Pt/Al2O3@Ce/ZrO2-S bifunctional catalysts prepared by mechanically milling for selective catalytic oxidation of high-concentration ammonia

• Published in: Environmental science and pollution research international 2024-05, Vol.31 (25), p.37746-37756
• Main Authors: Tian, You, Han, Zhitao, Li, Yeshan, Zhao, Hongzhe, Zeng, Qingliang, Cheng, Shaoshi
• Format: Article
• Language: English
• Subjects: adsorption; Aluminum oxide; Ammonia; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Catalysts; Catalytic oxidation; Chemical reduction; Chemical synthesis; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Exhaust emissions; Exhaust gases; Low temperature; Oxidation; Research Article; Selective catalytic reduction; Selectivity; surface area; temperature; Waste Water Technology; Water Management; Water Pollution Control; Zirconium dioxide
• ISSN: 1614-7499; 0944-1344; 1614-7499
• DOI: 10.1007/s11356-024-33744-6

The selective catalytic oxidation (SCO) is an effective method for removing slipped high-concentration ammonia from NH 3 -fueled engine exhaust gas. Herein a novel bifunctional catalyst was synthesized by mechanically mixing sulfated Ce/ZrO 2 (Ce/ZrO 2 -S) with a small fraction of Pt/Al 2 O 3 (Pt 0.1 wt.%) for SCO of NH 3 . As expected, the introduction of a small amount of Pt/Al 2 O 3 significantly improved NH 3 conversion ability of Ce/ZrO 2 -S catalysts toward low-temperature direction. When the mass ratio of Pt/Al 2 O 3 to Ce/ZrO 2 -S was 7.5% (the corresponding mixed catalyst was denoted as P@CZS-7.5), T 90 temperature was 312 °C. More importantly, P@CZS-7.5 catalyst exhibited a much better N 2 selectivity (> 96%) in a wide temperature range (320 ~ 450 °C). H 2 -TPR results revealed that the addition of a trace amount of Pt/Al 2 O 3 significantly led to a distinct shift of reduction temperature peak toward low-temperature direction, thereby greatly improved the low-temperature redox performance of mixed catalysts. Furthermore, NH 3 -TPD and BET results showed that P@CZS-7.5 catalyst exhibited a similar NH 3 adsorption capacity to Ce/ZrO 2 -S catalyst, while the former had a relatively higher specific surface area than the latter. It was considered as a crucial factor for P@CZS-7.5 catalyst maintaining superior N 2 selectivity in high-concentration NH 3 (5000 ppm) removal processes. In situ DRIFTS results indicated that P@CZS-7.5 catalyst followed the internal selective catalytic reduction (i-SCR) mechanism in NH 3 -SCO reactions.