Modification And Growth Process Of Fluoridecontaining NaY Zeolite Membrane

The generation of defects would affect the performance of membrane.In addition,fluoride in the synthesis gel is beneficial to prepare a continuous,dense and pure phase zeolite membrane with few defects,but the formation process and mechanism of zeolite membrane layer is unclear,the repeatability and stability of zeolite membranes are poor.Therefore,acid post-treatment method is applied to improve PV performance of NaY zeolite membrane and formation process of NaY zeolite membrane in fluorine-containing synthesis gel is explored in this work.The main contents of the dissertation are as follow:（1）Modification of NaY zeolite membrane by acid post-treatment:Improving the separation performance of NaY zeolite membrane by acid post-treatment,p H value of HAc solution,treatment time and temperature are 3,0.5 h and 25℃.Compared with fresh NaY zeolites,N₂adsorption/desorption and ICP characterization results show that the BET surface area and pore volume of NaY zeolites decrease after acid treatment,while the Si/Al ratio of the zeolite by acid treatment is increased slightly.When the acid-treated zeolite membrane is applied in 10 wt.%Me OH/MMA（methyl methacrylate）mixture,the average flux and separation factor are increased by 71%and9%by acid post-treatment.（2）Growth process of NaY zeolite membrane in fluorine-containing systems:Investigating the formation processes of fluoride-free and fluoride-containing NaY zeolite membranes by the XRD,SEM and FT-IR characterization results.The irregular octahedral NaY zeolite crystals are dissolved into amorphous by the fluoride-containing precursor synthesis gel initially,small zeolite crystals gradually grow up and aggregate into octahedral crystals.When the synthesis time is 6.5 h,pure phase and dense NaY zeolites layer is covered on the support.The thickness and Si/Al ratio of membrane are ca.7μm and 1.93,respectively.Moreover,effects of support,fluorine source,materials manufacturer,aging time and crystallization time on the PV performances of NaY zeolite membranes are explored.（3）Pervaporation performance of NaY zeolite membrane:Because of the large pore size（0.74 nm）,the NaY zeolite membrane is applied to separate short chain alcohols from organic mixtures.In this study,the NaY zeolite membrane is applied to separate 10 wt.%Me OH/MMA,10 wt.%Me OH/DMC,10 wt.%Me OH/MA and 10wt.%Et OH/ETBE mixtures,exhibiting a good PV performance and reproducibility.When the separation system and temperature were 10 wt.%Me OH/MMA and 50°C,the flux and the separation factor could reach to 1.34 kg·m^-2·h^-1 and 5900,respectively.