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.