Investigation on the redox/acidic features of bimetallic MOF-derived CeMOx catalysts for low-temperature NH3-SCR of NOx

• Published in: Applied catalysis. A, General General, 2022-08, Vol.643, p.118796, Article 118796
• Main Authors: Zhou, Qimin, He, Kailin, Wang, Xiaoxiang, Lim, Khak Ho, Liu, Pingwei, Wang, Wenjun, Wang, Qingyue
• Format: Article
• Language: English
• Subjects: Ammonia; Bimetallic oxides; Bimetals; Catalysts; Cerium oxides; Chemical reduction; Conversion; Low temperature; Low-temperature NH3-SCR of NOx; Metal-organic frameworks; Redox property; Selective catalytic reduction; Selectivity; SO2 resistance; Substitution reactions; Surface acidity; Titanium; X ray photoelectron spectroscopy
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2022.118796

Low-temperature selective catalytic reduction with NH3 (LT-SCR) is a promising approach for NOx remediation. This work utilized bimetallic metal-organic frameworks (MOFs) to prepare CeMOx (M=Ti, Cu) catalysts allowing the homogeneous distribution of promoters to investigate LT-SCR explicitly. The strong interfacial interaction between nanoscale-mixed components was characterized on CeTiOx by HRTEM, micro-Raman, and XPS, resulting in high acidity and good redox properties with abundant Ce3+ and Ti4+. It obtained over 80% conversion from 180 °C to 300 °C with 100% N2 selectivity, and maintained stable performance in SO2/H2O at a high GHSV of 150,000 h−1. In situ DRIFTS reveals that NH3 adsorption was promoted on CeTiOx, which accelerated reaction between NOx and adsorbed NH3 via Eley-Rideal mechanism. Meanwhile, the aliovalent substitution of ceria by Cu2+ was observed on CeCuOx, forming oxygen vacancies. Its high redox properties enhanced NOx conversion by Langmuir-Hinshelwood mechanism, but triggered NH3 peroxidation, leading to poor N2 selectivity. [Display omitted] •Bimetallic MOF-derived catalysts exhibited a homogenous nanoscale distribution.•Bimetallic oxides were used to study effect of redox/acidic properties on NH3-SCR.•Strong acidity of CeTiOx improved N2 selectivity and broadened working temperature window.•High redox properties of CeCuOx enhanced LT activity but led to NH3 peroxidation.•An insight into the catalyst design is provided for low-temperature NH3-SCR.