Macroporous SmMn2O5 mullite for NOx-assisted soot combustionElectronic supplementary information (ESI) available: Soot combustion catalytic activity of Pt, reproducibility of catalysts, NO + O2-TPRD results of catalysts, etc. See DOI: 10.1039/c6cy02478e

A series of mullite SmMn 2 O 5 oxides were prepared by citric acid (CA), hydrothermal (HT) and co-precipitation (CP) and combustion of ethylene glycol and methanol solutions (EG&M) methods, and tested for NO x -assisted soot combustion. The catalyst performance tests were conducted under "loose" contact conditions and the physical and chemical properties characterized by XRD, FTIR, BET, SEM, XPS, and O 2 -TPD and H 2 -TPR measurements. The SmMn 2 O 5 -EG&M catalyst possessed a distinct morphology with slabs separated by interconnected macropores, and exhibited the overall highest catalytic activity for soot combustion. The corresponding T 10 , T 50 , and T 90 were 283 °C, 368 °C, and 420 °C, respectively, and the CO 2 selectivity was 99.6%. The soot combustion activation energy for the SmMn 2 O 5 -EG&M catalyst is 65 kJ mol −1 . O 2 -TPD and H 2 -TPR measurements demonstrated higher mobility and better reducibility of surface adsorbed oxygen for the EG&M sample. The soot combustion is greatly accelerated by the NO 2 -assisted mechanism under a NO + O 2 atmosphere and further enhanced by the interconnected macropores of the catalyst, facilitating an intimate contact between the soot and the catalyst. Our study reveals that SmMn 2 O 5 mullite is an effective catalyst for NO x -assisted soot combustion. A series of mullite SmMn 2 O 5 oxides were prepared by citric acid (CA), hydrothermal (HT) and co-precipitation (CP) and combustion of ethylene glycol and methanol solutions (EG&M) methods, and tested for NO x -assisted soot combustion.