新型负载全氟磺酸树脂催化剂的制备、表征及应用研究

Solid acid catalysts have served as very important functional materials for the petroleum refinery industry and for the production of chemicals. Silica-supported acid polymer resins as organic−inorganic composite solid acid has received and is still receiving today much attention, because such materials are reusable, cost-efficient and environmentally friendly, and can also catalyze a large variety of reactions. Aquivion is a brand new promising perfluorosulfonic acid resin that can become a good alternative to H2SO4, but it suffers from swelling in solvents and rather low surface area for practical and even commercial use. There is little literature showing its application as acid catalyst. Therefore, it is highly desirable to design and engineer new recyclable Aquivion-based solid acid materials and to screen their application scope. The objective of the present work is to develop various materials supported Aquivion resin as solid acid catalysts by advanced preparation methods. The obtained catalysts will be fully analyzed by many different physico-chemical techniques. Moreover, the key properties of final catalysts, such as acidity, distribution of acid sites, porosity and amphiphilicity need be carefully tuned and verified. The developed supported Aquivion heterogeneous catalysts will be applied to the direct etherification of (5-(hydroxymethyl)furfural (HMF), a versatile platform molecule derived from renewable biomass. The target product is regarded as high value-added biofuels, i.e., biodiesel and additives of biodiesel. The influence of a series of reaction parameters will be studied, and finally the active site and possible reaction mechanism will be discussed.

固体酸催化剂对石油炼制和化学品生产至关重要。作为适用范围广泛的有机-无机复合固体酸，二氧化硅负载酸性高分子树脂一直以来都受到高度关注。因为此类催化剂能够回收使用，经济环保。新一代全氟磺酸树脂Aquivion是可以跟H2SO4媲美的超强酸，但其比表面积很小，在溶剂中会发生溶胀，这些缺陷极大地限制了它的实际应用。目前文献中鲜有Aquivion酸催化方面的报道。因此，设计开发新型可循环使用的负载Aquivion固体酸以及探索其催化应用成为亟需解决的问题。本项目旨在采用高等合成方法制备和表征不同载体负载的Aquivion树脂固体酸催化剂；调控催化剂酸度、酸性位点分布、孔道结构和表面两亲性等重要性质；研究负载Aquivion多相催化剂上多功能生物质平台分子5-羟甲基糠醛（HMF）直接醚化反应，合成生物柴油（添加剂）；考察反应参数对催化剂性能的影响；探究催化剂活性相、构效关联和反应机理。

布朗斯特固体酸催化剂对石油炼制和生物质炼制至关重要。Aquivion全氟磺酸树脂是新一代固体超强酸，但在溶剂中会发生溶胀且酸性位点分布过于密集，亟需设计合成新型负载Aquivion催化剂。但是，传统负载型催化剂的制备方法基本失效。在本项目中，我们巧妙地利用Aquivion树脂的两亲性和强酸性，分别水解四硅酸乙酯、异丙醇铝和原钛酸酯生成溶胶-凝胶成功制备出了氧化硅、氧化铝、聚钛氧烷固载的Aquivion全氟磺酸树脂有机-无机复合固体酸。Aquivion树脂与载体材料之间通过分子间氢键和静电吸附的强相互作用力，实现高分散与高稳定性。固体酸表面的磺酸基团因此得以跟反应物发生更加有效的接触。我们通过控制Aquivion树脂与载体前驱体的比例、焙烧条件、保护剂的使用可以调变催化剂最终的酸强度、酸性位点分布、多孔结构、表面两亲性等关键性质。我们使用广角/小角X射线粉末衍射，傅里叶变换红外、拉曼散射、固体核磁，扫描/透射电镜，元素分析，电位滴定和热重分析等物理化学表征技术对上述催化剂性质进行了指认和分析。实验结果表明，Aquivion复合固体酸兼具载体材料（择形效应、表面两亲性、路易斯酸性）和含氟磺酸树脂（超强酸）的优点，可以应用到多种布朗斯特酸催化的反应中制备高附加值的精细化学品。我们研发的Aquivion复合固体酸可以高效催化（1）果糖脱水制备生物质平台化合物5-羟甲基糠醛，（2）5-羟甲基糠醛与异丁烯醚化制备生物燃料添加剂5-(叔丁氧基甲基)糠醛，（3））果糖直接脱水制备生物质平台化合物乙酰丙酸，（4）乙酸与苄醇酯化制备生物质油添加剂，（5）三氟-对甲苯基-1,3-丁二酮和4-肼基苯磺酸酰胺缩合闭环制备药物分子环氧化酶抑制剂，并且催化剂均显示良好的循环使用性能。我们系统地考察并优化了主要的反应参数，基本阐明了催化剂的构效关系。与文献报道的参照系催化剂比较，我们研发的Aquivion复合固体酸均显示出可比的或更优越的催化性能。本项目的研究成果（包含未发表的成果）丰富了固体酸材料的种类和应用，对于Aquivion全氟磺酸树脂的催化应用有重要意义。我们发展的有机-无机复合固体酸制备方法，未来有望推广至更多类型的氧化物载体上，制备出更多具有多功能的固体酸，高效催化复杂的反应体系。