The key role of Brønsted acid sites in olefin metathesis over promoted MoO3/Al2O3 catalytic systems

[Display omitted] •Olefin metathesis is a commercially successful method for converting less valuable olefins into more valuable ones;•Modification of the γ-Al2O3 acidic properties by treatment with NH4HF2, (NH4)2SiF6, H3BO3 leads to a significant increase in the catalytic activity of MoO3/Al2O3 systems in propylene metathesis;•An increase in conversion in the propylene metathesis reaction correlates with an increase in the concentration of strong Brønsted acid sites on the surface of the catalysts;•The formation of centers active in propylene metathesis occurs when the substrate interacts with strong Brønsted, but not Lewis acid sites on the surface of the catalyst;•Highly selective promoted olefin metathesis catalyst provides propylene conversion 8.5 times higher compared to classical, unmodified MoO3 /Al2O3 systems. One important way to increase the production of higher-margin products from less valuable unsaturated hydrocarbons is the widely used process of catalytic metathesis. Progress in the development of more advanced metathesis catalysts is hampered by obvious gaps in scientific knowledge about this process. This work is aimed at establishing the influence of physicochemical properties of Mo-containing lower olefins metathesis catalysts and developing methods for increasing their activity through promotion. A classic support for Mo-oxide metathesis catalyst was promoted with NH4HF2, (NH4)2SiF6, H3BO3 additives. The synthesized systems were analyzed by a large set of methods. The catalytic properties of obtained systems were determined in the propylene metathesis reaction. It was shown that the proposed promotion leads to an increase in activity of the catalyst up to 8.5 times. It was shown that strong Brønsted acid sites play a decisive role in increasing activity. In addition, it has been experimentally proven that the formation of active centers occurs when the substrate interacts with Brønsted, but not Lewis acid sites on the surface of the catalyst. The discoveries obtained in this work can serve as the basis for the creation of a new generation highly active lower olefins metathesis catalysts.