吸附剂的表面化学特性对深度脱除汽油中噻吩类含硫化合物的影响及吸附机理研究

As an important source of SOx formation, vehicle emissions have caused serious environmental problems. It has been a matter of urgency to control the release of pollutants from automobile exhaust. Deep desulfurization of thiophenic S-containing compounds in gasoline is the key to solving this problem. However, the industrialized catalytic hydrogenation method is not very useful to remove thiophene and its derivatives, and thus an supplementary method is required. Adsorption as a method of desulfurization has attracted wordwide attention because of the advantages of low energy consumption and environmental friendliness. But it has not been substantially applied because of relatively poor selectivity and low sulfur capacity. It is necessary to fully investigate the relationship between the chemical properties of the sorbent surface and its desulfurization behavior, and the adsorption mechanism. Based on the above consideration, this project will focus on the influence of the chemical properties of the sorbent surface, such as the concentration of L and B acid sites of different acid strength, and the valence state and distribution of different active metal elements on the desulfurization behavior. The adsorption mechanism will be investigated by using different thiophenic S-containing compounds, olefins and aromatic hydrocarbons to characterize competitive adsorption behavior of olefins or aromatic hydrocarbons and comparing the results obtained for pure components and conventional gasoline. These investigations would lead to the preparation of an excellent sorbent with high adsorption capacity and selectivity, which can remove the sulfur in gasoline to the level reauired in the Fifth Stage Gasoline National Standard.

作为SOx的重要排放源，汽车尾气引起的环境问题亟待解决，汽油中硫化物的深度脱除是解决该环境问题的前提。已工业化的催化加氢工艺很难实现油品中噻吩类含硫化合物的深度脱除，仍需要其它方法进行辅助。吸附法脱硫因能耗低、环境友好等优点被人们所重视，但必须首先解决选择性和硫容相对较差的问题。这就需要充分认知吸附剂的表面化学特性与其脱硫活性间的关联、并深入揭示吸附脱硫机理。基于此，本项目拟将探讨吸附剂表面酸性位的强度和酸类型，表面金属活性元素的种类、价态及分布等表面化学特性对噻吩类硫化物吸附的影响；选取噻吩类含硫模型化合物及烯烃和芳烃模型化合物深入探讨噻吩类硫化物的吸附机理，并与市售汽油中的脱硫实验结果相结合，揭示汽油中烯烃和芳烃对噻吩类硫化物的吸附产生竞争作用的内在机制；在上述研究工作的基础上，制备出吸附量大，选择性高，能将现有汽油中的硫深度脱除至符合我国第五阶段车用汽油标准要求的性能优异的吸附剂。

汽车尾气是SOx的主要排放源之一，为了降低尾气中SOx含量，减少其对环境产生的危害，对汽油中硫化物的深度脱除势在必行。我国汽油硫含量要求已于2017年由国IV标准中的50 ppm降为国V标准的10 ppm，在此基础对汽油中含硫化合物进一步脱除是需要考虑的问题。已工业化的催化加氢工艺较难实现油品中噻吩类含硫化合物的深度脱除，需要其它方法进行辅助。吸附法脱硫因操作简便、能耗低等优点被人们所重视，但必须解决脱硫选择性和硫容相对较差的问题。这就需要充分认知吸附剂的表面化学特性与其脱硫活性间的关联、并揭示脱硫机理。.基于此，本项目以r-Al2O3、NaY、SBA-15、MCM-41、SiO2为载体，对其进行了表面酸改性或金属元素修饰，制得了不同吸附剂。探讨了吸附剂表面酸性，表面金属活性元素的种类表面化学特性对噻吩类硫化物吸附的影响；选取了噻吩类含硫模型化合物和芳烃模型化合物探讨了噻吩的吸附机理，初步揭示了汽油中芳烃对噻吩吸附产生竞争作用的原因；优化得到了Ag/-Al2O3吸附剂，CeY和Ag/SBA-15分子筛吸附剂，以及Ag/Fe3O4@SiO2磁性纳米吸附剂，并考察了Ag/Fe3O4@SiO2吸附剂在市售93#国IV汽油中的脱硫性能。研究结果表明：吸附剂上中强B酸位和L酸的增加有利于提升吸附的脱硫性能。酸和金属元素逐级改性得到的MHY型吸附剂的脱脱硫性能较单独酸改性和单独金属元素改性所制得的吸附剂好。银改性有利于提高吸附剂对硫化物的吸附量，铈改性有利于提高选择性。噻吩可通过S-Ce键以及大键和硫原子与吸附剂上酸性位的作用吸附在CeY吸附剂上。苯在CeY上的吸附通过大键与吸附剂上酸性位的结合而进行，苯对噻吩产生的竞争作用是通过竞争吸附剂上的酸性位，络合作用形成的。优化得到的Ag/Fe3O4@ SiO2磁性纳米吸附剂在市售93#国IV汽油中，剂油比为0.13 g/mL时，可将汽油中的硫由44.7 ppm脱除至4.5 ppm，达到了国V标准对汽油中硫含量的要求。项目执行期间，培养硕士研究生2名，在Green Chemistry、Fuel Processing Technology等国内外学术期刊上表发论文6篇，所得结果可为我国汽油品质的进一步升级提供理论支撑，具有环境效益和社会效益。