Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology , 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Republic of Korea.
Environ Sci Technol. 2014 Jun 17;48(12):6597-603. doi: 10.1021/es405099z. Epub 2014 May 29.
In this study, we examined various CO2 hydrate phase equilibria under diverse, heterogeneous conditions, to provide basic knowledge for successful ocean CO2 sequestration in offshore marine sediments. We investigated the effect of geochemical factors on CO2 hydrate phase equilibrium. The three-phase (liquid-hydrate-vapor) equilibrium of CO2 hydrate in the presence of (i) organic matter (glycine, glucose, and urea), (ii) phyllosilicates [illite, kaolinite, and Na-montmorillonite (Na-MMT)], and (iii) mixtures of them was measured in the ranges of 274.5-277.0 K and 14-22 bar. Organic matter inhibited the phase equilibrium of CO2 hydrate by association with water molecules. The inhibition effect decreased in the order: urea < glycine < glucose. Illite and kaolinite (unexpandable clays) barely affected the CO2 hydrate phase equilibrium, while Na-MMT (expandable clay) affected the phase equilibrium because of its interlayer cations. The CO2 hydrate equilibrium conditions, in the illite and kaolinite suspensions with organic matter, were very similar to those in the aqueous organic matter solutions. However, the equilibrium condition in the Na-MMT suspension with organic matter changed because of reduction of its inhibition effect by intercalated organic matter associated with cations in the Na-MMT interlayer.
在这项研究中，我们研究了各种不同的、非均相条件下的二氧化碳水合物相平衡，为海洋中在近海海底沉积物中成功封存二氧化碳提供了基础知识。我们研究了地球化学因素对二氧化碳水合物相平衡的影响。在（i）有机物（甘氨酸、葡萄糖和尿素）、（ii）层状硅酸盐[伊利石、高岭石和钠蒙脱石（Na-MMT）]和（iii）它们的混合物存在的情况下，测量了二氧化碳水合物在 274.5-277.0 K 和 14-22 bar 范围内的三相（液相-水合物-气相）平衡。有机物通过与水分子结合抑制二氧化碳水合物的相平衡。抑制效果按以下顺序降低：尿素 < 甘氨酸 < 葡萄糖。伊利石和高岭石（不可膨胀的粘土）几乎不影响二氧化碳水合物相平衡，而 Na-MMT（可膨胀的粘土）由于其层间阳离子而影响相平衡。在含有有机物的伊利石和高岭石悬浮液中，二氧化碳水合物的平衡条件与含有有机物的水溶液非常相似。然而，由于与 Na-MMT 层间阳离子结合的插入有机物降低了其抑制作用，因此在含有有机物的 Na-MMT 悬浮液中的平衡条件发生了变化。
