Petroleum coke - also known as green petroleum or petcoke - is a byproduct produced during oil refining. The coke contains almost 100% carbon and only a small amount of sulfur and metals. It is a low-cost, energy-dense fuel that can be burned in power plants and steel furnaces. Its high heating value, low sulfur and ash content make it a desirable feedstock for the manufacture of graphite electrolytes for lithium-ion battery.
The coke's natural characteristics make it a promising pre-cursor for the production carbon nanomaterials, such as graphene, and its derivatives. Its unique microscopic structure makes it a versatile material that can be used for many applications. These include energy storage, sensing technology, advanced oxidative processing, and luminescence. Its low cost also makes it an attractive alternative to natural graphite which is limited in availability and usually expensive.
The research team used a process called electrochemical exfoliation to transform petroleum coke into graphene. The researchers were able extract 5 grams graphene per kilogram of parent coal, which is an impressive result. They also studied the graphene produced and found it to have a high conductivity, comparable to the electrodes used in Li-ion batteries.
The graphene-derived from coke has a conductivity that is 50 siemens/meter higher than the conventional electrodes available today. This improvement will lead to better lithium-ion cell technology that is more durable, cheaper and with a greater capacity. The researchers, however believe that they can boost graphene’s conductivity with a simple thermal treatment.
The team analysed the morphology of the graphene they produced by Raman spectroscopy. They found that a 2D peak appeared in the CK-1d Raman spectra, indicating that the material had a classic graphene signature. In contrast, the parent coke exhibited no 2D peak, suggesting that it did not contain sufficient graphitic carbon to produce this characteristic.
Petroleum coke has a limited supply and can be dangerous. It is stored in open pit cokeyards that are exposed to extreme weather conditions, which can cause fires or explosions. As such, proper safety precautions must be taken when handling it, including wearing protective clothing, avoiding skin contact, and using regular equipment maintenance. These conditions, which are characterized by high temperatures and humidity, can also cause equipment to corrode or oxidize. The progress being made towards producing needle coke out of renewable sources such a biomass and plastic scraps can be used in a more permanent way to replace petroleum-derived coal when it comes to the production or high-value carbon material such as graphene. This could shift oil industry focus from energy intensive applications to a more sustainable generation of low-emissions technologies.
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