Catalytic oxidation of CO by O₂ over nanosized CuO–ZnO system prepared under various conditions

Abstract

A series of copper and zinc mixed oxides composed of equimolar ratio and treated with 0.05 Al 2 O 3 /mol catalyst has been prepared by coprecipitation method using their nitrates in presence of 1 M NaOH solution. The precipitation was carried out at a pH 9.5 and 50 • C. The results revealed that the bulk of various solids consisted of CuO and ZnO having ratios varying between 0.84 and 0.98. On the other hand, the values of surface concentrations of copper and zinc were bigger than those present in the bulk. The values of surface Cu/Zn ratio varied between 1.04 and 1.46 depending on the mode of preparation and calcination conditions. The mixed solids existed as nanocrystalline CuO and ZnO phases. The surface characteristics are strongly dependent on mode of coprecipitation and calcination temperature. The computed S BET values varied between 146 and 23 m 2 /g depending on mode of coprecipitation and calcination temperature. The increase of calcination temperature of different adsorbents within 300-400 • C led to a significant progressive decrease in the BET-surface area with subsequent increase in the values of mean pore radius. All adsorbents are mesoporous solids. All prepared solids showed a good catalytic activity in CO oxidation by O 2 , which proceeds via first order kinetics in all cases. The activation energy of the catalysed reaction was determined for various solids and the computed values were very small indicating the big catalytic activity of the investigated solids.On a préparé une série d'oxydes mixtes de cuivre et de zinc composés d'un rapportéquimolaire et traités avec un catalyseur de 0,05 Al 2 O 3 /mol par la méthode de la coprécipitation en utilisant leurs nitrates en présence de 1 M de solution de NaOH. La précipitation s'est effectuéeà un pH de 9,5 età une température de 50 • C. Les résultats ont révélé que la majeure partie de divers solides consistait en du CuO et du ZnO selon des rapports variant entre 0,84 et 0,98. D'un autre côté, les valeurs des concentrations superficielles de cuivre et de zincétaient supérieuresà celles présentes dans ce lot de solides. Les valeurs du rapport superficiel Cu/Zn variaient entre 1,04 et 1,46 selon le mode de préparation et les conditions de calcination. Les solides mixtes existaient sous forme de phases nanocrystallines du CuO et du ZnO. Les caractéristiques superficielles dépendent fortement du mode de coprécipitation et de la température de calcination. Les valeurs S BET calculées variaient entre 146 et 23 m 2 /g selon le mode de coprécipitation et la température de calcination. L'augmentation de la température de calcination de différents agents d'adsorption dans les limites de 300 et 400 • C a menéà une diminution progressive importante de l'aire superficielle BET, de même qu'une augmentation ultérieure des valeurs du rayon moyen des pores. Tous les agents d'adsorption sont des solides mésoporeux. Tous les solides préparés ont montré une bonne activité catalytique dans l'oxydation du CO par l'O 2 , qui suit une cinétique du premier ordre dans tous le...

Improvement of dyes removal from aqueous solution by Nanosized cobalt ferrite treated with humic acid during coprecipitation

“…where d is the mean crystalline diameter, λ is the X-ray wavelength, K is the Scherrer constant (0.89), β 1/2 is the full width at half maximum (FWHM) of the main diffraction peaks of the crystalline phase present and θ is the diffraction angle. The area of main diffraction peak of the present phases was used as a quantity for their degree of crystallinity [37].…”

Structural, surface and catalytic properties of pure and ZrO2‐doped nanosized cobalt‐manganese mixed oxides

“…EDX investigation of pure and doped solids calcined at 300–500°C was determined as the relative atomic abundance of manganese, cobalt, oxygen and zirconium species present in the uppermost surface layers of the calcined solids, which is given in Table . It is well known that the EDX technique supplies an accurate determination of relative atomic concentration of different elements present on their outermost surface layers . The bulk concentration of solids investigated was readily determined on the basis of nominal composition of these solids.…”

“…It is well known that the EDX technique supplies an accurate determination of relative atomic concentration of different elements present on their outermost surface layers. [34][35][36][37][38][39][40] The bulk concentration of solids investigated was readily determined on the basis of nominal composition of these solids. Surface and bulk compositions of various solids are given in Table 3.…”

Wettability of porous two‐dimensional ZnO nanocrystal films

“…As an important functional material, ZnO is widely applied in various fields, such as catalysis (Ei-Shobaky et al, 2009), piezoelectric devices, and surface acoustic wave devices. Recently, ZnO nanocrystal films were intensively investigated for their potential applications and various configurations of ZnO nanocrystals could be synthesised by simple solution technique (Cheng et al, 2006a,b;Xu and Cai, 2008).…”