基于Cu(I)的高性能吸附剂的可控构筑及价态转变机制研究

Due to their low cost and high performance, much attention has been paid to supported Cu(I) adsorbents for deep desulfurization of transportation fuels. The key point for the preparation of adsorbents is the controllable reduction of Cu(II) to Cu(I). The reduction by using hydrogen leads to the formation of Cu(0) rather than Cu(I), while harsh conditions (≥700℃ ) are compulsory for the widely used approach, high-temperature autoreduction. In addition, the mechanism for the conversion of Cu(II) to Cu(I) is unexplored. Aiming to solve the abovementioned problems, we propose a vapor-assisted reduction (VAR) strategy for the fabrication of Cu(I)-containing adsorbents. Reducing agents such as methanol are supposed to generate vapors at elevated temperatures, and diffuse into the pores to react with Cu(II), leading to formation of Cu(I). Computational simulations predict that the activation energy is greatly decreased by using the VAR strategy, and thus the formation of Cu(I) is possible to be realized under mild conditions. Moreover, the suitable reducing ability and transfer mode of the reducing agents may avoid the produce of Cu(0) and the aggregation of active sites. By monitoring reducing process and utilizing computational simulations, the reduction mechanism will be clarified and the optimization of the type of reducing agents and reduction conditions will be achieved. The obtained materials will be employed for adsorptive desulfurization, and the structure-activity relationship will be proposed. The findings of this project may guide the development of high-performance adsorbents.

因其价格低廉和性能出色，基于Cu(I)的担载型吸附剂在燃料油深度脱硫中备受关注，而如何将Cu(II)可控还原为Cu(I)是吸附剂制备的关键。氢气等会将Cu(II)直接还原为Cu(0)而非Cu(I)；目前普遍采用的高温自还原法存在还原条件苛刻（≥700℃）等问题。此外，对Cu(II)转化为Cu(I)的机制缺乏深入的研究。针对上述问题，项目提出利用蒸汽诱导还原策略制备Cu(I)吸附剂，拟通过甲醇等诱导剂挥发产生蒸汽，扩散到孔道内与Cu(II)作用形成Cu(I)。理论计算的结果预测蒸汽诱导还原法能够大幅度降低还原过程的活化能，从而有望实现温和条件下Cu(I)的构筑；而诱导剂适中的还原能力和传质方式有望避免Cu(0)的生成和活性位的聚集。通过监测还原过程和计算机模拟，剖析还原机制，实现诱导剂和还原条件的优化选择。将所合成的材料应用于燃料油脱硫，剖析构效关系，以期为高性能吸附剂的开发提供指导。

Cu(I)担载型吸附剂在燃料油深度脱硫中备受关注，然而如何可控构筑Cu(I)活性位是这类吸附剂应用的前提。为弥补目前制备方法的不足，本项目首先开发蒸汽诱导还原策略实现了在不同多孔材料上Cu(II)的可控还原。利用诱导剂挥发进入纳米孔道，与Cu(II)反应选择性地形成Cu(I)。结合分子模拟技术，揭露了Cu(II)的转化机制，结果表明温和的反应速度和活化能是蒸汽诱导还原法可在温和条件下实现Cu(I)可控构筑的关键。与传统制备方法相比，蒸汽诱导还原策略可使Cu(I)收率得到显著提升（~100%），所制备材料表现出良好的深度脱硫性能。在此基础上，利用孔道的限域效应，开发双溶剂策略在纳米孔道内构筑Cu(I)，合成了Cu(I)活性位限域在孔道内且高度分散的复合材料，显著提升了活性位利用率。此外，还研究了其它变价过渡金属对于Cu(I)构筑和活性的影响，结果表明Fe(II)的引入增强了Cu(I)稳定性和分散性以及吸附活性。项目揭示了系列Cu(II)前驱体在不同多孔载体中的转化机制，提出了调控Cu(II)还原过程、Cu(I)稳定性和分散性的普适性方法，阐明了复合材料结构与性能之间的关联，为新型吸附材料的设计和开发提供理论指导和实验依据。