Al-modified mesocellular silica foam as a superior catalyst support for dibenzothiophene hydrodesulfurization

Abstract A series of Al-containing mesostructured cellular silica foams (Al-MCFs) with different Si/Al molar ratios ( x ; x = 10, 20, 30, 40, or 50) were prepared by a post synthetic method using aluminum isopropoxide as an alumina source. The corresponding NiMo catalysts supported on Al-MCFs were prepared and evaluated using dibenzothiophene (DBT) as the probe reactant. All the synthesized samples were characterized by small-angle X-ray scattering, scanning electron microscopy, nitrogen adsorption-desorption, UV-Vis diffuse reflectance spectroscopy, H 2 temperature-programmed reduction, 27 Al MAS NMR, temperature-programmed desorption of ammonia, pyridine-FTIR, Raman spectroscopy, HRTEM, and X-ray photoelectron spectroscopy to analyze their physicochemical properties and to gain a deeper insight of the interrelationship between the structures and the catalytic performance. The synthesis mechanism was proposed to involve the formation of Bronsted acid and Lewis acid sites through the replacement of Si 4+ with Al 3+ . Aluminum introduced into MCFs by the post synthetic method has a negligible influence on the mesostructure of the parent MCFs but can form silicoaluminate materials with moderate Bronsted acidity. For Al-MCFs( x ) materials, the detection of tetrahedrally coordinated Al 3+ cations demonstrated that the Al species had been successfully incorporated into the silicon frameworks. Furthermore, the DBT hydrodesulfurization (HDS) catalytic activity of the NiMo/Al-MCFs( x ) catalysts increased with increasing Si/Al molar ratio, and reached a maximum at a Si/Al molar ratio of 20. The interaction of Ni and Mo species with the support became stronger when Al was incorporated into the MCFs supports. The high activities of the NiMo/Al-MCFs catalysts for the DBT HDS were attributed to the suitable acidity properties and good dispersions of the Ni and Mo active phases.