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Role of synthesis media on properties of tin and copper incorporated SBA-15 catalysts and their activity in selective oxidation of ethanol

Akti, Filiz
Doğu, Timur
Hydrothermal synthesis of metal/SBA-15 catalysts were performed by adding of metal sources before or after silica precursor, as powder or after dissolving in alcohol. Novel catalysts were developed carrying out synthesis in competitive (aluminum) ion media. XRD patterns and TEM images showed that uniform hexagonal arrays of SBA-15 support were not affected with metal loadings. Metal addition and dissolution in alcohol enhanced textural and ordered properties. Proposed ion attractions in highly charged media by presence of metals could explain wall thickness increase of SBA-15. Positive effects of aluminum environment on tin loading were supported by XRD, TEM, EDS and ICP-MS. Metal incorporation resulted in drastic changes in OH stretching region and remarkable increases in Bronsted and Lewis acid sites in FTIR spectrums. Aluminum and its quantity increase in synthesis solution enhanced surface acidity. The catalysts yielded conversion values reaching to 0.95 at moderate temperatures in oxidation of ethanol. The highest acetaldehyde-which was the major product- selectivity was observed as 0.58 at 300 degrees C. Distribution of species in the reactor outlet was tried to explain by Marsvan Krevelen adsorption/desorption surface mechanism of ethanol on the active sites.