Co(HCOO)2-based hybrid membranes for the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures

In this work, Co(II)-formate (Co(HCOO)2) has been demonstrated feasible to be used as stable aromatic hydrocarbon transport carrier for facilitating aromatic hydrocarbon transport membranes. Metal-organic framework Co(HCOO)2 materials with different particle sizes were prepared through a solvothermal synthetic method, and then were doped into poly(ether-block-amide) (PEBA). The resulting hybrids were finally deposited on the outer surface of tubular ceramic substrate with a dynamic pressure-driven assembly method. The morphologies and structures of the resulting Co(HCOO)2/PEBA membranes were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDX), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), positron annihilation lifetime spectroscopy (PALS), and nanoindentation. These membranes were then used in separating aromatic/aliphatic hydrocarbon mixtures through pervaporation. When the feed solution is 10 wt% toluene/n-heptane mixtures, the permeate flux of the membrane is 771 g/(m2 h) with a separation factor of 5.1. Meanwhile, due to the immobilization effect of the Co(HCOO)2 for Co(II) ions, the Co(HCOO)2/PEBA membrane showed stable separation performances.