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Catalytic reduction of NO by CO has been studied over a battery of Cu 3 Ce x Al (1−x) composite oxide catalysts prepared by coprecipitation method. The solids were further characterized by Xray diffraction, laser Raman spectra, N 2 -physisorption (Brunauer−Emmet−Teller (BET)), H 2 -temperature-programmed reduction, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy techniques. The assessment on the catalytic properties were conducted with the NO + CO model reaction. The influences of Cu and different ratios of Ce and Al on the catalytic performance have been investigated. When the ratio of Ce and Al was 1:4, this sample possessed the best catalytic properties, which was exactly derived from hydrotalcite-like compounds. The introduction of a few cerium species (Cu/Ce = 15:1) in the structure improved the activity/selectivity toward selective catalytic reduction of NO by lowering the temperature of carbon monoxide oxidation.

This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N2 physisorption, X-ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by hydrogen and by oxygen (H2 -TPR and O2 -TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M(x+) into the lattice of CeO2 increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O2 (-) (and/or O(-) ) species of these Ce20 M1 Ox composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce20 Cr1 Ox exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near-surface Ce(3+) and Cr(3+) . Finally, a possible reaction mechanism was tentatively proposed to understand the reactions.

Foi desenvolvido um método altamente sensível, seletivo e rápido para a determinação de mercúrio, a partir da reação rápida de mercúrio(II) com 5-(p-aminobenzilideno)-tiorodanina (ABTR) e posterior extração em fase sólida do quelato colorido, utilizando discos C 18 . Em pH 3,5 e na presença do emulsificante-OP, ABTR reage com mercúrio(II) para formar um quelato vermelho na razão molar 1:2 (mercúrio:ABTR). O quelato foi enriquecido pela extração em fase sólida com discos C 18 e o quelato retido, eluído com dimethyl formamida (DMF). Um fator de enriquecimento na ordem de 50 foi obtido. Em DMF, a absortividade molar do quelato é 1,21×10 5 L mol -1 cm -1 a 545 nm, e a lei de Beer é obedecida no intervalo 0,01~3 μg mL -1 na solução medida. O desvio padrão relativo para onze replicatas a 0,01 μg mL -1 é 1,7%. Este método foi aplicado para a determinação de mercúrio em tabaco e aditivos de tabaco. Bom coeficiente de preconcentração foi encontrado, comparando-se o método proposto com outros similares.A highly sensitive, selective and rapid method for the determination of mercury based on the rapid reaction of mercury(II) with 5-(p-aminobenzylidene)-thiorhodanine (ABTR) and the solid phase extraction of the colored chelate with C 18 disks has been developed. At pH 3.5 and in the presence of emulsifier-OP medium, ABTR reacts with mercury(II) to form a red chelate of a 1:2 (mercury to ABTR) molar ratio. This chelate was enriched by solid phase extraction with C 18 disks and the retained chelate eluted form the disks with dimethyl formamide (DMF). An enrichment factor of 50 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.21×10 5 L mol -1 cm -1 at 545 nm, and Beer's law is obeyed in the 0.01~3 μg mL -1 range in the measured solution. The relative standard deviation for eleven sample replicate measurements at the 0.01 μg mL -1 level is 1.7%. This method was applied to the determination of mercury in tobacco and tobacco additives and good preconcentration was found between proposed and comparative methods results.