高稳定片层PtSn/Al2O3催化剂的设计合成与丙烷脱氢性能研究

The preparation of supported precious metal catalysts with high stability is one of the most challenging tasks in the field of heterogeneous catalysis, which suffers sintering and deactivation under real reaction conditions. Based on controlled synthesis of Al2O3 support with desired sheet morphology, pore structure and exposing surface, the project aims to improve the stability and durability of supported Pt-based catalysts through the combination of space confinement, metal-support interaction and good diffusion efficiency. This project includes the following four parts: (1) the controlled synthesis of thin porous Al2O3 nanosheet using amino acid as structure-directing agent; (2) the modification and characterization of sheet-like Al2O3 microstructure by doping with Mg2+; (3) the fabrication of PtSn/Al2O3 catalyst, where the PtSn nanoparticle is deposited in the pores of the sheet-like Al2O3; (4) the PtSn/Al2O3 catalysts are tested with propane dehydrogenation reaction, and the effect of the sheet thickness, pore structure, surface structure and the local state of Al cations of Al2O3 support on the stability of the PtSn nanoparticles is investigated. As a consequence, the influence of the support structure on the stability of supported precious metal catalysts will be figured out. This study may deepen the fundamental understanding of metal-stabilization mechanism on the surface of an oxide support, and provides scientific basis for the design and development of precious metal-supported catalysts with high stability.

负载型贵金属纳米催化剂在工况条件下的稳定性是众多反应所面临的严峻挑战。本项目立足于对Al2O3载体纳米结构的精准调控，拟借助物理限制、化学锚定和加速扩散三者综合作用，开展改善Pt基贵金属催化剂稳定性的研究。主要内容包括：① 从氨基酸结构导向出发，构筑多孔片层Al2O3载体；② 选用碱土金属 (Mg) 掺杂修饰Al2O3载体表面；③ 将PtSn纳米粒子共落位进入片层载体孔隙；④ 以丙烷催化脱氢为探针反应，系统研究载体片层厚度、孔隙结构、表面晶格排布、Al阳离子局域环境等微结构参数对PtSn纳米颗粒稳定性的影响，揭示载体多孔片层结构及表/界面化学性质与贵金属组分稳定性的本征关联。研究结果将为准确理解贵金属在氧化物表面的稳定机制提供科学依据，为进一步合理设计高稳定贵金属纳米催化剂提供理论基础。

丙烷催化脱氢是工业上增产丙烯的重要途径，可有效缓解我国丙烯原料对石油资源的过度依赖。其中高比表面积Al2O3负载的Pt系催化剂应用最为广泛，然而，在苛刻的丙烷脱氢条件下，由积碳和烧结引发的Pt系催化剂的失活仍然是该反应亟待解决的难题。本项目从创新Al2O3载体结构出发，发展了氨基氢键作用诱导-层状前驱体分解-原位气体剥离新方法，实现了表面富含缺陷位和开放孔Al2O3纳米片的宏量定制，建立了Al2O3表面缺陷位的定量新方法。以高缺陷Al2O3为基础，成功实现了PtSn纳米簇的二维分散和稳定，促进了丙烷催化脱氢制丙烯反应性能，揭示了载体表面缺陷位对活性相几何、电子结构的调变规律。动力学考察显示片层催化剂纳米尺度的二维构造和浅坑孔道可加速反应物和产物的传质、扩散过程，揭示了二维片层催化剂构造对催化脱氢反应的促进效应。进一步通过碱土金属Ca助剂修饰PtSn/Al2O3纳米片催化剂，开发出了具有高反应活性和产物选择性、优越抗积碳和抗烧结稳定性的PtSn/Al2O3丙烷脱氢催化剂，结合球差电镜、同步辐射、原位光谱等揭示了碱土助剂Ca在丙烷脱氢反应和抗积碳行为中的促进效应本质。本项目研究内容在Angew. Chem. Int. Ed.等期刊发表学术论文3篇，申请国内专利1项。该项目成果不仅为认知载体纳米结构和表面微环境与活性相几何/电子结构以及脱氢反应行为之间的本征关联提供了新思路，也为进一步精准设计高稳定贵金属催化剂以及为低碳烷烃的高品质高附加值开发利用提供科学依据。