MAGIC-ANGLE SPINNING NUCLEAR-MAGNETIC-RESONANCE STUDIES OF WATER-MOLECULES ADSORBED ON BRONSTED-ACID AND LEWIS-ACID SITES IN ZEOLITES AND AMORPHOUS SILICA-ALUMINAS
MAGIC-ANGLE SPINNING NUCLEAR-MAGNETIC-RESONANCE STUDIES OF WATER-MOLECULES ADSORBED ON BRONSTED-ACID AND LEWIS-ACID SITES IN ZEOLITES AND AMORPHOUS SILICA-ALUMINAS
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DOI：
10.1039/ft9918700657
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发表时间：
1991-02-21
期刊：
影响因子：
--
通讯作者：
PFEIFER, H
中科院分区：
文献类型：
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作者：
HUNGER, M;FREUDE, D;PFEIFER, H
在弱复水脱铝沸石和无定形硅铝上，可以通过质子幻角旋转核磁共振(H-1MAS)测量来确定不同类型酸中心的存在。在约6.5ppm处的H-1核磁共振谱线是由水在Lewis酸中心上的吸附引起的。对于水化样品，Bronsted酸中心(桥接OH基团)的H-1核磁共振谱线向低场移动可以用水分子、桥接OH基团和氢离子之间的快速质子交换来定量解释。
On weakly rehydrated dealuminated zeolites and amorphous silica-aluminas the presence of different types of acidic centres can be ascertained by proton magic-angle spinning nuclear magnetic resonance (H-1 MAS NMR) measurements. A H-1 NMR line at ca. 6.5 ppm is caused by water adsorption on Lewis-acid sites. The shift of the H-1 NMR line of Bronsted-acid sites (bridging OH groups) to lower field for hydrated samples can be interpreted quantitatively by a fast proton exchange between water molecules, bridging OH groups and hydroxonium ions.