ABSTRACT
Four copper - zinc aluminium mixed oxides having different composition were prepared by coprecipitation method. The prepared solids were calcined at 400 - 800 degree C. Some physicochemical, surface and catalytic properties of the systems investigated were studied using XRD, EDX, nitrogen adsorption at 196 degree C and catalytic oxidation of CO by O2 at 100 - 200 degree C.The results revealed that all investigated solids consisted of nanocrystalline CuO and ZnO phases even those calcined at 800 degree C.The surface characteristics of different adsorbents were strongly dependent on their chemical composition and calcination temperature. The SBET decreased by increasing both the copper oxide content and calcination temperature. The value of 132m 2/g was computed for the system containing the smallest amount of CuO and being calcined at 400 degree C. The activation energies of sintering for different solids were determined from the values of SBET as being influenced by calcination temperature. The catalytic activities, in CO - oxidation by O 2, for all solids were found to increase by increasing both CuO content and calcination temperature. The activation energies of the reaction have been determined
ABSTRACT
The effect of A1[2]O[3] on the thermal decomposition of cobalt nitrate and its interaction with the produced cobal oxides were investigated using DTA, TG, DTG, X-ray diffraction and IR absorption spectometry techniques. The results obtained evealed that, A1[2]O[3] enhanced the thermal decomposition of cobalt nitrate and decreased its decomposition temperature from 230 to 200C. The produced CoO reacted simultaneously with the evolved NO[2] gas and atmospheric O[2] giving Co[3]O[4] whichremained thermally stable up to about 900C due to dissolution of some of AL[2]O[3] in its lattice resulting in an increase of its oxidation state. Co[3]O[4] interacted with AL[2]O[3] at about 1000C yielding wellcrystalline CoAL[2]O[4] spinel. The AL[2]O[3] employed was poorly crystalline gamma-alumina, being treated with small amount of Co[3]O[4] [.05 mole] and heated in air at 1000C it crystallized to well-crystalline alpha-corrundum which was found to be mostly converted to well-crystalline delta -AL[2]O[3] when subjected to slow cooling [25C/min] to room temperature
Subject(s)
Gamma Rays/statistics & numerical dataABSTRACT
A series of Co[3]O[4] supported on gamma-AL[2]O[3] was prepared by impregnating a finely powdered poorly crystalline gamma-alumina samples with cobalt nitrate solution containing different proportions of Co[No3][2] using a pore-filling method. The obtained solids were dried at 100C then roasted at temperatures between 450 and 750C. The cobalt content was varied between 10.5 to 37.1 Wt.% Co[3] O[4]. The surface charateristics namely, specific surface area, total pore volume and mean pore radius of various supported catalysts were determined from N[2] adsorption isotherms measured at 77CK. The results obtained revealed that both specific surface area and total pore volume of the employed alumina support display an important decrease by loading with cobalt oxide. The SBET of certain of the investigated solids decrease progressively by increasing the roasting temperature from 450 to 750C. The SBET of all samples decreases at 750C. This decrease becomes more pronounced on increasing the Co[3]O[4] content from 0.05 to 0.1 mole/mole AL[2]O[3] and less pronounced thereafter. The surface area is largely stabilized in the samples with 0.25 Co[3] O[4] alumina