Phosphotungstic acid immobilized on amino functionalized spherical millimeter-sized mesoporous γ-Al2O3 bead and its superior performance in oxidative desulfurization of dibenzothiophene

The composite material HPW/NH 2 –Al 2 O 3 was successfully prepared by immobilization of phosphotungstic acid H 3 PW 12 O 40 (HPW) on the surface of amino functionalized spherical millimeter-sized mesoporous γ-Al 2 O 3 beads (NH 2 –Al 2 O 3 ), that featured high specific surface area, remarkable enhanced mechanical strength, chemical stability and low cost. This composite material was characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Brunner−Emmet−Teller (BET) and mechanical strength measurements. The experimental results showed that introduction of NH 2 group in between HPW and Al 2 O 3 surface not only provide strong binding sites for catalytic centers HPW to get high dispersion on the carrier surface but also prevent HPW from structural decomposition. As a consequence, the prepared HPW/NH 2 –Al 2 O 3 exhibited excellent catalytic performance in the oxidative desulfurization of model oil composed of dibenzothiophene (DBT) and n-octane. The 350   ppmw S of sulfur content in 20   mL of n-octane can be dropped down to 2.8   ppmw S in 2   h using 60   mg of HPW/NH 2 –Al 2 O 3 catalyst under the optimal conditions. Remarkably, the catalyst can be conveniently recycled by simple decantation method. After 10 times recycling, the oxidation desulfurization efficiency just dropped down slightly from 99.2% to 98.6%. The results indicate that synthesized HPW/NH 2 –Al 2 O 3 beads have great potential as a catalyst in oxidative desulfurization for special practical applications.