(605f) Grain Boundary Defect Engineering in a MFI Type Zeolite Membrane by Rapid Thermal Processing
AIChE Annual Meeting
2009
2009 Annual Meeting
Separations Division
Characterization and Simulation of Novel Membranes and Separations
Thursday, November 12, 2009 - 5:00pm to 5:21pm
Defect-free zeolite membranes [1, 2] could contribute considerably to energy-savings in separation processes as alternative to conventional cost-intensive counterparts (distillation, crystallization, etc.).[3, 4] However, despite the expected high separation performance, there has been a rather limited industrial realization of zeolite membranes.[5, 6] This can be attributed in part to the lack of methodologies to control non-zeolitic defects that are known to be detrimental to membrane performance.
Here we demonstrate a simple but surprisingly effective way to eliminate or at least reduce the non-zeolitic defects, especially grain boundary defects, by using lamp-based rapid thermal processing (RTP). The separation performance of alumina supported c-oriented MFI membranes was significantly improved for both aromatics (~ 120 p-/o-xylene separation factor) and linear/branched alkanes (~ 34 n-/i-butane separation factor), as compared to that of conventionally calcined ones. This was attributed to the lessened density of grain boundary defects between MFI polycrystalline grains as evidenced by Fluorescence Confocal Optical Microscopy (FCOM) images.[7, 8] The RTP strategy was further successfully applied to c-oriented MFI membranes made on industrially desirable stainless steel tubes leading to very good separation performance (~ 28 p-/o-xylene separation factor). A robust but easy fabrication protocol for zeolite film manufacturing on stainless steel tubes facilitates the scale-up of zeolite membranes at the large scale for separations as well as the integration with a reaction system for membrane reactor applications. We believe this RTP strategy can be extended to other polycrystalline membranes that suffer from defects.
References
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