基于柴油加氢的金属/石墨烯纳米催化剂的界面交互作用及结构设计

New type of catalysts for diesel hydrogenation with high activity is in great need to produce clean diesel in order to alleviate the environmental pollution. Activity of hydrogenation catalysts is affected not only by the intrinsic specific characteristics of active components, but also by the properties of support meterials. The rising of graphene opens up new opportunities for design of novel catatlysts for the diesel hydrogenation. 2-dimentional graphene nanosheets may also have a great application potential as support materials for hydrogenation catalysts of diesel, because graphene possesses many excellent properties. However, to best of our knowledge, no reports on the use of graphene-based metal catatlysts in the field of hydrogenation of diesel or model compound up to now. In this program, the design of graphene-based metal nanocomposites are used as catalysts for diesel hydrogenation will be carried out based on the interfacial interaction between active components and graphene. The structural control of active components will be come true by two synthesis approaches: solid metal oxide/graphene nanocatalysts will be obtained by the co-pyrolysis of graphene and metal compounds (Mo, Co, W, Ni etc.) at the temperature in the range of 300-600 ℃, and hollow metal oxide/graphene nanocatalysts will be prepared by the assist of Kirkendall effect via air oxidation at 200-350 ℃. And the adjustment of interfacial interaction between graphene and active components will be realized by both the modification of graphene (functional groups, defects etc.) and synthesis conditions (pyrolysis or oxidation temperature etc.). Then, the presulfurization of as-prepared graphene/metal oxide nanocomposites will be developed, and the effect of interfacial interaction on the morphology and structures of sulfide will also be investigated. At last, the hydrogenation activity of graphene-based nanocatalyst will be examined by hydroprocessing of diesel or model compounds, and the realationships between interfacial interaction and activity will also be investigated. The resulting objectives of this program are to prepare the graphene-based nanocatalysts with high activity, high selectivity, and long lifetime. This program will be of great significance for design of new type of graphene-based catatlysts, intergration of petrochemistry and material science, and clarification of fundamental science about interfacial interaction between metal and graphene.

针对清洁柴油的生产对于高活性新兴催化剂的需求，本课题着眼于一种新型的加氢催化剂材料的结构设计，拟以石墨烯和金属化合物为原料通过共热解法或Kirkendall效应制备石墨烯负载纳米实心或空心金属氧化物（Mo、W、Co、Ni等）颗粒，获得金属颗粒（5-40nm）均匀锚定在石墨烯表面的复合催化材料，并通过调整石墨烯的边界、空位、官能团以及合成工艺参数控制石墨烯与金属的界面交互作用，考察界面交互作用对于硫化时金属催化剂的形态、结构及性能的影响。将此用于模型化合物、实际油品等加氢反应，考察催化剂结构、界面交互作用与催化效果的关系。优化催化剂结构，最终合成出活性组分高度分散，又具有合适的界面交互作用，并能阻止催化过程中活性组分团聚和长大的新型催化材料，赋予其长使用寿命。为提高纳米金属催化剂的综合性能、促进石油化工催化新材料的发展及材料学与催化科学的交叉融合奠定基础。

本课题着眼于石墨烯/金属氧化物复合材料的制备、改性及催化和储能性能研究，主要研究了石墨烯的制备、表面改性，石墨烯负载纳米金属氧化物催化剂/锂离子电池负极材料的形貌、结构及界面交互作用，深入探讨了这种界面交互作用对柴油催化加氢脱硫和锂离子电池电极材料性能的影响规律，为提高纳米加氢催化剂和电极材料的性能，促进石油化工、新材料、新能源领域的进步奠定技术基础。研究结果表明：氧化石墨烯（Graphene oxide, GO）在金属盐的作用下表面官能团会发生可逆的转化，包括环氧的可逆开环/闭环反应、羧基的耦合配位以及羟基与金属盐的可逆反应。当GO表面负载金属氧化物/氢氧化物（CuO/GO、MnO2/GO、Ni(OH)2/GO）时，氧化石墨烯表面的官能团消失；当使用盐酸除去复合材料中的金属氧化物/氢氧化物时，氧化石墨烯表面的官能团又可以可逆的恢复。这个有趣的现象不仅有利于丰富氧化石墨烯表面官能团的反应性，而且可以为设计性能优异的石墨烯基纳米复合材料提供新的思路。在氧化铜与石墨烯之间、氧化亚铜与石墨烯之间均形成了Cu-O-C键。除去氧化亚铜这个界面会改变复合材料结构并导致性能的巨大变化，包括：Cu-O-C共价键含量的减少、石墨烯大π键的恢复以及电化学性能的巨大变化（包括首次可逆容量增加约21%；循环性能以及倍率性能的变差；电荷传递电阻的明显增加）。在研究石墨烯复合纳米片的金属含量、表面性质、电子结构、热稳定性、气体吸/脱附性能的基础上，以加氢处理反应为探针反应研究了石墨烯/纳米金属复合纳米片的催化活性、选择性和稳定性，并与常规Al2O3和活性炭为载体的催化剂进行比较，发现石墨烯担载金属催化剂在相同反应条件下显示更高的催化活性和催化反应寿命，其原因来源于石墨烯与金属催化剂颗粒的界面交互作用，进而抑制了催化剂的迁移和长大。其结果为提高选择性加氢催化剂的性能提供理论和实践指导。