CO2 converted into a diesel blend fuel

Researchers from Monash University and Hokkaido University have developed a method that converts carbon dioxide into a diesel-range fuel and has the potential to produce a net-zero liquid fuel alternative to power cars more sustainably. Their work has been published in the Journal of Energy Chemistry.

When carbon dioxide (CO₂) is added to the manufacturing process of fuel production, it has the capability to produce fuels that reduce or reverse the net CO₂ emissions. When the hydrogen required for this process is supplied via solar-powered water electrolysis, the entire process becomes completely renewable. The end result is a net-zero-carbon-emitting fuel product such as oxymethylene ethers (OME), explained Associate Professor Akshat Tanksale from Monash University.

“OME is a diesel blend or substitute fuel for which we are reporting the best yield to the best of our knowledge anywhere in the world and, when coupled with green hydrogen, the manufacturing method we’re proposing can provide net-zero liquid fuel,” said Assoc Prof Tanksale, lead author of the new study.

Dimethoxymethane (DMM), which is a diesel blend fuel and the simplest form of an OME, is currently being researched with high interest due to its unique properties. Commercially, it can be produced via a two-step process of methanol oxidation to make formaldehyde, followed by coupling with methanol. However, currently, both methanol and formaldehyde are produced from natural gas.

In the method developed by Monash, carbon dioxide, hydrogen and methanol are used as a feedstock for producing DMM in a single reactor. The team developed a novel catalyst based on ruthenium nanoparticles which make this reaction possible. An added advantage is that this reaction takes place at much lower temperatures than conventional methanol and formaldehyde production methods, making it more energy-efficient. Monash engineers are also working on a methanol synthesis method from carbon dioxide and hydrogen, closing the carbon loop to renewables only.

“In this study, we developed a unique pore structure that could synthesise large molecules like DMM,” said Dr Waqar Ahmad, who recently completed his PhD on this project. “The particle size of ruthenium, along with the pore size and acidity of the catalyst, is extremely important for this reaction to take place. By precisely controlling these parameters, we were able to achieve the highest yield of DMM reported in the literature.”

The project has recently received funding for further research into the industrialisation and scale-up of this state-of-the-art catalyst and process by the Hindustan Petroleum Corporation Limited (HPCL), India. This work will bring net-zero liquid fuels closer to reality.

“CO₂ valorisation to fuels is one of the prominent pathways to achieving net zero in the future and researchers are exploring efficient processes for this conversion,” said Dr G Valavarasu from HPCL. “We’re currently focusing on several CO₂ conversion technologies for the development of industrially scalable catalysts and processes.

“Our collaboration with Monash University to develop and scale up OME production from CO₂ will certainly contribute to the development of a process for CO₂ conversion into fuels, which is proving necessary in the current climate.”

Image caption: A graphical representation of how carbon dioxide can be converted into a diesel-range fuel. For a clearer image, click here.

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