Ru/FeO_x catalyst performance design: Highly dispersed Ru species for selective carbon dioxide hydrogenation
高分散Ru/FeO_x催化剂在二氧化碳选择加氢反应中的应用及其催化活性的调控
查看参考文献40篇
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文摘
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A series of Ru/FeO_x catalysts were synthesized for the selective hydrogenation of CO_2 to CO. Detailed characterizations of the catalysts through X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and temperature-programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism. Highly dispersed Ru species were observed on the surface of FeO_x regardless of the initial Ru loading. Varying the Ru loading resulted in changes to the Ru coverage over the FeO_x surface, which had a significant impact on the interaction between Ru and adsorbed H, and concomitantly, the H_2 activation capacity via the ability for H_2 dissociation. FeO_x having 0.01% of Ru loading exhibited 100% selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H, which limits the desorption of the activated H species and hinders over-reduction of CO to CH_4. Further increasing the Ru loading of the catalysts to above 0.01% resulted in the adsorbed H to be easily dissociated, as a result of a weaker interaction with Ru, which allowed excessive CO reduction to produce CH_4. Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO_2. |
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其他语种文摘
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由于化石能源的大量开采和利用造成CO_2过度排放,从而导致严重的温室效应和气候环境问题,给人类生存带来极大威胁. CO_2选择加氢反应可以将CO_2催化加氢生成高附加值的CO产物.与其他的CO_2转化反应策略相比,该过程中H_2的消耗更少,成为可有效处理及转化CO_2的手段之一.同时,应尽可能抑制CO_2深度加氢以及甲烷的产生,研制及设计具有高CO选择性的新型高效催化剂及其构效关系的分析仍十分重要.据报道,负载型贵金属基催化剂的使用有利于H_2分子的活化,具有优异的催化活性,因而广泛应用于多种催化反应中.然而,贵金属催化剂实现工业应用的最大挑战是资源的限制及其高额的成本.近年来,由贵金属制备的负载型亚纳米团簇受到广泛关注,主要包括如Au, Pt, Pd, Ru等贵金属,可有效应用于多相催化反应.人们还致力于提高负载型亚纳米团簇的分散度,促进催化剂活性位点的有效暴露,有利于大幅度提高催化剂的有效利用率.本文采用共沉淀法成功制备了超高分散的负载型Ru基催化剂,通过CO_2选择加氢-程序升温表面反应(TPSR)和质谱联用技术测试了催化剂性能,发现CO_2加氢反应生成CO选择性达100%.采用XRD, BET和TEM等方法对催化剂结构进行表征,并结合H_2-TPR, H_2-TPD和XPS等表征结果深入探讨了催化剂构效关系,并提出了针对该催化剂体系较为合理的反应模型.在CO_2选择加氢反应的催化性能测试中, 2.50%Ru/FeO_x催化剂对目标产物CO选择性仅为41%;随着Ru负载量降低至0.25%和0.1%时, CO选择性明显提高至80%;当进一步降低Ru含量至0.01%时, CO选择性接近100%,且表现出优异的反应速率.在360 ℃时, 0.01%Ru/FeO_x催化剂的相对反应速率为7.71 molCO_2 molRu -1 min-1,是2.50%Ru/FeO_x催化剂相对反应速率的154倍. H_2-TPR结果表明,贵金属Ru可以明显促进载体FeO_x的还原,并产生丰富的氧空位,进而促进CO_2的吸附、活化.而且CO_2选择加氢TPSR结果显示,目标产物CO的起始生成温度总是滞后于原料H_2的初始活化温度,与H_2-TPR结果及文献报道的CO_2选择加氢反应机理一致.通过H_2-TPD深入理解H_2在催化剂表面的活化和氢溢流现象,以及H_(ads)与不同催化剂之间的相互作用力, 0.01%Ru/FeO_x催化剂相对较高的H_2脱附峰温度表明,该样品中Ru与H_(ads)具有极强的相互作用力,相对抑制了H_(ads)与COads深入加氢生成CH_4,从而提高了CO选择性,而2.50%Ru/FeO_x催化剂的情况则与此相反.本文提出了从H_(ads)吸附作用力强弱来考虑CO_2选择加氢反应选择性的新思路,同时为设计CO_2选择加氢制高附加值CO的高催化反应速率、高CO选择性的高分散Ru基催化剂提供了一种经济简易的催化剂设计思路. |
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来源
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Chinese Journal of Catalysis
,2018,39(1):157-166 【核心库】
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DOI
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10.1016/S1872-2067(17)62967-X
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关键词
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Highly dispersed Ru/FeO_x catalyst
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Temperature-programmed surface reaction
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CO_2 selective hydrogenation
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Product selectivity
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Hydrogen adsorption
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地址
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1.
Department of Chemical Engineering, & Institute of New Energy and Low Carbon Technology, Sichuan University, Sichuang, Chengdu, 610065
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Institute of Metal Research, Chinese Academy of Sciences, Shenyang National Laboratory for Materials Science (SYNL), Liaoning, Shenyang, 110016
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Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy (DNL), Liaoning, Dalian, 116023
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语种
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英文 |
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文献类型
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研究性论文 |
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ISSN
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0253-9837 |
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学科
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化学;化学工业 |
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基金
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中国博士后科学基金
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国家自然科学基金
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文献收藏号
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CSCD:6160945
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