Haldor Topsoe A/S today announced the publication of a breakthrough study in the peer-reviewed scientific journal Angewandte Chemie. The research article, describes how Topsoe’s researchers for the first time ever have made the Co-Mo-S catalyst’s crystallites – that are only a few nanometers wide – visible to the human eye.
The Co-Mo-S is the scientific term for the active part that is found in Haldor Topsoe’s series of TK catalysts that are used by oil refineries all over the world for a range of different applications. The obtained images disclose detailed knowledge about the structure of the catalyst and have been achieved following decades of attempts. The research could mean more efficient catalysts for oil refineries in the near future, promoting a cleaner environment and helping industry to deal with increasingly tight and more stringent environmental legislation.
“These first-ever images show exactly how the individual atoms in the catalysts are arranged. Knowing how the atoms are arranged in the real catalysts helps to explain what makes a catalyst good or bad. In particular we need to know the exact position of Co, as that element is a spice that really makes the catalyst stand out,” says Stig Helveg, senior research scientist in Topsoe and one of the authors behind the Angewandte Chemie article.
Atom by atom understanding
“Such images are very difficult to obtain and at the edge of what is physically possible, simply because we need to distinguish each and every atom in the crystallites. We have therefore worked for a long time with Dr. Quentin Ramasse at the SuperSTEM facility in Daresbury and Dr. Christian Kisielowski at Lawrence Berkeley National Lab. Especially Quentin has a highly sophisticated microscope available that made it possible to obtain these first-ever images,” continues Stig Helveg.
Having the right microscope available, however, is only part of why the researchers were able to produce the images. Equally important has been the close collaboration between Topsoe’s researchers and Christian and Quentin over the last five years, which has now led to the third out of three cover-page articles in Angewandte Chemie.
“During this period we were able to develop the skills that allowed us to get the images. It is just like driving a car. You may turn the wheel or push the gas pedal, but only when you do it in the right way you hit your end target, says Stig Helveg.”
Improved oil refinery catalysis
Gasoline, diesel and other fossil fuels contain small amounts of sulfur and nitrogen which are emitted to the atmosphere during fuel combustion. These elements are harmful to the human health and the environment. Catalytic processes are therefore implemented in oil refineries to reduce the S and N emissions. However, more efficient catalysts are urgently needed to keep up with the increasing oil consumption, dirtier oil wells as well as tighter and more stringent environmental legislation.
“To design such boosted catalysts, we need a detailed picture of how the catalyst looks and functions at the atomic level,” Stig Helveg says.
Today the catalyst consists of small crystallites of the mineral molybdenum disulfide (MoS2); the crystallites are just a few nanometers wide – that is a millionth of a millimeter in diameter. Moreover cobalt (Co) atoms are attached the crystallites to boost the catalysis.
Since the 1970’es, the structure of the catalyst has been debated intensively in the scientific world. In the 1980’s, researchers at Topsoe suggested the so-called Co-Mo-S model which at that time was fundamentally different from established beliefs and thus created much debate. Although the model is widely accepted today, no one has ever seen, atom-by-atom, the Co-Mo-S catalyst of the type used in oil refineries.