A core/shell catalyst produces a spatially confined effect and shape selectivity in a consecutive reaction
A core/shell catalyst produces a spatially confined effect and shape selectivity in a consecutive reaction
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DOI：
10.1002/anie.200703335
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Tsubaki, Noritatsu
中科院分区：
文献类型：
--
作者：
Bao, Jun;He, Jingjiang;Tsubaki, Noritatsu
一般来说，连续反应（A！B！C）的活性催化剂通常具有两种类型的活性位点，其中一种加速A到B的反应，另一种加速B到C的反应。以合成气（CO+H2）合成异链烷烃为例，最有效的催化剂通常同时包含费托合成（FTS）位点和酸性位点。[1] FTS位点将合成气转化为直链烃，然后迁移到酸性位点，在那里进行进一步加氢裂化和异构化，形成支链烃。改善这两种活性位点的分散性，同时确保它们仍然彼此靠近，是增强催化性能的最有效方法。 [2]然而，影响该连续反应的产物选择性的一个关键因素是第一个反应产物迁移到第二个反应的活性位点的难易程度。传统双功能催化剂中的不同活性位点随机分布在其表面上，这提供了不受限制的开放反应环境，即使两个活性位点之间的距离很短，偶联反应也可以独立且随机地发生。这意味着从第一反应位点解吸的产物可以离开催化剂，而不会在其他活性位点进一步反应。
In general, an active catalyst for a consecutive reaction (A! B! C) usually has two types of active sites, one of which accelerates the reaction of A to B and the other the reaction of B to C. Taking the synthesis of isoparaffins from syngas (CO+ H2) as an example, the most efficient catalysts usually contain both Fischer–Tropsch synthesis (FTS) sites and acidic sites.[1] The FTS sites convert the syngas into linear hydrocarbons, which then migrate to the acidic sites where they undergo further hydrocracking and isomerization to form branched hydrocarbons.Improving the dispersion of these two kinds of active sites whilst ensuring they are still close to each other is the most efficient approach to enhancing catalytic performance.[2] However, a crucial factor that affects the product selectivity of this consecutive reaction is the ease of migration of the first reaction products to the active sites of the second reaction. The different active sites in conventional bifunctional catalysts are randomly distributed on their surface, which provides an unrestricted, open reaction environment where the coupled reactions occur independently and randomly even though the distance between the two active sites is very short. This means that the products desorbed from the first reaction sites can leave the catalyst without reacting further at the other active sites.