(568f) Pervaporation of Methanol/ Dimethyl Carbonate Using Porous Ceramic Membranes

Dimethyl carbonate (DMC), which is an environmentally friendly chemical, is expected to be used for practical application such as precursor for polycarbonate resins and electrolyte of lithium-ion cell. Separation of MeOH/ DMC mixtures is important because DMC production process includes separation from methanol (MeOH) in many cases. However, separation of these mixtures is not easy due to its azeotropic system. Pervaporation has been expected for a separation of azeotropic or close boiling point mixtures [1].

In this work, several types of silica membranes such as pure SiO2, steam-treated SiO2, SiO2-ZrO2, and SiO2-TiO2, were prepared on porous alumina supports by sol-gel processing [2], and applied for pervaporation separation of MeOH/ DMC mixtures at 50C. Pore size distribution of microporous membranes was estimated by Nanopermporometry [3] by using water as a condensable vapor, showing a successful tuning of average pore sizes in the range of 0.4-1.0 nm. In order to characterize the surface property of SiO2 membranes, some powdered samples, prepared from the colloidal sols by firing at specific temperatures, were used for adsorption experiment of vapor (MeOH, DMC) in single and mixtures, revealing increased MeOH selective adsorption by increasing hydrophilicity and reducing pore sizes..

Although SiO2-ZrO2 membranes having controlled average pore sizes from 0.6 to 1.2 showed separation factors less than 10, SiO2 porous membrane were found to show increased separation factor raging from 10-200. Silica membranes having an average pore size of 0.4 nm showed the highest permselectivity of methanol with separation factor of 150 and methanol flux of 160 mol/(m2h) for MeOH 50 mol% at 50 C. Steam-treatment was found to be effective to improve separation performance because of controlled pore size and surface properties.

Pervaporation performance will be discussed based on the surface properties obtained from the adsorption experiment. In addition, the effect of adsorption of MeOH and DMC in SiO2 membranes will be discussed based on the transient measurement of MeOH/ DMC mixtures using mass-spectroscopy (AMETEK).

[1] J. Yang, T. Yoshioka, T. Tsuru, M. Asaeda, Pervaporation characteristics of aqueous-organic solutions with microporous SiO2- ZrO2 membranes: Experimental study on separation mechanism, Journal of Membrane Science, 284 (2006) 205-213.

[2] T. Tsuru, Nano/subnano-tuning of porous ceramic membranes for molecular separation, Journal of Sol-Gel Science and Technology, 46(2008) 349-361

[3] T. Tsuru, T. Hino, T. Yoshioka, M. Asaeda, Permporometry Characterization of Microporous Ceramic Membranes, Journal of Membrane Science, 186 (2001) 257-265.