Zeolites are porous, crystalline structures with uniform molecular-sized pores ranging from 0.35 to 1.3 nm. Zeolite crystals have been assembled into continuous membranes by hydrothermal synthesis onto porous supports for chemical separation. Because of the complex crystallization and crystal intergrowth processes and complicated interaction between zeolite crystals and porous supports, which may be affected by gel composition, aging time, and hydrothermal synthesis conditions, it is very challenging to prepare high quality zeolite membranes with negligible defects. Our research in this direction is focused on optimizing zeolite membrane growth processes and developing novel synthesis methods and exploring the potential of these membranes for mixture separations.
Under the support by DOE/ARPA-E, we obtained the following key results and reported them in peer-reviewed journals:
· We found a Na+-gated water-conducting zeolitic nanochannel that only allows water to permeate through while blocking molecules as small as H2.
· We showed high-aspect-ratio seeds were effective for high quality zeolite membrane growth.
· We designed a novel process to selectively block non-selective defects in zeolite membranes.
· We developed a gel-modulated growth process to improve the equality of zeolite membranes.
Recently, we found surprisingly fast zeolite crystallization rate by contacting the “clean” seeds with synthesis gel only at the actual synthesis temperature; using this new strategy, we can grow high quality zeolite membranes within 1 min, which is 2 to 3 orders of magnitude faster than traditional methods. We are conducting more detailed research work to understand the crystallization mechanism and exploring its potential for initiating the second-generation zeolite and zeolite membrane synthesis. We built a startup company, E2H2Nano LLC, to explore the potential of Na+-gated water-conducting nanochannel membrane for renewable methanol production, ammonia separation, and food drying.