纤维素连续水解加氢的粘土基催化剂端面并层间协同构造及催化机理研究

The preparation of well-designed inorganic solid catalysts combining acidic sites and reduction sites is a primary issue for one-pot catalytic conversion of cellulose to polyols (sorbitol). Based on previous studies on the catalysts for catalytic hydrolysis of cellulose and clay-based materials, the present proposal suggests an innovative novel methodology for the preparation of the multifunctional clay-based catalysts by means of respectively modifying the end face of layer by sulfonic groups and intercalating the interlayer by noble metal nanopillars. In this way, a type of solid catalysts with coexisting acidic and reduction sites for catalytic consecutive hydrolysis-hydrogenation of cellulose can be obtained. In particular, physicochemical approaches to grafting sulfonic groups on the end face and intercalating noble metal nanoparticles will be developed and the formation mechanism will be examined. And the effects of the substitution of layer, the layer charge density, the end face charge, the size of layered precursors on the amount, type, distribution of metal nanopillars and end face acidic sites, microstructure, chemical bonds and catalytic performances of the resulting catalysts will be investigated. Emphasis will be put on revealing the formation mechanism, the tuning methods and principles of acidic sites and reduction sites in the resulting catalysts. The effect of the support to the structure and catalytic activity of the resulting catalysts should also be indentified carefully. For such catalysts, the correlation among the preparation factors, the structural parameters and the catalytic properties in the heterogeneously catalytic consecutive hydrolysis-hydrogenation of cellulose will be disclosed and inherent reasons will be theoretically elaborated. It belongs to a multidisciplinary topic involving in catalysis, clay minerals and bio-based chemicals. The research would provide a scientific and theoretical basis for the conversion of cellulose and the design of advanced clay materials.

实现清洁高效催化纤维素“一锅”连续转化为山梨醇等多元醇，制备出集成水解和加氢功能的固体催化剂是核心和关键。基于申请者对纤维素水解和粘土基新材料合成的前期研究，项目提出以具有独特片层结构的蒙皂石粘土为基体，采用对层板端面及层间两个位置分别修饰的新思路，构造既相互独立又固定在同一个基体上的两类催化活性中心。主要研究在层板端面接枝有机磺酸基团，强化酸催化功能，并在层间构造贵金属纳米柱实现造孔和加氢功能。考察粘土基体尺度、层板取代、电荷密度、端面电荷等因素对催化剂酸性位和加氢活性位数量、分布、键合状态、微结构和催化性能的影响，重点揭示载体特征对固体材料结构及催化性能的影响，获得催化剂中酸性位和加氢活性位的调控机制，认识纤维素水解加氢连续反应生成多元醇的内在原因和界面作用原理，阐明催化剂制备、结构和催化作用特征之间的相互关系。项目涉及催化、粘土和生物基化学品化工的交叉研究，具有科学意义和应用前景。

纤维素作为丰富的可再生资源，通过经济有效的途径转化利用可以在一定程度上减少化石资源的消耗。高效利用纤维素的关键是将其水解为葡萄糖，葡萄糖可进一步转化为醇、醛等高附加值的化工产品。因此，设计制备高效的固体催化剂将纤维素水解为葡萄糖，进而转化为精细化学品及液体燃料具有重要的研究价值。本研究选取来源广泛、具有独特层状结构的粘土为基体，对粘土材料的层板和层间进行改性，设计合成具有良好纤维素水解转化性能的粘土基固体催化剂。研究首先通过离子交换的方法在粘土层间引入H+、Zr-S复合氧化物、石墨相氮化碳（g-C3N4）等物种，制备了系列插层复合材料。进一步，对粘土表面进行磺酸基及离子液体的接枝改性，并考察了在层间引入金属纳米粒子的协同作用。最后，对纤维素水解固体残余物的再利用性能进行了探索。探讨了材料的构效关系并解析了催化反应机理。结果表明：（1）比较研究几种粘土层间插层改性的固体催化剂可知，在S/Zr比为0.3，在500℃下焙烧2h制得的Zr-S/粘土催化剂纤维素水解性能最佳。在 200℃，催化剂/纤维素比例为 1：4，反应2.5h，还原糖收率可达 32.1%，纤维素转化率为 59.0%。此外，质子化改性的g-C3N4/蒙脱石复合材料比未质子化的材料具有更佳的纤维素水解性能。（2）粘土基材料的表面接枝研究表明，中性离子液体接枝的蒙脱石显示出了良好的纤维素水解性能，还原糖收率可达35.7%。表明在粘土基体表面的弱酸性和IL对纤维素良好溶解能力的协同作用下促进了材料纤维素转化能力的提升。进一步在粘土层间引入Ru纳米粒子后，还原糖收率有所下降。（3）对纤维素水解回收固体残余物的再利用研究表明，该材料作为吸附剂对亚甲基蓝的饱和吸附量达到138.1 mg/g。以上研究表明，层状粘土材料不仅是良好的纤维素转化催化剂基体，而且其反应固体残余物在吸附领域亦体现了良好的应用前景。