Polyurethane-Silica Nanocomposite Membranes for Separation of Propane/Methane and Ethane/Methane

Abstract

This study examines the role that silica nanoparticles play on the permeation of methane, ethane, and propane gases through two types of polyurethane (PU) membranes: one based on polyether and the other based on polyester. These PU membranes are synthesized from polycaprolactone (PCL225) polyester and polypropylene glycol (PPG) polyether in a 1–3–2 mol ratio of polyol/hexamethylenediisocyanate/1,4-butane diol. The prepared PU-silica membranes are characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and wide-angle X-ray diffraction (WAXD) analyses. The characterization analyses confirmed the nanoscale distribution of silica particles within the polymer matrix. Permeation experiments reveal that in polyether-based PU, permeability first increases by increasing silica content up to 2.5%, and then decreases. The permeability of gases in polyester-based PU constantly decreases by increasing silica nanoparticle loading. The selectivity for C3H8 over methane increases with the inclusion of silica particles in the polyether-based PU membranes, while it decreases in polyester-based PU membranes. Our results indicate high propane permeability and propane/methane selectivity of polyether-based mixed matrix membranes (MMMs) containing 12.5% silica at 2 bar pressure up to, 118 barrer and 7.01, respectively.