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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

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


Authors

AN Mendes

V Zholobenko

F Thibault-Starzyk

P Da Costa

C Henriques



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.

Acceptance Date May 4, 2016
Publication Date May 6, 2016
Publicly Available Date Mar 29, 2024
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

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