Synthesis Of NaY Zeolite Membrane By Epitaxial Growth Using EMT As Seed And Study On Pervaporation

NaY zeolite membrane has advantages in separating macromolecularmaterial due to special three-dimensional12-membered ring pore openings (0.74nm), high aluminum content of framework and highly dispersed Na+around thecage make NaY zeolite membrane has certain hydrophilicity and polarity, so ithas good separation selectivity for the hydrophilic and strong polar molecules.DMC is prepared using MeOH as raw material, azeotropic mixtures of DMCand MeOH will form during the process, which are difficult to separate. In theesterification reaction of preparing DPC, the equilibrium conversion is low dueto limitation of thermodynamic equilibrium, otherwise DMC and MeOH canform azeotropic mixtures which are difficult to separate, so seperating MeOHimmediately from the process can improve conversion effectively. The kineticdiameter of MeOH is0.38nm, DMC has the similar molecular structures asketone and ether groups with acetone (0.47nm) and methy-tert-butyl-ether (0.63nm), so the kinetic diameter of DMC is close to them. MeOH molecule is notonly smaller than DMC, but also more hydrophilic and polar than DMC, so NaYzeolite membrane can adsorpt methanol preferentially and show alcoholselectivity. NaY zeolite membrane has good stability, using it to separateMeOH/DMC mixtrues can get rid of disadvantages swelling of organic films.In this thesis, the effects of synthesis conditions (seed and seed layers, composition of gel) on microstructure of zeolite membranes were studied,continuous and dense NaY zeolite membranes were synthesized using EMTzeolite as seed on α-Al2O3support by secondary growth. The EMT zeolite seed,seed layers and NaY zeolite membranes were characterized by X-ray diffraction(XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM). Then, we studied the pervaporation performance of membranes forseparation of MeOH/DMC mixtrues. The results as follows:1. EMT zeolites with hexagonal morphology and crystal size20to30nmwere synthesized in the absence of template agent and low temperatureconditions. When alcohol as dispersion medium, seed concentration was0.1%,the seed amount was1.0mL, the seed crystals can cover the α-Al2O3supportcompletely and prepare uniform and complete seed layer. Based on the completeseed layer, continuous and dense NaY membrane with12um was prepared.2. Continuous, dense and highly pure NaY zeolite membranes weresynthesized when the aluminosilicate gel with a molar composition10SiO2:Al2O3:14Na2O:840H2O were stirring aged for24h at ambient temperature andcrystallized for6h at100℃.3. NaY zeolite membranes synthesized were used to separate the mixture ofMeOH/DMC (50wt%) at50℃by pervaporation, good membrane stability andoperation durability were maintained along the permeation time, total flux was0.110-0.120Kg/(m2·h), separation factor was about18; With the increase ofmethanol concentration (20-80wt%), the total fluxes (0.115-0.137Kg/(m2·h))increased, separation factors (34.2-5) decreased. With the increase oftemperature (30-80℃), the total fluxes (0.09-0.179Kg/(m2·h)) increased,separation factors (20.9-3) decreased.