Coal-Conversion Tech: Researchers Microwave Coal Powder Into Graphite

With the standard household microwave oven, copper foil, and glass containers, researchers from the University of Wyoming have turned coal powder into graphite.

The new experiment demonstrates a method for turning pulverized coal into higher-value nano-graphite and is a potentially game-changing solution for the Equality State's Powder River Basin Coal. Coal demands have seen a sharp decline due to their contributions toward climate change, especially energy solutions.

Their study's procedures and results are published in the journal Nano-Structures & Nano-Objects, made available online on January 5.

A More Ecological and Economical Method

In their report, researchers detail creating a localized environment inside a conventional microwave oven, converting raw coal powder into nano-graphite. Natural nano-graphite is a high surface material used in a wide variety of applications - from lubricating dies used in hot steel extrusion processes to the production of piston rings, bearings, and shafts. The material is also used in fire extinguishers to lithium-ion batteries.

The convenient and efficient "metal-assisted microwave treatment" is a novel approach that could revolutionize coal-conversion processes. Researchers add in the paper's abstract: "Refinement of this technique is possible to yield a higher quality and quantity of nano-graphite materials for a wider range of applications."

"This method provides a new route to convert abundant carbon sources to high-value materials with ecological and economic benefits," the research team also included in their report. The team is led by TeYu Chien, from the UW Department of Physics and Astronomy.

Turning Coal into Graphite

While previous studies have demonstrated the ability of microwaves in reducing the moisture content of coal or even remove imperfections such as sulfur, proposed methods of doing so require the use of other chemicals or pretreatment processes on the coal. However, in the UW experiment, ground raw coal powder from the Powder River Basin was used in itself, without any catalysts.

The pulverized coal is then wrapped in copper foil and sealed in glass containers with a gaseous mix of argon and hydrogen. This sealed setup is then placed in a microwave oven, one that was readily available and could meet the radiation levels required in the study.

"By cutting the copper foil into a fork shape, the sparks were induced by the microwave radiation, generating an extremely high temperature of more than 1,800 degrees Fahrenheit within a few seconds," explains Christoffer Masi, lead author of the study also from UW's Department of Physics and Astronomy. He also notes that the same phenomenon explains why people should not put metal forks inside a microwave oven.

Sparks from the microwave to the foil creates extremely high temperatures that allow the changing of coal powder into polycrystalline graphite, further encouraged by the copper foil and hydrogen gas in the enclosure.

Researchers also varied the glass containers' exposure time to the microwave, ranging from 3 to 45 minutes. They reported that the optimal exposure time was 15 minutes.

The researchers also noted that their proposed coal-conversion method is a "great alternative," especially after considering environmental concerns.