Featured Lendület Researcher: Zoltán Novák
The chemical and pharmaceutical industries would be unthinkable today without catalysts. Therefore, the development of increasingly efficient catalysts is one of the most important goals of chemistry, as these catalysts make chemical synthesis cheaper, more sustainable and environmentally friendly. Zoltán Novák, professor in the Department of Organic Chemistry at ELTE and head of the Sustainable Catalytic Processes Research Group, and his colleagues are also working on the development of new types of catalysts which are partially recyclable and reusable and require only small amounts, can be activated by controllable external impulses, and do not require expensive precious metals.
Novák has been working on the synthesis of small molecules in ELTE’s Department of Organic Chemistry since 2007. Modern organic chemical syntheses are almost unthinkable without the use of catalysts. Catalysts are atoms or molecules that facilitate chemical reactions and can be recovered from the system at the end of the process, so they are not incorporated into the products. Enzymes act as catalysts in an organism, making all molecular biological reactions possible. But most modern chemical and pharmaceutical processes, and processes using all kinds of chemical reactions in general, cannot be imagined without catalysis, so the development of more efficient and sustainable catalysts is of huge importance.
Trends and alternatives
In the Sustainable Catalytic Processes Research Group at ELTE, mainly precious metals (such as palladium, ruthenium and rhodium) are used as catalysts, which are quite rare and expensive. Thus, the question naturally arises every day in chemical research groups worldwide which use precious metals as to how long these metals will be available and affordable. This could, for example, have a decisive effect on the synthesis of future drug molecules.
“Current trends in the field of science are pointing towards the replacement of these precious metal catalysts, for example, by iron or other cheaper, more abundant metals instead of precious metal-based catalysts,” says Novák, professor and research group leader. “Of course, this is easier said than done, since it was not by chance that palladium and other precious metals were first used: their special properties are very difficult to imitate with the help of cheaper metals. The other trend is that if we have to use expensive precious metals, we should use them as efficiently as possible, so that the catalysts can be recovered and reused and only a small amount of them is needed.”
For the chemical reactions that are currently performed routinely, about one percent of catalyst must be added, that is, one catalyst molecule (or atom) is required to convert one hundred molecules of material. In theory, however, this efficiency can even be raised to the part-per-million range, when each catalyst particle would be able to make one million molecules react. Reducing the catalyst amount would also be important because, for example, during pharmaceutical chemical reactions, the catalyst must be recovered almost perfectly and cannot remain in the product. If little catalyst is added to the system in the first place, purification is also easier.
The popular fluorine atom
The goal of the Momentum Research Group is therefore to develop systems in which known and new reactions can be carried out using fewer precious metal catalysts, sustainably and economically. In modern chemistry, catalysts are already being designed for the reactions to be carried out, and Novák and his colleagues are partly preparing for this.
Activation – but with what and how?
As new types of catalysts are designed, different ways of activating them will also be experimented with. The activation of the catalyst starts the chemical reaction itself, so by modifying the external energy required to activate it, the process can be controlled. Depending on the composition of the catalyst, it can be activated, for example, by heat, light, electrochemical or mechanochemical pulses (the latter can be done in ball mills, for example). The research team has already worked on catalyst activation by light, and the grant will help them try to develop this research further.
In addition to catalysts, substrates (the materials whose transformation is facilitated by the catalyst), and activation, solvents are another factor that can be used to influence catalysis. In organic chemistry, organic solvents are generally used because substances are most soluble in substances of similar polarity. However, these solvents can have disadvantages, such as being expensive, flammable, toxic and the raising of environmental concerns.
The replacement of traditionally used organic solvents with water would be a major improvement and would solve many problems, but most relatively apolar organic compounds are poorly soluble in water. This difficulty can be overcome by the addition of surfactants. Like soap, surfactants can bind to both polar and apolar molecules to form micelles. The micelles trap the apolar molecules inside them, which then have a very high local concentration, accelerating the reactions amongst them. The research team will also investigate the usability of these micelle systems.
“Our concept would be to use biologically produced and biodegradable micelle-forming agents, even from organic waste, to carry out catalytic processes,” says Novák. “Biosurfactants are now produced in the chemical industry on a tonnage scale and are widely used in household products and cosmetics. We are trying to establish their application in the pharmaceutical industry. To this end, we are already in contact with interested industrial partners.”