负载型分子筛纳米晶体设计及高效催化纤维素制备山梨醇

Biomass is one of the significant renewable natural resources for the production of oils and chemicals; however, it is still short of highly efficient solid catalysts to transform cellulose to soribitol. This project aims to design “Pt-nanozeolite” bifunctional catalysts (using HY、HZSM-5 and Hβ as typical zeolites, and TiO2 nanofibers as supports), which possesses highly dispersive zeolite nanocrystals and Pt nanoparticles and offers an opportunity for Pt sites and acid sites to match closely and for reactants to access active centers conveniently, thus initiating reactions at relatively low temperatures to curb side reactions, reduce coke or carbon deposition and to prolong the catalyst lifetime. Moreover, the size of zeolite nanocrystals are controllable and arranged with a certain orientation, in this regard, the reactant molecules could arrange on the catalyst surfaces with a certain orientation, and this orientated arrangement will selectively make the molecules or their functional groups interact with active centers to react, thus improving the selectivity of a product. As to the catalytic performances, newly-developed catalysts can improve the selectivity of sorbitol from cellulose, compared with published work. In addition, new understanding and discoveries are expected as to catalytic mechanism and pathway, so that they can serve to novel catalyst design, optimization, and practical applications.

生物质是一种重要的可持续自然资源来生产油品与化学品；但是由纤维素制备山梨醇依然缺乏高效的催化剂。本项目拟开发“Pt-取向纳米分子筛晶体”双功能催化剂（以TiO2纳米纤维为载体，以HY、HZSM-5和Hβ为典型分子筛），它能提供高分散的分子筛纳米晶体和Pt金属颗粒，既能使金属位与酸性位亲密接触又能使活性位与反应物充分接触，因而能使反应在较低温度下进行，以抑制副反应、减少结焦/炭和延长催化剂寿命。并且，分子筛晶体尺寸可控而且空间排列有取向，这样反应物分子在催化剂表面的排列就会有一定的取向，这种取向排列或吸附可使反应物分子或官能团有选择性地与活性位发生相互作用而反应，从而提高产物的选择性。在催化反应效果方面，相比于文献已经报道的催化剂，新催化剂能提高纤维素转化效率和山梨醇选择性。在反应机理和历程的方面能有新的理解和认识，以指导新催化剂体系的设计、优化及应用。

生物质是一种重要的可持续自然资源，主要包括纤维素、半纤维素和木质素，其中纤维素含量丰富，可以用来生产油品与化学品；但是由纤维素制备山梨醇依然缺乏高效的催化剂。项目针对纤维素制备山梨醇，构建了‘Pt与取向分子筛纳米晶体’双功能催化剂；项目采用纳米纤维为载体，实现了高分散纳米分子筛晶体的制备，并应用于纤维素转化到山梨醇的水相反应体系。项目取得主要成果如下：（1）成功控制了HY纳米晶体在TiO2纤维上的尺寸大小（40-60nm），解决了团聚问题。在纤维素水解到葡萄糖的反应中，新结构的催化剂HY-TiO2与传统HY分子筛相比，提高了反应速率，确立了催化剂结构设计与催化性能之间的“构效关系”。（2）实现了“金属-固体酸”双功能催化剂（Pt/HY-TiO2）结构的设计与制备。在反应机理和历程的方面，与现有文献报道相比，有了新的理解和认识。总之，上述研究成果可用于指导新催化剂体系的设计、优化及应用。