B-MWW Zeolite: The Case Against Single-Site Catalysis.
B-MWW Zeolite: The Case Against Single-Site Catalysis.
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DOI：
10.1002/anie.201914696
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发表时间：
2020-04-16
期刊：
影响因子：
--
通讯作者：
Hermans I
中科院分区：
文献类型：
--
作者：
Altvater NR;Dorn RW;Cendejas MC;McDermott WP;Thomas B;Rossini AJ;Hermans I
含硼材料最近已被确定为用于烷烃氧化脱氢（ODH）成烯烃的高选择性催化剂。先前已经通过几种光谱表征技术证明，这些含硼ODH催化剂的表面在反应条件下氧化和水解，形成无定形B2（OH）2xO（3 - x）（x = 0 - 3）层。然而，活性位点的确切性质仍然难以捉摸。在这篇文章中，我们提供了一个详细的表征沸石MCM-22同晶取代硼（B-MWW）。使用11B固态NMR光谱，我们表明，大多数的硼物种在B-MWW存在作为孤立的BO 3单元，完全纳入沸石框架。然而，该材料对丙烷到丙烯的ODH没有显示出催化活性。B-MWW对丙烷ODH的催化活性否定了硼基催化剂中活性中心是孤立的BO 3单元的假设。这一观察结果与其他传统研究的催化剂（如钒基催化剂）不一致，并提供了一个重要的机制难题。详细的固态核磁共振光谱表征水热合成的B-MWW揭示，硼是完全纳入沸石框架作为三价BO 3单元。这些孤立的网站是无活性的丙烷氧化脱氢（ODH），这驳斥了假设，网站孤立的硼物种是含硼ODH催化剂上的活性位点。
Boron-containing materials have recently been identified as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins. It has previously been demonstrated by several spectroscopic characterization techniques that the surface of these boron-containing ODH catalysts oxidize and hydrolyze under reaction conditions, forming an amorphous B2(OH)2xO(3 – x) (x = 0 – 3) layer. Yet, the precise nature of the active site(s) remains elusive. In this communication, we provide a detailed characterization of zeolite MCM-22 isomorphously substituted with boron (B-MWW). Using 11B solid-state NMR spectroscopy, we show that the majority of boron species in B-MWW exist as isolated BO3 units, fully incorporated into the zeolite framework. However, this material shows no catalytic activity for ODH of propane to propene. The catalytic inactivity of B-MWW for ODH of propane falsifies the hypothesis that site-isolated BO3 units are the active site in boron-based catalysts. This observation is at odds with other traditionally studied catalysts like vanadium-based catalysts and provides an important piece of the mechanistic puzzle. Detailed solid-state NMR spectroscopic characterization of hydrothermally synthesized B-MWW reveals that boron is fully incorporated into the zeolite framework as trivalent BO3 units. These isolated sites are inactive for oxidative dehydrogenation (ODH) of propane, which refutes the hypothesis that site-isolated boron species are the active site on boron-containing ODH catalysts.
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影响因子：
2.2
作者：
Trebosc, J.;Hu, B.;Gan, Z.
通讯作者：
Gan, Z.
影响因子：
2.8
作者：
Eden, Mattias;Zhou, Dan;Yu, Jihong
通讯作者：
Yu, Jihong
影响因子：
7.3
作者：
Corma, A;MartinezTriguero, J
通讯作者：
MartinezTriguero, J
DOI：
10.1016/0144-2449(93)90072-b
发表时间：
1993-02-01
期刊：
ZEOLITES
影响因子：
--
作者：
DERUITER, R;KENTGENS, APM;VANBEKKUM, H
通讯作者：
VANBEKKUM, H
影响因子：
2.2
作者：
Bak, M;Rasmussen, JT;Nielsen, NC
通讯作者：
Nielsen, NC