Organotemplate-free Synthesis Of MOR And ZSM-5 Membranes For Pervaporation Dehydration

Dehydration of organics under acidic conditions (such as acetic acid) is not only a great demand for highly purified organic products in industry but also one of the main challenges in the field of membrane research. Synthesis of high performance membrane for dehydration of organics under acidic conditions is urgent necessary for the national energy saving and emission reduction. MOR and ZSM-5 zeolite membranes have unique pore structure, and exhibit some advantages such as excellent thermal, chemical and mechanical stability as well as adjustable framework Si/Al molar ratio. These advantages make the membranes as excellent acid-proof and water perm-selectivity membrane materials, which is suitable to separate water from organics, especially under acidic conditions.In this work, preparation and separation performance of MOR and ZSM-5 membranes with good hydrophilicity and acid resistance were studied based on the development of the acid-proof and water perm-selectivity zeolite membrane material. High performance MOR membrane was prepared by a new strategy, and the microstructure of ZSM-5 membrane was optimized to improve the performance for dehydration of acetic acid. Moreover, the effects of different membrane preparation parameters on the morphology, structure and separation properties of ZSM-5 zeolite membranes for dehydration of isopropanol were investigated and explored. The main research contents and results are as following:(1) High performances MOR membranes were successfully prepared in a short synthesis time from fluoride-containing dilute solution without organic template under microwave-assisted heating. The effects of crystallization temperature, fluoride ion and aluminum source on the MOR membrane morphology and separation performance were systematically investigated. The MOR membranes displayed high pervaporation performances for dehydration of 90 wt%AcOH and good acid stabilities. The permeation fluxes were 0.87-0.06 kg·m-2·h-1 and corresponding separation factors were higher than 10000 at 75 ?. The use of the cheap macroporous supports and dilute solution without organic template, which decreased usage amount of reagents, resulted in reducing the cost of production which enhances the possibility of industrialization.(2) High performance ZSM-5 membrane with homogeneous Al spatial distribution was prepared on cheap coarse macroporous ?-Al2O3 tubes by organic template-free route. The effect of synthesis gel without/with organic template on the spatial distribution of Al atoms in the ZSM-5 membrane layer was investigated. It is found that the Al spatial distribution of ZSM-5 membranes are largely dependent on the synthesis route. The synthesis gel without organic template tends to achieve relatively homogeneous Al spatial distribution in the ZSM-5 membrane layer, whereas the addition of TAPOH in the gel leads to an inhomogeneous Al spatial distribution.(3) The effect of Al spatial distribution of ZSM-5 membrane on separation performance for dehydration of acetic acid was investigated. The spatial distribution of Al atoms of ZSM-5 membrane plays a great influence on separation performance of dehydration of acetic acid. The ZSM-5 membrane with homogeneous Al spatial distribution showed higher separation performance, in contrast, the ZSM-5 membrane with inhomogeneous Al spatial distribution showed poor separation performance. Therefore, ZSM-5 membrane with lower Si/Al ratio and homogeneous Al spatial distribution was prepared and displayed excellent separation property for dehydration of acetic acid. The as-synthesized ZSM-5 membrane showed a flux of 1.13 kg-m-2·h-1 for dehydration of 90 wt.% AcOH/H2O at 75 ? with a corresponding separation factor of oo, and had good acid-proof stability.(4) The effects of seeded layer, crystallization time, NaF/SiO2 ratio and aluminum source on the growth, morphology and pervaporation (PV) performances of the as-synthesized membranes were investigated for dehydration of isopropanol. Under optimized synthesis conditions, a continuous and well-intergrown ZSM-5 membrane with low Si/Al ratio of 10.3 and thickness of 4.0 ?m successfully grew on the surface of the macroporous support. The obtained ZSM-5 membrane showed high separation performance for dehydration of isopropanol at 75 ?, and the flux and separation factor were 3.85 kg·m-2·h-1 and higher than 10000. The as-synthesized ZSM-5 membranes displayed high reproducibility and low cost. It also showed high separation performance for dehydration of 90 wt.% n-PrOH/H2O, n-BtOH/H2O and i-BtOH/H2O. It provides the feasibility for commercial production of high property ZSM-5 membranes, promoting the broad commercialization of hydrophilic ZSM-5 membranes.