Flash Joule heating turns asphaltenes into graphene

Muhammad Rahman, an assistant research professor of materials science and nanoengineering at Rice University, is leading the effort to utilise a material otherwise burned for reuse as fuel or discarded into tailing ponds and landfills.

According to Rice, there is a global reserve of over one trillion barrels of asphaltene, which is a by-product of crude oil production.

“Asphaltene is a big headache for the oil industry, and I think there will be a lot of interest in this,” said Rahman, who characterised the process as a scalable and sustainable way to reduce carbon emissions from burning asphaltene.

Rahman is a lead corresponding author of the paper in Science Advances co-led by Rice chemist James Tour, whose lab developed flash Joule heating, materials scientist Pulickel Ajayan and Md Golam Kibria, an assistant professor of chemical and petroleum engineering at the University of Calgary, Canada.

Asphaltenes are 70 to 80 per cent carbon already. The Rice lab combines it with about 20 per cent of carbon black to add conductivity and flashes it with a jolt of electricity, turning it into graphene in under a second. Other elements in the feedstock, including hydrogen, nitrogen, oxygen and sulphur, are vented away as gases.

“We try to keep the carbon black content as low as possible because we want to maximise the utilisation of asphaltene,” Rahman said in a statement.

“The government has been putting pressure on the petroleum industries to take care of this,” said Rice graduate student and co-lead author M.A.S.R. Saadi. “There are billions of barrels of asphaltene available, so we began working on this project primarily to see if we could make carbon fibre. That led us to think maybe we should try making graphene with flash Joule heating.”

Assured that Tour’s process worked as well on asphaltene as it did on various other feedstocks, including plastic, electronic waste, tyres, coal fly ash and even car parts, the researchers set about making things with their graphene. 

Saadi mixed the graphene into composites, and then into polymer inks bound for 3D printers.

“We’ve optimised the ink rheology to show that it is printable,” he said, noting the inks have no more than 10 per cent of graphene mixed in. Mechanical testing of printed objects is forthcoming, he said.