异丁烷/丁烯烷基化氧化铝基固体酸催化剂的制备及催化性能

Alkylation of isobutane with butenes is an industrial processes of great importance for the production of high octane gasoline. Due to growing awareness of environmental issues, efforts are directed towards safer and easily regenerable catalysts. Solid acid catalysts are receiving increased attention. Among thevarious parameters affecting, acid properties are probably the most important as it is known that acid strength affects the protonation of the olefin and the rate of hydride transfer. Sulfated alumina-based metal oxides as the new solid acid catalysts will be prepared, which own controllable structure, high surface area, high thermal stability and adjustable acidic center. The project aims to.improve the understanding of binding state between sulphur oxides and the surface of alumina-based mesoporous materials with different composition and structure and how this bonding interaction influences the stability and acidity of solid acid catalysts, and further to design a new and controllable approach for synthesis of highly ordered mesoporous aluminum-based oxides. By optimizing the cooperative co-assembly synthetic conditions and the hydrolysis, condensation of Al and metal heteroatom precursors can be controlled to adjust the amount of Al and heteroatom hydroxyl groups and the interaction between Al and heteroatom species. As a result, the coordination status, electronic properties, type and content of surface hydroxyl will be controlled at the atomic scale by the selective incorporation of metal heteroatoms with different atomic radius and electronegativity into mesoporous framework of alumina. The quantum chemical method based on density functional theory and various characteristic techniques will be applied to study the intrinsic correlation between reactant and catalyst, mesostructure, acidity of resultant sulfated alumina-based catalysts and their catalytic performance, which may be further used to clarify the mechanism of isobutane/ butene alkylation. The design of new solid acid catalyst with ordered structures, high stability and adjustable acidic strength will increase the.efficiency of alkylation, which may find broader applications in petrochemical industry.

异丁烷/丁烯烷基化反应生产高辛烷值清洁汽油的固体酸催化剂研发面临诸多方面的挑战。本课题针对异丁烷/丁烯烷基化反应对固体酸催化剂比表面积高、表面酸性适中和低温活性好的要求，提出了基于氧化铝基金属氧化物来制备介孔固体酸催化剂的研究思路。通过优化自组装条件，调控掺杂金属原子和铝物种的水解－聚合速率，改变硫酸根的引入方式，实现在介观尺度上自组装的同时，在微观尺度上调节氧化铝基金属氧化物中无机物种的配位状态、铝羟基含量和电子性质，达到对硫化后所形成酸性位的强度、密度及类型的有效调控，从而提高异丁烷/丁烯烷基化反应的反应效率。借助理论计算，通过现代表征技术，探究硫酸根与载体表面的结合方式，阐明催化剂表面性质与催化稳定性之间的关系，揭示催化剂的催化作用及失活机理，实现高效烷基化固体酸催化剂的可控制备，为硫化氧化铝基固体酸催化剂在异丁烷/丁烯烷基化反应中的工业化应用奠定基础。

高辛烷值烷基化汽油具有绿色、清洁的优点，能较好地解决能源供应与环境保护对油品的要求。异丁烷/丁烯烷基化反应生产高辛烷值清洁汽油的固体酸催化剂研发仍面临诸多方面的挑战。本项目针对异丁烷/丁烯烷基化反应对固体酸催化剂比表面积高、表面酸性可调和低温活性好的要求，制备了基于氧化铝基系列金属氧化物（包括Mg-Al复合氧化物、Zr-Al复合氧化物、Cu-Al复合氧化物及纳米氧化锆等多种材料的可控合成），进而获得了介孔固体酸催化剂。通过采用水热合成、溶剂挥发自组装等合成方法，优化了自组装条件，调控了掺杂金属原子和铝物种的水解－聚合速率，改变了硫酸根的引入方式，实现在介观尺度上自组装的同时，在微观尺度上调节氧化铝基金属氧化物中无机物种的配位状态、铝羟基含量和电子性质，达到了对硫酸化后所形成酸性位的强度、密度及类型的有效调控。以生物柴油的酯交换反应为探针反应，考察了硫酸根引入量对催化剂的酸量、酸类型及分布、酸强度的影响。阐明了表面硫物种与金属离子的键合状态，并将其酸性能与催化活性及稳定性进行了关联。理论计算的结果表明，硫酸根吸附位置和氢原子的位置分布决定L酸与B酸中心的结构，其中独立的三足离子态硫酸根结构为活性中心B酸最为稳定的存在形式。同时，对异丁烷/丁烯烷基化反应装置的反应流程进行了优化，并以不同酸强度的Y型沸石分子筛为例，对反应条件进行了探索优化。对合成的系列氧化铝基氧化物固体酸催化剂进行了烷基化性能表征，得到了初步的结果，目前催化剂的表面性能与目标产物的选择性的关系及失活机理仍在进一步研究中。以期通过高效表面酸性可调的固体酸催化剂的制备，为硫酸化氧化铝基固体酸催化剂的工业化应用奠定基础。