Influence of Sodium Halides on the Kinetics of CO sub(2) Hydrate Formation

The mechanism of gas hydrate formation in the presence of kinetic influencing additives has attracted much interest due to the importance of optimizing hydrate formation in areas such as energy supply and the environment. This paper presents experimental studies into hydrate formation of CO sub(2) gas in the presence of sodium halide salts. Pressure and temperature changes versus time during the hydrate formation process were measured under the isochoric conditions. The effect of anion type and concentration on gas maximum uptake, conversion, storage capacity, induction time, and hydrate growth rate has been examined. Surface potential measurements of the hydrates provided further understanding of how halide anions affect CO sub(2) hydrate formation kinetics. It is shown that sodium halides at an approximately 50 mM (mmol/L) concentration can increase gas consumption and conversion to hydrates, and sodium iodide and sodium bromide in a range of concentrations between 50 and 250 mM can significantly increase the hydrate formation kinetics. It has been concluded that, although salts are known as thermodynamic inhibitors, they can be kinetic promoters at low concentration, which enhances hydrate formation. It is argued that halide ions can significantly influence CO sub(2) hydrate formation due to their strong effect on bulk and surface water structures.