Experimental study on carbon dioxide hydrate formation in the presence of static magnetic field

•Magnetic field promotes CO2 hydrate formation in water or NaCl solution.•Magnetic field enhances the phase equilibrium temperature of CO2 hydrate.•Magnetic field affects the dissociation enthalpy of CO2 hydrate. The formation kinetic parameters, phase equilibrium and dissociation enthalpy of carbon dioxide hydrate in the presence of static magnetic field were investigated in this work. The experiments were carried out in pure water and (0.029, 0.056 and 0.110, mass fraction) sodium chloride (NaCl) aqueous solution with a magnetic field of 0.39 T. The experimental results showed that the induction time of carbon dioxide hydrate nucleation was shortened, the consumption amount and rate of carbon dioxide were significantly increased with the magnetic field. This phenomenon is mainly attributed to the fact that the magnetic effect decreases the contact angle between water and solid surface to reduce the critical size and critical free energy of hydrate nucleation. Moreover, the phase equilibrium of carbon dioxide hydrate in both pure water and NaCl aqueous solution shifted to lower pressure or higher temperature with the magnetic field, and the equilibrium temperature in pure water decreased by 3.0 K, which is due to the change of the hydrogen bond in small clusters and ions mobility by magnetic effect. In addition, the dissociation enthalpies of carbon dioxide hydrate in pure water and (0.029, 0.056 and 0.110) NaCl solution calculated by Clausius-Clapeyron equation were 91.5, 91.4, 62.8 and 52.0 kJ·mol−1, respectively, in the magnetic field, which is related to the movements of ions caused by magnetic effect and heat absorption.