基于温和定向加氢裂解与分级萃取的中低阶煤高效分级利用的基础研究

Coal is rich in aromatic rings. Many aromatic rings with side chain groups are connected with bridged bonds. Selectively cleaving bridged bonds and side chain groups in organic matter of the coals is crucially important for the coal directional depolymerization and subsequent efficient and classified utilization, and the key is to construct a high activity catalyst. In the project, we synthetize Fe3O4 nanoparticles outside the reverse micelles, and prepare magnetic Fe3O4/SiO2 core-shell nanoparticles in the reverse micelles by hydrolyzing and condensing tetraethyl orthosilicate, incorporate the powders with proper adhesive and template materials, and wash out the template for making mesopores in the support, and then impregnate superacids into the mesopores to finally prepare magnetic supported super acid with nanosize and core-shell structure (MSSA) under microwave radiation. Multiple advanced instruments were used to understand microstructure and properties of the MSSA. Model compounds with bridged bonds connecting the aromatic rings and side chain groups were hydrocracked over MSSA. The aim is to examine the selective catalytic activation of model compounds over the MSSA surface and reveal the mechanisms for the directive MSSA-catalyzed cleavage of the bridge bonds contained in model compounds by using the isotope tracer method. Under the mild conditions below 300oC of temperature, MSSA catalyzes middle- and low-rank coals via hydrocracking to effective break bridged bonds and side chain groups. Then the reaction mixtures was extracted by various solvents. The extracts and raffinate were analyzed to determine the tapes of aromatic rings and bridged bonds, and examine the relationships between the structure of catalyst and corresponding hydrocracking activity as well as the recoverability and change in the activity of MSSA for catalytic hydrocracking during repeated use. These investigations will provide a new idea and method for efficient and classified utilization of middle- and low-rank coal under mild conditions.

中低阶煤富含芳环，其中芳环由桥链相连且含侧链。在温和条件下选择性切断中低阶煤中的桥键和侧链对于其定向解聚和后续的高效分级利用至关重要，其关键是构建高活性的催化剂。本项目在反胶束外合成纳米Fe3O4，胶束内通过硅源水解、缩合及添加粘合剂和模板剂包覆Fe3O4制备核壳结构的纳米Fe3O4/SiO2；在微波辐射下浸渍液体超强酸到Fe3O4/SiO2中形成磁性纳米负载型超强酸(MSSA)，借助多种手段了解MSSA的结构和性能。以含连接芳环的桥键和侧链的化合物为模型，考察MSSA催化的模型化合物的加氢裂解，结合同位素示踪法了解桥键和侧链断裂的机理。在低于300oC的温和条件下，用MSSA催化中低阶煤的加氢裂解，使桥键和侧链有效断裂，继而在磁力搅拌和超声辐射协同作用下萃取反应混合物，分析萃取物和萃余物，考察MSSA的结构与其定向加氢裂解活性的关系。基于上述研究为中低阶煤高效分级利用提供新思路、新方法。

山西中低阶煤储量丰富，合理和有效利用这一宝贵资源对于山西国民经济的可持续发展非常重要。中低阶煤富含芳环，其中芳环由桥链相连且含侧链。在温和条件下选择性切断中低阶煤中的桥键和侧链对于其定向解聚和后续的高效分级利用至关重要，其关键是构建高活性的催化剂。.本项目首先合成纳米Fe3O4，再通过硅源水解、缩合及添加粘合剂和模板剂包覆Fe3O4制备Fe3O4/SiO2；在微波辐射下浸渍液体超强酸三氟甲磺（TFMSA）、AlCl3和硫酸锆到Fe3O4/SiO2中形成磁性纳米负载型超强酸催化剂。以二苄醚、二（1-萘）甲烷和2-乙氧基萘等为煤模型化合物，考察其催化加氢裂解过程，了解桥键和侧链断裂的机理。在低于300oC的温和条件下，用所制备的催化剂催化临汾褐煤和大同次烟煤及其萃余物的加氢裂解，继而对反应残渣进行分级萃取，得到相应组分，揭示煤催化加氢断裂机理。.研究结果表明，制备的催化剂具有核壳结构、较大的比表面积、丰富的介孔、较强的酸性和良好的磁性，活性组分与载体之间有较强的作用；路易斯酸和布朗斯特酸的共同存在更有助于煤及模型化合物的催化加氢裂解，表现出更好的催化活性、选择性和可循环利用性。制备的催化剂在低至160oC、5 MPa以下时即可催化煤及模型化合物中芳环间氧桥键的断裂；在300oC、5 MPa时可催化芳环间碳桥键和侧链的断裂，通过分级萃取获取了芳烃及其衍生物、酚和脂肪烃及其衍生物等。催化剂中的TFMSA释放H+， AlCl3、硫酸锆和三氟甲磺酸根共同使氢气异裂生成H+和H-；H+和H-继而进攻或结合反应底物，进行相应的催化反应。煤有机质中芳环、桥链和支链中的氧及烯丙位的碳原子都是富电子部位，容易受到质子的进攻而导致桥链和与杂原子相连的共价键的断裂，生成的阳离子离去基团夺取结合于酸性组分的阴离子而形成分子，最终导致煤有机质中桥键的断裂和侧链的脱除。