
Unimagined effect: The grinding process in a ball mill activates a catalyst in such a way that it facilitates the synthesis of ammonia at a much lower temperature and pressure than is necessary in the well-established Haber-Bosch process.
Five hundred degrees Celsius and 200 bar - these are the conditions usually required to get nitrogen to combine with hydrogen to generate ammonia. Only in this form can the nitrogen be used by plants. Despite all the controversy surrounding mineral fertilizers, the Haber-Bosch process is making an essential contribution to feeding the growing world population. It is thus no wonder that Fritz Haber and Carl Bosch as well as Max Planck researcher Gerhard Ertl, who elucidated exactly what happens in the process, were awarded the Nobel Prize in Chemistry. Nevertheless, chemists are still fixated on the synthesis of ammonia. "This has been a dream reaction for 100 years", says Ferdi Schüth, Director at the Max-Planck-Institut für Kohlenforschung in Mülheim an der Ruhr. This expresses both how economically important the transformation is and how difficult it is to achieve. Because ammonia is considered a potential storage medium for hydrogen produced with renewable energy, it could become even more important.
Chemists would like to dispense with the harsh reaction conditions - also because of the amount of energy required. Considerable efforts have been made to find an alternative method of production: other catalysts, light as an energy source, electrolysis, and even mechanocatalysis - processes that take place in a ball mill. But these methods have yielded only minute amounts of ammonia (if any at all).















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