An extraordinary deactivation offset effect of calcium and arsenic on CeO-WO catalyst had been found for selective catalytic reduction of NO with NH (NH-SCR). It was discovered that the maximum NO conversion of As-Ca poisoned catalyst reached up to 89% at 350 °C with the gaseous hourly space velocity of 120 000 mL·(g·h). The offset effect mechanisms were explored with respect to the changes of catalyst structure, surface acidity, redox property and reaction route by XRD, XPS, H-TPR, O-TPD, NH-TPD and in situ Raman, in situ TG, and DRIFTS. The results manifested that Lewis acid sites and reducibility originating from CeO were obviously recovered, because the strong interaction between cerium and arsenic was weakened when Ca and As coexisted. Meanwhile, the CaWO phase generated on Ca poisoned catalyst almost disappeared after As doping together, which made for Brønsted acid sites reformation on catalyst surface. Furthermore, surface Ce proportion and oxygen defect sites amount were also restored for two-component poisoned catalyst, which favored NH activation and further reaction. Finally, the reasons for the gap of catalytic performance between fresh and As-Ca poisoned catalyst were also proposed as follows: (1) surface area decrease; (2) crystalline WO particles generation; and (3) oxygen defect sites irreversible loss.
The
effect of Mn on the catalytic performance of V2O5/TiO2 catalyst for the selective catalytic reduction
of NO
x
by NH3 (NH3-SCR) has been investigated in this study. It was found that the
added Mn significantly enhanced the activity of V2O5/TiO2 catalyst for NH3-SCR below 400
°C. The redox cycle (V4+ + Mn4+ ↔
V5+ + Mn3+) over Mn-promoted V2O5/TiO2 catalyst plays a key role for the high catalytic
deNO
x
performance. The redox cycle promotes
the adsorption and activation of NH3 and NO, forming more
reactive intermediates (NH4
+, coordinated NH3, NO2, and monodentate nitrate species), thus promoting
the NH3-SCR to proceed.
Mn-based
catalysts hold the promise of practical applications in
catalytic ozonation of toluene at room temperature, yet improvement
of toluene conversion and CO
x
selectivity
remains challenging. Here, an innovative α-MnO2/ZSM-5
catalyst modified with SO4
2– was successfully
prepared, and both characterizations and density functional theory
(DFT) calculations showed that SO4
2– introduction
facilitated the formation of oxygen vacancies, Lewis and Brönsted
acid sites, and active oxygen species and enhanced the adsorption
ability of toluene on α-MnO2/ZSM-5. Characterizations
also showed that SO4
2– introduction made
the catalyst possess larger specific surface area, superior reducibility,
and stronger surface acidity. As a result, α-MnO2/ZSM-5 with a S/Mn molar ratio of 0.019 exhibited the best toluene
conversion and CO
x
selectivity, 87 and
94%, respectively, after the reaction for 8 h at 30 °C under
an initial concentration of 5 ppm toluene and 45 ppm ozone, relative
humidity of 45%, and space velocity of 32,000 h–1, far superior to those of non-noble catalysts reported to date under
comparable reaction conditions. The synergistic role of increased
oxygen vacancies and acid sites of α-MnO2/ZSM-5 modified
with SO4
2– resulted in excellent toluene
conversion and CO
x
selectivity. The findings
represented a critical step toward the rational design and synthesis
of highly efficient catalysts for catalytic ozonation of toluene.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.