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Abstract: A series of copper-containing SBA-15 samples were successfully synthesized via evaporation-induced self-assembly route. The resulting materials were characterized by X-ray diffraction (XRD), 29Si MAS NMR spectroscopy, transmission electron microscopy (TEM), N2 sorption, inductively coupling plasma-atomic emission spectrometer (ICP-AES), thermogravimetry, and differential thermal analysis (TG–DTA), Fourier-transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectra (UV–vis) and X-ray photoelectron spectroscopy (XPS). The results indicated that: (1) all the samples exhibited typical hexagonal arrangement of mesoporous structure; (2) copper ions could be incorporated into the framework of SBA-15; (3) the addition of urea in the hydrothermal stage efficiently reduced the leaching of copper and improved the thermal stability of the mesoporous materials. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H2O2. The catalytic tests showed that the synthesized materials exhibited high activity for this reaction and copper ions in the framework were more active than copper species in the extra-framework position. The nitric acid treatment on the samples removed the bulk CuO species, which resulted in a dramatic increase in the catalytic activity. [Copyright &y& Elsevier]

[Display omitted] • The CeCoMnO x spinel-type catalyst prepared using oxalic acid precipitant has a more favorable physicochemical structure for NO conversion than that prepared using alkaline precipitant. • 400 °C is the optimum calcination temperature for oxalic acid precipitated CeCoMnO x spinel for NH 3 -SCR reaction. • The oxalic acid precipitated CeCoMnO x calcined at 400 °C has nearly 100 % NO conversion at 100–200 °C at GHSV = 15,000 mL·g−1·h−1. • An interface-enhanced redox macrocycle mechanism incorporating acid cycling is proposed for oxalic acid precipitated CeCoMnO x catalysts. CeCoMnO x spinel-type catalysts for the selective catalytic reduction of NO using NH 3 (NH 3 -SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnO x spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH 3 -SCR activities of the CeCoMnO x spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnO x spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnO x -C) have larger specific surface area, more mesopores and surface active sites, stronger redox properties and adsorption activation properties than those prepared by the traditional ammonia co-precipitation method at 400 °C (CeCoMnO x -N-400), and thus CeCoMnO x -C have better low-temperature NH 3 -SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnO x -C-400 exceeds 89 % and approaches 100 % within the reaction temperature of 100–125 °C, which is 14.8 %-2.5 % higher than that of CeCoMnO x -N-400 at 100–125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnO x -C surface, as well as the enhanced monoadsorption Eley-Rideal (E-R) and double adsorption Langmuir-Hinshelwood (L-H) reaction mechanisms, are also derived from XPS and in situ DRIFTS characterization. [ABSTRACT FROM AUTHOR]

[Display omitted] This work investigated the influence of introduction methods of cerium and tin on the physicochemical properties as well as the activity and durability of titanium-based catalysts for the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). Precipitation and impregnation methods were adopted to synthesize a series of cerium-tin-titanium catalysts. These catalysts were characterized by XRD, Raman, N 2 adsorption–desorption, HRTEM, EDS mapping, XPS, H 2 -TPR, NH 3 -TPD and in situ DRIFT. Notably, Ce/Sn/Ti(imp) catalyst prepared by stepwise-impregnation method could provide an interface between Ce and Sn for more facile electron transfer than Sn/Ce-Ti(co), Ce/Sn-Ti(co) and Sn/Ce/Ti(imp) catalysts. It promoted the redox equilibrium of Ce4+ + Sn2+ ↔ Ce3+ + Sn4+ shifting to right to produce adequate Ce3+ and surface adsorbed oxygen, resulting in optimal reducibility and surface acidity of Ce/Sn/Ti(imp) catalyst. Besides, the activation of NH 3 and desorption of NO x readily occurred on the surface of Ce/Sn/Ti(imp), which were favorable for the proceeding of subsequent reactions and excellent performance of NH 3 -SCR. [ABSTRACT FROM AUTHOR]

Abstract: The present work focuses on the combination of ceria with another oxide of different ionic valences from period 3 (Mg2+, Al3+, and Si4+) using coprecipitation method, followed by calcination at 450 and 750°C, respectively. The textural, structural, morphological and redox properties of nanosized ceria–magnesia, ceria–alumina and ceria–silica mixed oxides have been investigated by means of N2 physisorption, XRD, Raman, HRTEM, DRS, FT-IR, and H2-TPR technologies. XRD results of these mixed oxides reveal that only nanocrystalline ceria (ca. 3–6nm for the 450°C calcined samples) could be observed. The grain size of ceria increases with the increasing calcination temperature from 450 to 750°C due to sintering effect. The highest specific surface area is obtained at CeO2–Al2O3 mixed oxides when calcination temperature reaches 750°C. Raman spectra display the cubic fluorite structure of ceria and the existence of oxygen vacancies, and displacement of oxygen ions from their normal lattice positions in the ceria-based mixed oxides. DRS measurements confirm that the smaller the grain size of the ceria, the higher indirect band gap energy. H2-TPR results suggest that the reductions of surface and bulk oxygen of ceria were predominant at low and high calcination temperature, respectively. Finally, CO oxidation were performed over these ceria-based mixed oxides, and the combination of CeO2–Al2O3 exhibited highest activity irrespective of calcination temperature, which may due to excellent textural/structural properties, good homogeneity, and redox abilities. [Copyright &y& Elsevier]

Catalytic reduction of NO by CO was studied over a series of CuO-CoO x /γ-Al 2 O 3 catalysts prepared by co-impregnation with different copper and cobalt precursors (acetate and nitrate) to evaluate the structure–activity relationship. The obtained samples were characterized in detail by means of XRD, LRS, XPS, H 2 -TPR and in situ FT-IR technologies. Results indicate that copper oxide is agglomerated while cobalt oxide is dispersed on γ-Al 2 O 3 for the catalyst prepared from copper acetate and cobalt acetate precursors (CuACoA); Cu x Co 3-x O 4 spinel is formed and agglomerated on the catalyst prepared from copper nitrate and cobalt nitrate precursors (CuNCoN); while both copper oxide and cobalt oxide could be homogeneously dispersed for the catalyst prepared from copper nitrate and cobalt acetate precursors (CuNCoA), which exhibits the best activity for NO reduction by CO. Probably the synergistic effect between dispersed copper oxide and cobalt oxide is propitious to the oxygen transfer, which could be the reason for its high activities. Finally, a possible reaction mechanism was tentatively proposed to explore the different catalytic performances in NO reduction by CO model reaction. [ABSTRACT FROM AUTHOR]