Promotional Effect of Preparation Methods on Catalytic Reduction of NO by CO over CoCeO_x Catalysts

Abstract

In this study, a series of CoCeO x catalysts were prepared by template, solid-state grinding with cobalt sulfate or cobalt acetate as the precursor and the oil bath method for catalytic reduction of NO x by CO (CO–NO). These catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction of H2, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results indicated that CoCeO x -TA and CoCeO x -SS catalysts exhibited much higher activity, which were attributed to excellent reducibility property, abundant chemical adsorbed oxygen, and NO absorption sites. In the presence of O2, the activity decreased obviously over CoCeO x -TA, CoCeO x -SS, and CoCeO x -SA catalysts. However, the activity increased at high temperatures over the CoCeO x -OA catalyst. According to the result of in situ DRIFTS, nitrate species decreased over CoCeO x -TA, CoCeO x -SS, and CoCeO x -SA catalysts in the presence of O2, which might inhibit the reduction efficiency of NO. Moreover, NO adsorption was not affected by O2 over CoCeO x -OA catalyst, which could contribute to its high activity in the CO-selective catalytic reduction reaction.

Negatively Charged Single-Atom Pt Catalyst Shows Superior SO2 Tolerance in NOx Reduction by CO

“…As shown in Figure a, for NO-50, the observed strong band at 1372 cm –1 corresponds to NO 3 – free ions, and a small shoulder band at 1344 cm –1 is attributed to cis -N 2 O 2 2– . , In the NO-200 case, the latter is significantly enhanced, and a new strong band (1392 cm –1 ) assigned to M-NO 2 appears. − As observed from the enlarged view at 1500–2000 cm –1 (Figure b), with a temperature increase from 50 to 200 °C, the visible band at 1765 cm –1 , ascribed to the chemically adsorbed NO on isolated Pt atoms in the bending coordination, becomes significantly weak . Moreover, two weak bands at 1601 and 1627 cm –1 attributed to the bridged monodentate NO 3 – and bridged bidentate NO 3 – vanished, , and instead, there is the emergence of a new strong band at 1557 cm –1 related to the vibration of (M–O) 2 = NO, suggesting that these bridged bidentate nitrates gradually decompose at higher temperatures. In both cases, the bands at 1845 and 1905 cm –1 are attributed to gaseous NO .…”

“…S16). According to our DRIFT results and the related literature, 55,65,66 the CO-SCR process can be expressed by the following six-step elementary reactions: S19), Pt mainly serves as the adsorption and activation sites for NO, and Cu acts as the adsorption sites for CO. The projected densities of the states (PDOS) of the three models are calculated and displayed in Figure 7c to reveal the effect of supports on the electronic structure of the Pt reactive center.…”

“…61−63 As observed from the enlarged view at 1500−2000 cm −1 (Figure 6b), with a temperature increase from 50 to 200 °C, the visible band at 1765 cm −1 , ascribed to the chemically adsorbed NO on isolated Pt atoms in the bending coordination, becomes significantly weak. 64 Moreover, two weak bands at 1601 and 1627 cm −1 attributed to the bridged monodentate NO 3 − and bridged bidentate NO 3 − vanished, 65,66 and instead, there is the emergence of a new strong band at 1557 cm −1 related to the vibration of (M−O) 2 = NO, 62 suggesting that these bridged bidentate nitrates gradually decompose at higher temperatures. In both cases, the bands at 1845 and 1905 cm −1 are attributed to gaseous NO.…”

C,N‐modified TiO2‐supported Mn–Ce–Cox‐based catalyst for low‐temperature NH3‐SCR

“…11 CeO 2 has excellent oxygen storage and release capabilities. 12 It can store and release oxygen through the redox conversion between Ce 3+ and Ce 4+ , and it is easy to form oxygen vacancies, promote O 2 adsorption and activation, and facilitate the formation of active oxygen species. It has been found that Ce doping can greatly improve the catalytic activity and SO 2 resistance of Mn/TiO 2 catalysts.…”

Simultaneous Selective Catalytic Reduction of NO and N2O by NH3 over Fe-Zeolite Catalysts

“…It was reported that the N 2 O decomposition was notably promoted under the SCR condition in the presence of reductant, such as NH CO. 13 However, the catalytic activity in CO-SCR for NO or N 2 O removal was limited because of the insufficient reducing ability, particularly in the presence of O 2 . 14 It is difficult to achieve the goal of simultaneous SCR of NO and N 2 O. Furthermore, the activity for N 2 O decomposition was improved in the presence of minor NH 3 and became more active with increasing NH 3 content in the gas flow.…”