Pervaporation of methanol/dimethyl carbonate using SiO₂ membranes with nano-tuned pore sizes and surface chemistry

Abstract

Porous silica membranes with different pore sizes (average pore size: 0.3–1.2 nm) and surface chemistry were prepared from SiO₂, steam-treated SiO₂, SiO₂ZrO₂, and SiO₂TiO₂ by sol-gel processing, and were applied to the pervaporation (PV) separation of methanol (MeOH) /dimethyl carbonate (DMC) mixtures at 50°C. Although SiO₂ZrO₂ membranes demonstrated a separation factor of <10, the SiO₂ porous membranes had an increased separation factor from 10–160. Silica membranes with an average pore size of 0.3 nm showed the highest permselectivity of methanol with a separation factor of 140 and a methanol flux of 180 mol/(m²h) for MeOH 50 mol% at 50°C. To characterize the surface property of SiO₂ membranes, SiO₂ powdered samples were used for an adsorption experiment of vapor (MeOH, DMC) in single and mixed systems, revealing increased MeOH selective adsorption for SiO₂ powders with hydrophilic and small pores, which was consistent with PV performance. © 2010 American Institute of Chemical Engineers AIChE J, 2011