Polyoxomolybdate based ionic-liquids as active catalysts for oxidative desulfurization of simulated diesel

Abstract

This work compares the stability and the catalytic efficiency of different ionic liquid phosphomolybdates ([BPy]3[PMo12O40] and [BMIM]3[PMo12O40]) with a cationic (propylpyridinium) functionalized mesoporous silica nanoparticle composite (PMo12O40@PPy-MSN). These were used as solid catalysts for the oxidative desulfurization of a multicomponent model diesel using hydrogen peroxide as oxidant and a polar immiscible extraction solvent. Ionic liquid ([BMIM][PF6] was successfully used as solvent to extract sulfur compounds from model diesel. The ionic liquid phosphomolybdates showed partial solubility in the ionic liquid phase, occurring some decomposition of their Keggin structure in the soluble reaction media, probably caused by their interaction with oxidant. On the other hand, the phosphomolybdate composite PMo12O40@PPy-MSN presented high structural stability and only negligible leaching occurrence after various consecutive reaction cycles. The model diesel was near complete desulfurized after 3 h and consecutive desulfurization cycles were performed without loss of activity. Therefore, the immobilization of Keggin phosphomolybdate structure [PMo12O40]3− using cationic propylpyridinium silica nanoparticle is an assertive strategy to produce stable and active heterogeneous catalysts.