PhD researcher develops inexpensive, sustainable production method in just 2 years

Delft University of Technology PhD candidate Maaike Kroon has developed a sustainable and inexpensive production method for the chemical industry. This method combines reactions and separation processes, does not produce chemical waste and uses much less energy. After just two years of PhD research, she will receive her doctorate degree based on this research subject on December 11. Maaike Kroon (25) is regarded as an exceptionally talented young researcher.

Maaike Kroon has developed a sustainable production method for the chemical industry that combines reaction and separation processes. She used this new method in trial experiments to reproduce a (already existing) medicine for Parkinson's disease. In doing so, no chemical waste was produced nor harmful solvents used, and the process required 75 percent less energy than is normally used. Moreover, not only is the end product extremely pure, but Kroon's method is also faster and less expensive. If used for this specific medicine, her production method would result in possible savings of 11 million euro per year.

The method combines so-called ionic liquids and separation with supercritical carbon dioxide. Using this combination was Kroon's idea, which Delft University of Technology has since patented.

The raw materials for the medicine are dissolved in ionic liquid. Ionic liquids are fluid salts that serve as clean solvents. Carbon dioxide is added to this liquid under high pressure. The high pressure propels the CO2 gas to the so-called supercritical phase, during which it assumes the properties of both a gas and a liquid. This causes everything present to fully mix in a homogenous phase. The resulting reactions occur much more quickly than during the reaction processes currently used. A further advantage of Kroon's method is that all the raw materials are transposed into the end product without containing any by-products. The separation process occurs after the reaction. For this to occur, the pressure in the kettle is reduced, causing the CO2 and material produced to evaporate and float in a gas bubble on top of the liquid. It is easy to remove this gaseous mixture. The ionic liquid's fluid mixture and the catalyst remain behind in the kettle for reuse. The pressure is lowered further for the gaseous mixture, causing the end product to separate into a solid or liquid form.

Kroon says that there are no technical obstacles preventing the industry from using this method. Kroon: "Unfortunately, we must however consider the investments that companies have already made in existing production plants. Many companies will therefore only use this new method if a new factory is built." The combination of ionic liquids with supercritical carbon dioxide can in principle be used for the production of many other materials. Three new PhD candidates will conduct further research in this area at Delft University of Technology.


Maaike Kroon is regarded as an exceptionally talented young researcher and has received her PhD degree remarkably quickly: in just two years. Kroon had previously won the award for best Delft University of Technology graduate of the class of 2004-2005. This past summer she was also invited to participate as a researcher in the exclusive annual meeting of Nobel Prize Winners in Chemistry, which was held in the German city of Lindau. In 2007, Kroon will become an assistant professor at Delft University of Technology. She will work in the DelftChemTech section and concentrate on nanochemistry. "I like to see new scientific discoveries actually being applied. This is currently an exciting challenge in nanotechnology." In the autumn of 2007, Kroon will conduct research at the Institut de Cičncia de Materials in Barcelona for a year.

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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