Abstract: CeO(2)-TiO(2) (CeTi) catalysts synthesized by an ultrasound-assisted impregnation method were employed to oxidize elemental mercury (Hg(0)) in simulated low-rank (sub-bituminous and lignite) coal combustion flue gas. The CeTi catalysts with a CeO(2)/TiO(2) weight ratio of 1-2 exhibited high Hg(0) oxidation activity from 150 to 250 °C. The high concentrations of surface cerium and oxygen were responsible for their superior performance. Hg(0) oxidation over CeTi catalysts was proposed to follow the Langmuir-Hinshelwood mechanism whereby reactive species from adsorbed flue gas components react with adjacently adsorbed Hg(0). In the presence of O(2), a promotional effect of HCl, NO, and SO(2) on Hg(0) oxidation was observed. Without O(2), HCl and NO still promoted Hg(0) oxidation due to the surface oxygen, while SO(2) inhibited Hg(0) adsorption and subsequent oxidation. Water vapor also inhibited Hg(0) oxidation. HCl was the most effective flue gas component responsible for Hg(0) oxidation. However, the combination of SO(2) and NO without HCl also resulted in high Hg(0) oxidation efficiency. This superior oxidation capability is advantageous to Hg(0) oxidation in low-rank coal combustion flue gas with low HCl concentration.

Abstract: Traditional nanostructured design of cerium oxide catalysts typically focuses on their shape, size, and elemental composition We report a different approach to enhance the catalytic activity of cerium oxide nanostructures through engineering high density of oxygen vacancy defects in these catalysts without dopants The defect engineering was accomplished by a low pressure thermal activation process that exploits the nanosize effect of decreased oxygen storage capacity in nanostructured cerium oxides

Abstract: The cerium supported palladium oxide (PdO/CeO(2)) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter The oxalate was degraded into CO(2) during the catalytic ozonation The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water The catalytic zonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO(2) of the catalyst forming surface complexes, and 2) O(3) was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O(2)), and O(2) gas in sequence The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO(2) in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter

Abstract: Cerium chloride (CeCl 3 ) doped polyvinyl alcohol (PVA) films were prepared by casting technique. The effect of CeCl 3 concentrations on the structural, optical and thermal properties of the PVA films was studied by X-ray diffraction (XRD), FT-IR, UV-visible, transmittance ( T ), reflectance ( R ), differential scanning calorimetry (DSC) and thermogravimetry (TG). Both of the XRD and the DSC results affirm the increase in amorphousity. Absorption spectra of the doped films have shown an absorption band at 260 nm assigned to the trivalent state of cerium ions. Absorption, transmittance and reflectance spectra were used for the determination of the optical constants. The results indicate that the optical band gap ( E g ) was derived from Tauc's extrapolation and decreases with the cerium content. The refractive index increases with monotonic behavior as the cerium content increases. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple–DiDomernico model for obtaining the dispersion parameters. The obtained optical parameters were found to be strongly affected by CeCl 3 dopant. Thermal analysis showed that the thermal parameters of PVA are enhanced by CeCl 3 . The dependence of the activation energy of the decomposition temperature on doping level was estimated.

Abstract: A highly atom-economic one-pot synthesis of functionalized tetrahydropyridines by a multicomponent condensation reaction of β-keto ester, two equivalents of aromatic aldehyde, and two equivalents of amine in the presence of a catalytic amount of cerium ammonium nitrate (CAN) is reported. In this way, a series of pharmacologically interesting substituted piperidine derivatives were obtained in moderate to good yields at room temperature.

Abstract: Heterogeneous ruthenium-based catalysts were applied in the selective, aerobic oxidation of 5-hydroxymethylfurfural, a versatile biomass-derived chemical, to form 2,5-furandicarboxylic acid. The oxidation reactions were performed in water with dioxygen as the oxidant at different pressures without added base. Catalysts were prepared by depositing catalytically active Ru(OH)x species on a number of different supports, such as titanium-, aluminum-, cerium-, zirconium-, magnesium- and lanthanum oxides, magnetite, spinel, hydrotalcite and hydroxyapatite. All the catalysts were found to be active in the oxidation reactions, and the choice of support was demonstrated to be important for the catalytic performance.

Abstract: CeO2 as one of the most promising oxidation catalysts has attracted much attention because of its superior performance. The extent of oxidation properties is controlled by the ratio of Ce3+/Ce4+, particle size, and surface area. Here, a facile low-temperature aqueous solution-based chemical route for the synthesis of CeO2 and samarium-doped CeO2 (Sm−CeO2) nanoparticle aggregates, with high content of Ce3+ and surface area, using aqueous solution of ammonium carbonate complex of cerium is presented. The morphologies and structures of the prepared CeO2 nanoparticle were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed desorption. The synthesized CeO2 and Sm−CeO2 nanoparticle aggregate showed significantly improved catalytic activity toward allylic oxidation to corresponding en-ones compared to bulk CeO2. The present method provides a new and facil...

