煤焦油中多环芳烃选择性加氢裂化的催化基础及其介孔沸石型催化材料的制备研究

The catalytic hydrocracking is one of the most important approach for highly-efficient and clean utilization of coal tar, in which the efficient conversions of polycyclic aromatic hydrocarbons (PAHs)，which are main components of coal tar, are the key of issue. In present project, the polycyclic aromatics with tri-, tetra- and penta-cyclic aromatic rings are selected as representative model hydrocarbons to get the relation between the chemical structure and hydrocracking reactivity of PAHs. By means of quantum chemical calculations, the steric structures, energies of the model molecules to account for structural properties as well as the possibility of selective hydrogenation of PAHs and further selective ring-opening on the acidic zeolitic materials. Based on theoretical guidance，the novel mesoporous zeolitic catalytic materials with metal clusters encapsulated in the channel intersections of the zeolites as hydrocracking catalysts are designed and prepared, in which the hydrocracking reactions of PAHs carry on acid sites of mesoporous surface through the hydrogen spillover from metal cluster located in micropores. The characteristic of catalyst designated is that the active sites for hydrogenation and cracking are isolated. Hence, the rate of surface diffusion of active hydrogen species and surface acidity of zeolite may be controlled respectively by adjusting the size of metal cluster, Si/Al ratio, and mesoporous surface to obtain the better balance between the hydrogenation, ring-opening and cracking functions. By combining the theoretic calculation and experimental results, the relation for the molecular structure of PAHs, the structure of the mesozeolitic catalysts encapsulated metal clusters, as well as hydrocracking reactivity of PAHs and corresponding products distribution are revealed, so as to develop general principles for the design of highly-efficient and selective catalysts of hydrocracking of PAHs. Ultimately, the theoretic and experimental bases for the design and preparation of catalyst of selectively hydrocracking for coal tars are established.

加氢裂化是煤焦油高效清洁利用的重要途径之一，其多环芳烃的有效转化是问题的关键所在。本项目以煤焦油中富含的三、四和五环多环芳烃为主要研究对象，借助于量化计算，从理论上解析多环芳烃选择性加氢和进一步选择性开环裂解的可能性以及对催化活性位的要求；在此基础上，通过原位合成等多种途径制备封装有金属簇的介孔沸石催化材料，利用微孔内金属簇的氢溢流效应和介孔沸石外表面酸中心对多环芳烃的可接近性，进行多环芳烃的加氢裂化反应。其特点在于将氢解离与多环芳烃加氢裂化过程相分隔，利用金属簇大小、沸石骨架Si/Al比和介孔表面积的可调控性，调节氢溢流程度和表面酸性分布，以达到多环芳烃选择加氢与开环裂解活性的良好匹配。理论计算和实验结果相结合，系统地考察多环芳烃分子结构-介孔沸石及催化剂结构-加氢裂化活性与产物分布关系；形成适合多环芳烃加氢裂化的催化剂设计原则，为面向煤焦油加氢裂化高效催化剂的研制奠定理论和实验基础。

加氢裂化是煤焦油高效清洁利用的重要途径之一，其多环芳烃的有效转化是问题的关键所在。本项目以煤焦油中富含的三环多环芳烃为主要研究对象，主要研究了9,10-二氢菲和9,10-二氢蒽的加氢裂解，借助于量化计算，从理论上解析了多环芳烃选择性加氢和进一步选择性开环裂解的可能性以及对催化活性位的要求；在此基础上，通过研究无有机胺模板剂法、“键阻断”法、廉价有机模板剂法等多种途径制备了多级孔ZSM-5和Beta沸石催化材料，成功实现了廉价有机模板剂法制备多级孔Beta沸石的工业放大；通过不同大小的碱性分子吸附的红外表征，研究了多级孔沸石的吸附扩散性能；研究了几种大分子有机物分子参与的模型反应，从而建立了多级孔沸石合成条件、沸石孔结构、酸性和催化性能之间的关系。揭示了沸石中多级孔结构对碳氢化合物在沸石内的吸附、扩散和催化反应的促进作用及本质。研究了介孔沸石外表面酸中心对多环芳烃的可接近性，并探究了沸石单独作为催化剂及负载Ni与Mo的Y型沸石进行稠环芳烃的加氢裂化反应，充分认识了该反应中金属组份与沸石酸性活性中心协同作用的重要性。经过理论计算和实验结果相结合，系统地考察多环芳烃分子结构-介孔沸石及催化剂结构-加氢裂化活性与产物分布关系；通过理论计算，证明了9,10-二氢蒽加氢过程的主要的反应位点，为后续催化原理的解释提供了理论支撑。通过项目研究，形成适合多环芳烃加氢裂化的催化剂设计原则，为面向煤焦油加氢裂化高效催化剂的研制奠定了理论和实验基础。