Strontium(II)-added CoAl2O4 nanocatalysts for the selective oxidation of alcohols

Abstract

Strontium added CoAl2O4 nanocatalysts with spinel structure were prepared by a modified sol–gel method using ethylene diamine followed by sintering at 900 °C. The samples were labeled as CoSA1-900, CoSA2-900, CoSA3-900, CoSA4-900, CoSA5-900, CoSA6-900, where the molar ratios of Co:Sr were 1.0:0.0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.6:0.4 and 0.5:0.5 and the aluminum molar ratio was kept constant, 900 referring to the sintering temperature. The effect of Sr addition on the structural and morphological properties of cobalt aluminate nanocatalysts was investigated by X-ray diffraction, Fourier transform infrared spectra, high resolution scanning electron microscopy, energy dispersive X-ray analysis, nitrogen adsorption/desorption isotherms, temperature dependent conductance measurements and thermoelectric power measurements. The addition of Sr improves the performance of the nano cobalt aluminate catalyst towards the selective oxidation of alcohols and decreases the grain size. The effect of solvent, oxidant and reaction time on the Sr(II)-added cobalt aluminate nanocatalysts for the oxidation of benzyl alcohol was studied. Higher activity was obtained for the conversion of benzyl alcohol to benzaldehyde for 0.3 molar percentage Sr(II) added cobalt aluminate catalyst (CoSA4-900) which was used for the selective oxidation of other alcohols. The stability and reusability of the catalyst were also investigated.