沸石笼中金属簇的氢溢流和多级孔沸石表面酸性的协同效应

本项目针对稠环芳烃加氢反应中的选择性开环和抗硫性等关键问题，在设计负载贵金属双功能催化剂的过程中，提出了将贵金属纳米簇封装于小孔方钠石或经孔口修饰的沸石笼中，并以此为核在其表面生长具有酸性能可调的多级孔沸石薄膜壳层，制备具有以抗硫氢解离催化剂为核和择形酸催化剂为壳新型复合结构的选择开环催化剂。该思路利用SOD和经修饰后沸石较小孔口对H2S分子（包括有机硫）进入其孔道所具有的限制作用，来阻止封装于沸石笼中的金属簇与硫化物相接触，提高催化剂的抗硫性能，同时利用所筑沸石壳层的酸性中心可为活性氢的迁移提供路径有利于氢溢流进行的这一特点，将沸石笼中金属簇的氢溢流和沸石壳层酸性功能有机地结合起来，通过二者的协同作用来实现对稠环芳烃的选择开环。该项目的实施可为高抗硫性能、高催化活性和选择性的新型稠环芳烃选择开环催化剂的研制、开发和工业应用提供新的路径。

Selective ring-opening of ployaromatic hydrocarbons to reduce the aromatic content and increase the desiel cetane index is the important process for diesel improvement. But in this catalytic process, the used noble catalysts are easily poisoned by sulfur even at a trace level. Therefore, how to increase the sulfur-tolerance of the noble catalysts in this catalytic process is a challenge. In the proposed project, a novel strategy, involving encapsulation of noble metal clusters within sodalite crystal and decorated zeolites, then overgrowth of a hierachical zeolite shell with tunable pore structure and acidity, is suggested for the preparation of high sulfur-tolerance catalysts in selective ring-opening of ployaromatic hydrocarbons. According to the proposed strategy, organosulfur compounds even H2S molecules are selectively excluded from the small pores. Thus, encapsulation within zeolite protects clusters from contact organosulfur and H2S and increase the sulfur-tolerance ability of the prepared catalysts. While H2 molecules can enter into sodatite or the decorated zeolites, be dissociated on metal sites, and be transported between the core and the formed shell by hydrogen spillover. Hence, the selective ring opening of ployaromatic hydrocarbons on the prepared hybrid catalysts can be realizes via the synergistic effects of hydrogen spillover and the acidic sites from the overgrown zeolite shell. It is expected that the the project can provide a new route for the preparation, development and industrial application of novel catalysts with high sulfur tolerance, activity and selectivity in selective ring opening of polyaromatic hydrocarbons.