Synthesis Of NaX Membranes And Application To Separating Benzene And Nitrogen Mixture

In many petrochemical plants, a mass of benzene and nitrogen mixture in benzene stock tanks is discharged into atmosphere. The precious resource is wasted and the environment is polluted. Because of this background, synthesis of continuous NaX membranes by seeded method are studied thoroughly on the outer surface α -alumina tube support with pores of 3⁵ μm (13 mm o.d, and 9 mm i.d.). The membranes apply to separate the benzene and nitrogen mixture successfully as a new separation method. The main work of this thesis is:Effects of some important factors such as tempreture, alkalinity, Si/Al and synthesis time on the preparation of zeolite are thoroughly studied. When the Al fountain is changed, the crystal size also changes thoroughly. The molar composition of the seeding is SiO₂/Al₂O₃=3.85, Na₂O/SiO₂=1.2-1.5, H₂O/Na₂O=46-55; The molar composition of the starting gel of NaX membranes is SiO₂:Al₂O₃=3.85⁴.2,Na₂O:SiO₂=1.2¹.5,H₂O:Na₂O=40⁶0.The influence of crystallization methods, crystallization times and the methods of introducing seeds are studied thoroughly. The result shows that using self-product 500-1000nm NaX zeolite as seeds and using hot-dipping method crystallize about 4 times, integrated and continuous membranes are gained. The NaX zeolite membranes are successfully synthesized using Al₂O₃ crystal and CMC as transition layers for the first time. The penetration of H₂ is 4.88 × 10-7 mol·m2 ·s-1 · Pa-1, C3H8 is 6.91 × -8 mol · m2 · s-1 · Pa-1, and the ideal selectivity of H₂/C₃H₈ is 7.19 when the membranes transition layer is Al2O3. The penetration of H2 is 2.09 × 10-6 mol m2 ·s-1 ·Pa-1, C3H8 is 3.02 × -7 mol ·m2 ·s-1·Pa-1, and the ideal selectivity of H2/C3Hg is 7.19 when the membranes transition layer is CMC .NaX zeolite membranes are used to separate the mixture of benzene and nitrogen as a new method. The influence of pressure difference, the speed and concentration of the mixture and ion-exchanged degree are studied thoroughly. The result shows that the separation factor is changed with the pressure difference, speed and concentration change. Membranes show better separation ability when they are exchanged with Ag+. When the pressure is 40KPa, the speed is 180ml/min and the concentration is 17%, Ag+-exchanged completely membranes gain the best separation factor, 30.1.