| Air pollution has drawn wide attentions which can not only result in the deterioration of air quality directly, but also lead to the water pollution and soil pollution and thus arose a serious hazard for sustainable development including ecological balance, human health and socio-economic. Air pollutants included dust, toxic gases, greenhouse gases, metals, and metal salts, among which the poisonous gases were widely distribution, serious harm and difficult harness. The poisonous gases including SOX, NOx and other volatile organic compounds and the sulfide in the fuel will burn to emit SOX. It is calculated that 40.25 million tons of sulfur will emit into the atmosphere from 2010 to 2035, if failure to take measures to reduce the sulfur content of the fuel. This could not only directly affect human health, and will form acid rain and smog, which is the main reason for the formation of soil and atmospheric pollution. The traditional fuel desulfurization mainly adopts hydrodesulfurization (HDS) technology. However, HDS often require high temperature under high pressure, high energy consumption and costs, while poor desulfurization performance for some aromatic sulfur compounds such as thiophene and its derivatives. At present, a variety of fuel desulfurization technologies have been developed, including adsorption, extraction, biological and oxidative desulfurization. Among them, the oxidative desulfurization has attracted more attentions due to the mild operating conditions, low energy consumption, and fast desulfurization rate. In this paper, a series of ionic liquid supported heterogeneous catalysts have been prepared and applied for oxidative desulfurization of fuels.Supported ionic liquid catalyst was synthesized by grafting Fenton-like ionic liquid on MCM-41. The as-synthesized catalyst material was employed for the oxidative desulfurization from model oil. A series of characterizations such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and N2 adsorption-desorption have been used to determine the structure and explore the property of the as-prepared catalysts. Researches reveal that the catalysts have the mesoporous material supported structure with Fenton-like ionic liquid supporting on the surface of MCM-41. Through varying the various parameters such as temperature, solvents, the dosage of H2O2, and different sulfides, the optimum desulfurization condition has been determined. By using [Omim]BF4 as the extractant and H2O2 as the oxidant, the MCM-41 supported Fenton-like ionic liquid display the high catalytic activity at room-temperature (30℃) condition via a extraction coupled with catalytic oxidative desulfurization (ECODS) action mechanism. The dibenzothoiphene sulfone was determined to be the exclusive product of dibenzothiophene oxidizing reaction by using the gas chromatography-mass spectrometer (GC-MS) technique and further confirm the action mechanism is ECODS process for sulfur removal in this system.Mesoporous material SB A-15 supported iron-based redox ionic liquids catalysts have been synthetized successfully via a grafted process and the as-prepared catalysts were used for desulfuration from model oil. The as-prepared catalysts were characterized systematically by XRD analysis, N2 adsorption-desorption, transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS). The as-prepared catalysts possess high surface area and are accessible for substrate and oxidant. In this system, the extractive combined catalytic oxidation was determined to dominating the desulfurization process. During this process, the ionic liquid [Omim]BF4 acted as the extractant, the reaction media and the co-catalyst at the same time. The desulfurization rate could achieve 94.3% at the optimality condition. Also, the possible mechanism of action in this system was proposed.A heterogeneous catalyst system was synthesized by immobilizing phosphotungstic acid on ionic liquid-modified mesoporous silica SBA-15 and applied in oxidative desulfurization. Structure and properties of catalyst were characterized by the contact angle, the XRD, N2 adsorption-desorption, SEM and TEM results and the results demonstrated that the synthesized catalyst possessed ordered mesoporous structure and high special surface area. The FTIR and XPS analysis revealed that HPW-IL was successfully immobilized on SBA-15. Due to the introduction of imidazole-based ionic liquid, the catalyst exhibited good wettability for model oil, which had significant contribution to desulfurization activity. Both DBT and 4,6-DMDBT could be removed completely at mild conditions (60℃,40 min). The removal of BT also can reach 81.3% within 60 min. Furthermore, the catalyst was recovered and reused in four reaction runs with a slight decrease in activity.Hydrogen peroxide is usually used as an oxidant in oxidative desulfurization. However, in order to reach a high level of sulfur removal, excess of hydrogen peroxide needs to be added into the oxidative system. In this study, phosphomolybdic acid immobilized on imidazole-based ionic liquid modified mesoporous SBA-15 (HPMo-IL/SBA-15) was prepared. The as-prepared material combines the advantages of H3PMo12O40 (HPMo) and SBA-15. The high special surface area of SBA-15 could well disperse the HPMo active species. The results show that HPMo could be steadily immobilized across the surface of SBA-15 by using an imidazole-based ionic liquid. At the same time, after the introduction of the imidazole-based ionic liquid, HPMo-IL/SBA-15 material exhibited hydrophobic property. Experiments demonstrated that the hydrophobic catalyst exhibited a high activity in oxidative desulfurization. When hydrogen peroxide with a stoichiometric ratio (H2O2/sulfur mole ratio is 2) was used, the removal of dibenzothiophene (DBT) could achieve levels of above 90% at 60℃ in 90 min. When the concentration of hydrogen peroxide was slightly increased (H2O2/sulfur mole ratio increased from 2 to 2.5), the sulfur removal reached 100% in 40 min. Moreover, the synthesized catalyst could adsorb dibenzothiophene sulfone (DBTO2). In this regard, HPMo-IL/SBA-15 served as not only a high-efficiency catalyst but also an adsorbent.Supported catalyst HSiW-IL/SBA-15 was synthesized by immobilized H4[SiO4(W3O9)4] (HSiW) on the ionic liquid modified SBA-15. The structure and morphology of the catalysts were investigated by multiple techniques. The results demonstrated that HSiW was successfully immobilized on the ionic liquid modified SBA-15 and the mesoporous structure of SBA-15 was remained. Compared with HSiW and HSiW/SBA-15, HSiW-IL/SBA-15 exhibited high desulfurization efficiency. The high activity of HSiW-IL/SBA-15 was attributed to two aspects:the catalyst possessed the high specific area and large pore size, which was conducive to mass transfer; the catalyst showed some hydrophobic, enabling well wettability for model oil. The catalysts were calcined at different temperatures. The result showed that 400℃ catalyst-treated, it can achieve 100% sulfur removal in 30 min. The heterogeneous catalyst has good recyclability. The sulfur removal was still kept at 93.6% after 5 times recycling. |
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