Catalysis: the key to the success of chemical processes
CONICET/DICYT At a single glance, an exhaust pipe and a washing powder seem to have nothing in common; however, they both contain therein substances, catalysts, which accelerate the rate of a chemical reaction without changing the end product. From the times of the old alchemists to this time, scientists have studied the mixtures of products that increase the efficiency of the new compounds that are produced from them. Nowadays, more than 80% of the industrial products we consume are produced from catalysis.
“Many production processes include at least one catalytic process based on the addition of external material, called catalyst, in the reaction. Our group studies conventional and biological catalysis. There are conventional catalysts such as metals, oxides, sulphides of metallic and semi metallic elements, and there are others biological ones like the enzymes”, Daniel Damiani, CONICET principal researcher at the Planta Piloto de Ingeniería Química (PLAPIQUI, CONICET-UNS) [Chemical Engineering Pilot Plant] and director of the Área de Catálisis de la Planta [Catalysis Area of the Plant], explains.
Damiani states that the research team looks for an integral approach, both from the point of view of engineering as well as physics and chemistry, in order to study not only new catalysts. The researchers also assess the processes already established to find new catalysts, considering a sustainable chemistry perspective that demands less energy and strengthens the processes to reduce costs, simplify steps and obtain better quality products.
“In most cases, it is possible to improve the processes so as to make them continuous, that is to say, to have a permanent production. Several process associated to biochemistry are discontinuous and the catalyst tends to be lost because it is necessary to filter it. A new design will avoid this step and recover the catalyst. Therefore, it would be possible to minimize the disposal costs since usually conventional catalysts are heavy metals and it is not easy to dispose them. Researchers seek for improvements to obtain sustainability in time, in order to reduce energy, steps and environmental impact”, the scientist adds.
As regards that, Damiani highlights the study conducted by María Luján Ferreira, CONICET principal researcher at the PLAPIQUI who focuses on biological catalysis, where chemical reactions are catalysed by proteins called enzymes. Enzymes work at the body temperature of living organisms and are very selective, that is to say that they act on a specific substance, which eliminates the need to separate different products and the catalysts in the final mixture.
“The enzymes are interesting because they could be used in industrial processes and work at low temperatures, which reduces the energetic and separation costs. This catalysis has a promising future but there are many problems to be solved, such as immobilizing the enzymes to use them with the ordinary catalysts and put them on a stand”, Ferreira states.
The researcher explains that generally the enzymes are bought from international companies and are very expensive. She studies how to immobilize enzymes to stabilize, use and reuse them without the need of a stand. “In enzymatic catalysis, the premise is to find a niche to substitute imports. We are in charge of immobilizing the enzymes, and there will be people devoted to grow a fungus or bacterium from where enzymes are extracted”, she explains.
However, Ferreira comments that despite their several advantages the enzymes have associated problems, such as the fact that they do not work above 90ºC. “What is saved on the one hand becomes more expensive on the other. Therefore, many times the enzymes are interesting as a benchmark to things similar to them, such as mimetic or biometics. These can withstand higher temperatures and resist, so they do not stop working as catalysts”, the researcher adds.
Catalysis in oleochemical industry
The PLAPIQUI team studies this process to use it in the transformation of vegetable oil to produce biofuel, food and cosmetics, among other products”, Gabriela Tonetto, CONICET independent researcher at the PLAPIQUI, states.
“We use heterogeneous and enzymatic catalysis in order to increase the added value of the products made of oil. We study the modification of the oil hydrogenation process to lower costs and improve the production process of the biodiesel.”
The scientist explains that the biorefineries use very corrosive and inexpensive catalysts such as sodium methoxide, so they study its replacement with less aggressive compounds such as zinc salts.
As regards the production of hydrogenated oils, industries tend to use nickel as a catalyst, as a fine powder. Once the product is obtained from the hydrogenation process it is necessary to filter it hot. A great percentage of the cost of production of that oil corresponds to that procedure. “In order to solve that problem, we study structured catalysts. We put the catalyst in structure that has the shape of a honeycomb that also acts as a reactor agitator. This enables the easy separation of product avoiding the filtering stage and makes the process more profitable”, Tonetto states.
For his part, Damiani affirms that the advances in the hydrogenation process of oil can be extrapolated to any reaction of the same type, in which the catalyst is a very fine powder that has to be separated through filtration.
Finally, Tonetto comments that together with Ferreira they study the development of structured triglycerides from glycerol. They modify the components of the structure of common oil to use it for nutritional complexes and hypolipidemic diets.
“In terms of heterogeneous catalysts, we work with very economical and solid oxides that can also be filtered and are not corrosive. What we are doing with enzymatic catalysis has as an advantage:the fact that it allows us to obtain a selective product. This is really interesting because we develop a very expensive product, such as an oil with selective functions, from something very cheap”, the scientist concludes.