(513ci) Novel Design of Co/SiO2@Al2O3 Catalysts for Propane Dehydrogenation

The catalytic conversion of propane to propylene via dehydrogenation reaction is one of the highly efficient and selective processes. Apart form industrially used Pt and Cr based catalysts being investigated for the propane dehydrogenation, other transition metal-based catalysts have also shown promising performance for the dehydrogenation reaction. Cobalt is an inexpensive and environmentally friendly catalysts investigated for the alkane dehydrogenation. However, the key drawback of cobalt-based catalysts is the formation of large CoO_X crystals which lead to cracking reaction thus increasing the coke deposition on active sites and lower the activity of the catalysts over the reaction time. Herein, we propose a hierarchical design of catalyst with Co/SiO₂ spheres as a core and a layer of porous alumina covering the sphere, represented as SiO₂@Co@Al₂O₃. The catalysts were characterized using different techniques including TPR, XRD, XPS, pyridine FTIR, in-situ propane and propylene adsorption study and HRTEM. The premilinary studies performed on catalysts that Co/SiO₂ spheres show a very low dehydrogenation activity, as the cobalt is present in octahedral coordination with silica obtained from UV-Vis analysis. However, after incorporating smaller fraction of alumina on the Co/SIO₂ spheres resulted in 3 times increase in catalytic activity owing to the acidic nature and interfacial interaction of Co with SiO₂ and Al₂O₃ which was investigated using pyridine FTIR, TPR and XPS analysis of the series of catalysts. With the hierarchical structure, the coke formation was reduced to 5 times as compared to Co/ Al₂O₃ which has high activity but lower propylene selectivity. This study shows a novel approach to reduce the coke formation and metal sintering which can also be applied to other catalytic systems.