Molecular Simulation Study of Montmorillonite in Contact with Variably Wet Supercritical Carbon Dioxide
KAUST DepartmentComputational Transport Phenomena Lab
Physical Sciences and Engineering (PSE) Division
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AbstractWe perform grand canonical Monte Carlo simulations to study the detailed molecular mechanism of intercalation behavior of CO2 in Na-, Ca-, and Mg- montmorillonite exposed to variably hydrated supercritical CO2 at 323.15 K and 90 bar, The simulations indicate that the intercalation of CO2 strongly depends on the relative humidity (RH). The intercalation of CO2 in the dehydrated interlayer is inhibited, followed by the swelling of the interlayer region due to uptake of water and CO2 as the RH increases. In all of the hydrated clay samples, the amount of the intercalated CO2 generally decreases as a function of increasing RH, which is attributed mainly to the weakening of the interaction between CO2 and clay. At low RH values, Ca- and Mg- montmorillonite are relatively more efficient in capturing CO2. The amount of CO2 trapped in all clay samples shows similar values above RH of similar to 60%. Molecular dynamics simulations show that the diffusion coefficient of each species generally increases with increasing RH due to the associated expansion of the interlayer distance of the clay. For all the hydrated samples, the diffusion coefficients of CO2 and water in the interlayers are mostly comparable due to the fact that CO2 molecules are well solvated. The diffusion of CO2 in each hydration state is mostly independent of the type of cation in accordance with the fact that CO2 molecules hardly migrate into the first hydration shell of the interlayer cations.
CitationKadoura A, Narayanan Nair AK, Sun S (2017) Molecular Simulation Study of Montmorillonite in Contact with Variably Wet Supercritical Carbon Dioxide. The Journal of Physical Chemistry C 121: 6199–6208. Available: http://dx.doi.org/10.1021/acs.jpcc.7b01027.
SponsorsThe research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST), Kingdom of Saudi Arabia. A.K. and A.KN.N. gratefully acknowledge computational facilities and the MedeA environment provided at KAUST. A.K. also acknowledges Prof. Abbas Firoozabadi and Dr. Zhehui Jin at Yale, and IFP-EN and Laboratory of Chemical Physics, CNRS-Universite Paris Sud (MedeA) for helpful comments on their Monte Carlo simulation codes.
PublisherAmerican Chemical Society (ACS)