The equilibrium conditions, hydrate formation and dissociation rate and storage capacity of ethylene hydrate in presence of 1,4-dioxane

The effect of 1,4-dioxane on ethylene hydrate was investigated at three additive molar concentrations of 2.78%, 5.56% and 8.34%. The equilibrium conditions for hydrate dissociation were obtained by step heating method. The results showed that addition of 1,4-dioxane concentration increases the pressure of hydrate dissociation. Diagram of Ln(Peq) vs. Teq demonstrated that system of 1,4-dioxane + ethylene + water form ethylene hydrate with structure I. In fact 1,4-dioxane cannot participate in hydrate structure because ethylene molecules are not a good help gas for occupation of S-cages in structure II. So, in this condition only ethylene hydrate with structure I could be formed. The experimental results on hydrate formation indicted that 1,4-dioxane accelerates the hydrate growth rate by increasing the solubility of ethylene in water and a maximum storage capacity of (VSTP/VH) = 146 is obtained in a critical dioxane concentration of 5.56% by mole. Also hydrate dissociation experiments revealed that maximum dissociation percentage is related to pure water (48%) and 1,4-dioxane decreases dissociation percentage of ethylene hydrate.

► The equilibrium data of hydrate formation for ethylene + 1,4-dioxane have been obtained.
► 1,4-Dioxane enhances the storage capacity of ethylene hydrate remarkably.
► The addition of 1,4-Dioxane results in an increase in the hydrate formation pressure.
► 1,4-Dioxane accelerates the hydrate growth rate.
► 1,4-Dioxane decreases dissociation percentage of ethylene hydrate.