物理化学学报 >> 2020, Vol. 36 >> Issue (9): 1912001.doi: 10.3866/PKU.WHXB201912001

所属专题: 精准纳米合成

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理性设计核-壳Rh-石催化材料用于二烯烃选择加氢反应

张建1, 王亮2,*(), 伍芷毅1, 王成涛3, 苏泽瑞1, 肖丰收1,2,3   

  1. 1 北京化工大学北京软物质科学与工程高精尖创新中心,北京 100029
    2 浙江大学化学工程与生物工程学院,生物质化工教育部重点实验室,杭州 310027
    3 浙江大学化学系,浙江省应用化学重点实验室,杭州 310028
  • 收稿日期:2019-12-02 录用日期:2020-01-06 发布日期:2020-02-14
  • 通讯作者: 王亮 E-mail:liangwang@zju.edu.cn
  • 基金资助:
    国家重点研发计划(2018YFB0604801);国家自然科学基金(21822203);国家自然科学基金(91645105);国家自然科学基金(91634201);浙江省自然科学基金(LR18B030002);北京化工大学高精尖研究中心科研启动费(21530009067);中央高校基本科研基金(2019XZZX004-02)

Rational Design of a Core-Shell Rh@Zeolite Catalyst for Selective Diene Hydrogenation

Jian Zhang1, Liang Wang2,*(), Zhiyi Wu1, Chengtao Wang3, Zerui Su1, Feng-Shou Xiao1,2,3   

  1. 1 Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China
    2 Key Lab of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
    3 Key Laboratory of Applied Chemistry of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310028, P. R. China
  • Received:2019-12-02 Accepted:2020-01-06 Published:2020-02-14
  • Contact: Liang Wang E-mail:liangwang@zju.edu.cn
  • Supported by:
    The project was supported by the National Key Research and Development Program of China(2018YFB0604801);the National Natural Science Foundation of China(21822203);the National Natural Science Foundation of China(91645105);the National Natural Science Foundation of China(91634201);the Natural Science Foundation of Zhejiang Province, China(LR18B030002);the Beijing Advanced Innovation Center for Soft Matter Science, Engineering of the Beijing University of Chemical Technology, China(21530009067);the Fundamental Research Funds for the Central Universities, China(2019XZZX004-02)

摘要:

不饱和烃类如二烯烃和炔烃催化转化为单烯烃是制药和有机合成领域中的重要反应。催化剂的理性设计在实现这一过程中起到关键作用,而控制二烯烃分子的吸附姿态是常用的策略。对金属纳米颗粒的定向修饰可以实现这一策略。例如,将Bi元素引入Rh纳米颗粒后,RhBi/SiO2在1, 4-己二烯的转化率为95%时对于2-己烯的选择性达到90%,这是因为1, 4-己二烯内部C=C键的吸附受到抑制。但是,这种策略却大大降低了纳米颗粒的活性,未修饰的Rh/SiO2比RhBi/SiO2的活性高了约27倍。二烯烃分子的吸附姿态也可以通过在金属纳米颗粒周围构筑多孔孔道来调控。例如,金属有机骨架(ZIF-8)或中孔二氧化硅(MCM-41)包裹的贵金属纳米颗粒对末端C=C键的加氢具有很高的选择性。然而,这些催化剂的热/水热稳定性却并不能令人满意。相比之下,沸石却具有非常高的稳定性,但却较少用于半加氢反应。我们最近发现,固定在沸石晶体(例如ZSM-5和Beta)中的金属纳米颗粒可以有效地选择加氢多取代的化合物。受这些工作的启发,我们通过转晶合成方法将Rh纳米颗粒封装在CHA沸石晶体中。这种催化剂首先是将Rh物种引入到Y沸石中(Rh@Y),然后在水热条件下将Y沸石转化为CHA沸石而合成的。XRD图谱,N2吸附等温线,SEM和TEM照片以及探针反应均表明Rh纳米颗粒是封装在CHA沸石晶体内部的。和设想的相同,Rh@CHA催化剂对二烯烃的氢化具有很高的选择性。在催化1, 4-己二烯加氢反应过程中,Rh@CHA给出了86.7%的2-己烯选择性和91.2%的1, 4-己二烯转化率。在同样条件下,常规方法制备的Rh纳米颗粒催化剂(Rh/CHA)的2-己烯选择性仅为37.2%。考虑到Rh@CHA和Rh/CHA具有相同的CHA沸石晶体和相似的Rh纳米颗粒尺寸,Rh@CHA催化剂的高选择性主要归因于二烯烃分子在CHA沸石的微孔孔道控制下只能以直立的姿态吸附在Rh纳米颗粒上。本文的工作表明,具有核-壳结构的沸石封装金属纳米颗粒催化剂对于催化二烯烃选择加氢具有较好的效果。

