By Dr. Matthew Lui, Ms. Lisa Cattelan and Ms. Lisa Player (supervised by A/Prof. Anthony Masters and Prof. Thomas Maschmeyer)



A simple, low energy method to reduce nitrogen content of fuels has the potential to reduce air pollutants generated from combustion.

Researchers, led by Professor Thomas Maschmeyer, from the Laboratory of Advanced Catalysis for Sustainability at The University of Sydney, have developed a simple technique to reduce the amount of nitrogen-based compounds commonly found in biocrude oils, when generated from biomass that contained some residual protein, e.g. algae, seaweed or municipal green waste. These nitrogen-containing residues interfere with traditional refining methods and need to be removed, prior to their integration in the supply chain.

Increasing energy demands combined with the environmental impact of fossil fuel-derived feedstocks have highlighted the need to move towards sustainable alternatives. Of particular interest is the need for clean and renewable transport fuels, such as biofuels. A promising feedstock is represented by macroalgae, the conversion of which is a topic of research in the Advanced Catalysis and Sustainability group.

However, one of the major drawbacks of producing biofuels from algae is the high nitrogen content in the unrefined product. In addition to the issues outlined above, direct combustion of the unrefined biocrude generates a higher load of nitrogen oxides, which cause substantial environmental damage and are health hazards, and additional post-combustion treatment of the exhaust gases would need to be implemented.

Despite the presence of nitrogen in many biocrude oils that are described in the academic literature, the practical problem of removing these prior to petrochemical refining or direct combustion is not often addressed.

The Sydney University researchers have developed a low-energy method to remove aromatic nitrogen-containing compounds using ionic liquid technology.

Ionic liquids are organic salts that are usually defined to have a melting point below 100˚C, and are often referred to as ‘green solvents’, boasting properties such as non-volatility, non-flammability, high recyclability, and tunable solvation properties.

The work demonstrated that specific ionic liquids are able to efficiently solubilize and extract nitrogen-containing compounds, while remaining immiscible in biofuel, which can easily be removed and further processed.

Co-author and PhD candidate Lisa Player believes the promising outcomes stem from “the tunable properties of ionic liquids” that provide maximum extraction efficiency of these compounds”.

Co-author and postdoctoral fellow Dr. Matthew Lui, says that "This study provides an important foundation for future studies in improving the extraction of a range of compounds from biofuels."

"We’ve demonstrated that through studying the fundamental interactions occurring in the system, we were able to design ionic liquids which selectively extract nitrogen-containing compounds, without contaminating the fuel. The effectiveness of this extraction method is a promising alternative to the currently used denitrogenation methods, taking us one step closer to minimising the pollution generated from bio-fuel use."

The results of this study were published in the March 2017 issue of Energy and Fuels1 (American Chemical Society).

This work was completed as part of an international cotutelle agreement between the University of Sydney, Ca’ Foscari University of Venice and Universita’ degli studi di Trieste. Co-author, Lisa Cattelan is completing her PhD candidate as part of this program, having spent a year in the Laboratory of Advanced Catalysis for Sustainability, as a recipient of the Erasmus + scholarship. Lisa comments that "The close international collaboration between the two groups has been highly beneficial for my development as a researcher and the quality of the research environment provided at The University of Sydney’s School of Chemistry has provided a major boost for my PhD studies, having already published two papers from the twelve months here".

Two current University of Sydney students, from the Advanced Catalysis for Sustainability group are completing part of their PhD in Venice under this agreement, with a total of six cotutelle PhD students shared so far between the two laboratories.

  1. M. Y. Lui, L. Cattelan, L. C. Player, A. F. Masters, A. Perosa, M. Selva, T. Maschmeyer, "Extractive Denitrogenation of Fuel Oils with Ionic Liquids: A Systematic Study", Energy Fuels, 2017, 31(3), 2183–2189. DOI: 10.1021/acs.energyfuels.6b02157

Posted 21 April 2017