基于液态有机氢化物脱氢的贵金属/水滑石负载型催化剂的构筑及其反应机理研究

The hydrogen storage technology by liquid organic hydrides (LOHs) can effectively meet with the demand of high density storage and large-scale transportation of gaseous hydrogen in its utilization. However, how to realize the hydrogen release from the LOHs with a rapid velocity at lower temperature, is still a big difficulty for the application of the technology. Aimed at improving the low activity, high reaction temperature and easy carbon deposition or bad anti-coking performance of the catalyst in the dehydrogenation of the LOHs, this project proposes to prepare a hydrotalcite supported noble metal dehydrogenation catalyst with high dispersion of active component and controllable acidic site amount on the catalyst surfaces by supersonic-assisted dispersion technique. Through characterizing the catalyst, the inter-action and/or the synergy mechanisms between the active components and the active component and the hydrosulfite supporter are to be revealed. Meanwhile, the acidity and the structure effects of the catalyst on the dehydrogenation are to be explored and the preparation conditions of the catalyst are to be optimized. Combined the characterization of the catalyst with the evaluation of its reactivity, the de-activation mechanism of the catalyst and the reaction mechanism of dehydrogenation are to be investigated. Base on these researches, the kinetic models of the catalytic dehydrogenation are to be built and the parameters of the process are to be obtained. By the studies, the core preparation technologies of the hydrotalcite supported noble metal catalyst with low reaction temperature and high dehydrogenation activity will be developed. Furthermore, these researches will help scientists to better understand the selective and controllable C–H bond cracking mechanism in the dehydrogenation of LOHs, which will greatly promote the industrial application of the hydrogen storage technology.

有机液体储氢技术可有效解决氢气能源利用过程中高密度储存和大规模输送的困难。但如何实现其低温、快速释氢仍是该技术应用面临的瓶颈。针对现有液体有机氢化物脱氢催化剂存在的低脱氢活性、高反应温度和易结焦失活等问题，本项目拟利用超声波辅助分散技术，制备活性组分高度分散、表面酸性中心便于调控的Mg-Al水滑石负载型贵金属脱氢催化剂；通过催化剂表征，揭示其活性组分之间、活性组分与载体之间的相互作用与协同机制，阐明其结构性能及酸碱性对脱氢活性的影响规律并据此优化催化剂制备条件；结合表征和反应性能评价结果，探讨催化剂失活机理及脱氢反应机理，构建有机氢化物催化脱氢反应体系的动力学模型，优化脱氢反应工艺条件。从而：①掌握低温、高活性贵金属/水滑石脱氢催化剂制备及液体有机氢化物催化脱氢反应的核心技术；②为相关碳氢化合物C–H键的选择性可控断裂提供基础理论支持和实验借鉴，以推动有机液体储氢技术及其成果的工业化应用。

化石能源的不断枯竭及其利用过程的环境问题，使发展清洁、高效的氢气能源倍受关注。有机液体储氢技术可有效解决氢气能源利用过程中高密度储存和大规模输送困难。但如何实现其低温、快速释氢仍是该技术应用面临的瓶颈。本课题针对现有液体有机氢化物脱氢催化剂存在的低脱氢活性、高反应温度和易结焦失活等问题，通过采用超声波辅助分散共沉淀法制备出了具有较低脱氢反应温度、活性组分高度分散、表面酸性中心便于调控的Mg-Al水滑石负载型贵金属Pt和双金属Pt-M型脱氢催化剂。研究了催化剂的形貌结构及助剂组成对催化活性的影响规律，通过优化制备条件及反应参数，使所制得的催化剂在脱氢温度≤300℃下，反应转化率和选择性分别高达98.5%和99.9%，产氢速率达到82.0 mmol H2/gcat/h，实现了预期的催化剂产氢速率目标。通过表征分析，揭示了甲基环己烷脱氢过程中催化剂活性组分之间、活性组分与载体之间的相互作用与协同机制，掌握了贵金属Pt在催化剂载体上的分散规律及催化剂表面酸碱活性中心调控关键技术。研究表明，弱碱性条件下制备的具有层状结构的Mg-Al水滑石载体，可在一定程度上抑制催化剂在脱氢过程的结焦失活；第二组分Ir、Ni和Sn等的引入，可使催化剂的脱氢活性、抗积碳性能以及稳定性得到不同程度的提升。通过运用密度泛函理论DFT计算与分析，获得了有机氢化物在单金属Pt和双金属Pt-M等负载型催化剂上分步脱氢时相关物种在Pt(111)表面上的吸附性质、第二金属（活性组分）的加入对有机氢化物脱氢反应路径和速率控制步骤的影响规律，为相关碳氢化合物C–H键的选择性可控断裂和提高催化剂的活性稳定性提供了理论支持。通过建立脱氢反应体系的动力学模型，优化了反应工艺条件，为开发具有工业应用前景的有机液体脱氢催化剂的制备核心技术奠定了科学基础。项目研究有利于推动和促进我国氢能源的开发利用及环境保护。