Aksnes D W, Kimtys L
Department of Chemistry, University of Bergen, Allegaten 41, Bergen N-5007, Norway.
Solid State Nucl Magn Reson. 2004 Jan;25(1-3):146-52. doi: 10.1016/j.ssnmr.2003.03.001.
The pore size distributions of four controlled pore glasses and three silica gels with nominal diameters in the range 4-24 nm were determined by measuring the 1H and 2H NMR signals from the non-frozen fraction of confined benzene and perdeuterated benzene as a function of temperature, in steps of ca. 0.1-1 K. The liquid and solid components of the adsorbate were distinguished, on the basis of the spin-spin relaxation time T2, by employing a spin-echo sequence. The experimental intensity curves of the liquid component are well represented by a sum of two error functions. The mean melting point depression of benzene and perdeuterated benzene confined in the four controlled pore glasses, with pore radius R, follows the simplified Gibbs-Thompson equation DeltaT=kp/R with a kp value of 44 K nm. As expected, the kp value mainly determines the position of the pore size distribution curve, i.e., the mean pore radius, while the transition width determines the shape of the pore size distribution curve. The excellent agreement between the results from the 1H and 2H measurements shows that the effect of the background absorption from protons in physisorbed water and silanol groups is negligible under the experimental conditions used. The overall pore size distributions determined by NMR are in reasonable agreement with the results specified by the manufacturer, or measured by us using the N2 sorption technique. The NMR method, which is complementary to the conventional gas sorption method, is particularly appropriate for studying pore sizes in the mesoporous range.
通过测量受限苯和全氘代苯的非冻结部分的¹H和²H NMR信号随温度的变化（步长约为0.1 - 1 K），测定了四种标称直径在4 - 24 nm范围内的可控孔径玻璃和三种硅胶的孔径分布。基于自旋 - 自旋弛豫时间T2，采用自旋回波序列区分吸附质的液体和固体成分。液体成分的实验强度曲线可以很好地用两个误差函数的和来表示。在四种孔径半径为R的可控孔径玻璃中受限的苯和全氘代苯的平均熔点降低遵循简化的吉布斯 - 汤姆逊方程ΔT = kp/R，kp值为44 K nm。正如预期的那样，kp值主要决定孔径分布曲线的位置，即平均孔径，而转变宽度决定孔径分布曲线的形状。¹H和²H测量结果之间的出色一致性表明，在所使用的实验条件下，物理吸附水和硅醇基团中质子的背景吸收影响可忽略不计。通过NMR测定的总体孔径分布与制造商指定的结果或我们使用N2吸附技术测量的结果合理一致。NMR方法是对传统气体吸附方法的补充，特别适用于研究介孔范围内的孔径。
