Preparation Of T/NaY Composite Zeolite Membrane And Its Application In Solvent Dehydration

Continuous and dense zeolite membranes commonly have high water flux and high separation selectivity for different mixtures due to their uniform micropores and surface chemical property.Features of simple process,easy operation,and low energy consumption give this process a huge advantage for separating azeotropic or close-boiling mixture solutions.At present,the NaA zeolite membrane has been used for dehydration on a large scale.However,NaA zeolite membrane is greatly limited in an acidic solution because of its high aluminum content framework.Therefore,the study and preparation of acid-resistance membrane have been an urgent problem.Both zeolites T and zeolite NaY have a good stability under acidic conditions due to their Si/Al ratio.The random distribution of zeolite T on the porous?-Al₂O₃ tube during growth greatly limits its application in the industry.In this study,the defective zeolite T layer is modified with zeolite NaY.As for NaY zeolite,the cubic structure has a good intergrowth.However,during the growth process,the zeolite NaY is prone to cluster growth,thereby resulting in uneven surface stress and cracking.In this study,the defective zeolite T layer is modified with zeolite NaY.A continuous,dense and acid-resistance zeolite T/NaY composite membrane is obtained.We prepared the high performance and repeatable T/NaY composite membrane by adjusting the synthesis conditions of zeolite T membrane layer and zeolite NaY membrane layer.The composite membranes is tested for pervaporation and acid resistance.The main results as follows:?1?When the molar ratio of zeolite T membrane synthesis solution is 20SiO₂:1Al₂O₃:5.2Na₂O:1.8K₂O:600H₂O,the?-Al₂O₃ support tube is pre-modified with 0.25wt%zeolite T seeds suspension.After synthesis at 140? for 5 h,the zeolite T layer with relatively stable pervaporation performance can be obtain.?2?The original synthesis solution of zeolite NaY have a mole ratio of 25SiO₂:1Al₂O₃:22Na₂O:600H₂O.When the deionized water is added as 3/4 of the original synthesis solution and aged for 18 h,the resultant gel is obtained.After hydrothermal synthesis at 100? for 7 h.T/NaY composite membrane with the best pervaportaion performance can be prepared.The water concentration of permeate can reach 99 wt%,and the permeate flux is above 2.56 kg·m^-2·h^-1.?3?We prepared zeolite T/NaY composite membrane under pilot experiment condition and the pervaporation performance was tested.The results showed that the ratio of the composite membrane with a water concentration in permeate of 99 wt%is85%.?4?The pervaporation performance of the zeolite T/NaY composite membranes were tested after treatment at different pH for different time.The results showed that the composite membranes could maintain good stability under acidic conditions of pH=5.