Physicochemical Properties of the Co3O4/Al2O3, Ag2O/Al2O3 and Ag2O-Co3O4/Al2O3 Systems and Their Catalytic Activities towards Acid-Base and Redox Reactions

• Published in: Adsorption science & technology Vol. 24; no. 8; pp. 657 - 672
• Main Authors: El-Sharkawy, E.A., Al-Shihry, Shar S., Youssef, A.M.
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.10.2006; Multi Science
• Subjects: Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Aluminium oxide; Mixed catalyst; Binary compound; Catalytic reaction; Cobalt Oxides; Transition metal Compounds; Supported catalyst; Silver Oxides; Heterogeneous catalysis; Acids; Alumina; Base reaction; Physicochemical properties
• ISSN: 0263-6174; 2048-4038
• DOI: 10.1260/026361706781355037

A Co3O4/Al2O3 catalyst containing 0.20 mol% Co3O4 and an Ag2O/Al2O3 catalyst containing 0.2 mol% Ag2O were prepared using the impregnation method. Co3O4–Ag2O/Al2O3 samples containing 0.2 mol% Co3O4 and varying small molar percentages of Ag2O were also prepared. Portions from the catalysts thus obtained were calcined at 773, 973 and 1173 K. The textural properties of the catalysts were determined from the adsorption of N2 at 77 K, while their structural properties were investigated using TG, DTA, XRD and TPR techniques. The surface acidities of the catalysts were determined via titration with n-butylamine in a non-aqueous medium. The conversion of propan-2-ol at 573 K was followed using the micro-catalytic pulse technique, whereas the decomposition of H2O2 at 298–313 K was followed by determining the volume of oxygen released with time. Solid-solid interactions between the components of the systems resulted in the formation of Co3O4 and CoAl2O4, their ratio depending on the chemical composition and heat-treatment temperature employed with Ag in its metallic form. The textural properties of the investigated catalysts also depended on the chemical composition and calcination temperature. The surface acidity of the catalysts is an important factor in determining their catalytic activity towards the conversion of propan-2-ol whereas the redox-reactive ion-pairs formed between Ag and Co determine their activity towards H2O2 decomposition.