Tubular MCM-41-supported transition metal oxide catalysts for ethylbenzenedehydrogenation reaction

MCM-41 in both tubular and particulate morphologies were used as the suppor t for molybdenum and iron oxide catalysts in ethylbenzene dehydrogenation r eaction. Different methods of catalyst preparation, such as solution impreg nation and physical mixing, were investigated. Nitrogen adsorption-desorpti on and TEM studies suggest extensive structural defects in tubular MCM-41. The former indicates the presence of an additional pore system at 37 Angstr om, while the latter revealed holes of even larger sizes. We thus suggest t hat the defects make the channels of tubular MCM-41 effectively interconnec ted and provide a better transport of reactant and product in catalytic rea ctions. In both fresh and regenerated catalysts, physically mixed samples h ave lower rates of deactivation and higher catalytic activities than soluti on impregnated ones. The support of the latter catalysts suffers more struc tural collapse than the former. The performance of the catalyst seems to de pend also on the nature of the support. MCM-41-supported samples performed better than amorphous silica-supported ones, and tubular MCM-41-supported s amples are better than particulate MCM-41-supported ones. We interpret the difference in catalytic performance in terms of the increased porosity of t he tubular MCM-41 support. (C) 2000 Elsevier Science B.V. All rights reserv ed.