Separation of Methane/Ethylene Gas Mixtures Using Wet ZIF-8

The separation of methane/ethylene gas mixtures by the adsorption-hydration method was investigated by using a wet zeolitic imidazolate framework (ZIF) microporous material, ZIF-8. The influences of the initial gas-solid ratio (the volume ratio of gas mixture to ZIF-8) and water content of wet ZIF-8 on the separation performance were studied systematically at 274.15 K The experimental results show that gas-solid ratio of ca. 310 and water content of ca. 38.50 wt % are the suitable conditions for the separation of methane/ethylene mixture with wet ZIF-8 on the premise of hydrate formation. When water content of wet ZIF-8 is 38.50 wt % and the gas-solid ratio is 297, the mole fraction of ethylene in gas phase decreases from 30.91% to 14.44%, the selectivity coefficient reaches 5.57, and the adsorption quantity of ethylene reaches 3.37 mmol/g after one stage of the adsorption-hydration process. Compared with a single adsorption method or hydration method, methane/ethylene gas mixtures can be further separated with the synergistic effect of gas adsorption and hydrate formation. The morphology and crystal structure of ZIF-8 remains after a series of processes of saturation with water, adsorption-hydration, hydrate decomposition, and drying.