Using copper foil, glassware, and a conventional household microwave oven, researchers at the University of Wyoming have shown that pulverized coal dust can be converted into higher-value nano-graphite.
The discovery is another breakthrough in an effort to find alternative uses for coal in the Powder River Basin of Wyoming, due to concerns about climate change at a time when coal demand is declining to generate electricity.
In a paper published in the journal Nano-Structures and Nano-Objects, UW researchers reported that they created an environment in a microwave oven to convert raw coal dust into nano-graphite, as a lubricant, and from fire extinguishers to lithium-ion batteries. “This one-step method with metal-assisted microwave treatment” is a new approach that can be a simple and relatively inexpensive technology for converting coal.
“This method provides a new way to convert many carbon sources into high-value materials with ecological and economic advantages,” wrote the research team, led by Associate Professor TeYu Chien, in the UW Department of Physics and Astronomy.
Others involved in the project were Professor Jinke Tang, from the Department of Physics and Astronomy; Associate Professor Brian Leonard, Department of Chemistry; Professor Maohong Fan, Department of Petroleum Engineering and School of Energy Resources; Rabindra Dulal, a graduate student from Nepal, Joann Hilman, Laramie, Chris Masi, Syracuse, NY, and Teneil Schumacher, Buffalo; and post-Dr. Gaurab Rimal, a researcher from Nepal, and Bang Xu, from China.
Previous research has shown that microwaves can be used to reduce the moisture in coal and remove sulfur and other minerals, as most of these methods require specific chemical pre-treatment of coal. In their experiment, UW researchers turned Powder River Basin into raw coal dust.
This powder was placed on copper foil and sealed in glass jars with a mixture of argon and hydrogen gas before being placed in the microwave. The conventional microwave oven was chosen for convenience and because it provided the desired level of radiation.
“When the copper paper was cut in the form of a fork, the sparks were generated by microwave radiation, creating a very high temperature of over 1,800 degrees. Fahrenheit in a few seconds, “says Masi, the paper’s lead author.” That’s why you shouldn’t put a metal fork in the microwave. “
Microwave-induced sparks created the high temperatures required to convert coal dust into polycrystalline graphite, as copper foil and hydrogen gases also contributed to the process.
Although the experiment had a microwave duration of 3 to 45 minutes, the optimal duration was observed to be 15 minutes.
Researchers say this new method of converting coal could be refined and made on a larger scale to achieve higher quality and quantity of nano-graphite materials.
“Finite graphite reserves and environmental concerns about graphite extraction procedures make this method of converting coal to graphite an excellent alternative source of graphite production,” the scientists wrote.
Reference: Christobfer A. Masi, Teneil A. Schumacher, Joann Hilman, Rabindra Dulal, Gaurab Rimal, Bang Xu, Brian Leonard, Jinke Tang, Maohong Fan and TeYu Chien, January 5, 2021, Nano-Structures and Nano-Objects.
DOI: 10.1016 / j.nanoso.2020.100660