Effect of AlSiOx support modification by alkali or alkaline earth metals on propene formation in the metathesis of C2H4 and 2-C4H8 over MoOx-based catalysts

The metathesis of ethylene with 2-butene to propene is currently applied for large-scale on-purpose production of this building block of the chemical industry. MoOx-based supported catalysts are promising alternatives to the industrially applied WOx-containing systems. The activity of such catalysts depends on the amount of active Mo-carbene (Mo=CHR) sites formed in situ upon reaction of supported MoOx species with olefins. Herein, we demonstrate a way to control the ability of such species on the surface of AlSiOx to be transformed into Mo-carbenes by promoting the support with tiny amounts of alkali or alkaline earth metal (Li, Sr, Ca, Mg, Na, K, Ba, Rb, or Cs) oxides. The electrophilic properties of these additives were established to be relevant for in situ transformation of supported MoOx species into Mo-carbenes. The additive electronegativity (Pauling scale) affects olefin adsorption and therefore the formation of carbenes.

Automated summary

The metathesis reaction of ethylene and 2-butene to produce propene is widely used in the chemical industry. MoOx-based supported catalysts show potential as alternatives to the currently employed WOx-containing systems. The activity of these catalysts depends on the formation of active Mo-carbene sites, which can be controlled by promoting the support with small amounts of alkali or alkaline earth metal oxides. The electronegativity of the additives affects olefin adsorption and carbene formation.