Industrial & Engineering Chemistry Research, Vol.47, No.23, 9544-9551, 2008
Recovery of Petroleum Ether from Solanesol Extracting Solution through Vacuum Hydrophilic Membrane Distillation
The objective of this work is to study the feasibility of vacuum membrane distillation (VMD) by hydrophilic membranes to recover petroleum ether from the extracting solution of solanesol. Being different from the traditional membrane distillation (MD) process, hydrophilic membranes were used to avoid the membrane wetting for the nonaqueous solutions. The VMD performances of polyvinylidene fluoride (PVDF) membrane and two kinds of polyacrylonitrile (PAN) membranes with different structures were compared in the process of recovering petroleum ether. The results showed that good solvent flux (> 15 kg/m(2) h) and solanesol rejection (> 98%) for the PAN membranes were obtained, indicating that PAN membranes had considerable potential use in this area, while the PVDF membrane was not appropriate for the nonaqueous solution system because of membrane wetting. The effects of operation conditions on VMD performances of the two PAN membranes were investigated, and it was found that high-feed temperatures, low-downstream pressures enhanced the permeate flux for both membranes, and the flux of PAN1 membrane decreased more obviously than that of PAN2 membrane under high-feed concentration because of its larger pore size. General models including Knudsen and viscous flows were proposed, and a good agreement between the experimental and the theoretical fluxes was obtained. Additionally, temperature and concentration polarizations were proved to have an obvious influence on mass transport of PAN1 membrane. It was advisable to work at the downstream pressure of 20 kPa, the feed temperature of 30 degrees C, and the feed flow rate of 27.5 mL/s to obtain favorable results for PAN2 membrane.