An Effective Magnetic Catalyst for Oxidative Desulfurization of Model and Real Fuels: Fe3O4/ZIF-8/TiO₂

Abstract

In the current research, an advanced and innovative composite based in zeolitic imidazolate framework-8 (ZIF-8) incorporating magnetic and effective oxidative catalytic properties was successfully used to prepare ultra-low sulfur model and real fuels by oxidative desulfurization (ODS) process. To this purpose, the surface of ZIF-8 was decorated by TiO 2 and Fe 3 O 4 nanoparticles (NPs) to prepare the composite catalyst (Fe₃O₄/ZIF-8/TiO₂). Structural characterization was performed by XRD, FT-IR, SEM, EDS, TEM, N 2 adsorption-desorption isotherm and VSM. TEM images showed that the semi-spherical TiO 2 and Fe 3 O 4 NPs are fairly doped. The effect of TiO 2 and Fe 3 O 4 NPs incorporated in ZIF-8 support allowed an efficient catalytic oxidative desulfurization of model fuel (500 ppm of dibenzothiophene, DBT) and real fuels (gasoline, diesel, among others) using tert-Butyl hydroperoxide (TBHP) as oxidant under a solvent-free system. Optimization studies were performed and complete desulfurization of model fuel was found after 6 h using O/S = 3 at 80 °C, instead of the 33% of desulfurization obtained with the pristine ZIF-8. Under optimized conditions, sulfone was the only product observed. The stability and the recycle capacity of the Fe₃O₄/ZIF-8/TiO₂ composite catalyst was confirmed and after ten consecutive ODS cycles only a slight decrease of desulfurization efficiency was detected (around 10%). Therefore, the results here presented confirm that the magnetic catalyst conciliates efficiency, stability and easy recovery, that are essential properties for future industrial application. • Magnetic catalytic composite has been prepared based on ZiF-8 support. • Fe 3 O 4 /ZIF-8/TiO 2 presents high catalytic efficiency for oxidative desulfurization of model and real fuels. • Solvent-free oxidative catalytic system was successfully used. • Complete desulfurization was achieved after 6 h using O/S = 3. • Catalyst presented high stability and recycle capacity for 10 consecutive desulfurization cycles.