磺酸官能化有机硅杂化纳米催化剂的形貌调控及其性能研究

It is one of the effective ways to ease the energy crisis by designing environmental friendly and sustainable biomass conversion processes, and preparation of effective and stable solid acid catalysts as well as studies on the mechanism of the solid acid-catalyzed biomass conversion processes are the key scientific problems. In this program, one step cocondensation strategy will be designed to construct sulfonic acid functionalized organosilica hybrid materials with hollow nanospherical, nanotubular and ordered nanoporous morphologies by fine tuning preparation conditions; meanwhile, the formation mechanism of as-prepared materials with various morphologies will be studied. It is expected that the catalytic activity of sulfonic acid functionalized silica materials can be further improved by combination of unique morphology and porosity properties, tunable Brønste acid properties and surface hydrophilcity/hydrophobicity of as-prepared nanohybrid catalysts; additionally, synthesis of fuel additives from biomass-derived platform molecules (e.g. glycerol, levulinic acid and furanyl alcohols) by esterification, ethanolysis and etherification can be performed from the point of atom economy. By studying the above catalytic processes, influence of morphologies of the nanohybrid catalysts on their heterogeneous acid catalytic activity will be found, factors affected the selectivity of the nanohybrid catalysts will be elucidated, the mechanism will be revealed, and the reusability of the catalysts can be evaluated. The program will combine catalysis with green chemistry and nanoscience, and it is expected to provide new idea and foundation to design hybrid solid acid catalysts for biomass conversion processes with high activity, selectivity and stability.

设计环境友好和可持续的生物质转化过程是缓解能源危机的有效途径之一，其中，制备高效稳定的固体酸催化剂并探究其催化的生物质转化过程的机理是其关键科学问题。本项目拟采用一步共缩合路径，通过调控制备条件，分别制备磺酸官能化有机硅中空纳米球、纳米管和有序纳米孔杂化材料，探究其形貌形成机理；利用此类材料优异的形貌特征和孔隙率特性以及可调控的Brønsted酸性和表面亲疏水性，进一步提高磺酸功能化硅基材料的酸催化活性，并实现在原子经济下完成以生物平台分子（甘油、乙酰丙酸和呋喃醇类化合物）为原料合成化石柴油添加剂的酯化、醇解和醚化等反应；通过对以上催化过程的研究，揭示杂化纳米催化剂的形貌对其活性的影响规律，阐明影响催化剂选择性的因素，揭示反应机理，评价杂化催化剂的稳定性。本研究将催化化学、绿色化学和纳米科学相互融合，可望为设计高活性、高选择性和高稳定性的应用于生物质转化过程的固体酸催化剂提供新思路和依据。

固体酸催化剂在可持续转化生物质（生物质衍生平台化合物）合成含氧油品过程中起关键作用，设计制备高效稳定的固体酸催化剂并探究其催化转化生物质过程的机理始终是具有挑战性的热门研究课题。围绕此科学问题，本项目设计了多条新颖的制备路径，分别以有机磺酸、杂多酸和酸性离子液体为酸性组分，制备了三类新型杂化固体酸纳米催化剂，包括磺酸官能化有机硅中空纳米球、纳米管和核壳纳米球，杂多酸和ZrO2（Nb2O5）双功能化有机硅纳米管和有序纳米孔以及酸性离子液体官能化碳或硅纳米棒、中空纳米球、枝状纤维纳米球和等级孔，设计制备的重点集中在催化剂的形貌、孔隙率和表面亲疏水性的调控，同时保证酸性组分与载体通过共价键相结合。通过分析各种表征结果，揭示了不同形貌杂化固体酸纳米催化剂的形成机理。通过以生物质衍生平台化合物如乙酰丙酸、糠醇、果糖、葡萄糖和甘油等为原料合成含氧油品如乙酰丙酸酯、5-乙氧基甲基糠醛、月桂酸甘油单酯、月桂酸甘油二酯、乙酸甘油三酯等为模型反应，系统评价了以上制备的杂化固体酸的催化活性和稳定性，揭示了纳米催化剂的形貌、孔隙率特性和表面亲疏水性与其活性之间的关系，阐明了影响催化剂选择性的因素，探讨了反应机理。研究发现，以上制备的催化剂呈现出较常用传统固体酸更高的活性，主要源于其超强的Brønsted酸性和独特的纳米结构的协同效应，通过加快反应速度、增加酸性位点数目、降低反应物及产物的扩散阻力并缩短传质距离而显著提高了反应物分子与酸性位点的接触机会；此外，杂化固体酸催化剂的表面亲疏水性通过改变反应物、产物和副产物的吸附性能而在一定程度上也影响其活性和稳定性。以上催化剂均表现出良好的循环使用性能，归因于酸性组分与载体之间的化学作用。本研究开发的固体酸催化剂环境友好，具有潜在的应用前景。本工作为设计制备高效稳定的应用于生物质转化的固体酸催化剂提供了重要的参考。