Study on the development of ZIF-8 membranes for gasoline vapor recovery

The recovery of gasoline vapor is still a major challenge in the petrochemical industry. In this study, a zeolitic imidazolate frameworks (ZIFs) membrane has been developed and first applied to gasoline vapor recovery. Zeolitic imidazole framework (ZIF-8) membranes were fabricated by a facile solvothermal seed growth method on ZrO₂ supports. X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis measurements were conducted to study the morphologies, structure, and physical and chemical properties of ZIF-8 membranes. The effects of trans-membrane pressure drop, operating temperature, feed concentration, and stage cut on the separation performances of ZIF-8 membranes were systematically investigated. At 293 K, the ZIF-8 membrane showed an optimum n-hexane (n-C₆H₁₄) permeance of 7.16 × 10^-8 mol/(m²·s·Pa) with the corresponding separation factor of 2.46 for the nitrogen/n-hexane model mixtures at a trans-membrane pressure drop of 0.05 MPa, a stage cut of 0.293, and a n-hexane volume fraction of 30%. Moreover, the separation factor for the multicomponent alkanes decreased with increasing the number of n-alkanes because of competitive adsorption of the n-alkanes in membrane pores. Experimental results indicated that the ZIF-8 membrane is a fairly promising candidate for the application in gasoline vapor recovery.