Hydrate equilibrium of carbon dioxide in aqueous solutions of 1,4-cyclohexanedione as a thermodynamic inhibitor

In oil and gas transportation pipelines, hydrate formation brings serious pipeline blockage risk. Injecting thermodynamic hydrate inhibitors will prohibit hydrate formation. The effect of 1,4-cyclohexanedione as a thermodynamic inhibitor on hydrate equilibrium conditions of CO₂ was studied using isochoric stepwise heating method. The experimental results show that 1,4-cyclohexanedione can inhibit hydrate formation of CO₂. Aqueous solutions with 1,4-cyclohexanedione effectively moves the equilibrium boundary to the direction of lower temperatures and higher pressures. The testing data also show that CO₂ hydrate equilibrium pressures increased more when the concentration of 1,4-cyclohexanedione increased. The temperature shift reaches 2.05 K at 2.57 MPa by adding 15 wt % CHD. The inhibitory effect of CHD on carbon dioxide hydrate formation is similar to that of n-ethyl-n-methylmorpholinium bromide and tetramethyl ammonium chloride.