Sn1Pt单原子合金催化剂在丙烷脱氢反应中的应用  

S_(n1)Pt single‐atom alloy evolved stable PtSn/nano‐Al_(2)O_(3)catalyst for propane dehydrogenation

作　　者：邢亚楠 康磊磊 马静远 蒋齐可 苏杨[1] 张盛鑫 徐晓燕 李林[1] 王爱琴[1] 刘智攀 马思聪[3] 刘晓艳 张涛[1,2] Yanan Xing;Leilei Kang;Jingyuan Ma;Qike Jiang;Yang Su;Shengxin Zhang;Xiaoyan Xu;Lin Li;Aiqin Wang;Zhi‐Pan Liu;Sicong Ma;Xiao Yan Liu;Tao Zhang(CAS Key Laboratory of Science and Technology on Applied Catalysis,iChEM,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China;University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Synthetic and Self‐Assembly Chemistry for Organic Functional Molecules,Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences,Shanghai 200032,China;Shanghai Synchrotron Radiation Facility,Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201204,China;Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials,Key Laboratory of Computational Physical Science,Department of Chemistry,Fudan University,Shanghai 200433,China)

机构地区：[1]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 [2]中国科学院大学,北京100049 [3]中国科学院上海有机化学研究所,有机功能分子合成与自组装化学重点实验室,上海200032 [4]中国科学院上海高等研究院,上海同步辐射光源,上海201204 [5]复旦大学化学系,计算物理科学重点实验室,分子催化与创新材料上海重点实验室,上海200433

出　　处：《Chinese Journal of Catalysis》2023年第5期164-174,共11页催化学报（英文）

基　　金：国家自然科学基金(22102180);中国科学院洁净能源创新研究院合作基金(DNL202002);辽宁省“兴辽英才计划”项目(XLYC2007070);中央高校基本科研业务费专项资金(20720220009).

摘　　要：丙烯是生产聚丙烯、各类丙烷氧化物、丙烯腈的重要化工原料.近年来,随着丙烯需求量日益增长,作为一种专产丙烯的生产方式,丙烷脱氢(PDH)受到了越来越多的关注.PtSn/Al_(2)O_(3)是一种典型的工业丙烷脱氢催化剂,其特征是催化活性会随反应时间的推移而下降,因此需要反复再生以保证丙烯产率.提高PtSn催化剂的稳定性,需要明确反应状态下PtSn的催化性能与其结构之间的关系.然而,Pt和Sn的价态及其相互作用,对制备方法、预还原条件、载体类型等因素非常敏感,此外,从Pt-Sn二元相图来看,二者在高温(~600℃)还原性反应气氛下可形成多种合金结构,因此,PtSn在丙烷脱氢中的活性位结构的认识颇具挑战,目前文献报道结果仍存在争议.本文选用商业化的纳米级γ-Al_(2)O_(3)作为载体,通过利用纳米载体上只能担载有限数量的金属原子和加入过量的第二金属Sn稀释活性金属Pt的方式,得到高分散的PtSn/nano-Al_(2)O_(3)催化剂.当Pt和Sn的负载量分别为0.1 wt%和1 wt%时,其初始丙烯产率可达到47.6 molC_(3)H_(6)gPt^(-1)h^(-1),高于文献已报道的PtSn双金属催化剂,该催化剂经3-10 h活性快速下降期(k_(d-3h):0.11h^(-1))后,表现出较好的稳定性(k_(d-10~40h):0.0026 h^(-1)).球差电镜(AC-HAADF-STEM)表征结果显示,该催化剂经500℃焙烧后,Pt及Sn在Al_(2)O_(3)载体上均呈单原子分散状态;经600℃氢气还原后,Pt团聚为平均直径约0.85 nm的纳米颗粒;通过对其进行能谱点扫分析,发现Pt纳米颗粒上分布有少量的Sn原子,而剩余大量的Sn原子则继续以单原子形式分布在载体上.进一步原位X射线光电子能谱和原位X射线吸收能谱结果证明,该催化剂中纳米颗粒的具体组成为Sn单原子分散在Pt纳米颗粒表面,形成S_(n1)Pt表面单原子合金结构.密度泛函理论理论计算证明了S_(n1)Pt表面单原子合金结构的稳定性及其在丙烷脱氢中的高活性.最后结�The PtSn/Al_(2)O_(3)is a prototypical industrial catalyst for propane dehydrogenation(PDH).However,the local structures of the active sites are still inconclusive under the operation conditions.Herein,the evolutions of the Pt‐Sn active centers supported on nano‐Al_(2)O_(3)are definitely discerned at the atomic level during PDH reaction.By combining complementary in situ characterizations and theoretical calculations,we demonstrate that a highly productive S_(n1)Pt single‐atom alloy(47.6 molC_(3)H_(6)g_(Pt)^(-1) h^(-1))forms after the reduction,and thereby self‐assembles to the Pt_(3)Sn intermetallic compound during the reaction,which exhibits a rather stable performance(k_(d‐10~40h):0.0026 h^(-1)).Intriguingly,the results of in situ diffuse reflectance infrared Fourier‐transform spectroscopy further corroborate that the adjacent Pt atoms with terrace sites aggravating the coke deposition can be circumvented through this single‐atom alloy mediated reconstruction.Our findings depict an unprecedented evolution process of the active sites of the PtSn/Al_(2)O_(3),and afford an effectual nanostructure engineering pathway for stable PDH catalysts.

关 键 词：丙烷脱氢 丙烯 Pt-Sn催化剂 结构重构 单原子合金 

分 类 号：TQ221.212[化学工程—有机化工] TQ426