Deng F, Du Y, Ye C, Kong Y
Laboratory of Nuclear Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics, Chinese Academy of Sciences.
Solid State Nucl Magn Reson. 1993 Dec;2(6):317-24. doi: 10.1016/0926-2040(83)90003-6.
The adsorption of Na+ on gamma-alumina surfaces at four coverages of Na2CO3[5, 10, 15 and 20% w/w)] was characterized by solid-state 23Na and 27Al nuclear magnetic resonance (NMR) spectroscopy. The experimental results suggest that two distinct adsorbed species are present on the alumina surface: surface species and surface salts. At the lower coverages of Na2CO3 (5 and 10%), the surface species is predominant, in which the Na+ cations are associated with the oxygen atoms of gamma-alumina. Increasing the loading level to 15% results in the appearance of a second adsorbed species that is attributed to the surface salt, Na2CO3, deposited on the solid surface. Further adsorption of Na2CO3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. 1H-27Al Cross-polarization magic angle spinning (CP-MAS) experiments give the evidence that some Na+ cations in the form of surface species are coordinated with the Brönsted acid sites of gamma-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of an Na2CO3-Al2O3 catalyst.
通过固态23Na和27Al核磁共振（NMR）光谱对在四种碳酸钠覆盖度（5、10、15和20% w/w）下Na+在γ-氧化铝表面的吸附进行了表征。实验结果表明，氧化铝表面存在两种不同的吸附物种：表面物种和表面盐。在较低的碳酸钠覆盖度（5%和10%）下，表面物种占主导，其中Na+阳离子与γ-氧化铝的氧原子结合。将负载量增加到15%会导致第二种吸附物种的出现，这归因于沉积在固体表面的表面盐Na2CO3。进一步吸附Na2CO3会导致表面盐的量增加，而表面物种的量保持不变。1H-27Al交叉极化魔角旋转（CP-MAS）实验提供了证据，表明一些以表面物种形式存在的Na+阳离子与γ-氧化铝的布朗斯特酸位点配位。这可能是显著提高Na2CO3-Al2O3催化剂催化效率的主要驱动力。
