One-pot synthesis of inorganic-organic hybrid ionogel membrane for propylene/propane separation via olefin-facilitated transport

Abstract

Silver-assisted facilitated transport membranes have gained increasing interest for propylene/propane separation. Herein we used a one-pot synthesis sol-gel method to prepare novel organic/inorganic hybrid ionogels with high ionic liquid (IL) loading without leakage, which was constructed from [3-(2,3-Epoxypropoxy)propyl]-trimethoxysilane, [C4mim] [BF4] IL, AgBF4, and catalysts. The ionogels can incorporate up to 73 wt% of IL loading in a self-standing membrane with desirable properties. The ionogels were characterized with respect to their reactive formulation, formation mechanism and chemical structure, morphology, pore features, mechanical properties, and transport properties. Besides, molecular dynamics (MD) simulation and density functional theory (DFT) calculation were employed to investigate the interactions among gas species, IL electrolyte, and silicon scaffold. Results indicate that the presence of epoxy and silanol groups on the solid framework could enhance the ionic dissociation of silver salt and IL, providing more free silver ions to form a complex via propylene molecules. Upon the addition of AgBF4 up to 1 M, the propylene permeability and propylene/propane selectivity were remarkably increased to 208.7 Barrer and 67.09, amounting to 7.8 and 15.3 times enhancement, respectively, compared to the membrane without silver salt. Accordingly, the prepared ionogels can surpass Robeson’s upper limit and possess a promising potential for propylene/propane separation.