Phase behaviour of gas hydrates of carbon dioxide in the presence of tetrahydropyran, cyclobutanone, cyclohexane and methylcyclohexane

This paper presents experimental data on gas hydrate phase behaviour of ter nary systems containing water + carbon dioxide + additive. The four additiv es studied are tetrahydropyran, cyclobutanone, cyclohexane and methylcycloh exane. Since all organic additives are very poorly soluble in water, they w ill be referred to as insoluble. Compared to the additive-free binary carbo n dioxide system, reduction of the gas hydrate equilibrium pressure was obs erved in all systems. The pressure reducing effect of the additives on the hydrate equilibrium was similar for ternary systems with water + methane additive and water + carbon dioxide + additive. However, the phase behaviou r of the latter type of systems is more complex, due to the occurrence of a liquid carbon dioxide phase. Quintuple points (H-L-w-L-a-L-hc-V) are repor ted for these systems. In the presence of tetrahydropyran, cyclobutanone an d cyclohexane sII hydrates are assumed to be formed, while the hydrate phas e with methylcyclohexane may be either sI or sH hydrate. (C) 2001 Elsevier Science B.V. All rights reserved.