Asphaltenes, a carbon-rich by-product of crude oil production, can be used as a feedstock for making graphene, according to a new study (Sci. Adv. 2022, DOI:10.1126/sciadv.add3555).
Asphaltenes are used for roofing and paving, and some refineries make synthetic fuel from the heavy residue. But the compounds can be a massive environmental headache. Like all fossil fuels, they produce to carbon emissions when burned, and if they’re discarded into landfills and tailing ponds, they pollute land, water, and air.
The study’s objective, says coauthor Md Golam Kibria of the University of Calgary, was to create a higher-value material from the thousands of metric tons of asphaltenes being produced from oil sands operations in Alberta, Canada.
Earlier this year, Kibria and colleagues made carbon fiber—in huge demand for automotive and aerospace materials—from waste asphaltenes (Carbon 2022, DOI: 10.1016/j.carbon.2022.01.011). Kibria says that they then started looking at other ways to use asphaltenes and zeroed in on a technique called flash Joule heating (FJH), in which a short pulse of current is passed through two electrodes attached to a material containing carbon. As the temperature increases above 2,000 ºC, the material turns into loosely aligned graphene in a matter of seconds. No furnaces, solvents, or reactive gases are needed.
Kibria—along with Pulickel M. Ajayan, Muhammad M. Rahman, and James M. Tour of Rice University and their colleagues—demonstrated that FJH can turn asphaltenes into a carbon allotrope called asphaltene-derived flash graphene (AFG). Because asphaltene is a poor conductor, a small amount of conductive carbon black was added to the raw powder to make AFG. The graphene produced can be used to make nanocomposite materials.
Elham Fini, a researcher in sustainable engineering in the built environment at Arizona State University who was not involved in the work, says that the study’s novelty is in the way the researchers use this blend of carbon black and asphaltene.
The researchers also performed a life-cycle assessment and found that the environmental footprint of their process was significantly lower compared with other conventional methods of graphene production.
This story was updated on Dec. 30, 2022, to correct the spelling of a study coauthor's name. It is "Md Golam Kibria," not "Md Gholam Kibria."