Preparation and characterization of PFSA–PVA–SiO2/PVA/PAN difunctional hollow fiber composite membranes

Perfluorosulfonic acid–poly(vinyl alcohol)–SiO2/poly(vinyl alcohol)/polyacrylonitrile (PFSA–PVA–SiO2/PVA/PAN) difunctional hollow fiber composite membranes (DHFCMs) with catalytic activity and selectivity have been prepared by dip-coating method. Both layers of DHFCMs were optimized independently. Firstly, separation-function hollow fiber composite membranes (SHFCMs) were prepared. The effects of different glutaraldehyde (GA) concentrations on SHFCMs and morphologies were investigated by FTIR and SEM. The separation performances of SHFCMs were measured by dehydrating the top product (water, ethanol and ethyl acetate ternary azeotropic system) of reactive distillation. Secondly, DHFCM was prepared by casting PFSA–PVA–SiO2 catalytic solution on the top layer of SHFCM-4 with the best separation performance. The effects of different PFSA and nano-SiO2 concentrations on DHFCMs, morphologies, element distribution, crystal structures and weight loss were investigated by FTIR, SEM, EDX, XRD and TGA. DHFCMs were evaluated by dehydrating the top product of reactive distillation and esterification reaction with acetic acid and ethanol. It was found that DHFCMs had better separation performances than single-separation-function HFCMs. DHFCMs with different PFSA and nano-SiO2 concentrations manifested similar catalytic activity. DHFCM-1 had flux of 162 g/(m2 h), separation factor of water to ethanol of 379, no ethyl acetate in the permeate. DHFCM made from DHCM-1 had the best separation performance and catalytic activity.