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

Abstract

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. MoO_x-based supported catalysts are promising alternatives to the industrially applied WO_x-containing systems. The activity of such catalysts depends on the amount of active Mo–carbene (MoCHR) sites formed in situ upon reaction of supported MoO_x species with olefins. Herein, we demonstrate a way to control the ability of such species on the surface of AlSiO_x 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 MoO_x species into Mo–carbenes. The additive electronegativity (Pauling scale) affects olefin adsorption and therefore the formation of carbenes.