The experimental and theory research on the sorption kinetic of CH4 and C2H4 in ZIF-8/water-glycol slurry

The zeolitic imidazolate framework (ZIF)-8/water-glycol slurry shows great potential in separating low carbon hydrocarbons. In the present study, the physical properties of the ZIF-8/water-glycol slurry were determined, and the hydrophobicity and glycophilicity of the ZIF-8 material were demonstrated by measuring the contact angle between liquid droplets with a ZIF-8 material, for the first time. It was observed that the increase in pressure could weaken the hydrophobicity of ZIF-8. In addition, the sorption kinetics of CH4 and C2H4 in the slurry were investigated. It was noted that the relatively high temperature and pressure could increase the dissolution rates of CH4 and C2H4 in the slurry. A kinetic model for describing the dissolution of CH4 and C2H4 in the slurry was proposed, wherein the diffusion of gas molecules in the glycol membrane around ZIF-8 particles and those in the inner pores of ZIF-8 were concurrently considered for the first time. The simulation results correlated with the experimental data. Finally, multistage simulation separation experiments for CH4/C2H4 gas mixtures using the slurry were performed. It was observed that after a four-stage simulation separation operation, the concentration of C2H4 decreased from 49.72 mol% in the feed gas to 4.68 mol%. The experimental and modeling results will be helpful for the practical separation application of the ZIF-8 slurry system.