Facile fabrication of confined spaces with molybdenum atoms for fast oxidative desulfurization of fuel oil

Molybdenum-based heterogeneous catalysts are promising for oxidative desulfurization (ODS) of fuel oil. However, the catalytic activity is linked with the dispersibility of Mo atoms on appropriate carriers. Here, Mo-based mesoporous silica was constructed by using confined spaces of as-synthesized SBA-15 (AS), where Mo atoms are homogeneously dispersed. By utilizing facile solid phase grinding followed by calcination, the Mo precursor was introduced into the confined spaces between template and silica walls to form Mo-O-Si structure during which the template P123 was also released. Characterization results revealed that up to 5 wt% of Mo can be well dispersed while sever aggregation takes place in the catalysts derived from template free SBA-15(CS) at similar loading. Confined spaces and abundant hydroxyl groups played a significant role for Mo dispersion. The catalysts derived from AS showed superior ODS activity to their counterparts from the CS and converted 100 % of DBT in 25 min at T = 30 °C, O/S = 5 and a catalyst dose of 0.1 g. The kinetic studies revealed that the DBT oxidation follow pseudo-first-order kinetic process and the activation energy of DBT calculated via Arrhenius equation is 36.97 kJ/mol and 33.88 kJ/mol over Mo-AS and Mo-CS, respectively. The thermodynamic studies demonstrated that DBT oxidation is endothermic with positive Gibbs free energy, suggesting the non-spontaneity of ODS of DBT over Mo based catalysts. Furthermore, the stability and regeneration capability of Mo-AS made it promising for ODS technology for fuel oil.