Separation of ethane from natural gas using porous ZIF-8/water-glycol slurry

The high efficiency separation of ethane from natural gas becomes significant due to the occurrence of revolution in shale gas. Herein a new approach of continuous sorption separation was developed using a flowable zeolitic imidazolate framework-8 (ZIF-8) slurry. First, the sorption isotherms of CH4 and C2H6 in the ZIF-8 slurry were measured at 273.15-293.15 K, and the corresponding desorption heats are 13 and 20 kJ/mol, respectively. In comparison with the light oil absorption, higher ethane solubility in the slurry was observed. Next, the influences of temperature, equilibrium pressure, initial gas-slurry volume ratio, and feed gas composition on separation performance were studied by systematically measuring gas-slurry equilibria for CH4 + C2H6 mixtures. The pseudo P-T-x-y phase diagram shows that a minimum stage number of 6 was required for a thorough separation. Finally, the Langmuir equation was modified to fit gas slurry equilibrium data by introducing cross interaction parameters. Both the experimental data and model are significant for the following design of the separation process using the ZIF-8 slurry.