High-Performance MFI-Type Zeolite Hollow Fiber Membranes for Organics/Water Separation


Most zeolite membranes used in industrial processes are selective for water over organic compounds. Due to their good chemical stability, unique framework, and intermediate pore sizes, the hydrophobic MFI-type zeolite membranes have been extensively considered for a wide range of separation processes, particularly for pervaporation separation of organics from organic/water mixtures. Such membranes, if prepared on hollow fiber supports with high packing density (membrane surface area/volume ratio >1000 m2/m3), are attractive for industrial pervaporation separation of organic/water, such as ethanol/water separation involved in bio-fermentation ethanol production. However, reproducible synthesis of MFI zeolite membranes with high organic selectivity remains a challenge.

Invention Description
Researchers at Arizona State University have developed a new synthesis method consisting of dual-layer seeding and varying-temperature secondary growth for the synthesis of hydrophobic MFI zeolite membranes on alumina hollow fiber supports. The effects of seeding method, seed particle size, seed size ratio, and variable temperature/time profile on the microstructure, hydrophobicity and gas perm-selectivity of the membranes are investigated leading to identification of optimum seed structure and secondary growth conditions for synthesis of MFI zeolite membranes with high ethanol/water separation performance. The high-performance MFI zeolite membrane has a microstructure consisting of a thin, fully inter-grown, and dense top zeolite layer responsible for high selectivity, and a porous low inter-grown bottom zeolite layer minimizing resistance and retarding aluminum transfer from the support to zeolite. The best hollow fiber supported MFI zeolite membrane with a Si/Al ratio of 187 exhibits ethanol/water pervaporation separation factor of 160 with total flux of 3 kg m-2 h-1

These MFI zeolite membranes offer highest ethanol to water selectivity. 

Potential Applications
•  Separation of organics from water mixtures
•  Ethanol/water or methanol/water separation
•  Membrane reactors for production of ethanol and methanol

Scanning electron microscopy (SEM) images of surface and cross section of hollow fiber α-alumina support.

Related Publication: High-performance MFI zeolite hollow fiber membranes synthesized by double-layer seeding with variable temperature secondary growth

Research Homepage of Professor Jerry Lin

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