Effects of the surface structure and experimental parameters on the isopropanol decomposition catalyzed with sol-gel MgO

Isopropanol decomposition was used as a probe reaction for characterizing the surface properties of sol-gel MgO catalysts. The specific surface area and the pore size distribution of the samples, calcined at different temperatures, were measured with the BET method. Acidity and basicity of the catalyst were determined by using TPD-NH₃ and TPD-CO₂ techniques. The total conversion and acetone selectivity depended on the experimental conditions. Increasing reaction temperature significantly improved the total conversion, but reduced acetone selectivity. The activity and acetone selectivity obtained at the initial reaction were higher than that obtained after 15 min and 30 min of reaction. When water was added in the reaction stream, hydroxyl groups were formed on the MgO surface, a remarkable enhancement of the conversion and of the acetone selectivity was observed. The structural defects and the specific surface area of the catalyst are also related to the activity and selectivity of the isopropanol decomposition. Two mechanisms were suggested for the explanation of acetone formation: in the case of water absent in the fed stream, the acetone was produced by the dehydrogenation route; in the case of water present in the reaction mixture, acetone was produced by the pathway of dehydrogenation accompanying the dehydration.