Synthesis Of Sn-ZSM-5 Zeolite And Membrane And Application In The Separation Of Acetic Acid From Water

Zeolite generally refers to the aluminum silicate with regular periodic channels structure, and molecular sieve with the aperture, catalysis and absorption of adjustable, thus realizing precise control of the zeolite catalyst and membrane separation. As Silicalite-1 zeolite framework does not contain aluminum atoms, but silica oxygen tetrahedral structure, it has a unique hydrophobic property. However, the silicalite-1 membrane shows a low selectivity for the pervaporation separation acetic acid from its low concentration aqueous solution. By either introducing different heteroatom (Me) to its skeleton or regulating the Si/Me ratio, the surface hydrophilic/hydrophobic property of zeolite membranes can be modified. This thesis deals with the following research tasks: the introduction of heteroatom (Sn) into silicalite-1 framework was systematically carried out in order to enhance its surface hydrophobicity, then changed the affecting factors of formation of the membrane, finally the obtained membranes were applied to separate and recover the acetic acid from the dilute aqueous solution which was discharged as industrial waste liquid. The synthesis and application of heteroatom zeolite is of significance to the industry.The Sn-ZSM-5 zeolite is prepared by hydrothermal Synthesis. SEM, XRD, IR, and UV analysis confirm that the stannum (Sn) atoms are introduced into the skeleton of zeolite. The seeding method is employed to synthesize the Sn-ZSM-5 zeolite membrane, crystalline conditions of the membranes were determined based on the Sn-ZSM-5 zeolite powders. Finally both the Sn-ZSM-5 zeolite membrane and Sn-ZSM-5 zeolite adsorbent are used to separate and recover the acetic acid in low-concentration solution by pervaporation and adsorption process respectively. The thesis consisted of the following parts:1, Using TPABr as the template and SnCl₄ as the stannum source, the Sn-ZSM-5 zeolite with the same size and the uniform shape are successfully synthesized. The gel composition, the crystallization time and the temperature are optimized, and then the best conditions are determined.2, The dense and continuous Sn-ZSM-5 zeolite membranes are prepared successfully on the ceramic tubes, carbon and stainless steel carrier by the secondary growth method. The seed size, the gel composition, the synthesis time and the carrier are inspected systemically for the membrane properties. The permeation tests were measured through Sn-ZSM-5 membranes using the single gas (H2, N₂, and SF₆). The permeation flux of H₂ and the ideal separation factor H₂/N₂ and H₂/SF₆ indicate that the Sn-ZSM-5 membranes have no disfigurements.3, The pervaporation performance of Sn-ZSM-5 zeolite membranes in the separation of acetic acid and water is discussed. The results reveal that: the Sn-ZSM-5 zeolite membranes are more hydrophobic than the Silicalite-1 membranes. In the solution the acetic acid penetrate through the membrane preferentially. Because of the advantages of the ceramic carrier in diameter and mechanical strength, the Sn-ZSM-5/ceramic membrane has more excellent performance in the pervaporation.4, The column Sn-ZSM-5 zeolite adsorbent is prepared with SiO₂ as binder by extrusion method. The static absorption amount of the Sn-ZSM-5 zeolite reach to 0.330 g (acetic acid) / g (zeolite), and then the adsorbent is used to deal with the acetic acid / water mixture flow. And the adsorption method using Sn-ZSM-5 as adsorbent is effective alternation for recovery of acetic acid from its dilute aqueous solution.