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Pioneering Method for Synthesizing Zeolites Used for CO2 Capture

Distinguished Professor H. Henning Winter and Associate Professor Wei Fan, both of the Chemical Engineering Department, have been issued U.S. Patent 10,793,442, which is called “Exfoliation of Zeolites in Functionalized Polymers.” Winter and Fan explain that their patented new method is a groundbreaking shortcut for synthesizing zeolites that are vital for capturing carbon-dioxide (CO2) pollutants from electric power emissions using coal and natural gas, responsible for nearly one-third of total CO2 emissions in the United States. Zeolites also have widespread applications as a catalyst.

In their research, Winter and Fan have created a novel method for drastically cutting down the fabrication steps needed to form two-dimensional porous zeolites for gas separation and other advanced applications.

As Winter and Fan explain the background of their patent, two-dimensional zeolites (2DZs) are a new class of porous materials with open pores of about 1 nanometer small and propagating only in two dimensions.

“2DZs can be used to fabricate high-throughput nanometer-thick separation membranes with molecular recognition which can separate molecules at sub-nanometer level, such as separating CO2 from nitrogen gas,” say Winter and Fan. “It is crucial for CO2 capture from the emission of electric power sector using coal and natural gas, which causes around 30 percent total CO2 emission in the U.S. In addition, 2DZs can be also used as catalysts, having potential to enhance the moving of molecules during their reactions and maximizing their catalytic performance.” 

According to Winter and Fan, the problem is that, although 2DZs have shown very promising properties, the synthesis of 2DZs is still a challenge and requires multiple steps. Their new patented method is a possible answer to that challenge.

“In this recent invention,” say Winter and Fan, “we invented a facile, efficient, and reproducible exfoliation method to fabricate one unique 2DZ with MWW structure which has a pore size of around .3 nanometers using commercially available liquid hydroxyl-terminated polybutadiene (HTPB). The process only requires manually mixing the zeolite precursors in the liquid HTPB, avoiding other complicated exfoliation steps.”

Winter and Fan explain that they monitored their exfoliation process using rheology experiments and studied it by tuning the composition of the zeolite precursors, type of the liquid polybutadiene, and organic components used in the zeolite precursors.

“It was found that the interaction between the layered zeolite precursor and the hydroxyl group of the liquid polybutadiene allows the polymer to intercalate the precursor and exfoliate it into nanosheets,” say Winter and Fan.

Winter and Fan add that the presence of framework aluminum and the nature of the organic structure directing agents are key parameters affecting the exfoliation process. “Currently,” they say, “we are focusing the fabrication of the 2DZ nanosheets into membrane and studying their applications in gas separation.”

Winter’s research group measures, analyzes, and models the rheology of soft matter. As Winter says, “This includes materials with dynamically evolving properties, such as physically and chemically crosslinking systems, crystallizing polymers, colloidal glasses, microphase-separating block copolymers, drying paints, aging bitumen, and structuring nanocomposites. It also includes complex materials, such as molten polymers, coacervates, adhesives, and hydrogels with molecular sensors. We place particular focus on the development of advanced experimental methods and models, as needed.”

Fan heads the Porous Materials Research Group. “The research of our group focuses on the rational synthesis of nanoporous materials for biorefinery and drug delivery,” says Fan. “The pore structure and size, surface properties, and active sites, are tailored based on the comprehensive understanding of their crystallization mechanism.” (February 2021)

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