期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 20, 期 40, 页码 13009-13015出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201403139
关键词
catalysis; mesaporous; materials; NMR spectroscopy; porous media; relaxation I 5; surfaces and interfaces
资金
- CASTech (EPSRC grant) [EP/G011397/1]
- Technology Strategy Board [TP/7/ZEE/6/I/N0262B]
- Wolfson College, Cambridge
- Engineering and Physical Sciences Research Council [EP/G011397/1] Funding Source: researchfish
- EPSRC [EP/G011397/1] Funding Source: UKRI
Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate adsorbent interactions in liquid-saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T1IT2) is related to an adsorbate adsorbent interaction energy, and we introduce a quantitative metric esurf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO2 anatase, TiO2 rutile, 7-Al2O3, SiO2, 0-Al2O(3) and ZrO2) and show that esurf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the esurf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T11T2 measurements may become a useful addition to the methods available to characterise liquid-phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate surface interactions in liquidphase catalysis.
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