High technology catalysts towards 100% selectivity: Fabrication, characterization and reaction studies
High technology catalysts towards 100% selectivity: Fabrication, characterization and reaction studies
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DOI：
10.1016/j.cattod.2004.07.059
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发表时间：
2005-02
期刊：
影响因子：
5.3
通讯作者：
G. Somorjai;R. Rioux
中科院分区：
文献类型：
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作者：
G. Somorjai;R. Rioux
世纪的催化主要集中在活性上，即增加周转率以在单位时间内产生更多的分子。高选择性不太受关注，因为处理不需要的副产物并不昂贵，而且原材料丰富。这种情况在21世纪发生了变化，因为现在废物处理费用昂贵，而且对生态的负面影响也有充分的记录。因此，目前催化科学的重点和路线图是在所有基于催化剂的化学过程中实现高选择性。与我们对活性的理解相比，我们对影响选择性的分子成分的了解很差。有六个可识别的特征影响催化剂活性和选择性。它们是金属表面结构，键合改性剂添加剂，金属簇的迁移率，以重组以及这些簇上的吸附物的迁移率，选择性位点阻断，双功能性，和氧化物-金属界面的网站。确定催化剂活性和选择性的分子成分为催化剂设计、组合催化剂合成、表征和反应研究提供了机会。为了获得朝向100%选择性的最终目标的高选择性，必须开发能够对金属纳米颗粒和催化剂促进剂的尺寸、位置、结构进行分子控制的合成方法。我们正试图通过制造二维和三维催化剂来实现这一目标。二维纳米颗粒或纳米线阵列催化剂通过电子束光刻（EBL）或尺寸减小光刻（SRL）来制造。用EBL方法制备了金属表面积约为1 mm ~ 2或109个纳米粒子的阵列。这些模型催化剂系统使高周转反应，如乙烯加氢的研究成为可能。SRL和光刻聚合物印迹技术用于生产纳米线或纳米点阵列模型催化剂，金属表面积高达1cm 2或1011纳米颗粒。高比表面积（1 m2或1015纳米颗粒）是通过一步法制备的，其中聚合物稳定的单分散纳米颗粒在溶液中合成，并通过机械或水热合成掺入高比表面积的介孔二氧化硅中。两种类型的模型催化剂的特征在于各种物理和化学技术，并且对于烃转化测试反应是催化活性的。我们的催化剂设计方法结合了合成（制造），表征和反应研究。
Catalysis in the 20th century focused primarily on activity, increasing turnover rates to produce more molecules per unit time. High selectivity was of lesser concern because disposal of undesirable byproducts was not costly and raw materials were abundant. This has changed in the 21st century because waste disposal is now expensive and the negative ecological impacts are well-documented. As a result, the present focus and roadmap of catalysis science is to achieve high selectivity in all catalyst-based chemical processes. Our knowledge of the molecular ingredients that influence selectivity is poor compared to our understanding of activity. There are six identifiable features that influence both catalyst activity and selectivity. They are metal surface structure, bonding modifier additives, mobility of metal clusters to restructure as well as the mobility of adsorbates on these clusters, selective site blocking, bifunctionality, and oxide-metal interface sites. Identification of the molecular ingredients of catalyst activity and selectivity provides opportunity for catalyst design, combined catalyst synthesis, characterization and reaction studies. In order to obtain high selectivity towards the ultimate goal of 100% selectivity, synthetic methods that enable molecular control over the size, location, structure of the metallic nanoparticles and catalyst promoters must be developed. We are attempting to do this by fabricating two- and three-dimensional catalysts. Two-dimensional nanoparticle or nanowire array catalysts are fabricated by electron beam lithography (EBL) or size reduction lithography (SRL). Arrays with metal surface areas of about 1mm2or 109nanoparticles are fabricated by EBL. These model catalyst systems enable the study of high-turnover reactions such as ethylene hydrogenation. SRL and a lithographic polymer imprinting technique are used to produce nanowire or nanodot array model catalysts with metallic surface areas up to 1cm2or 1011nanoparticles. High surface area (1m2or 1015nanoparticles) is produced by a one-step method in which polymer-stabilized monodisperse nanoparticles are synthesized in solution and incorporated into high-surface area mesoporous silica mechanically or through hydrothermal synthesis. Both types of model catalysts are characterized by a variety of physical and chemical techniques and are catalytically active for hydrocarbon conversion test reactions. Our catalyst design approach combines synthesis (fabrication), characterization and reaction studies.