Y分子筛选择性封装Pt颗粒及其与临氢再生性能间构效关系的研究

With Pt nanoparticle loaded, deactivated zeolite Y could be effectively regenerated to recover its isobutane/butene alkylation capability via.hydrogenative regeneration treatment. However, when impregnation method and ion-exchange method were employed to support Pt nanoparticle, the distribution and size of synthesized Pt nanoparticle were uneven and ununiform, which brought out the difficulty in explanation of the relationship between the Pt distribution and corresponding regeneration performance, and then prevent the design of highly efficient regenerative Pt/Y catalyst. In this project, we plan to use the strategies of selective occupancy of supercage with structure directing agent, the coupling of in situ synthesis and solid-liquid extraction technology and using the adsorption-diffusion difference in zeolite channels to achieve selective encapsulation of Pt nanoparticle into SOD cage and supercage respectively, and construct the model catalysts for the study of desired relationship. On the basis of selective encapsulation of Pt nanoparticle, the influence of Pt distribution on the H2 dissociation and hydrocracking process for coking precursor can be investigated with H2-D2 exchange experiment and in situ FT-IR analysis through the synergy of confinement effect and shape-selective effect. Corresponding, the structure-activity relationship between the selective encapsulation of Pt nanoparticle in SOD cage/supercage and hydrogenative regeneration performance can be illustrated clearly. The development of this research will provide a new synthetic method for the encapsulation of noble metal into zeolite, and further complementary the hydrogenative regeneration theory.

负载Pt纳米颗粒临氢再生是解决Y分子筛在催化异丁烷/丁烯烷基化过程中积炭失活问题的有效手段。但传统浸渍法和离子交换法负载的Pt颗粒存在分布不均匀、尺寸不均一的问题，导致无法建立Pt颗粒分布和催化剂再生性能间的构效关系，阻碍了高效再生Pt/Y催化剂的设计开发。本项目首先拟通过结构导向剂的选择性占位、原位合成与固液萃取技术的耦合、及分子筛孔道内吸附扩散的差异性，分别实现Y分子筛SOD笼和超笼对Pt颗粒的选择性封装，为构效关系的探明构筑结构均一的模型催化剂体系。其次，通过H2-D2交换实验并结合原位FT-IR技术，基于限域效应和择形效应的协同作用，阐明模型催化体系中Pt颗粒分布对H2解离过程及积炭前身物氢解过程的影响机制，从而建立Pt分布-临氢再生性能间的构效关系。本项目的开展不仅可为分子筛封装贵金属提供新的制备方法，也可进一步完善贵金属临氢再生的理论。

Y分子筛在催化异丁烷/丁烯烷基化反应时易积炭失活，负载Pt颗粒临氢再生是解决Y分子筛积炭失活问题的有效手段。但传统浸渍和离子交换法负载的Pt颗粒存在分布不均、尺寸不均的问题，导致无法建立Pt颗粒分布和催化剂再生性能间的构效关系，阻碍了高效再生Pt/Y催化剂的设计开发。本项目优选氯化胆碱为结构导向剂来对超笼占位，筛选乙二胺为H2PtCl6的配体来强化Pt前驱体与SOD笼的相互作用，通过原位合成策略，利用Pt前驱体与SOD笼间的相互作用强于与超笼间相互作用的特点，成功实现了Y分子筛SOD笼选择性封装Pt原子(Pt@Y-SOD)。本项目也基于固液萃取技术，通过原位封装将乙二胺配位的Pt前驱体同时封装进Y分子筛SOD笼和超笼，再分别以乙醇和水为萃取剂，交替萃取出位于超笼的Pt，再通过焙烧和还原也可制备SOD笼选择性封装的Pt原子。优选Pt(acac)2为前驱体，EtOH为溶剂，Si/Al≤4的HY分子筛为载体，利用Pt(acac)2可扩散进入超笼而会被SOD笼阻止的特点，在60oC和1 atm H2还原条件下，成功实现了超笼对Pt颗粒的封装。本项目通过原位封装Pt(NH3)4(NO3)2前驱体，再经过350oC空气焙烧和300oC H2还原也可完成Y 分子筛超笼对Pt颗粒(Pt@Y)的选择性封装。H2-D2交换实验表明，相比与Pt@Y催化剂，Pt@Y-SOD有更低的H2转化频率，说明了SOD笼孔口对H2造成的更大扩散阻力是降低Pt@Y-SOD对H2解离速率的关键。得益于更高的H2解离速率，相比于Pt@Y-SOD，Pt@Y催化剂在异丁烷/丁烯烷基化反应中也展现了较好的临氢再生性能，临氢再生3次后，Y分子筛的活性仍能有所恢复。本项目不仅开发了分子筛封装贵金属的新方法，也丰富了贵金属临氢再生理论。