Al2O3载体结构调控及对丙烷脱氢Pt系催化剂稳定性的影响机制研究

With the enormous demand of propylene and scarcity of oil resources, propane dehydrogenation has become an important way for producing propylene. However, a big challenge is the deactivation of supported precious metal catalysts, which originates from carbon deposition and sintering. This project aims to obtain highly dispersed Pt species by tuning the microstructure of Al2O3 to prohibit carbon deposition. The project includes the following parts: synthesis of nanoarchitectured Al2O3 with controlled morphologies, sizes and surface structures via a self-assembly approach thorough molecular design and using desirable structure-directing agents; study on the assembly mechanism and understanding of the formation mechanism of novel structures and their influence on the catalyst activity and stability; identification and quantification the defect sites and Al coordination state using solid NMR and FTIR and then revealing the intrinsic relationship between the dispersion of Pt species and high temperature stability. As a consequence, this study may deepen the fundamental understanding of the influence of support structure on the stability of propane dehydrogenation and provides scientific basis for the design and development of Pt-based catalysts with high stability for propane dehydrogenation.

随着丙烯需求量的增加及石油资源的日益匮乏，丙烷脱氢已成为丙烯增产的重要途径。其中，由积碳和烧结引发的贵金属催化剂的失活是该反应面临的挑战。本项目提出通过调控氧化铝载体的微结构实现Pt物种的高分散，抑制积碳，同时利用载体效应以及Sn助剂保证高分散Pt物种在工况条件下的稳定性。主要研究内容包括：从分子底层设计的角度出发，选取合适的结构导向剂，通过自组装得到形貌、尺寸及表面结构可控的纳米结构氧化铝；研究制备过程的组装化学，理解新结构的形成机制及载体结构、表/界面对催化剂分散性和稳定性的影响；利用固体核磁、红外及理论计算指认和量化载体表面的缺陷位、铝配位状态，揭示Pt物种在氧化铝载体上的分散状态和高温稳定性等的本征关联，期望准确理解载体结构对丙烷脱氢稳定性的影响机制；引入Sn助剂，协同提高丙烷脱氢催化剂的稳定性，为改善Pt物种在真实反应条件下的稳定性提供科学依据。

随着丙烯需求量的增加及石油资源的日益匮乏，丙烷脱氢已成为丙烯增产的重要途径。其中，由积碳和烧结引发的贵金属催化剂的失活是该反应面临的挑战。本项目从创新氧化铝载体结构出发，通过精准调控溶液体系自组装过程和前驱物热解过程，发展了氧化铝载体形貌、孔道和表面缺陷调控新方法，成功制备了表面富含不饱和配位Al3+离子的氧化铝纳米片和纳米棒载体, 发展氧化铝表面拓扑结构的二维27Al MQ MAS NMR谱测试和精准定量方法，开展了系列氧化铝载体的放大制备和成型过程研究，可以实现20L反应釜水热合成。成型后样品机械强度120N/cm。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，实现了PtSn纳米簇的二维分散和稳定，纳米簇粒径约为1.3 nm，Pt分散度接近100%，丙烷转化率得到48.8%，丙烯选择性为99.4%，催化剂计算的单程寿命约为180小时。利用固体核磁、红外及分析，揭示了Pt物种在氧化铝载体上的分散状态和高温稳定性等的本征关联。进一步引入Ca助剂，有效改善积碳，促进催化剂的反应稳定性。