Study the effect of Ag nanoparticles on the kinetics of CO2 hydrate growth by molecular dynamics simulation

M. H. Mahmoodi, M. Manteghian, P. Naeiji, Journal of Molecular Liquids, 343, 117668 (2021). (DOI: 10.1016/j.molliq.2021.117668)

This paper aims to study the effect of silver nanoparticles on the kinetics of CO2 hydrate growth at dif- ferent P-T conditions using the molecular dynamics (MD) technique.Three nanofluid models containing 2, 4 and 6 nanoparticles (NPs) as well as a base model (without NPs) were designed to study the effect of nanoparticle concentration on the gas hydrate system. The profiles of potential energy (PE), mean squared displacement (MSD) and density along the simulation box, and the number of CO2 molecules at the hydrate-liquid interfaces, diffusion coefficient, three-body structural order (F3) and also radial dis- tribution function (RDF) were calculated from the simulation. The results revealed that the rate of hydrate growth increases as the temperature increases from 250 K to 260 K at a constant pressure of 30 MPa. A similar trend was also achieved for decreasing the pressure from 30 MPa to 15 MPa at constant temperature of 250 K, however, increasing the temperature to 270 K at 30 MPa decreased again the growth rate.Among the simulation models, the 2-NP fluid model at 260 K and 30 MPa was found to have the highest hydrate growth rate. It was found that nanoparticles have several impacts on the CO2 hydrate system as follows: they could lower the potential energy of the system, increase the peak’s height of the carbon–oxygen and carbon–carbon RDFs, facilitate CO2 dissolution, enhance the diffusion coefficient, and improve the migration of CO2 molecules from the bulk of the solution to the interfaces, and also could physically block the CO2 migration at high concentrations. Finally, form the RDF calculations, the results of our simulation are in good agreement with those reported in the literature with an average error of less than 10%.

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