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Herein, we investigated the NOx reduction performance of Sb-V-CeO2/TiO2 (SbVCT) catalyst subjected to hydrothermal aging, where 6 vol% of H2O was fed to the SbVCT for 16 h with variable temperatures of 550-750 °C. The structural, morphological, redox, and acid properties of fresh and aged catalysts were comprehensively characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, N2-physisorption, temperature programmed reduction/desorption (H2-TPR/NH3/NO-TPD) and in situ DRIFTS. The XRD, Raman and TEM results of the fresh and the one hydrothermally aged at 550, 600 °C catalysts indicated the presence of finely dispersed polymeric vanadia, antimony, and nano-crystalline ceria species on TiO2 support. The SbVCT catalysts hydrothermally aged at the temperatures ≤ 600 °C showed better NOx conversions than the others aged > 600 °C. This was because aging at the temperatures ≤ 600 °C could help to minimize the loss of surface redox/acid properties that were originally inherent to surface vanadyl and CeO2 species that went into CeVO4 and large CeO2 aggregates. This in turn led to the loss of surface redox and acidic characters indigenous to the SbVCT and reduced its NOx reduction performance. Moreover, the NOx reduction performance of hydrothermally aged V-WO3-TiO2 catalyst, when compared with that of SbVCT catalyst, showed relatively low NOx conversions at the temperatures below 300 °C. [ABSTRACT FROM AUTHOR]

Manganese-based catalysts have attracted much attention due to their excellent performance for NO reduction with NH3 (NH3-SCR) at low temperatures. In the current study, the novel metal Sb was modified into Mn/TiO2 and Fe-Mn/TiO2, and the NOx conversion was compared with those of Mn/TiO2 and Fe-Mn/TiO2 catalysts to investigate the effect of the Sb. The NOx reduction activities of the catalysts were evaluated in the temperature range of 100-250 °C at a space velocity of 60,000 h−1. The physicochemical properties of all the catalysts were characterized by Brunauer-Emmett-Teller surface area, temperature-programmed desorption of ammonia, temperature-programmed reduction, X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Interestingly, the Sb-promoted Mn-based catalysts showed significantly higher NOx conversion than the other catalysts with or without 6 vol% of H2O. The high performance of the Sb-modified catalysts could be related to the increase of acid sites and redox properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Addition of ceria enhanced NO x conversion and induced SO2 and water resistance. [•] The ceria loading increased the Brønsted acidity was investigated by DRIFTS. [•] Enhanced NO x conversion above 350°C by retarding direct oxidation of NH3. [•] Increase in total acidity, reducibility and surface oxygen species (Oα,Oβ) was observed. [ABSTRACT FROM AUTHOR]

Abstract: CeO2 nanofibres have been prepared by means of the co-precipitation and ripening method. The morphology of the CeO2 and the synthesis duration were influenced by changes in the mole ratio of the NaOH/citric acid. Three kinds of precipitates were obtained by increasing the NaOH/citric acid ratio: stuck-in-bundle, fibre and flake morphologies. The cobalt was impregnated on the prepared CeO2 (0.8) nanofibres and the physico-chemical properties, soot combustion activities and deactivation were investigated. The Co/CeO2 (0.8) nanofibres were evaluated for soot combustion in O2 and NO/O2. The morphology of the fibrous structure of CeO2 (0.8) and Co/CeO2 (0.8) was observed through FE SEM images. The presence of cobalt in Co3O4 form was confirmed by means of XRD and TPR analyses. The Co/CeO2 (0.8) fibre catalysts showed improvements in soot combustion at low temperatures of around 400°C with 10% O2 and a decrease in the peak soot combustion temperature at about 40°C was observed with the addition of 500ppm NO. The XPS results of the Co 2p spectra of the Co/CeO2 (0.8) catalysts confirmed the presence of Co in the Co3+, Co2+ oxidation states. The thermal stability and the resistance to SO2 poisoning of the 10% Co/CeO2 (0.8) fibre catalyst were examined by ageing it in air and 1030ppm SO2 at 800°C for 12h. [Copyright &y& Elsevier]

Dendrimer encapsulated Pt nanoparticles were prepared by using hydroxyl terminated generation four (G4OH) PAMAM dendrimers (DEN) as the templating agents. The encapsulated Pt nanoparticles were dispersed on γ-Al2O3 at room temperature by impregnation. Pt/Al2O3 (DEN) catalysts were then subjected to thermal treatments in oxidizing and reducing atmospheres at different temperatures. These catalysts were characterized by Transmission Electron microscopy (TEM) and In situ Fourier-Transform Infrared (FTIR) spectroscopy. The TEM analysis of the as synthesized catalysts revealed that the Pt nanoparticles were found to be 2–4 nm in size. It is observed that the Pt particle size in 0.5% Pt/Al2O3 (DEN) catalyst increased upon thermal decomposition of the dendrimer. The in situ FTIR results suggested that the presence of oxygen and the Pt nanoparticles in the Pt-dendrimer nanocomposite accelerate the dendrimer decomposition at low temperatures. All the catalysts were tested for the reduction of NO x with CH4 in the temperature range of 250–500 °C. NO x reduction efficiency of Pt/Al2O3 (DEN) catalysts were compared with the Pt/Al2O3 (CON; conventional) catalyst. The conversion of NO x was started from the low temperatures over Pt/Al2O3 (DEN) catalysts. The high selectivity of NO x to N2 of 74% was obtained over 0.5% Pt/Al2O3 (DEN) catalyst at low temperatures around 350 °C. [ABSTRACT FROM AUTHOR]

