The Effect of Calcium Doping on the Surface and Catalytic Properties of Cobaltic Oxide Catalysts

The effects of calcium oxide doping (0.75, 1.5 and 3 mol% CaO) and calcination temperature (400, 500, 600 and 700°C) on different surface properties of Co3O4 were investigated. The structural properties of pure and doped oxide samples were determined by XRD methods, the textural properties were investigated via the adsorption of nitrogen at −196°C while the hydrogen peroxide decomposition activity of the investigated solids was determined by oxygen gasometric measurement of the reaction kinetics at 20–40°C. The dissolution of calcium ions in the Co3O4 lattice at temperatures in the range 400–600°C was accompanied by a marked decrease in the mean hydraulic radii (rh) and an increase in the surface area (SBET) and total pore volume (Vp) of the prepared oxide samples. In contrast, doping at 700°C brought about a decrease in the SBET and Vp values of the investigated solids. The catalytic activity for H2O2 decomposition on cobaltic oxide calcined at 400–700°C was found to decrease considerably on doping with CaO. The activation energy for sintering (ΔEs) of the pure and doped solids was determined from the variation in their SBET values as a function of the calcination temperature of these solids. Calcium oxide treatment resulted in a 50% increase in the activation energy of sintering of cobaltic oxide solid calcined at 400–600°C. This increase reflects the role of CaO doping in hindering the sintering of cobaltic oxide.

[1]  N. Deraz.  Surface and catalytic properties of Cu/Zn mixed oxide catalysts , 2001 .

[2]  G. El-Shobaky,et al.  Surface and catalytic properties of cobaltic oxide supported on an active magnesia , 2001 .

[3]  G. El-Shobaky,et al.  Catalytic decomposition of H2O2 on Co3O4 doped with MgO and V2O5 , 2000 .

[4]  K. Khalil,et al.  Surface Characteristics of the Pure and Li2O-doped MoO3/Al2O3 System , 1998 .

[5]  Sheng-Yuan Cheng,et al.  Preparation and characterization of bimetallic oxides of chromium and titanium , 1990 .

[6]  G. El-Shobaky,et al.  Effects of lithium doping on textural characteristics of Co3O4 catalyst , 1985 .

[7]  K. Sing.  Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Recommendations 1984) , 1985 .

[8]  G. El-Shobaky,et al.  Thermal behaviour of cobaltic and cobaltous oxides as influenced by doping with some alkali metal oxides , 1983 .

[9]  W. E. Mourad,et al.  Pore analysis of NiO-SiO2 catalyst , 1981 .

[10]  G. El-Shobaky.  Low temperature doping of finely divided NiO catalyst , 1978 .

[11]  G. Ertl,et al.  Physical and Chemical Aspects of Adsorbents and Catalysts , 1972 .

[12]  S. Brunauer,et al.  Pore structure analysis without a pore shape model , 1967 .

[13]  J. H. de Boer,et al.  Studies on pore systems in catalysts: V. The t method , 1965 .

[14]  S. Koide.  Electrical Properties of Li x Ni (1− x ) O Single Crystals , 1965 .

[15]  D. Nicholson.  Variation of surface area during the thermal decomposition of solids , 1965 .

[16]  J. Dere.  Physicochemical and catalytic properties of the system chromium oxides-oxygen-water , 1963 .

[17]  J. Haber,et al.  Physico-chemical properties of alkali- and iron-doped nickel oxide , 1962 .

[18]  F. Stone,et al.  Oxidation reactions catalyzed by doped nickel oxide , 1959 .

[19]  J. Boer.  Untersuchungen über mikroporöse Salz‐ und Oxyd‐Systeme , 1958 .

[20]  G. Schwab,et al.  On Selective Catalysis , 1949 .

[21]  N. K. ADAM,et al.  The Adsorption of Gases and Vapours , 1945, Nature.

[22]  G. F. Hüttig.  Die Reaktionsarten von dem Typus A starr+B starr→AB starr , 1942 .

[23]  E. Teller,et al.  ADSORPTION OF GASES IN MULTIMOLECULAR LAYERS , 1938 .