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 t he surface properties of sol-gel MgO catalysts, The specific surface area a nd the pore size distribution of the samples, calcined at different tempera tures, were measured with the BET method. Acidity and basicity of the catal yst were determined by using TPD-NH3 and TPD-CO2 techniques. The total conv ersion and acetone selectivity depended on the: experimental conditions. In creasing reaction temperature significantly improved the total conversion, but reduced acetone selectivity. The activity and acetone selectivity obtai ned 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 conv ersion and of the acetone selectivity was observed, The structural defects and the specific surface area of the catalyst are also related to the activ ity and selectivity of the isopropanol decomposition, Two mechanisms were s uggested for the explanation of acetone formation: in the case of water abs ent in the fed stream, the acetone was produced by the dehydrogenation rout e; in the case of water present in the reaction mixture, acetone was produc ed by the pathway of dehydrogenation accompanying the dehydration. (C) 1999 Elsevier Science B.V. All rights reserved.