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Posted: Apr 04, 2017
Controlled catalysis for ultra-clean fuels
(Nanowerk News) Catalysts are essential for a lot of chemical production processes, accelerating and enhancing chemical reactions to produce plastics, medicines and fuels more efficiently. Now, thanks to EU-funded research, catalysts are being made more precise and effective with potentially significant benefits for industry and the environment, not least through the development of ultra-clean fuels.
“Without catalysts society would not exist as we know it today,” says Krijn de Jong, professor of inorganic chemistry and catalysis at Universiteit Utrecht in the Netherlands. “Catalysts are crucial for energy conversion, chemicals production and environmental processes such as cleaning exhaust gases.”
In spite of their importance, the processes involved in producing some essential catalysts have not been well understood until now. In fact, their synthesis from simpler chemical compounds has frequently been likened to an art more than a science. This is especially true of bifunctional nanoparticle metal catalysts that are almost exclusively synthesised in liquid-phase processes. De Jong describes these as a technique akin to a ‘black box’ in which ingredients are put in and catalysts are produced but the processes involved are not precisely understood.
With the support of the European Research Council (ERC), De Jong and fellow researcher Jovana Zecevic set out to clarify and characterise liquid-phase synthesis in a project called NanoPartCat that aims to not only fundamentally improved scientific understanding of how catalysts are produced, but is also lead to innovative ways to control the process. That in turn could result in improved catalysts and chemicals, including fuels with fewer waste by-products and diesel with an optimised molecular structure so vehicles emit less carbon dioxide and fine particle matter.
“By characterising what occurs during liquid-phase synthesis we were able to control and optimise the process, resulting in more efficient and effective catalysts,” De Jong says.
Their research was enabled by recent advances in electron microscopy that have made it possible to image the molecular interactions taking place during synthesis at nanometre resolution in real time, even within a liquid.
What De Jong and his team saw fundamentally challenged existing theories about the optimal positioning of compounds within bifunctional metal catalysts, which are used widely in fuel production for a process known as cracking, which breaks down complex heavy molecules into simpler ones creating diesel, gasoline or propane.
The importance of nanoscale intimacy
Such bifunctional hydrocracking catalysts contain metal sites and acid sites, and for more than 50 years the so-called ‘intimacy criterion’ has dictated the maximum distance between the two compounds, beyond which catalytic activity decreases.
“It had long been thought that placing the acid and metal sites as close as possible produced the best results, but in fact the optimal distance varies depending on the feedstock. An analogy for the intimacy criterion in catalysts is the intimacy between two people talking: you can be too far away or too close for comfort,” De Jong says. “By optimising for this in cooperation with Professor Johan Martens at KU Leuven, we were able to develop a technique to produce high-quality diesel fuel that uses feedstock more efficiently, generates fewer by-products and which, when burnt, results in considerably lower emissions.”
The findings of the NanoPartCat project could not only have an impact on the production of ultra-clean diesel but will likely change the way catalysts are synthesised for other fuels, including high-octane gasoline, and could have applications in other industries such as water and air treatment or pharmaceuticals.
Further uses will all but certainly emerge over time as De Jong continues his research, which he says would not have been possible without ERC funding.
“This is high-risk fundamental research with no guarantee of success. ERC support has therefore been absolutely essential in achieving this breakthrough, and it has had a multiplier effect through university co-funding and will lead to collaborations with industry and other researchers in the future,” he explains.