Separation of ethyl acetate (EA)/water by tubular silylated MCM-48 membranes grafted with different alkyl chains

The MCM-48 type materials and membranes had been successfully silylated with different alkyl chains (methyl, propyl and n-octyl). The silylated MCM-48 membranes prepared on supports with pore size of 1 μm had a good effect on separation of the ethyl acetate (EA)/water mixture. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR spectroscopy, pervaporation. These results showed that the silylated MCM-48 type materials could adsorb large amount of EA, about 145 mg/g for C8H17-MCM-48 at 7 kPa at the room temperature, which was ten times of the Si-MCM-48′. Besides this, the C8H17-MCM-48 membranes had EA/H2O separation factor of 251 at room temperature and 123 at 50 °C with the total flux 4.3 and 6.6 kg/(m2 h), respectively. The long-chain alkyl groups grafted in the membrane pore could enhance temperature tolerance of the membrane for separating EA/H2O. Under the same conditions, the CH3- and C3H7-MCM-48 membranes had lower separation factor and larger total flux. The phenomenon in the separation experiments was controlled by the solution-diffusion mechanism. EA molecules were firstly adsorbed in the silylated pores selectively and made up a compact hydrophobic membrane, which could prevent the penetration of the water, resulting in the high EA selectivity.