温和条件下,燃油深度脱硫一直是非常重要的研究课题.目前,加氢脱硫(HDS)是石油工业上广泛采用的脱硫技术,它能够有效脱除燃油中的硫醚、硫醇和等无机硫化物,但对于芳香族硫化物(如二苯并噻吩、4,6-二甲基二苯并噻吩等),则效果较差.对于上述有机硫化物的深度脱除,现有的加氢脱硫技术需要更为苛刻的反应条件,如高温、高压、高活性贵金属催化剂等,这势必导致燃油成本的大幅上升.因此,世界各国科学家都加强了高效非加氢脱硫方法的研究,主要包括氧化脱硫法、吸附脱硫法、萃取脱硫法和生物脱硫法等,其中氧化脱硫法是一种公认的具有应用前景的高效脱硫技术,该技术只需在常温常压下进行,可将含硫化合物氧化成其相应的砜类物质后,再用溶剂萃取法或吸附法除去.氧化脱硫反应中所涉及氧化剂有过氧化氢、有机过氧化物和氧气等.在这些氧化剂中,过氧化氢由于其活性高,在氧化反应后的副产物只有水,而被广泛研究. 离子液体作为一种低温熔融盐,因其独特的理化性质,如无蒸气压、低毒性、良好的溶解性以及结构可调等,受到了广泛的关注.其中,功能化多酸基离子液体不仅具备离子液体的特点,还具备多金属氧酸盐的优势,已被用于燃油的均相氧化脱硫过程中.但是,此过程中离子液体往往用量较大,催化剂难于回收和循环利用,氧化剂用量较大,阻碍其在工业中的应用.为了克服上述缺点,本课题组以多酸基离子液体[C16mim]3PW12O40和正硅酸四乙酯为原料通过溶胶-凝胶法直接合成了一系列含钨功能化介孔复合材料 W-SiO2,其中咪唑型阳离子作为介孔模板剂,而多酸阴离子作为金属源.采用 XRD, IR, Raman, BET, DRS, TEM等测试手段对所合成的材料进行了表征.结果表明,钨活性物种是以氧化钨的形式存在,并且能够均匀地分散在载体二氧化硅上,所合成的材料比表面积为513–743 m2/g,孔体积为0.37–0.50 cm3/g,孔径为2.91–3.20 nm.将所合成的材料 W-SiO2-20应用于燃油氧化脱硫反应(过程中无需有机溶剂),结果表明,所合成的复合材料既能作为吸附剂来吸附有机硫化物,又能作为催化剂来活化过氧化氢以氧化有机硫化物.在最优条件(反应温度60oC, O/S摩尔比为2.5,反应时间40 min)下,二苯并噻吩脱除率可100%,而且反应体系易于循环使用,7次循环后脱硫率无明显降低.此外,还考察了复合材料在相同条件下对于不同硫化物的脱除效果,结果表明,反应活性顺序为4,6-DMDBT＞ DBT＞ BT＞ DT.%A series of functional, tungsten‐containing mesoporous silica materials (W‐SiO2) have been fabri‐cated directly from an ionic liquid that contained imidazole and polyoxometalate, which acted as mesoporous template and metal source respectively. These materials were then characterized through X‐ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectra (FTIR), diffuse reflectance spectra (DRS), and N2 adsorp‐tion‐desorption, which were found to contain tungsten species that were effectively dispersed throughout the structure. The as‐prepared materials W‐SiO2 were also found to possess a mesopo‐rous structure. The pore diameters of the respective sample W‐SiO2‐20 determined from the TEM images ranged from 2 to 4 nm, which was close to the average pore size determined from the nitro‐gen desorption isotherm (2.9 nm). The materials were evaluated as catalysts for the heterogeneous oxidative desulfurization of dibenzothiophene (DBT), which is able to achieve deep desulfurization within 40 min under the optimal conditions (Catalyst (W‐SiO2‐20)=0.01 g, temperature=60 °C, oxidant (H2O2)=20 µL). For the removal of different organic sulfur compounds within oil, the ability of the catalyst (W‐SiO2‐20) under the same conditions to remove sulfur compounds decreased in the order:4,6‐dimethyldibenzothiophene>Dibenzothiophene>Benzothiophene>1‐dodecanethi‐ol. Additionally, they did not require organic solvents as an extractant in the heterogeneous oxida‐tive desulfurization process. After seven separate catalytic cycles, the desulfurization efficiency was still as high as 90.3%. From the gas chromatography‐mass spectrometer analysis, DBT was entirely oxidized to its corresponding sulfone DBTO2 after reaction. A mechanism for the heterogeneous desulfurization reaction was proposed.
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