NEWLY DEVELOPED CERAMIC MEMBRANES FOR DEHYDRATION AND SEPARATION OF ORGANIC MIXTURES BY PERVAPORATION

摘要

Polymeric pervaporation membranes sometimes show great variety in performance when they are alternately used for different solvent mixtures, In addition, membrane stability in time is a problem in case of some solvents. Therefore, newly developed ceramic silica membranes with a ''dense'' top layer were tested for pervaporation. In dehydration of the lower alcohols methanol, ethanol and 2-propanol selectivities of 400, 200 and 600, respectively, were found at water concentrations of about 2 w/w% in the feed. Fluxes were 50, 150 and 160 g/m(2)/h, respectively. At higher water concentrations in the feed selectivities decreased and fluxes increased. Especially methanol selectivity decreased drastically at water concentrations above 5 w/w%. Fluxes increased significantly with water concentrations above 5 w/w% in the 2-propanol/water case. The overall performances were comparable with those found with commercially available polymeric membranes. The performance of the ceramic membrane did not decrease noticeably during an experimental period of three months, although a wide range of alcohols were tested with changing water concentrations. Also periodic changes to the system methanol/MTBE did not decrease the performance for dehydration, Methanol could be recovered from MTBE with selectivities of about 19 and fluxes of 41 g/m(2)/h with 9 w/w% methanol in the feed. Activated diffusive transport through micropores is the suggested separation mechanism for this membrane. [References: 7]