Promoting effects of acid enhancing on N2 selectivity for selectivity catalytic oxidation of NH3 over RuOx/TiO2: The mechanism study
Abstract
RuOx/TiO2 and RuOx/TiO2-SO42- catalysts were prepared and used for selective catalytic oxidation of ammonia (NH3-SCO). The results indicated that N2 selectivity over RuOx/TiO2 was significantly enhanced after the introduction of SO42-. The introduction of SO42- into RuOx/TiO2 observably increased the amount and strength of acid species on the surface of catalyst. Specifically, the RuOx/TiO2-SO42- sulfated treatment at 2 h possessed the optimal surface acidic property obtaining more than 85% N2 selectivity at 300 °C, which was apparently higher than that of RuOx/TiO2 with 66% N2 selectivity. The strong interaction between sulfated support and RuOx resulted in excellent redox property at high temperature, abundant surface oxygen and more Ru4+ species. Particularly, DRIFTS and NH3-TPD illustrated that the increased N2-selectivity was put down to Brönsted and Lewis acid sites augmented via sulfating treatment of TiO2, promoting the dehydrogenation of adsorbed ammonia species on the catalyst surface, then the formation of more sbnd NH2 species could facilitate the reduction of NO to harmless N2, meanwhile, the generation of HNO species also were reduced to N2 by NH. Therefore, the excellent acid properties of RuOx/TiO2-SO42- gave rise to the formation of few nitrate species with an iSCR mechanism, which ensured to the high N2 selectivity.
- Publication:
-
Applied Surface Science
- Pub Date:
- January 2020
- DOI:
- 10.1016/j.apsusc.2019.144044
- Bibcode:
- 2020ApSS..50044044Z
- Keywords:
-
- NH<SUB>3</SUB>-SCO;
- Ruthenium (Ru);
- TiO<SUB>2</SUB>-SO<SUB>4</SUB><SUP>2-</SUP>;
- Surface acidity;
- DRIFTS