Zn/ZSM-5催化剂中Zn物种与CO_(2)和正丁烷耦合反应间相关性研究  

Understanding the correlation between zinc speciation and coupling conversion of CO_(2)and n-butane on zinc/ZSM-5 catalysts

作　　者：孙旭科 刘荣升 范改丽 刘昱含 叶芳秀 于政锡[1] 刘中民[1,2] Xuke Sun;Rongsheng Liu;Gaili Fan;Yuhan Liu;Fangxiu Ye;Zhengxi Yu;Zhongmin Liu(National Engineering Research Center of Lower‐Carbon Catalysis Technology,Dalian National Laboratory for Clean Energy,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Chemistry,Dalian University of Technology,Dalian 116024,Liaoning,China;College of Chemistry and Chemical Engineering,China University of Petroleum(East China),Qingdao 266580,Shandong,China)

机构地区：[1]中国科学院大连化学物理研究所,洁净能源国家实验室,低碳催化技术国家工程研究中心,辽宁大连116023 [2]中国科学院大学,北京100049 [3]大连理工大学化学学院,辽宁大连116024 [4]中国石油大学(华东)化学化工学院,山东青岛266580

出　　处：《Chinese Journal of Catalysis》2024年第6期154-163,共10页催化学报（英文）

基　　金：国家自然科学基金(21991093,21991092,21991090);科技部国家重点研发计划(2022YFE0116000);中国科学院战略性先导科技专项(XDA29000000).

摘　　要：随着全球温室气体排放的持续增长,二氧化碳(CO_(2))的高效转化与利用已成为应对气候变化、推动可持续发展的重要途径之一.在本课题组的前期研究中,以正丁烷为模型化合物,成功实现了H-ZSM-5分子筛催化CO_(2)与正丁烷发生耦合反应.实验还发现,通过对H-ZSM-5进行Zn改性,可以显著提高其催化性能,这为CO_(2)的高效转化和利用提供了新的研究方向.然而,目前关于Zn-ZSM-5催化剂中Zn物种的具体存在状态及其与耦合反应性能之间的关系尚不明确,这限制了高效催化剂的进一步设计.因此,深入探究Zn物种在Zn-ZSM-5催化剂中的存在状态及其与催化性能之间的关联机制,从而设计和开发更高效的CO₂转化催化剂已成为当务之急.本文通过紫外-可见光漫反射光谱、X-射线光电子能谱和1H魔角旋转-核磁共振等多种技术系统地表征了Zn-ZSM-5分子筛中酸性中心和Zn物种存在状态的演变过程,讨论了Zn物种活性中心与耦合反应之间的构-效关系,阐明了耦合反应的机理.研究表明,Zn-ZSM-5分子筛中Zn物种主要以ZnO团簇、Zn-OH^(+)和(Zn-O-Zn)^(2+)的形式存在,且其含量随Zn负载量的变化而改变.其中,ZnO团簇及(Zn-O-Zn)^(2+)物种的含量随Zn负载量的增加而上升,而Zn-OH^(+)物种含量则先上升后下降,这是由于部分Zn-OH^(+)物种转化为(Zn-O-Zn)^(2+)物种.在CO_(2)与正丁烷的耦合反应中,正丁烷的转化受到Brønsted酸位点的减少、Zn活性位点的形成以及粗晶ZnO物种的堆积等多种因素的影响.Zn-OH^(+)物种是主要的CO_(2)催化转化活性中心,而芳烃的生成则主要受Zn-OH^(+)和(Zn-O-Zn)^(2+)物种的影响.Zn-OH^(+)和(Zn-O-Zn)^(2+)物种均具有较强的脱氢性能,可通过脱氢路径促进芳烃的生成.Zn5%-ZSM-5(Zn负载量为5 wt%)样品表现出最优的催化性能:正丁烷转化率为94.71%,CO_(2)转化率为30.43%,芳烃选择性为53.71%.原位实验进一步证实了内酯、羧酸和不饱�The coupling reaction of alkanes and CO_(2)into high value-added bulk chemical products is a promising way for CO_(2)utilization.The Zn-introduced ZSM-5 catalyst plays an essential role in this process;however,the correlation between the catalytic performance and Zn species of the catalyst has yet to be established.Herein,the structural properties,the acid sites,and the existence status of the Zn species in the Zn-introduced catalysts were systematically characterized by several techniques.And the influence of the state of Zn species in the coupling reaction was discussed.The results indicate that the Zn species exist in the form of ZnO cluster,Zn-OH^(+),and(Zn-O-Zn)^(2+)species,thereinto(Zn-O-Zn)^(2+)species are produced by the Zn-OH^(+)group with the increasing Zn loading.The decrease of Brønsted acid sites,the formation of newly active sites caused by Zn species,and the accumulation of coarse ZnO species,are responsible for the change of n-butane conversion.The Zn-OH^(+)group serves as the primary catalytic center for the conversion of CO_(2).Both the Zn-OH^(+)group and the(Zn-O-Zn)^(2+)species enhance the dehydrogenation performance of the Zn-introduced catalysts,thereby promoting the generation of aromatics.The Zn5%-ZSM-5 sample showed the most excellent catalytic performance;the n-butane conversion was 94.71%,the CO_(2)conversion was 30.43%,and the aromatics selectivity was 53.71%.Simultaneously,we propose a more specific mechanism for the coupling reaction.

关 键 词：耦合反应 CO_(2)利用 锌的引入 Zn-OH+ (Zn-O-Zn)^(2+) ZSM-5 

分 类 号：O621.251[理学—有机化学]