It is not a secret that the oil and natural gas are used today not only as a fuel but also as a raw material in a variety of industries. Organic synthesis is used in pharmaceuticals and petrochemicals, industrial production. You can not act without catalysts in the field of oil and natural gas, but today they invariably contain precious metals, such as palladium, platinum, iridium, rhodium and gold. These substances rare naturally occur, and their stocks are not limitless. Consequently, their use in the catalysts increases the cost of the entire production. Such catalysts, which are generally solid materials that accelerate the reaction and allow for more targeted use of resources (e.g., electricity), are used nevertheless in 90% of oil and natural gas processing, as well as for the neutralization of automobile exhausts.
A group of scientists from N.D. Zelinsky RAS Institute of Organic Chemistry under the guidance of Leonid Kustov, Doctor of Science, Professor, tends to make catalysts more accessible. "It would be very attractive to eliminate or at least reduce the content of precious metal in catalysts for the production of valuable organic products", - he said.
The main task of scientists is to develop technology to produce cheaper catalysts, replacing precious metals with other metals, at the same time, retaining their functional properties.
Main characteristics of the catalyst are the active (the more active, the fewer of it is required), the selectivity (the more selectivity, the less byproducts are obtained). "Selectivity is very important, because if the selectivity of the catalyst is low, part of the raw material is lost: it will go into by-products, which in turn will require recycling or disposal", - Kustov explained.
Research is being conducted by scientists in several ways. Firstly, researchers are trying to change the structure itself of the catalyst metal: to use metal nanoparticles, which are more active than the larger particles. "We use original approaches, such as microwave radiation. Many people have wave ovens at home, and we use them to get the nanoparticles of the right size in catalysts", - Kustov said.
Secondly, scientists tend to use combined materials (bimetal systems), replacing the part of the precious metal by cheaper and affordable one.
"Imagine a cherry. Its "pit" is made of cheap metal, and its "peel", or rather "eggshell" is made of noble". In such embodiment, the noble metal is needed substantially less - only 3-5% of the amount required for conventional systems. In this case, according to Kustov, the precious metal content can be reduced by 10-20 times, and the functional properties of the catalyst will remain the same.
Scientists work out these techniques on a few selected groups of reactions, which are actively used in production.
The most common and popular group are the hydrogenation reactions, which are widely used in industry, petrochemical industry, pharmaceutical industry, production of special rubbers. "We are trying to replace today used metals - palladium, rhodium and others - by the less noble, as copper, nickel, cobalt and iron".
Iron nanoparticles work well in the hydrogenation, their properties are not inferior to palladiums and in some cases, for example, during the hydrogenation of rubbers, even exceed it. But iron is, in general, the cheapest of all metals known to man. It looks like we're going back to the Iron Age, at least in the field of hydrogenation, and it gives us the advantages".
Moreover, scientists are testing catalysts for reductive amination reactions, which allow to obtain the amines used in pharmaceutics, as well as to create fuel additives and other nutrients. This reaction, however, is applied narrower than the hydrogenation.
The third group of reactions is investigated by Japanese specialists. These are cross-coupling reactions. "In the cross-coupling reactions two organic molecules, often quite complex, react with each other, constituting a third, even more complex molecule. In this case, the reaction produce almost no waste", - Kustov said.
This type of reactions is used in pharmaceuticals and fine chemicals.
Now scientists have begun the second phase of the project. In the first stage, the most intense one, according to Kustov, scientists prepared an article «Selective oxidation of ethanol to acetaldehyde over Au-Cu catalysts prepared by a redox method», published in the specialized journal Catalysis Today and filed several patent applications, including European one, on catalysts manufacturing technology, hydrogenation of polymers and hydroamination. 3 more publications are scheduled before the end of the year, in addition, methods of new catalysts using in certain reactions will also be protected by patents.
The project "Development of catalysts containing no precious metals for the synthesis of valuable organic products" is supported by the Federal Target Program "Research and development in priority areas of scientific and technological complex of Russia for 2014-2020".
Source of illustrations: Elena A. Redina, Alexander A. Greish, Igor V. Mishin, Gennady I. Kapustin, Olga P. Tkachenko, Olga A. Kirichenko, Leonid M. Kustov, Selective oxidation of ethanol to acetaldehyde over Au-Cu catalysts prepared by a redox method, Catalysis Today 241 (2015) 246-254