The influence of different magnesium (Mg) weight percentages (1, 2.5, 5, 7.5 and 10) over silver (3 wt%) impregnated alumina (SA) catalyst was investigated for the reduction of NO by C3H6. Mg doped SA catalysts were prepared by conventional impregnation method and characterized by XRD, BET-SA, ICP-MS, XPS, SEM, UV-DRS, H2-TPR and O2-TPD. The existence of MgO and MgAl2O4 phases on Mg doped SA catalysts were observed from XRD and XPS analyses. Existence of high percentage MgAl2O4 phase on 5% Mg doped SA catalyst (Mg (5) SA) enhances the dispersion and stabilization of silver phases (Ag2O). Mg (5) SA catalyst shows a 51% of high selectivity (NO to N2) in presence of SO2 (80 ppm) at low temperatures (350 °C) and maintained high selectivity’s with a wide temperature window (350–500 °C). An optimal high surface availability of Ag0 and Ag+ species were observed from XPS analysis over Mg (5) SA catalyst. H2-TPR analysis shows high temperature reduction peak over Mg (5) SA compared to SA catalyst. XPS analysis confirms the high percent availability of MgAl2O4 species over Mg (5) SA catalyst. DRIFTS study reveals the molecular evidences for the evolution of enolic species during NO reduction over the highly active Mg (5) SA catalyst at low temperatures. It also confirms further transformation of enolic species into –NCO species with NO + O2 and finally into N2 and CO2. [ABSTRACT FROM AUTHOR]

Abstract: Noble metal nanocatalysts such as Pd, Pt, and Au were strongly immobilized on the inside walls of monolithic honeycomb-structured cordierite, in which bi-functional molecules were used as linkers for anchoring noble metal nanoparticles (NPs) on the cordierite surface. The supported nanocatalysts were characterized by ICP-MS, TEM, and X-ray powder diffraction. The efficiencies of the immobilized nanocatalysts for the removal of harmful nitrogen oxides (NO x ) have been investigated by measuring the deNO x capability as a function of temperature. The catalytic activities depend mainly on the compositions of the nanocatalysts. The Pd/Pt bi-metal catalyst anchored on the cordierite surface shows higher NO x conversion and better activity than the commercial emission catalyst at low temperature region, which could be due to the large portion of active surface areas of the catalysts with nanometer scale. [Copyright &y& Elsevier]

Abstract: To get the low temperature sulfur resistant V2O5/TiO2 catalysts quantum chemical calculation study was carried out. After selecting suitable promoters (Se, Sb, Cu, S, B, Bi, Pb and P), respective metal promoted V2O5/TiO2 catalysts were prepared by impregnation method and characterized by X-ray diffraction (XRD) and Brunner Emmett Teller surface area (BET-SA). Se, Sb, Cu, S promoted V2O5/TiO2 catalysts showed high catalytic activity for NH3 selective catalytic reduction (NH3-SCR) of NO x carried at temperatures between 150 and 400°C. The conversion efficiency followed in the order of Se>Sb>S>V2O5/TiO2 >Cu but Se was excluded because of its high vapor pressure. An optimal 2wt% ‘Sb’ loading was found over V2O5/TiO2 for maximum NO x conversion, which also showed high resistance to SO2 in presence of water when compared to other metal promoters. In situ electrical conductivity measurement was carried out for Sb(2%)/V2O5/TiO2 and compared with commercial W(10%)V2O5/TiO2 catalyst. High electrical conductivity difference (ΔG) for Sb(2%)/V2O5/TiO2 catalyst with temperature was observed. SO2 deactivation experiments were carried out for Sb(2%)/V2O5/TiO2 and W(10%)/V2O5/TiO2 at a temperature of 230°C for 90h, resulted Sb(2%)/V2O5/TiO2 was efficient catalyst. BET-SA, X-ray photoelectron spectroscopy (XPS) and carbon, hydrogen, nitrogen and sulfur (CHNS) elemental analysis of spent catalysts well proved the presence of high ammonium sulfate salts over W(10%)/V2O5/TiO2 than Sb(2%)/V2O5/TiO2 catalyst. [Copyright &y& Elsevier]