Ga and Al containing MCM-41 mesoporous molecular sieves: Structure and catalytic performance for the 4,6 dimethyldibenzothiophene hydrodesulfurization

MCM-41 type materials containing Al and Ga (Al-Ga-MCM-41) were prepared by a synthesis gel using cethyltrimethylammonium chloride as surfactant. In the preparation, Si/(Al + Ga) ratios were 21, 27 and 32 in the gel, maintaining the concentration of Al constant. The structures of the materials were characterized by X-ray diffraction (XRD), nitrogen physisorption, Fourier transform infrared spectroscopy (FTIR) of adsorbed pyridine, ²⁷Al MAS NMR, ²⁹Si MAS NMR and energy dispersive analysis of X-ray (EDX). Al-Ga-MCM-41 exhibited prominent characteristics as supports for the Ni-Mo-S type catalysts used in the hydrodesulfurization of 4,6-dimethyldibenzothiphene (4,6 DMDBT). The presence of Ga was detected by TEM with a resolution of 1.9 Å point to point; therefore the Ga is in the lattice. The amount of Ga in the support enhanced the activity of the catalysts and modified the products distribution. The maximum catalytic activity and direct desulfurization capability was achieved on the catalyst NiMo/Al-Ga-MCM-41 with Si/(Al + Ga) = 32 molar ratio.