Room-Temperature Metathesis of Ethylene with 2-Butene to Propene Over MoO x -Based Catalysts: Mixed Oxides as Perspective Support Materials

We investigated the effect of supports based on ZrO 2 , TiO 2 , Al 2 O 3 , and SiO 2 on the rate of propene formation in the metathesis of ethylene with 2-butene at 50 °C over Mo-containing catalysts possessing highly dispersed MoO x . Large improvements in this rate were achieved when using supports composed of mixed oxides (ZrO 2 –SiO 2 , ZrO 2 –PO 4 , TiO 2 –SiO 2 ; Al 2 O 3 –SiO 2 ) rather than of individual oxides (ZrO 2 , TiO 2 , Al 2 O 3 , SiO 2 ). Although previous literature studies dealing with the metathesis reaction over Al 2 O 3 - or SiO 2 -suppported catalysts at higher temperatures suggest the importance of redox or acidic properties of supported MoO x species for catalyst activity, we were not able to establish any general direct correlation in this regard. Contrarily, the rate of propene formation can be significantly enhanced when promoting supports with an oxide promoter. We suggest that the created support lattice defects may facilitate the transformation of MoO x to Mo carbenes under reaction conditions or improve the intrinsic activity of the latter. Graphic Abstract