Enhanced H2 Uptake of n-Alkanes Confined in Mesoporous Materials
Enhanced H2 Uptake of n-Alkanes Confined in Mesoporous Materials
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DOI：
10.1021/jp411526f
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发表时间：
2014-05-22
影响因子：
3.7
通讯作者：
Coasne, B.
中科院分区：
文献类型：
--
作者：
Clauzier, S.;Ho, L. Ngoc;Coasne, B.
混合吸附剂的氢吸收组成的正烷烃溶剂限制在介孔二氧化硅气凝胶在不同的温度从273至313 K和压力高达40巴测量。由于混合吸附剂的吸氢量远大于本体溶剂中的吸氢量，因此观察到明显的"过溶解”效应。发现混合吸附剂中的H-2吸收随着温度的升高而增加，这表明限制在气凝胶中的正烷烃分子的柔性和构象起着至关重要的作用;高熵（无序）烷烃构型导致产生许多空腔，这使得可以溶解大量的H-2分子。这与吸附驱动的溶解度效应不同，其中溶解的分子的数量随着温度的升高而减少。对于一个给定的温度和压力，它被发现，每单位体积的增溶的H-2分子的数量增加，减少烷烃链的长度。这种效果，这是观察到的散装烷烃和烷烃限制在二氧化硅气凝胶中，可以合理化考虑的数密度的CHx（x = 2或3）基团;对于一个给定的温度，后者的数密度随着烷烃链长度的减少，使自由体积增加，可溶解H-2分子。
The hydrogen uptake in hybrid sorbents consisting of n-alkane solvents confined in mesoporous silica aerogel is measured at different temperatures from 273 to 313 K and pressures up to 40 bar. An apparent oversolubility" effect is observed as the H-2 uptake in the hybrid sorbents is much larger than that in bulk solvents. The H-2 uptake in the hybrid sorbents is found to increase with increasing temperature, which suggests that the flexibility and conformation of n-alkane molecules confined in the aerogel play a crucial role; high-entropy (disordered) alkane configurations lead to the creation of numerous cavities which make it possible to solubilize a larger number of H-2 molecules. This departs from adsorption-driven solubility effects for which the number of solubilized molecules decreases with increasing temperature. For a given temperature and pressure, it is found that the number of solubilized H-2 molecules per unit volume increases with decreasing alkane chain length. Such an effect, which is observed for both the bulk alkanes and the alkanes confined in the silica aerogel, can be rationalized by considering the number density of CHx (x = 2 or 3) groups; for a given temperature, the latter number density decreases with decreasing alkane chain length so that the free volume available to solubilize H-2 molecules increases.