One of the most important reactions in organosilicon chemistry is hydrosilylation: this is how those silicones and organosilanes are obtained, without which it is difficult to imagine the modern chemical industry. Silicone materials are used in all industries, from agriculture to aviation. But the classic method of their production — hydrosilylation — is based on platinum catalysts. Platinum is quite expensive and it is difficult to separate it from the final product. Today, platinum costs account for about 30% of the cost of the silicon industry.

Earlier, a team of scientists from INEOS RAS, INHS RAS and Moscow State University proposed a stable and easy-to-use heterophase (biphasic) catalytic system for hydrosilylation. It is based on a simple and affordable platinum salt (K2PtCl4) as a source of catalytically active Pt, and cheap ethylene glycol as a solvent (phase) for the Pt catalyst. Due to the high hydrophilicity of such a catalyst, it does not mix with highly hydrophobic reagents and products (analog: water-oil), allowing the reaction to be carried out at the interface and the catalyst to be separated by conventional decanting.

"Our team is developing catalytic methods, mainly for the production of organosilicon compounds and silicone materials. Previously, we proposed heterophase catalytic systems for hydrosilylation, which combine the advantages of homogeneous and heterogeneous catalysts: the high activity of the former and the recyclability of the latter. Due to this, it is possible to carry out at least 40 recycling of such a catalyst under mild conditions: room temperature and atmospheric pressure.

At the same time, periodic recycling is labor- and time-consuming. In addition, difficulties arise when scaling the process due to problems of heat and mass transfer, which are most pronounced in such multiphase systems. These problems are already more technical and physical. Therefore, one of the most promising approaches to solve them is the use of flow–through microreactors and automation of the process," says Ashot Arzumanyan, Head of the INOES RAS and INHS RAS group.

To increase the efficiency of this process, it is necessary to increase the contact area of the two phases of the catalyst and reagents, as well as automate the process of separation and reuse of platinum. Microfluidic reactors are ideal for this. They consist of very narrow capillaries (less than a millimeter wide) in which catalyst droplets with a volume of less than a microliter move in an organized manner in a solution of reagents. This makes it possible to increase the contact area of the phases by an order of magnitude compared to simple mixing.

The production is based on the use of modern additive technologies. The complex geometry of microchannels in a matchbox-sized device is obtained by DLP printing by exposing a focused UV beam to a photopolymer resin. Scientists of the International Research Institute of Intelligent Materials of the Southern Federal University are engaged in the development of such microfluidic reactors for accelerated production of new materials within the framework of the Priority 2030 program (national project "Science and Universities").

Real-time monitoring of the reaction product output was required to implement the process in flow mode. To this end, the authors used confocal Raman microscopy.

At the same time, in terms of performance, the proposed continuous method is not inferior to the previously proposed periodic one – the reaction takes place in just five minutes. This will make it possible to scale the production of silicones many times in the future, reducing financial costs and minimizing manual labor.

"The developed solutions are also applicable to other multiphase chemical processes, including the production of a number of small and large-tonnage products. Cooperation with the leading academic institutions of the country allows us to continuously modernize the microfluidic devices and software being developed for new scientific tasks, as well as offer ready—made solutions for commercial companies," says Alexander Guda, head of the SFedU Youth Laboratory.