Tubular MCM-41-supported transition metal oxide catalysts for ethylbenzene dehydrogenation reaction

MCM-41 in both tubular and particulate morphologies were used as the support for molybdenum and iron oxide catalysts in ethylbenzene dehydrogenation reaction. Different methods of catalyst preparation, such as solution impregnation and physical mixing, were investigated. Nitrogen adsorption-desorption and TEM studies suggest extensive structural defects in tubular MCM-41. The former indicates the presence of an additional pore system at 37 Å, while the latter revealed holes of even larger sizes. We thus suggest that the defects make the channels of tubular MCM-41 effectively interconnected and provide a better transport of reactant and product in catalytic reactions. In both fresh and regenerated catalysts, physically mixed samples have lower rates of deactivation and higher catalytic activities than solution impregnated ones. The support of the latter catalysts suffers more structural collapse than the former. The performance of the catalyst seems to depend also on the nature of the support. MCM-41-supported samples performed better than amorphous silica-supported ones, and tubular MCM-41-supported samples are better than particulate MCM-41-supported ones. We interpret the difference in catalytic performance in terms of the increased porosity of the tubular MCM-41 support.