Abstract: Ti-HMS was synthesized at ambient temperature using dodecylamine as the template, tetraethylorthosilicate as the silicon source, tetrabutylorthotitanate as the titanium source, and incorporating straight chain alkanes as swelling agents. Effects of the dosage and the number of carbon atoms of the alkanes on the structural and catalytic properties of the Ti-HMS were investigated. The molecular sieve was characterized by X-ray diffraction (XRD), N2 physical adsorption, diffuse reflectance ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy (TEM). The catalytic performance of Ti-HMS was evaluated by the oxidative removal of4,6-dimethyl dibenzothiophene (4,6-DMDBT). The Ti-HMS samples obtained possess wormlike mesostructure, which was confirmed by XRD and TEM analysis. The Ti-HMS prepared with the addition of alkanes has lower crystallinity and framework titanium content than the original sample. The physical adsorption results exhibit that the pore diameter of Ti-HMS, as well as the surface area and pore volume, was enlarged with the addition of alkanes. In addition, the pore diameter of Ti-HMS increased with the increase in the dosage of alkanes and the number of carbon atoms in alkane molecules. The samples thus obtained have preferable activity than the original Ti-HMS for the oxidative removal of4,6-DMDBT, which can be attributed to the improvement of their diffusion performance arising from the larger pore diameter.

Key words: Ti-HMS molecular sieve, dodecylamine, hexane, octane, pore size expanding, dimethyl dibenzothiophene