Preparation And Application Of Difunctional Hollow-Fiber Ceramic Membranes With Catalysis And Pervaporation Capabilities

The hollow fiber ceramic (α-Al2O3) membrane was selected as substrate and coated by coating solutions for surface modification. Then perfluorosulfonic acid (PFSA) was used as catalyst to prepare difunctional hollow fiber composite membranes with separating function and catalytic function by dip-coating methods. The difunctional hollow fiber composite membranes with remarkable separating and catalytic function were used in esterification reaction. Pervaporation was coupled with reactions to prepare methyl laurate for improving reaction conversion.Firstly, the hollow fiber ceramic ((α-Al2O3) membrane was coated by polyamide acid(PA)-N,N-dimethyl acetamide (DMAc) and PA-SiO2particles-DMAc coating solutions. Then thermal imidizated at300℃vacuum calcinations and carbonized at800℃were used for the modification of hollow fiber ceramic substrate membrane to prepare four kind of modified membranes (MPD、MPDS、MPDC、MPDSC). On the basis, these membranes were dip-coated with10wt.%PVA solution, and the membrane surface was crosslinked by6wt.%GA crosslinking agent for the fabrication of the hollow fiber ceramic pervaporation (PV) composite membrane, which were characterized by SEM and dehydration methanol-water solution through pervaporation. The results show that MPD membrane had good capabilities.Secondly, the MPD membrane was selected as substrate and coated by8wt.%,10wt.%,12wt.%PVA solution and the membrane surface was crosslinked by4wt.%、6wt.%GA crosslinking agent. The separation performance of the membranes prepared with different PVA solution and crosslinking agent were investigated through experiment at different temperature and different feed compositions. The experimental results showed that the PMD modification membrane with12wt.%PVA solution dip-coated on and6wt.%GA crosslinking agent surface-crosslinked had good capabilities, whose separation property was as follows:permeation flux15g(m2-h) and separation factor25at40℃and96wt.%methanol aqueous solution.Finally, perfluorosulfonic acid (PFSA) was used as catalyst to be coated on the hollow fiber composite membrane with remarkable separation property to prepare difunctional hollow fiber composite membranes. Pervaporation was coupled with esterification reaction of methanol and lauric acid and alcohol to prepare methyl laurate for improving reaction conversion. The effects of the different catalysts, acid alcohol ratio, temperature, catalyst dosage on reaction conversion were investigated to seek for the optimum reaction conditions. Under the condition of n (lauric acid):n (methanol)=1:10,70℃,1wt.%catalyst(weight percent of feed) and reaction time was8h, the reaction conversion was81.5%.