Effect of diffusion in catalytic dehydration of alcohol over silica-alumina with continuous macropores

Bimodal porous silica-alumina catalysts with both continuous macropores and mesopores were prepared from tetraethyl orthosilicate in the presence of polyethylene oxide, and the effectiveness of macropores in vapor-phase dehydration of 2-propanol was evaluated by the comparison with silica-alumina having no macropores. The reaction rate of dehydration varies depending on the particle size and the presence of macropores as well as reaction temperature. For more detail data processing, diffusion coefficients in pores at each reaction temperature were theoretically calculated by assuming molecular diffusion and Knudsen diffusion for catalysts with and without macropores, respectively. Then, we compare the catalyst effectiveness factors obtained experimentally with the theoretical curve. The experimental data well agree with theoretical prediction. The results clearly show that the macropores with interconnected structure effectively work as pathways for rapid diffusion and improve the reaction kinetics.