promotion effects of MWCNT-W composite carriers for low temperature SCR activities and SO_2 tolerance of the catalysts were systematically investigated. Compared to traditional catalyst, Mn-Ce/MWCNT-W catalyst, with a 30% WO_X/MWCNT mass ratio, demonstrated improved SCR activity and high N_2-selectivity from 100°C to 200°C. A series of characterizations were carried out and it was found that there were more redox sites and the stronger the NH_3 adsorption capacity over the composite carrier-supported catalysts than traditional catalysts. Also, with this composite carrier-supported catalyst, the improvement of SCR reaction was considered to be from the abundance of high valence state Mn and well dispersed active components. Notably, compared to traditional catalyst, the composite carrier-supported catalyst exhibited the stronger sulfur resistance. Thus, using MWCNT-W composite carriers to prepare Mn-Ce/MWCNT-W catalysts resulted in excellent NO_X conversion and SO_2 resistance at low temperatures. Implications: LT NH_3-SCR of NO_X is an effective way to remove NO_X from stationary sources. The physicochemical properties of the support not only affect a catalyst's LT SCR activity but also affect the catalyst's anti-poisoning performance. The modified carriers could promote active component dispersion, which is conducive to SCR reaction. However, for LT SCR reactions, few reports have addressed the design and preparation of composite carrier-supported catalysts. The goal of this study was to design and synthesize Mn-Ce/MWCNT-W catalysts and to observe the influence of composite support in Mn-based catalysts on LT SCR activity and sulfur resistance.