Abstract: Spectral characteristics of a clad modified fiber optic gas sensor are studied for various concentrations (0–500 ppm) of ammonia, methanol and ethanol at room temperature. Cerium, aluminum and lithium doped (6 at.%) nanocrystalline zinc oxides are replaced with a clad and used as gas sensing materials. The study shows that the spectral intensity increases linearly with concentration for ammonia whereas it decreases for methanol and ethanol. The Ce doped ZnO exhibits higher gas sensitivity compared to Al and Li doped zinc oxides. The time response of the sensor is presented for a Ce doped ZnO with ammonia gas. A model is proposed for understanding the spectral intensity variations.

Abstract: A nano-size amorphous calcium–manganese oxide shows efficient water oxidation activity in the presence of cerium(IV) ammonium nitrate.

Abstract: The Hg0 removal ability of γ-Al2O3 impregnated with cerium dioxide (CeO2/γ-Al2O3) was tested in the experimental flue gas of N2 + O2 + NO + SO2 + H2O. Brunauer–Emmett–Teller (BET), X-ray diffractogram (XRD), and thermogravimetric (TG) analyses were used to characterize the samples. The effects of CeO2 loading values, reaction temperatures, reaction time, and individual flue gas components, including SO2, NO, O2, and H2O(g), on the Hg0 removal efficiency were investigated. The results show that the Hg0 removal efficiency of γ-Al2O3 can be greatly improved by CeO2 and, at a test temperature of 350 °C, the best suitable loaded mass percentage of CeO2 is 9%. In the temperature range from 150 to 350 °C, the Hg0 removal efficiency using CeO2/γ-Al2O3 increases with the increase of the temperature and then decreases above 350 °C, except virgin γ-Al2O3. In addition, the presence of O2 and NO have positive effects on the Hg0 removal efficiency, while the presence of SO2 and H2O inhibited it. Furthermore, prolonging...

Abstract: Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mossbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand.

Abstract: A study of the electrochemical behavior of CeCl3 in LiCl-KCl eutectic was performed in the temperature range 653-973K to ascertain if CeCl3 is a suitable surrogate for UCl3 in the development of nuclear fuel cycle technologies. Reduction of cerium occurs in a single 3-electron step that is quasi-reversible. The diffusion coefficient of Ce(III) was determined by linear sweep voltammetry and chronopotentiometry. The standard potential of Ce(III)/Ce(0) was measured and used to calculate Gibbs free energy and the activity coefficient. The nucleation of cerium on a tungsten substrate was determined to be instantaneous with hemispherical nuclei whose growth is controlled by linear or hemispherical diffusion. The order of magnitude of the exchange current density was determined by the linear polarization method. The electrochemical characteristics of CeCl3 were compared with those of UCl3 in LiCl-KCl to evaluate the potential of cerium as a surrogate for uranium electrorefining development.

Abstract: We report herein the fabrication of nanostructured and mesoporous iron-cerium mixed oxides for photocatalytic application. Phase, electronic structure and other properties of the products were characterized by both low-angle and wide-angle X-ray diffraction, diffuse reflectance spectroscopy, transmission electron microscopy, raman spectroscopy, X-ray photoelectron spectroscopy, and N 2 adsorption-desorption isotherm methods. Analytical results demonstrate that the catalyst is in the nano order and mesoporous in nature. These samples were screened for photocatalytic degradation of phenol, methylene blue (MB) and congo red (CR). About 13 % (phenol) and 93 % (MB) photodegradation were observed where as complete mineralization was obtained in case of CR. The reason for higher catalytic activity of 1:1 (Fe/Ce) sample is ascribed to their higher surface area, surface acidity which determines the active sites of the catalyst and accelerates the photocatalytic reaction. Keywords : Mixed oxide, photocatalyst, photodegradation International Journal of Engineering, Science and Technology , Vol. 2, No. 9, 2010, pp. 53-65

Abstract: Conversion of bioethanol into bulk chemicals besides ethylene is a promising process in which the stability of catalyst and the selectivity of products are important. In this study, a series of Ce-modified nanocrystalline HZSM-5 catalysts were prepared and their catalytic performance in the conversion of bioethanol into C2–C4 light olefins was investigated in a fixed-bed reactor at 400 °C under atmospheric pressure. The results show that the stability of catalyst and the distribution of products depend strongly on the content of cerium and the calcination temperature; both cerium content and calcination temperature affect not only the acid properties of the tested catalyst samples but also the composition of cerium species (Ce3+/Ce4+) as revealed by XPS. Among the tested catalyst samples, the catalyst with 5 wt% cerium loading and 520 °C calcination temperature exhibits the best stability and selectivity to C3–C4 light olefins.