Researchers from Monash University and Hokkaido University have developed a method to produce dimethoxymethane (DMM)—a diesel blend fuel currently of great research interest—via CO₂ hydrogenation in methanol over a novel ruthenium-based catalyst. DMM thus produced could be used as a fuel in a conceptual circular carbon cycle when produced using direct-air-capture CO₂ and green hydrogen.

Their paper is published in the Journal of Energy Chemistry.

Associate Professor Akshat Tanksale from the Department of Chemical and Biological Engineering at Monash University and co-corresponding author, says OME (oxymethylene ethers) are among a number of fuel alternatives that are attracting increasing attention for their net-zero carbon emitting properties.

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.

—Akshat Tanksale

Dimethoxymethane (DMM), which is the simplest form of an OME, can be produced commercially via a two step-process of methanol oxidation to make formaldehyde, followed by coupling with methanol. However, currently, both methanol and formaldehyde are mainly produced from natural gas.

In the new method, 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.

In this study, we developed a unique pore structure that could synthesise large molecules like DMM. 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.

—Dr Waqar Ahmad, lead author

An added advantage is that this reaction takes place at much lower temperatures than conventional methanol and formaldehyde production methods, making it significantly 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.

Recycling waste carbon dioxide to OME is a promising way to produce fuel with a significantly lower carbon footprint. We are glad we could collaborate with the team at Monash to further understand the role of catalysts in this state-of-the-art work.

—co-author Dr Abhijit Shrotri, Institute for Catalysis, Hokkaido University

The project has recently received funding for further research into the industrialization and scale-up of the catalyst and process by the Hindustan Petroleum Corporation Limited (HPCL), India.

CO₂ valorization to fuels is one of the prominent pathways to achieving net-zero in the future and researchers are exploring efficient processes for this conversion. 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.

—Dr G Valavarasu from HPCL

Resources

• Waqar Ahmad, Fan Liang Chan, Abhijit Shrotri, Yayati Naresh Palai, Huanting Wang, Akshat Tanksale (2012) “Dimethoxymethane production via CO₂ hydrogenation in methanol over novel Ru based hierarchical BEA,” Journal of Energy Chemistry, Volume 66, Pages 181-189 doi: 10.1016/j.jechem.2021.07.026