On the enhancing effect of Ce in Pd-MOR catalysts for NOx CH4-SCR: a structure-reactivity study

Mendes, AN; Zholobenko, V; Thibault-Starzyk, F; Da Costa, P; Henriques, C

Abstract

The effect of palladium and cerium species on the selective catalytic reduction (SCR) of NOx using methane as reductant (NOx CH4-SCR) has been investigated using Pd-HMOR and PdCe-HMOR system. The catalysts have been characterised by H2-TPR, DRS UV–Vis, TEM/EDS and FTIR using CO and pyridine as probe molecules. The oxidation of NO and CH4-SCR catalytic tests have been conducted using monometallic and bimetallic formulations.

Above 0.3 wt.% Pd, the increase in Pd loading leads to a decrease in NOx selectivity towards N2, with the formation of N2O, and a decrease in the CH4 selectivity towards SCR, due to CH4 direct combustion. H2-TPR and FTIR-CO studies indicate that palladium is stabilised as Pd2+ in ion-exchange position, probably in two different sites within the MOR framework.

The addition of cerium to Pd-HMOR enhances its catalytic performance for NOx CH4-SCR. With 1 wt.% Ce, both NOx conversion into N2 and CH4 selectivity towards SCR have increased. Small CeO2 clusters interacting with palladium are likely to play a major role in this catalytic reaction. The number of such species increases up to Ce loading of ca. 2 wt.%. However, above 3 wt%, NOx conversion values decrease with Ce loading, which is attributed to the formation of bulk CeO2 species not interacting with palladium.

Citation

Mendes, A., Zholobenko, V., Thibault-Starzyk, F., Da Costa, P., & Henriques, C. (2016). On the enhancing effect of Ce in Pd-MOR catalysts for NOx CH4-SCR: a structure-reactivity study. Journal of Catalysis, 121-131. https://doi.org/10.1016/j.apcatb.2016.05.004

• Acceptance Date: May 4, 2016
• Publication Date: May 6, 2016
• Journal: Journal of Catalysis
• Print ISSN: 0021-9517
• Publisher: Elsevier
• Pages: 121-131
• DOI: https://doi.org/10.1016/j.apcatb.2016.05.004
• Keywords: NOx HC-SCR; methane; MOR; palladium; cerium
• Publisher URL: https://doi.org/10.1016/j.apcatb.2016.05.004