SO2-Tolerant Selective Catalytic Reduction of NOx over Meso-TiO2@Fe2O3@Al2O3 Metal-Based Monolith Catalysts

• Published in: Environmental science & technology Vol. 53; no. 11; pp. 6462 - 6473
• Main Authors: Han, Lupeng, Gao, Min, Hasegawa, Jun-ya, Li, Shuangxi, Shen, Yongjie, Li, Hongrui, Shi, Liyi, Zhang, Dengsong
• Format: Journal Article
• Language: English
• Published: Easton American Chemical Society 04.06.2019
• Subjects: adsorption; Aluminum oxide; Ammonia; Ammonium nitrate; Catalysis; Catalysts; Composite materials; Decomposition; Density functional theory; Deposition; Electron transfer; ferric oxide; ferrous sulfate; heat; Heat treatment; High temperature; Iron sulfates; Low temperature; Monolithic materials; nitric oxide; nitrogen; Nitrogen oxides; Nitrous oxide; Oxidation; porous media; Selective catalytic reduction; Selectivity; Sulfates; Sulfur dioxide; Temperature effects; Temperature tolerance; Titanium dioxide
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.9b00435

It is an intractable issue to improve the low-temperature SO2-tolerant selective catalytic reduction (SCR) of NOx with NH3 because deposited sulfates are difficult to decompose below 300 °C. Herein, we established a low-temperature self-prevention mechanism of mesoporous-TiO2@Fe2O3 core–shell composites against sulfate deposition using experiments and density functional theory. The mesoporous TiO2-shell effectively restrained the deposition of FeSO4 and NH4HSO4 because of weak SO2 adsorption and promoted NH4HSO4 decomposition on the mesoporous-TiO2. The electron transfer at the Fe2O3 (core)-TiO2 (shell) interface accelerated the redox cycle, launching the “Fast SCR” reaction, which broadened the low-temperature window. Engineered from the nano- to macro-scale, we achieved one-pot self-installation of mesoporous-TiO2@Fe2O3 composites on the self-tailored AlOOH@Al-mesh monoliths. After the thermal treatment, the mesoporous-TiO2@Fe2O3@Al2O3 monolith catalyst delivered a broad window of 220–420 °C with NO conversion above 90% and had superior SO2 tolerance at 260 °C. The effective heat removal of Al-mesh monolithcatalysts restrained NH3 oxidation to NO and N2O while suppressing the decomposition of NH4NO3 to N2O, and this led to much better high-temperature activity and N2 selectivity. This work supplies a new point for the development of low-temperature SO2-tolerant monolithic SCR catalysts with high N2 selectivity, which is of great significance for both academic interests and practical applications.