Experimental measurement and thermodynamic modeling of cyclopentane hydrates with NaCl, KCl, CaCl₂, or NaCl‐KCl present

Abstract

Consistent phase equilibrium data for cyclopentane hydrates in presence of salts are vitally important to many industries, with particular interest to the field of hydrate-based water separation via cyclopentane hydrate crystallization such as desalination. However, there are very little experimental equilibrium data, and no thermodynamic prediction tools. Hence, we set up a method to generate a great deal of much needed equilibrium data for cyclopentane hydrates in diverse saline solutions with a wide range of salt concentrations. Our method does furnish verified, reliable and accurate equilibrium data. Plus, three thermodynamic approaches are developed to predict equilibrium, and provide tools for simulations, by considering the kind of salt and concentrations. All three models are in very good accordance with experimental data. One method, using a new correlation between occupancy factor and water activity, might be the best way to obtain consistent, quick, and accurate dissociation temperatures of cyclopentane hydrate in brine.a Dh b2L w j T 0 ;P 0 5 Dl b2I w j T 0 ;P 0 -6011, where 6011 is the enthalpy of ice (J mol 21 ).

Implementing Cyclopentane Hydrates Phase Equilibrium Data and Simulations in Brine Solutions

“…We believe that quick dissociation procedure likely misses the total dissociation temperature, i.e. the equilibrium temperature, as stated by Ho-Van et al 26 .…”

“…This can be attributed to the lower water activity and molality in presence of Na 2 SO 4 compared to others salt at same concentrations (in % mass) (see Appendix, Table A1). Relative uncertainty due to ion chromatography: 1.5% (see the supporting information from Ho-Van et al 26 for all uncertainty estimations). Indeed, as seen in Table A1 (in Appendix I), MgCl 2 -NaCl and MgCl 2 -NaCl-KCl mixtures have approximately the same molality at the same salt concentration (in % mass).…”

“…To determine the CPH dissociation temperatures, two procedures (quick and slow) are used as described in more detail in a previous article. 26…”

“…Images of the aqueous mixture are taken at every step. These images are then compared in order to determine the final step in which only two transparent phases of brine solution and CP can be observed as seen in the initial condition (pictures provided in the previous study 26 ).…”

“…Moreover, three thermodynamic methods were applied to simulate them. 26 Nonetheless, more phase equilibrium data in other salts are still required, and thermodynamic approaches still need to be compared to a wider range of experimental data.…”