Molecular insight into carbon dioxide hydrate formation from saline solution

Abstract

Carbon dioxide hydrate has been intensively investigated in recent years because of its potential use as gas and heat storage materials. To understand the hydrate formation mechanisms, the crystallization of CO₂ hydrate from NaCl solutions was simulated at a molecular level. The influence of temperature, pressure, salt concentration and CO₂ concentration on CO₂ hydrate formation was evaluated. Results showed that the amount of the newly formed hydrate cages pressure went through a fast linear growth period followed by a relatively stable period. Pressure had little effect on CO₂ hydrate formation and temperature had a significant influence. The linear growth rate was greatly reduced as the temperature dropped from 255 to 235 K. The salt ion pairs could inhibit CO₂ hydrate formation, suggesting that we should choose the lower salinity areas if we want to storage CO₂ as gas hydrates in the seabed sediments. The observations in this study can provide theoretical support for the micro mechanism of hydrate formation, and provide a theoretical reference for the technology of hydrate based CO₂ storage.