Discovery could greatly improve energy-efficiency of separation and purification processes in the chemical and petrochemical industries
A team of researchers, led by the University of Minnesota, has developed a groundbreaking one-step, crystal growth process for making ultra-thin layers of material with molecular-sized pores. Researchers demonstrated the use of the material, called zeolite nanosheets, by making ultra-selective membranes for chemical separations.
These new membranes can separate individual molecules based on shape and size, which could improve the energy-efficiency of chemical separation methods used to make everything from fuels to chemicals and pharmaceuticals.
The research is published today in Nature, the world's most highly cited interdisciplinary science journal. The researchers have also filed a provisional patent on the technology.
"Overall, we've developed a process for zeolite nanosheet crystal growth that is faster, simpler, and yields better quality nanosheets than ever before," said Michael Tsapatsis, a University of Minnesota chemical engineering and materials science professor and lead researcher on the study. "Our discovery is another step toward improved energy efficiency in the chemical and petrochemical industries."
Watch a video of the one-step process for growing zeolite nanosheets, ultra-thin materials made of crystal structures that could revolutionize chemical separations.
Today, most chemical and petrochemical purification processes are based on heat-driven processes like distillation. These processes are very energy-intensive. For example, chemical separations based on distillation represent nearly 5 percent of the total energy consumption in the United States. Several companies and researchers are developing more energy-efficient separations based on membranes that can separate molecules based on size and shape. One class of these membranes is based on zeolites, silicate crystals that have pores of molecular dimensions. However, the multi-step processes for manufacturing these membranes are costly and difficult to scale up, and commercial production remains a challenge.
In this new discovery, researchers have developed the first-ever, bottom-up process for direct growth of zeolite nanosheets. These nanosheets can be used to make high quality molecular sieve membranes. The new material, is only about five nanometers in thickness, and several micrometers wide (10 times wider than previous zeolite nanosheets). The new nanosheets also grow in a uniform shape making it much easier to make the membranes used in chemical purification.
"With our new material is like tiling a floor with large, uniform tiles compared to small, irregular chips of tile we used to have," said Mi Young Jeon, a University of Minnesota chemical engineering and materials science Ph.D. graduate and the first author of the study. "Uniform-shaped zeolite nanosheets make a much higher-quality membrane with surprisingly high separation values that can sieve-out impurities." The researchers' molecular dynamics calculations also support that separation values in excess of 10000 may be achieved with these nanosheets.
To grow the zeolite nanosheets, researchers begin with seed nanocrystals that, first, double in size and develop facets. The seed crystals then trigger the formation of a twin outgrowth that evolves to become the nanosheet. Nanosheets start to appear from one corner of the seed crystals and then continue to grow, completely encircling the seed to form a faceted nanosheet that is extremely thin and uniform in size and shape.
The uniform shape of the crystals came as quite a surprise, when it was first observed four years ago. "In my 25 years of studying zeolite crystal growth, I'd never seen anything like this before," Tsapatsis said.
Other researchers were also surprised with early results. "It was exciting and rewarding to look at these thin crystals under the electron microscope and study their structure," said Andre Mkhoyan, a University of Minnesota chemical engineering and materials science professor.
"After identifying the presence of a twin in the electron microscope, we knew we had found something that would be a big step forward in developing ultrathin porous crystals," added Prashant Kumar, a University of Minnesota chemical engineering and materials science senior graduate student who performed electron microscopy experiments.
"The nanosheet's ability to grow in only two dimensions was initially unexpected but we were able to systematically unravel its structure and crystal growth mechanism" said Peng Bai, a University of Minnesota postdoctoral researcher in both the Department of Chemistry and Department of Chemical Engineering and Materials Science who used quantum chemical methods to interpret the unique structure.
The research was funded by the Advanced Research Projects Agency (ARPA-E) of the U.S. Department of Energy (DOE), DOE's Center for Gas Separations Relevant to Clean Energy Technologies Energy Frontier Research Center, DOE's Nanoporous Materials Genome Center, the Deanship of Scientific Research at the King Abdulaziz University, and made use of several facilities including the Advanced Photon Source operated by Argonne National Lab, the Argonne Leadership Computing Facility, the Minnesota Supercomputing Institute and the Characterization Facility of the University of Minnesota.
In addition to Tsapatsis, Jeon, Kumar, Bai, and Mkhoyan, other key members of the research team included Ph.D. graduate Pyung Soo Lee, postdoctoral researcher Donghun Kim, and chemistry Professor J. Ilja Siepmann. Other members of the 21-person team include several graduate students and postdoctoral researchers from the University of Minnesota as well as contributors from the U.S. Department of Energy's Argonne National Laboratory, University of Massachusetts Amherst, and King Abdulaziz University in Saudi Arabia.
To read the full research paper, entitled "Ultra-selective high-flux membranes from directly synthesized zeolite nanosheets," visit the Nature website.
Rhonda Zurn | EurekAlert!
Let the good tubes roll
19.01.2018 | DOE/Pacific Northwest National Laboratory
Method uses DNA, nanoparticles and lithography to make optically active structures
19.01.2018 | Northwestern University
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy