Phosphotungestic acid and manganese containing periodic mesoporous organosilica with imidazolium ionic liquid framework: A robust and durable nanocomposite for desulfurization of aromatic sulfur in diesel fraction

As sulfur compounds produced by the combustion of fossil fuels are one of the main elements in air pollution, some strict legislation has been issued that specifies the sulfur ratios of different fuels. Therefore, periodic mesoporous organosilicas (PMO) composed of 1,3- bis(trimethoxysilylpropyl)imidazolium chloride ionic liquid, 1,2- bis(trimethoxysilyl)ethane, and phosphotungstic acid or permanganate as counter ions of imidazolium moieties in the framework of PMO-IL were fabricated to obtain highly reactive -MnO4 or -HPW12O40 based heterogeneous catalysts. The synthesized materials were characterized by FT-IR, N2 adsorption–desorption, low and wide-XRD, XPS, TGA, and HRTEM. The surface area was of 615, 425 and 347 m2 g–1 for PMO-IL, HPW12O40–PMO-IL and MnO4- PMO-IL, respectively. The desulfurization was studied on three types of aro- matic sulfur models. The results revealed that MnO4-PMO-IL and HPW12O40– PMO-IL outperform other catalysts in the oxidative desulfurization process of three kinds of aromatic sulfur compounds; comprising benzothio- phene, dibenzothiophene, and 4, 6-dimethyldibenzothiophene even at smaller O/S ratio. The MnO4–PMO-IL catalyst showed the maximum efficiency in reducing sulfur at 50 ◦C, as it achieved sulfur reduction rates of 93.2, 92.7, and 98.8% after 90 min, while the HPW12O40– PMO-IL catalyst showed a reduction of sulfur by 85.1, 94.3 and 98% after 120 min for BT, DBT, and 4,6-DMDBT compounds, respectively. The two catalysts can be sug- gested as effective catalysts for oxidative desulfurization of fuel. Furthermore, our research showed that the catalyst might be retrieved and reused at least nine times without a noticeable loss in performance.