Vanadium-Doped Acid-Prepared Mesoporous Silica:  Synthesis, Characterization, and Catalytic Studies on the Oxidation of a Mustard Gas Analogue

The room temperature, liquid-phase oxidation of 2-chloroethyl ethyl sulfide (CEES), an analogue of mustard gas, was investigated using vanadium-doped acid-prepared mesoporous silica (“V−APMS”) as a solid catalyst. The V−APMS samples were prepared by wet impregnation with NH4VO3, followed by calcination. XRD, N2 physisorption, SEM, and EPR were used to characterize the solid products. Samples with lower V contents (0.1−10 wt %) were found to contain isolated vanadyl species and were highly effective for oxidation of CEES to the corresponding sulfoxide and sulfone using tert-butyl hydroperoxide (TBHP) as the oxidant. Surface area and pore volume decreased significantly at higher loadings of V due to formation of V2O5 within the pores of the solid. The mechanistic route involved V5+/V4+ redox cycles during the catalysis process, as revealed by EPR studies.