Preparation And Pervaporation Of Methanol/methyl Acetate Mixture Through Zeolite -incorporated Pva/pvp Membrane

Pervaporation is a highly selective, simple and new energy-saving membrane separation tech- nology. Pervaporation can be used to separate azeotropes, close-boiling mixtures and thermally sensitive compounds which are difficult to separate by distillation and extraction. Poly(vinyl alcoh- ol) (PVA)/Poly(vinyl pyrrolidone) (PVP) blend membranes crosslinked with 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt were prepared and used to separate methanol/methyl acetate mi- xtures by pervaporation. The effects of DAS content, blending composition, operating temperature and feed composition were investigated. Based on the PVA/ PVP blend membrane , zeolite 4A–incorporated poly(vinyl alcohol)/poly(vinyl pyrrol-idone) hybrid membran e was prepared. The effects of zeolite content, operating temperature and f-eed composition were studied.The content of crosslinking agent had great influence on the blend membrane pervapo-ration. When the content was low, the PVP crosslinking degree was low and the separationfactor was low; When the DAS content was high, the separation performance of blend me-mbrane became bad too. When DAS/PVP ratio was 1∶3,PVP was crosslinked well and the membrane had good separation factor.The effects of blending composition was studied. With increasing the PVP content in the membrane, permeation flux increased, separation f-actor increased and then decreased. Membrane containing 30% PVP exhibited good perfor-mance and gave the highest separation factor 17.7,when the operating temperaturewas 35℃and 20wt% methanol in feed. In the DAS crosslinking PVA/PVP blend membrane separati-ng methanol/methyl acetate mixture experiments, with increasing operating temperature, the permeation flux increased, the separation factor decreased; With increasing methanol conce-ntration in feed, the permeation flux increased and the separation factor decreased. The eff-ects of zeolite 4A content on the pervaporation performance of PVA/PVP/4A hybrid membrane separating methanol/methyl acetate mixture was studied. With increasing the content of zeolite 4A in the hybrid membrane , permeation flux increased and separation factor incr-eased and then decreased. Membrane containing 2.5wt% 4A exhibited good performance a-nd gave the highest separation factor 34.4. In the experiment of PVA/PVP/4A hybrid mem-brane pervaporating methanol/methyl acetate mixture, with increasing operating temperature and methanol concentration in feed, the permeation flux increased and the separation factordecreased. The results of pervaporation indicated that blend membrane and hybrid membra-ne all can brake the azeotropic balance of methanol/methyl acetate, and separate methanol/methyl acetate mixture effectively.