Dip coating of ceria–manganese mixed oxides on cordierite and its CO oxidation activity

Abstract

Dip coating method was utilized for wash-coating alumina onto cordierite honeycomb substrate, followed by catalyst coating by sol–gel dip coating of CMX(X = 0, 5, 70, and 100 corresponding to Ce<inf>1-x</inf>Mn<inf>x</inf>O<inf>2-δ</inf>, where x = 0, 0.5, 0.7, and 1) to obtain CM0/Al<inf>2</inf>O<inf>3</inf>/Cord, CM5/Al<inf>2</inf>O<inf>3</inf>/Cord, CM70/Al<inf>2</inf>O<inf>3</inf>/Cord, and CM100/Al<inf>2</inf>O<inf>3</inf>/Cord. The sol–gel was obtained from the EDTA–citrate method. XRD, BET, and BJH analysis was conducted on samples Cord to CM100/Al<inf>2</inf>O<inf>3</inf>/Cord. An intense peak of ceria at 462.53 cm−1 and that of Mn<inf>3</inf>O<inf>4</inf> was observed at 658 cm−1 in the Raman spectra analysis. The adherence test was conducted to test the mechanical stability of the wash-coat and catalyst layer. The visual evidence of coating was furnished by optical imaging and FESEM analysis. Ultrafine particles with high porosity were observed in sample Al<inf>2</inf>O<inf>3</inf>/Cord. Cracks were observed in the FESEM images of CM0/Al<inf>2</inf>O<inf>3</inf>/Cord to CM100/Al<inf>2</inf>O<inf>3</inf>/Cord samples. CO oxidation studies were performed on the samples Cord to CM100/Al<inf>2</inf>O<inf>3</inf>/Cord. CM70/Al<inf>2</inf>O<inf>3</inf>/Cord performed the best among all other samples with a T<inf>50</inf> temperature of 157 °C. The activation energy of CO oxidation was calculated using the Ozawa method for samples CM0/Al<inf>2</inf>O<inf>3</inf>/Cord to CM100/Al<inf>2</inf>O<inf>3</inf>/Cord. 50 h long-term CO oxidation stability experiments were also conducted on samples CM0/Al<inf>2</inf>O<inf>3</inf>/Cord to CM100/Al<inf>2</inf>O<inf>3</inf>/Cord. The synergistic effects of ceria and manganese, combined with fine dispersion of the catalyst, pore characteristics, and cracks improving diffusivity, pitched CM70/Al<inf>2</inf>O<inf>3</inf>/Cord to have the best CO oxidation activity. © The Author(s), under exclusive licence to the Institute of Chemistry, Slovak Academy of Sciences 2024.