Fig nbsp a nbsp and

Our previous study on the o-xylene hydroisomerization over HMS-Ti modified with Ga demonstrated that R428 upon hydrogenation at atmospheric pressure the reaction proceeds exclusively via intramolecular mechanism (formation of m- and p-xylenes) and hydrogenation of benzene aromatic ring of o-, p- and m-xylenes did not occur [28]. Thus, we consider of interest to study the effect of hydrogen pressure on the reaction mechanism over Ga2O3/HMS-Ti systems. The structural and surface properties of the synthetized catalysts were evaluated by means of different characterization techniques in order to obtain catalyst activity–structure correlation.
2. Experimental
2.1. Catalyst preparation
The HMS-Ti substrate was synthetized according to a procedure reported by Gontier and Tuel [29] using neutral primary amine (dodecylamine: C12H25NH2, Aldrich 98%) as surfactant and a neutral tetraethylorthosilicate (TEOS, Si(OC2H5)4, 98% Acros) as inorganic precursor of silica. Mesitylene (C9H12, Aldrich 98%) and titanium(IV) butoxide (Aldrich 97%) were used as swelling agent and precursor of Ti4+ cations, respectively. The HMS-Ti material was prepared with a Si/Ti molar ratio of 40, which was demonstrated to be optimized Si/Ti molar ratio for HMS-Ti systems [30]. After filtration and washing the solid with distilled water, the solid was dried at room temperature for 24 h followed by drying at 103 °C for 2 h. Finally, the solid was calcined at 550 °C for 3.5 h with a heating rate of 2.5 °C min−1.