分子筛催化糖类选择性C-C键断裂制备甲醛的催化机制和反应机理研究

The conversion of biomass to formaldehyde is becoming a highly promising pathway in order to cope with the depletion of fossil resources and environmental pollution. However, such reports are few and scarce in literature. The key point and the main challenge for this process is to selectively cleave the C-C bond(s) in the carbohydrates to improve the yield of formaldehyde. To tackle this problem, we choose acidic zeolites as the catalysts for the shape selectivity of their micropores would induce the transformation of carbohydrate molecules from cyclic to acyclic configuration, which facilitates the following C-C bond cleavage into formaldehyde on the acidic sites of zeolites. To achieve this goal, the framework Al siting will be regulated to ensure the location of adequate strong B acid sites in the channels nearby the pores, on which the entered acyclic carbohydrate molecules undergo the selective cleavage of C-C bonds. In situ characterization techniques, isotope tracer experiments and density functional theory will be applied to understand comprehensively the structure-activity correlation of zeolites and the reaction mechanism of carbohydrates into formaldehyde. The results of this work will provide a new strategy for biomass conversion to fuels and chemicals and bridges the gap between biomass utilization and C1 chemistry.

将糖类清洁高效地转化为C1平台分子甲醛，具有重要的应用前景和理论价值，但目前鲜见文献报道。糖类衍生物转化为甲醛的关键科学问题和难点是选择性断裂C-C键。针对此问题，本项目拟利用利用微孔分子筛孔道的择形作用诱导糖分子的构像转变为链状，进一步在分子筛酸性位的催化下实现糖类选择性断裂C-C键。围绕这一思路，本项目通过控制分子筛中Al的落位调控分子筛的酸分布，使分子筛接近孔口的孔道内有足够多的强B酸位，选择性地将扩散进来的链状糖分子的C-C键打开，实现糖类高效转化为甲醛；借助原位表征技术、同位素示踪反应和DFT理论计算揭示分子筛酸分布影响糖类分子C-C键断裂的规律，建立分子筛催化糖类衍生物制备甲醛的机制和相应的反应机理。本项目的实施将为生物质资源和C1化学领域之间架起一座新的桥梁，有利于实现生物质资源的高效清洁转化为燃料和高附加值化学品，为生物质转化提供新的思路。

将糖类清洁高效地转化为C1平台分子甲醛，具有重要的应用前景和理论价值，糖类衍生物转化为甲醛的关键科学问题和难点是选择性断裂C-C键。本项目研究了典型分子筛催化剂孔道结构和酸性质（酸密度、酸强度和酸类型）对六碳糖选择性C-C键断裂制备甲醛和糠醛的影响机制。研究了溶剂对糖类选择性C-C键断裂的影响机制，结合同位素示踪实验及分子模拟计算重点研究了γ-丁内酯（GBL）促进六碳糖C-C键选择性断裂的机理。结合实验及表征，研究了典型分子筛催化六碳糖在转化中副反应的反应路径和机理。