In Situ 13C and 23Na Magic Angle Spinning NMR Investigation of Supercritical CO2 Incorporation in Smectite–Natural Organic Matter Composites

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• 作者：Geoffrey M. Bowers ; David W. Hoyt ; Sarah D. Burton ; Brennan O. Ferguson ; Tamas Varga ; R. James Kirkpatrick
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：February 20, 2014
• 年：2014
• 卷：118
• 期：7
• 页码：3564-3573
• 全文大小：283K
• ISSN：1932-7455

文摘

This Article presents an in situ NMR study of clay鈥搉atural organic polymer systems (a hectorite鈥揾umic acid [HA] composite) under CO₂ storage reservoir conditions (90 bar CO₂ pressure, 50 掳C). The ¹³C and ²³Na NMR data show that supercritical CO₂ interacts more strongly with the composite than with the base clay and does not react to form other C-containing species over several days at elevated CO₂. With and without organic matter, the data suggest that CO₂ enters the interlayer space of Na鈥揾ectorite equilibrated at 43% relative humidity. The presence of supercritical CO₂ also leads to increased ²³Na signal intensity, reduced line width at half height, increased basal width, more rapid ²³Na T₁ relaxation rates, and a shift to more positive resonance frequencies. Larger changes are observed for the hectorite鈥揌A composite than for the base clay. In light of recently reported MD simulations of other polymer鈥揘a鈥搒mectite composites, we interpret the observed changes to be due to an increase in the rate of Na⁺ site hopping in the presence of supercritical CO₂, the presence of potential new Na⁺ sorption sites when the humic acid is present, and perhaps an accompanying increase in the number of Na⁺ ions actively involved in site hopping. The results suggest that the presence of organic material either in clay interlayers or on external particle surfaces can significantly affect the behavior of supercritical CO₂ and the mobility of metal ions in clay-rich reservoir rocks.