Volume 12, Number 1, 2003
A faculty member in the College of Engineering is part of a research team that has reported a significant advance in the fabrication of zeolite membranes, which have important applications in the chemical industry.
Dionisios G. Vlachos, professor of chemical engineering, is co-author of a paper on the discovery that was featured in the April 18 issue of Science magazine.
His co-authors are Zhiping Lai, Griselda Bonilla, Isabel Diaz, Jose Geraldo Nery, Khristina Sujaoti, Miguel A. Amat, Efrosini Kokkoli and Michael Tsapatsis, all of the University of Massachusetts at Amherst, Robert W. Thompson of Worcester Polytechnic Institute and Osamu Terasaki of Tohoku University.
Zeolites are microporous crystalline solids with well-defined structures, containing silicon, oxygen and often aluminum in their framework and water or other molecules in their pores.
Since the 1960s, zeolites have been used as catalysts, ion exchangers and adsorbents. Zeolite membranes are used commercially in the separation of materials, such as water from ethanol.
Vlachos says the research team has made an important advance in the fabrication of zeolite membranes by creating films that can separate molecules more precisely, based on molecular sieving, instead of the less exacting adsorption rates of currently available commercial membranes.
The membranes were prepared using a seeded crystal growth method, in which the shape and growth rate are modified along certain crystal directions. The result is a very thin membrane with large in-plane crystals and an absence of defects. It has outperformed membranes with other microstructures in separation tests.
"This is the first time that we have been able to make zeolite films in a rational way," Vlachos says. "We can now manipulate the thickness to be just one micron, we can control the orientation of nanochannels through which molecules diffuse, and we can eliminate all detectable defects."
A result is high-performance separations. "Molecules can now travel through these films at commercial speeds with very high selectivity," Vlachos says.
He says possible applications of the new zeolite films include gas separations for the chemical industry that will carry with them energy savings and pollutant reduction, sensors against chemical and biological warfare agents and protective layers in cloth.
The overall approach, he adds, can be used in the fabrication of other complex materials and devices, including biomaterials, sensors and films for microelectronics.
Vlachos joined UD in 2000, as part of the College's Center for Catalytic Science and Technology. He previously was a member of the faculty at the University of Massachusetts at Amherst, where he was awarded a $300,000 grant from the Office of Naval Research and received a prestigious Career Award from the National Science Foundation. He earned his master's and doctoral degrees in chemical engineering at the University of Minnesota.
--Neil Thomas, AS '76