关键词: 多相催化, 二烯烃加氢, 铑纳米颗粒, CHA沸石, 核-壳结构, 转晶合成沸石

Abstract:

Selective hydrogenation of dienes and alkynes to monoenes is an important topic of research in the fields of pharmacology and organic synthesis. Catalyst design plays a key role in this process, where a general principle involves controlling the steric diene adsorption by modifying the surface of the metal nanoparticles. For example, upon introducing Bi species into Rh nanoparticles, the resulting RhBi/SiO2 showed 90% selectivity to 2-hexene, with 95% conversion of 1, 4-hexadiene under ambient conditions, because of the suppressed adsorption of the internal C=C bond. However, the catalyst activity decreased remarkably; that is, the activity of the unmodified Rh/SiO2 was about 27 times higher than that of RhBi/SiO2. Controlled steric adsorption of the diene molecules could also be achieved by the constructing porous channels around the metal nanoparticles. For example, metal-organic framework (ZIF-8) or mesoporous silica (MCM-41) encapsulated noble metals showed high selectivity for the hydrogenation of terminal C=C bonds. However, these catalysts had poor durability under the thermal/hydrothermal reaction/regeneration conditions. In contrast, zeolites have superior durability under harsh reaction conditions, but they are rarely used in semi-hydrogenation reactions. We recently found that metal nanoparticles fixed within zeolite crystals (e.g., ZSM-5 and Beta) efficiently catalyze the selective hydrogenation of molecules bearing multiple reducible groups. Thus inspired, we developed a catalyst by fixing Rh nanoparticles within zeolite crystals via an inter-zeolite transformation method. The Rh@CHA catalyst was synthesized by introducing Rh species into the parent Y zeolite (Rh@Y) and transformation of the Y zeolite to chabazite (CHA zeolite) under hydrothermal conditions. X-ray diffraction patterns, N2 sorption isotherms, scanning/transmission electron microscopy images, and model reactions (hydrogenation of probe molecules) confirmed the successful fixation of the Rh nanoparticles inside the CHA zeolite crystals. As expected, the Rh@CHA catalyst was highly selective for the hydrogenation of dienes. For example, Rh@CHA showed a 2-hexene selectivity of 86.7%, with 91.2% conversion of 1, 4-hexadiene. In contrast, the generally supported Rh nanoparticle catalyst (Rh/CHA) showed a low 2-hexene selectivity of 37.2% under identical reaction conditions. Considering that Rh@CHA and Rh/CHA comprise the same CHA zeolite crystals and have similar Rh nanoparticle sizes, the remarkably high selectivity of Rh@CHA is assigned to the steric adsorption of dienes on the Rh surface controlled by the micropores of the CHA zeolite. This work demonstrates that a zeolite-fixed metal core-shell structure is a powerful tool for developing efficient catalysts to be used in diene hydrogenation.

Key words: Heterogeneous catalysis, Diene hydrogenation, Rh nanoparticle, CHA zeolite, Core-shell structure, Inter-zeolite transformation

MSC2000: 

  • O643