摘要
本工作以生物质壳聚糖作为牺牲模板,乙酰丙酮钒为金属钒源,ZnCl_(2)为造孔剂,采用高温热解结合酸洗的策略制备出一种钒氮共掺杂多孔碳(V-N-C)催化剂。表征结果表明,V-N-C催化剂的比表面积高达1470 m^(2)·g^(-1),孔容为1.06 cm^(3)·g^(-1),质量分数为0.19%的钒物种可能以单原子VN_(x)形式高度分散在载体上。在苄胺氧化偶联合成亚胺的反应中,V-N-C表现出高催化性能,底物苄胺的转化率和产物亚胺的选择性均为99%,性能明显优于均相VO(acac)_(2)和多相V_(2)O_(5)催化剂。此外V-N-C催化剂连续重复使用9次也未出现任何活性衰减的问题,且对一系列含有不同官能团的底物也具有优良的普适性。机理研究表明,苄胺和氧气首先分别在催化剂VN_(x)和缺陷位点活化成苄基亚胺和H_(2)O_(2)中间体,然后苄基亚胺与苄胺缩合脱NH_(3)生成目标产物亚胺。
Synthesis of imine compounds via benzylamine oxidative coupling has become one of the most ideal methods due to its high atom economy and environmental friendliness.The key is to develop high-performance non-noble metal-based heterogeneous catalysts.In this work,a vanadium-nitrogen co-doped porous carbon(V-N-C)catalyst was prepared via high-temperature pyrolysis(900℃for 2 h in an inert atmosphere)combined with acidleaching(1 mol·L^(-1)HCl solution at 120℃for 12 h)approach by using biomass chitosan as the sacrificial template,vanadium acetylacetonate as the source of metal vanadium,and ZnCl_(2)as the pore-forming agent.Various characterization techniques including a high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM)investigation were used to analyze the composition,structure,vanadium species size,content,and other physical and chemical properties of the catalyst,and its catalytic performance was evaluated in the oxidative coupling reaction of benzylamine.The characterization results showed that the specific surface area of the V-N-C catalyst was as high as 1470 m^(2)·g^(-1),the pore volume was 1.06 cm^(3)·g^(-1),and the mass fraction of the vanadium species was 0.19%that were highly dispersed on the support likely in the form of single atoms(VN_(x)).In the oxidative selfcoupling reaction of benzylamine to the imine(reaction conditions:toluene as solvent,110℃,1.01×10^(5)Pa O_(2),12 h),the developed V-N-C exhibited excellent activity(99%),exclusive selectivity(99%),outperforming the homogeneous VO(acac)_(2) and heterogeneous V_(2)O_(5)catalysts.Moreover,V-N-C was repeatedly used 9 times without any decay in reactivity and stability.Furthermore,V-N-C presented excellent universality for a series of substrates containing different functional groups.Mechanism studies indicated that the reaction steps were involved in the initial formation of benzylimine and H_(2)O_(2)intermediates by activating benzylamine and oxygen molecules,respectively,on the VN_(x)and defect sites of V-N-C,then benzylimine and benzylamine condensed to release an NH_(3) molecule to generate the target product imine.
作者
吴晓雪
齐妍妍
王盈懿
王丽
涂高美
傅仰河
陈德利
朱伟东
张富民
WU Xiao-Xue;QI Yan-Yan;WANG Ying-Yi;WANG Li;TU Gao-Mei;FU Yang-He;CHEN De-Li;ZHU Wei-Dong;ZHANG Fu-Min(Key Laboratory of the Ministry of Education for Advanced Catalysis Materials,Institute of Physical Chemistry,Zhejiang Normal University,Jinhua,Zhejiang 321004,China)
出处
《无机化学学报》
SCIE
CAS
CSCD
北大核心
2022年第6期1049-1058,共10页
Chinese Journal of Inorganic Chemistry
基金
国家自然科学基金(No.21576243)资助。
关键词
选择性催化氧化
多相催化
钒氮共掺杂多孔碳
氧化偶联
selective catalytic oxidation
heterogeneous catalysis
vanadium-nitrogen co-doped porous carbon
oxidative coupling
作者简介
通信联系人:张富民。E-mail:zhangfumin@zjnu.edu.cn。
