疏水表面修饰镍纳米粒子催化褐煤含氧桥键温和定向加氢裂解

The organic matter of lignite is rich in oxygen-containing bridged bonds, especially for ethers C-O bonds, which is not readily cleaved due to the strong bond energies. However, the oxygen-containing functional groups on aromatic rings provide opportunities for the production of phenols from lignite. It is of great importance to achieve the selective cleavage of ethers C-O bonds and the avoidance of phenol hydrogenation at the same time for the production of value-added aromatic chemicals from lignite. In this project, the preparation of nickel nanoparticles coated by hydrophobic polyacetylene (Ni-HPO) is carried out based on metal catalyzed polymerization of acetylene. The hydrophobicity of Ni-HPO will be studied by changing the polymerization conditions. Quantitative evaluation of the effect of the hydrophobicity on the catalytic activity for the hydrogenolysis of ethers C-O bonds and the hydrocracking of lignite will be investigated. High stability of Ni-HPO could be achieved ascribed to the polyacetylene shell which keep the nanoparticles from aggregation. Due to the higher polarity of phenol, the adsorption on catalyst surface becomes more difficult which could avoid the hydrogenation of phenol to cyclohexanol and result in a high yield of aromatics. A mechanism for ethers C-O bond hydrogenolysis will be proposed that is expected to provide scientific basis for the selective depolymerization of lignite to aromatic chemicals. It could also help to understand the molecular structure of organic matter in lignite.

褐煤富含高稳定性的含氧桥键，使其难以进行加氢裂解。然而，褐煤芳环连有丰富的含氧官能团为其制备酚类等芳香族化合物提供了机遇。构建高效催化剂以实现温和条件下褐煤分子醚键的定向切断，同时避免原始结构中或裂解生成酚类的深度加氢，对于褐煤定向裂解制备高附加值芳香族化学品至关重要。本项目拟利用金属催化的乙炔分子聚合反应，合成疏水性聚乙炔包覆的镍纳米粒子。通过调节聚合反应条件实现对催化剂疏水性能的精准调控，提升其催化加氢反应活性，实现温和条件下褐煤中醚键的定向加氢裂解；构筑纳米粒子与聚乙炔核壳结构，抑制催化剂的团聚，从而实现高效稳定的加氢裂解；利用催化剂疏水性能和化合物分子间极性差异，营造竞争吸附环境，在醚键加氢裂解的同时抑制强极性酚类产物的加氢去芳构化，实现酚类芳香族化学品的定向制备。通过氢气与底物竞争吸附研究和裂解产物的分子结构分析，推测加氢裂解反应机理，为褐煤有机质分子结构的反演提供理论基础。

褐煤和木质素分子中的芳香环连接着丰富的含氧官能团，为其制备醇类等高附加值化合物提供了机遇。构建高效和选择性的金属催化剂以实现温和条件下生物质含氧桥键（例如醚键）的定向切断，对于生物质提质至关重要，但仍具较大挑战。基于木褐煤和木质素的分子结构特征，本项目构筑了两类金属纳米催化剂：亲水性镍和金属磷化物，实现了褐煤模型化合物、木质素及其衍生物的选择性转化。. 研究了金属Ni催化剂的亲疏水性能对芳基醚催化反应活性和选择性的影响。构筑了三种具有不同亲疏水性能的活性炭负载的Ni纳米催化剂。研究发现，活性炭载体的结构和性质对Ni纳米催化剂比表面积和亲水疏水性能的影响显著，进而影响褐煤模型化合物（二苯醚）降解反应性能。结果显示，高亲水性和大比表面积的Ni纳米催化剂能够促进二苯醚的选择性水解，在较为温和的条件下实现环己醇的定向制备，产率可达64%。该工作为通过催化剂载体结构设计进而实现生物质选择性解聚提供了一种思路。. 基于溶剂热还原合成工艺，实现了Pd-P细小纳米粒子的可控制备，建立了Pd-P催化芳基醚选择性部分加氢的反应体系。该工作首次实现了褐煤模型化合物二苯醚的部分加氢-还原水解串联转化，突破了从二苯醚到环己酮和环己醇（即KA油，尼龙的初始原料）的温和高效转化技术。此外，通过引入第三元素，制备了Pd-Ni-P三元纳米催化剂，进一步增强了芳基醚水解和加氢性能。通过芳基醚部分加氢-还原水解-加氢的多米诺反应，实现了芳基醚向环己醇（一种面向高分子的聚合反应原料）的高选择性转化。此外，直接使用商业木质素分子作为原料，同样实现了环己醇类化合物的选择性制备。该工作为生物质和褐煤等可再生生物质资源向高附加值化学品转化技术提供了一定的理论基础。