Preparation Of NaA Zeolite Membrane And Industrial Application

Pervaporation as a new membrane separation technology developed in recent years attracts widely attention all over the word. Compared to traditional separation method, it has advantages of better separation selectivity, lower energy consumption, higher efficiency and easier operation. NaA zeolite membranes have been ideal materials on dehydration of organic by pervaporation because of its high hydrophilicity and small pore size(0.41nm) which ranges between most organic solvents and water molecules. Therefore, NaA zeolite membranes have a broad application prospect in the field of organic solvents dehydration.In this paper,NaA zeolite crystals were firstly prepared to be used as seeds. Then, NaA zeolite membranes were synthesized by hydrothermal method and microwave method in clear solution with different synthesis conditions. Also, different operating conditions were studied to explore the changing trends of the pervaporation performance. Last,800mm NaA zeolite membranes were synthesized as industrial application. SEM、XRD and PV methods were used to characterize the membranes. The main conclusions were as follows:(1) NaA zeolite crystals with high crystallinity and uniform particle size (400～500nm) were preparated by the formulation1.2Na2O:Al2O3:2SiO2:58H2O,aging time of4h at25℃, crystallization time of3h,crystallization temperature of100℃.(2) NaA zeolite membranes were synthesized in the clear solution with the formulation of1Al2O3:5SiO2:50Na2O:1000H2O. When NaA zeolite membranes were synthesized under conditions that concentration of small seed solution was0.3wt.%and support surface was smooth without large defects, the PV performance for90wt.%ethanol/water mixture was high with its flux up to2.38kg·m-2·h-1and the separation factor of8089. NaA zeolite membranes synthesized by microwave method for45min at80℃had high performance with its flux up to2.69kg·m-2·h-1and the separation factor of2033.(3) PV performances of NaA zeolite membranes were studied under different operating conditions. With the concentration of isopropanol increasing, permeation flux significantly reduced. And with the temperature of feed rising, flux increased sharply. But both of water content in the permeate side was close to100wt.%and remained unchanged. The flux of NaA zeolite membrane in alkaline environment (PH=9) decreased obviously, and PV performance maintained stable within144h in constant concentration of90wt.%isopropanol/water mixture. (4) NaA zeolite membranes of800mm in length were synthesized in large autoclave which could contain8α-Al2O3supports and the repetition rate could reach80%at least. The industrial separation performance of NaA zeolite molecular sieve membrane was evaluated and the pervaporation dehydration scheme was designed.