Formation of isolated tungstate sites on hierarchical structured SiO2- and HY zeolite-supported WOx catalysts for propene metathesis

Abstract

The formation of isolated tungstate sites on hierarchical structured SiO2 nanoparticles and HY zeolite with high Si/Al ratio (Si/Al 500) was investigated in the self-metathesis of propene over supported WOx-based catalysts. The synthesis of hierarchical HY not only increased the tungsten dispersion in the forms of isolated tungstate oxo species (mono-oxo and di-oxo) by increasing the terminal silanol group density of the support for these oxides to be grafted on but also greatly reduced the heavy hydrocarbon formation simultaneously by elimination of some alumina from the zeolite. As a consequence, higher propene conversion was obtained without the undesired reactions especially during the initial stage, when the metallocarbene was not fully developed. The results present a facile method for the development of heterogeneous WOx-based metathesis catalysts and a better correlation between the surface properties of catalyst support and the formation of tungsten pre-catalysis active species.