Ceria‐modified Al‐Mn‐pillared clay catalysts for the selective catalytic reduction of NO with NH₃ at low temperatures

Abstract

The yCe/Al-Mn-pillared interlayered clay (PILC, y [Ce content] = 8-9 wt%) catalysts were prepared using the impregnation method. Catalytic activities of the materials for the selective catalytic reduction (SCR) of NO with NH 3 at low temperatures were evaluated, and physicochemical properties of the samples were characterized by X-ray diffraction, N 2 adsorption-desorption, temperature-programmed reduction, ammonia temperature-programmed desorption, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy techniques. It is found that introduction of cerium enhanced NO conversions at low temperatures, and the 8Ce/Al-Mn-pillared sample showed the highest NO conversion (92% at 300 C). The superior catalytic activity of 8Ce/Al-Mn-PILC was associated with the change in active component and increases in amounts of the surface chemisorbed oxygen species and the acid sites after ceria loading. Additionally, the SCR reaction mechanism over 8Ce/Al-Mn-PILC followed both Langmuir-Hinshelwood and Eley-Rideal mechanisms, with the former being dominant. K E Y W O R D SAl-Mn copillared clay, ceria loading, selective catalytic reduction, in situ DRIFTS | Al-Mn-PILC-supported ceria catalystsThe yCe/Al-Mn-PILC (y = 8 and 9 wt%) samples were prepared by impregnating the Al-Mn-PILC support with Ce (NO 3 ) 3 Á6H 2 O. Then, the sample was dried at 120 C for 6 hr and calcined at 400 C for 2 hr in an air atmosphere. | Al-PILC-supported Mn and claysupported Ce-Mn catalystsThe Mn/Al-PILC (Mn [i.e., Mn/{Mn + Al-PILC}] was 10 wt%, which was the same content of Mn in Al-Mn-2 of 14 CHENG ET AL.

The Deactivation Mechanism of the Mo-Ce/Zr-PILC Catalyst Induced by Pb for the Selective Catalytic Reduction of NO with NH3

“…Figure 2 shows their diffraction patterns. According to our previous research [ 13 ], the XRD pattern of the PILC sample displayed a high-intensity basement (001) reflection peak at 2 θ = 9.3°, indicating that the montmorillonite clay possessed a regular and ordered interlayer structure. The (001) reflection peak of the 3Mo4Ce/Zr-PILC and Pb-poisoned 3Mo4Ce/Zr-PILC catalysts was shifted to a lower angle and its intensity decreased, indicating an increase in interlayer distance and a disorder in the structure of the clay, which was caused by the effect of the strong delamination when the metal oxide entered the interlayer of clay.…”

Enhanced Resistance to Pb Poisoning of the Co‐modified Mn/Fe‐pillared Clay Catalysts for NH3‐SCR at Low Temperatures

“…Furthermore, the Mn 2p 3/2 signal of each catalyst could be deconvoluted into three components at binding energy (BE)=643.5–644.7, 641.7–642.9, and 640.5–641.7 eV, which were attributed to the surface Mn 4+ , Mn 3+ , and Mn 2+ species, [30–32] respectively. As reported previously, the Mn 4+ species were more active for the low‐temperature SCR reaction [30] . Molar ratios of Mn 4+ /(Mn 2+ +Mn 3+ +Mn 4+ ) on the sample surface were calculated, as summarized in Table 2.…”

“…As reported previously, the Mn 4 + species were more active for the low-temperature SCR reaction. [30] Molar ratios of Mn 4 + /(Mn 2 + + Mn 3 + + Mn 4 + ) on the sample surface were calculated, as summarized in Table 2. Mn 4 + /(Mn 2 + + Mn 3 + + Mn 4 + ) molar ratio decreased in the order of 2Co-4Mn/Fe-PILC (18.9 %) > 2Co-4Mn/Fe-PILC-Pb (16.2 %) > 4Mn/Fe-PILC (14.5 %) > 4Mn/Fe-PILC-Pb (10.3 %).…”

Improved sulfur dioxide resistance of the Mn/Fe-PILC catalyst by the doping of ceria in the selective catalytic reduction of NO with NH3

“…Figure 6B shows O 1s XPS spectra of the 4Mn/Fe-PILC and 4Ce-4Mn/Fe-PILC samples before and after SO 2 poisoning. O 1s XPS spectrum of each sample could be divided into three components: The rst component in the BE range of 528.9−529.7 eV corresponded to the surface lattice oxygen (O α ) species, the second one in the BE range of 530.8−531.8 eV was ascribed to the surface chemisorbed oxygen (O β ) species, and the third one in the BE range of 529.7−532.7 eV was attributed to the surface lattice oxygen (O γ ) species of the Si−O bonds in SiO 2 of montmorillonite clay [19,30]. It is well known that the surface chemisorbed oxygen (O β ) species was bene cial for NO removal in the NH 3 -SCR reaction [31].…”

“…Since Yang and coworkers [17] rst used pillared interlayered clay (PILC) as the low-temperature SCR catalyst in 1992, there have been more and more reports on the PILC-based catalysts. For example, Shen et al [18] found that MnO x /TiO 2 pillared montmorillonite exhibited high NH 3 -SCR activity after doping with a suitable amount of ceria; Cheng et al [19] claimed that the ceriamodi ed Mn-Al-pillared montmorillonite catalyst showed better performance than the commercial catalyst.…”