Three-dimensional structures of silicon and germanium will help refine oil

Russian scientists have created a new catalyst – a substance that accelerates the oxidation reaction of low-active, that is, poorly reacting, oil and gas components. The new method of processing hydrocarbons will make it possible to obtain such valuable organic substances as aldehydes, alcohols, etc., even at relatively low temperatures and pressures. The results were published in the Journal of Organometallic Chemistry.

“The catalysts we have created contain silicon (or germanium) and metals (copper, iron, cobalt, etc.) and are able to easily break bonds between carbon and hydrogen atoms in saturated and unsaturated hydrocarbons (which are the main components of oil and gas), converting them into valuable products: alcohols, acids, aldehydes, ethers, organic peroxides. One fact speaks about the relevance of this topic: works on the activation of carbon-hydrogen bonds were on the short list of nominees for the Nobel Prize in Chemistry 2017, ”says one of the authors of the article, assistant of the Department of Inorganic Chemistry of the RUDN University Alexei Bilyachenko.

In the course of the work, the scientists used synthetic methods that use the ability of organic derivatives of silicon and germanium to form unusual three-dimensional structures that include atoms of various metals. Such a framework ensures a high solubility of the catalyst in organic substances and thereby increases its duration of action. In addition, the very structure of the matrix determines the direction of the “catalytic attack” (for example, the oxidation of an organic molecule occurs in a strictly defined place).

The synthesized catalysts belong to the family of metallosilsesquioxanes – compounds in the form of a prismatic lattice of silicon or germanium oxide (at the edges) and metal oxides (in the middle part), combined with hydrocarbon rings.

Structural features and “nuclearity” (the number of metal atoms in the composition) strongly depend on the conditions for obtaining the catalyst, which creates certain difficulties for the researcher. One of the main results of this work is that the group has identified the necessary components of the reaction mixture, allowing to obtain a product with a certain number of metal atoms (this determines the activity of the catalyst, as well as its selectivity towards target molecules). In particular, when creating five- and six-nuclear compounds with copper and nickel, the presence of pyridine in the reaction mixture has been shown to have a strong effect on the reaction yield.

Another discovery was the possibility of synthesizing pentanuclear cobaltsilsesquioxanes in the presence of a solvent dimethylformamide, which is available and widely used in laboratory work. X-ray diffraction methods of investigation have made it possible to determine that the final compound consists of identical cells and, therefore, is stable and has a high accuracy of the “catalytic attack” sight. Moreover, it has good resistance to transitions between liquid and solid state, which can be useful in further practical use. These factors determine the increase in the use time and the efficiency of the catalyst.

The synthesized substance also copes with its main task, accelerating the oxidation reaction of hydrocarbons in oil and gas (as it was found out in experiments with copper-containing silsesquioxanes of various nuclearity). It is noteworthy that these reactions take place under “mild” conditions: relatively low temperature and pressure. This greatly simplifies their use as an industrial catalyst, since conventional technology requires maintaining a temperature of several hundred degrees and a pressure of about a dozen atmospheres using sophisticated and

expensive equipment.