Oxidation of ethanol and carbon monoxide on alumina-supported metal/metal oxide xerogel catalysts

Abstract

The main goal of the study is to investigate the effect of metal type, metal oxide type and metal/oxide loading on the conversion as a function of temperature for the complete combustion of ethanol and CO in air over single step sol-gel made Al2O3 supported metal and mixed metal oxides. Two types of catalysts, Pt/Al2O3 (1, 2, and 3 % Pt loaded) and CuO-Mn2O3/Al2O3, with Cu/Mn molar ratio of 1:1, 5:1 and 12:1, and 50, 70, and 90% metal loading, were synthesized by impregnation and single step sol-gel methods, respectively. In addition, by synthesizing CuO/Al2O3, Mn2O3/Al2O3 and Pd-Mn2O3/Al2O3, the catalytic activity relationship between metal and metal oxides were clarified. Characterization of the samples was performed by XRD, BET, and FT-IR techniques and it was observed that among the metal oxide catalysts, CuO-Mn2O3/Al2O3 (70 wt%; (Cu/Mn)molar=1) showed the highest activity due to the formation of Cu1.5Mn1.5O4 phase while 3% Pt loaded alumina was the catalyst demonstrated the highest catalytic activity among the noble metal catalysts. Also, Pd addition enhanced the activity of metal oxide catalyst by lowering the temperature at which ~99% ethanol conversion was obtained. Moreover, deactivation of CuO-Mn2O3/Al2O3 mixed oxides was observed due to the irreversible adsorption of CO2 on catalyst surface at low temperatures. Except for Pt containing catalysts, the catalysts that showed high catalytic activity in ethanol oxidation was also tested for CO oxidation and CO2 formation was detected qualitatively at varying operating temperatures.