Brønsted acid sites based on penta-coordinated aluminum species.
Brønsted acid sites based on penta-coordinated aluminum species.
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DOI：
10.1038/ncomms13820
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发表时间：
2016-12-15
影响因子：
16.6
通讯作者：
中科院分区：
文献类型：
--
作者：
沸石和无定形硅铝（ASA）都能提供Brønsted酸位（BASs），是化学工业中应用最广泛的固体酸催化剂。人们普遍认为，BASs仅由四配位铝位（AlIV）和桥接OH基团组成，这些基团位于ASA表面的沸石或硅烷醇附近。本文报道了用27Al-{1H}偶极体介导的二维核磁共振实验，在强磁场下，直接观察到一种新型的五配位铝（AlV）基BAS。BAS-AlIV和-AlV均表现出与质子酸探针分子氨相似的酸性。1H和27Al位点的定量评价表明，BAS-AlV与BAS-AlIV共存，而不是取代它，这为强烈增强这些常用固体酸的酸度开辟了新的途径。到目前为止，人们一直认为无定形硅-氧化铝中的Brønsted酸位仅由四配位（AlIV）位点形成。在这里，作者使用27Al-{1H}相关核磁共振实验确定了一个新的基于alv的Brønsted酸位点，这对提高固体酸催化剂的酸度具有重要意义。
Zeolites and amorphous silica-alumina (ASA), which both provide Brønsted acid sites (BASs), are the most extensively used solid acid catalysts in the chemical industry. It is widely believed that BASs consist only of tetra-coordinated aluminum sites (AlIV) with bridging OH groups in zeolites or nearby silanols on ASA surfaces. Here we report the direct observation in ASA of a new type of BAS based on penta-coordinated aluminum species (AlV) by 27Al-{1H} dipolar-mediated correlation two-dimensional NMR experiments at high magnetic field under magic-angle spinning. Both BAS-AlIV and -AlV show a similar acidity to protonate probe molecular ammonia. The quantitative evaluation of 1H and 27Al sites demonstrates that BAS-AlV co-exists with BAS-AlIV rather than replaces it, which opens new avenues for strongly enhancing the acidity of these popular solid acids. Until now, it has been believed that Brønsted acid sites in amorphous silica-alumina are formed from only tetra-coordinated (AlIV) sites. Here, the authors use 27Al-{1H} correlation NMR experiments to identify a new AlV-based Brønsted acid site, with implications for increasing the acidity of solid acid catalysts.
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影响因子：
2.9
作者：
Chizallet, Celine;Raybaud, Pascal
通讯作者：
Raybaud, Pascal
影响因子：
16.6
作者：
Huang, Jun;van Vegten, Niels;Baiker, Alfons
通讯作者：
Baiker, Alfons
影响因子：
--
作者：
DEWITTE, BM;GROBET, PJ;UYTTERHOEVEN, JB
通讯作者：
UYTTERHOEVEN, JB
影响因子：
--
作者：
COSTER, D;BLUMENFELD, AL;FRIPIAT, JJ
通讯作者：
FRIPIAT, JJ
DOI：
10.1016/0022-1902(78)80256-5
发表时间：
1978-01-01
期刊：
JOURNAL OF INORGANIC & NUCLEAR CHEMISTRY
影响因子：
--
作者：
JACOBS, PA;MORTIER, WJ;UYTTERHOEVEN, JB
通讯作者：
UYTTERHOEVEN, JB