Department of Civil and Environmental Engineering , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon , 34141 , Korea.
Environ Sci Technol. 2018 Mar 6;52(5):3267-3274. doi: 10.1021/acs.est.7b05477. Epub 2018 Feb 13.
Natural gas hydrates are found widely in oceanic clay-rich sediments, where clay-water interactions have a profound effect on the formation behavior of gas hydrates. However, it remains unclear why and how natural gas hydrates are formed in clay-rich sediments in spite of factors that limit gas hydrate formation, such as small pore size and high salinity. Herein, we show that polarized water molecules on clay surfaces clearly promote gas hydrate nucleation kinetics. When water molecules were polarized with an electric field of 10 V/m, gas hydrate nucleation occurred significantly faster with an induction time reduced by 5.8 times. Further, the presence of strongly polarized water layers at the water-gas interface hindered gas uptake and thus hydrate formation, when the electric field was applied prior to gas dissolution. Our findings expand our understanding of the formation habits of naturally occurring gas hydrates in clay-rich sedimentary deposits and provide insights into gas production from natural hydrate deposits.
天然气水合物广泛存在于富含粘土的海洋沉积物中,粘土-水相互作用对天然气水合物的形成行为有深远影响。然而,尽管存在限制天然气水合物形成的因素,如小孔径和高盐度,为什么天然气水合物仍然在富含粘土的沉积物中形成,目前还不清楚。在此,我们表明粘土表面的极化水分子明显促进了天然气水合物成核动力学。当水分子在 10 V/m 的电场中被极化时,水合物的成核明显更快,诱导时间缩短了 5.8 倍。此外,当在气体溶解之前施加电场时,在气-水界面处存在强极化水层会阻碍气体吸收,从而阻碍水合物的形成。我们的发现扩展了我们对富含粘土沉积物中天然天然气水合物形成习惯的理解,并为从天然水合物沉积物中生产天然气提供了思路。