乙炔选择加氢反应中碳化钯的动态精细调控: 气氛和氧化锌助剂的作用  

Fine tuning the dynamic PdCx formation for enhanced acetylene semi‐hydrogenation:The role of gas environment and ZnO addition

作　　者：陈欢 虞周楠 杨冰 张亚峰 车春霞 刘晓艳[2] 张峰 韩伟 温翯 王爱琴[2] 张涛 Huan Chen;Zhounan Yu;Bing Yang;Yafeng Zhang;Chunxia Che;Xiaoyan Liu;Feng Zhang;Wei Han;He Wen;Aiqin Wang;Tao Zhang(School of Chemistry,Dalian University of Technology,Dalian 116024,Liaoning,China;CAS Key Laboratory of Science and Technology on Applied Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China;Lanzhou Petrochemical Research Center,Petrochemical Research Institute,PetroChina,Lanzhou 730060,Gansu,China)

机构地区：[1]大连理工大学化学学院,辽宁大连116024 [2]中国科学院大连化学物理研究所,中国科学院应用催化科学技术重点实验室,辽宁大连116023 [3]中国石油石油化工研究院兰州化工研究中心,甘肃兰州730060

出　　处：《Chinese Journal of Catalysis》2024年第5期190-200,共11页催化学报（英文）

基　　金：国家重点研发计划(2023YFA1506603);国家自然科学基金(22132006,22072151);国家自然科学基金委“单原子催化”基础科学中心(22388102);中国博士后科学基金(2023M733452);中国科学院大连化学物理研究所创新基金(DICP I202107);中国石油-大连化物所能源化工联合研发中心科技项目(2017A-1808).

摘　　要：碳化钯通常被认为是乙炔选择加氢反应中原位生成的活性相,其生成有助于抑制次表面非选择性的氢化钯物种,从而实现高选择性乙炔加氢制乙烯的目标.次表面上碳化钯和氢化钯物种之间的竞争很大程度上决定了乙炔加氢反应的选择性.然而,由于实际反应环境的复杂性,反应环境下的两种物种之间的动态转化过程和竞争关系尚不清晰.特别是,反应环境(比如氢气组分)对碳化钯物种的调控机制仍不明确,也使得对碳化钯活性物种的精准调控变得困难.此外,氧化锌助剂作为乙炔选择加氢反应中最常用的助剂之一,存在典型的金属-氧化物界面相互作用,也会对渗碳过程产生重要影响.因此,从动态视角理解碳化钯物种的原位形成过程,对于精准设计和合成高性能乙炔选择加氢钯基催化剂具有重要的科学意义.近年来,先进原位表征光谱技术的不断发展使得从原子、分子层面理解原位过程机制成为可能.本文旨在通过先进的原位表征技术揭示乙炔选择加氢反应中碳化钯物种的动态生成过程,并进一步探究气氛环境、温度、助催化剂等参数对碳化钯物种的动态调控机制,从而为高性能乙炔选择加氢催化剂的精准设计和合成提供有力支撑.原位研究结果表明,在氢气升温还原条件下,空气焙烧后新鲜催化剂中氧化钯相首先转变为氢化钯相;随着还原温度升高,氢化钯相的含氢量逐渐降低.当切换至乙炔选择加氢反应原料气时,氢化钯相迅速分解为金属钯,并随着恒温碳化时间的延长,烃类裂解产生的碳原子逐渐渗入钯的体相,最终形成稳定的碳化钯活性相.通过移除乙炔加氢反应原料气氛中的氢气,考察了反应气中的氢气组分对碳化钯形成的调控机制.实验发现,在仅有乙炔和乙烯存在时,碳化过程仍能发生;而引入少量氢气(体积分数2.2%)后,碳化程度显著增强,C/Pd原子比从0.136提升�Palladium carbide(PdCx)has been extensively reported as active phase in acetylene semi-hydrogenation that can be dynamically formed during reaction.However,fine tuning of dynamic PdCx formation towards enhanced acetylene semi-hydrogenation is of great challenge and the dynamic insights remain elusive.In this paper,the state-of-the-art in situ characterizations have been adopted to elucidate the dynamic PdCx formation for acetylene semi-hydrogenation.The role of hydrogen atmosphere and ZnO addition in tuning the carburization process were clearly identified by in situ spectroscopies.The hydrogen in the gas environment assisted the carbon infiltration via PdHx hydrides,while the addition of ZnO suppress the carburization by the surface Zn alloy.As a result,the carbon content in PdCx can be precisely modulated by altering the hydrogen atmosphere and ZnO additives,and exhibits a linear correlation with the activity of acetylene semi-hydrogenation.The carbon insertion enriched the electron state of Pd sites in PdCx that favors the activation of hydrogen for acetylene semi-hydrogenation.This work thus provides a new route for the design of Pd catalyst for high-performance acetylene semi-hydrogenation by fine tuning the reaction environment and the degree of carburization during dynamic PdCx formation.

关 键 词：乙炔选择加氢 碳化钯 渗碳过程 原位光谱 动态机制 

分 类 号：TQ221.211[化学工程—有机化工] TQ426