Effect of the preparation method of Al-Mg-O catalysts on the selective decomposition of ethanol

Selective decomposition of ethanol was used as a test reaction at 350degreesC to evaluate the catalytic activity of two Al-Mg-O mixed oxides prepared by two different methods (wet impregnation and coprecipitation). The catalyst precursors were examined by TG and DTA and were calcined between 500-900degreesC for 5 h in air. The surface area of all catalysts was measured by N-2 sorption using the BET method. The total acidity and basicity were determined by TPD using pyridine and formic acid. The catalysts were characterized by XRD analysis. It was found that the preparation method of Al-Mg-O catalyst has a great effect on the selective decomposition of ethanol. Al-Mg-O (1) catalysts, prepared by wet impregnation, were more selective towards ethene formation during dehydration of ethanol. This is ascribed to their high total surface acidity. On the other hand, Al-Mg-O (H) catalysts, prepared by coprecipitation, were highly selective in the oxidative dehydrogenation of ethanol to yield acetaldchyde. This could be attributed to their high concentration of basic sites. In addition, the production of traces of diethyl ether was also observed (three times more for Al-Mg-O (H) than for Al-Mg-O (I)).