OLEFIN METATHESIS OVER SILICA-SUPPORTED MOLYBDENA CATALYSTS ACTIVATEDBY UV IRRADIATION IN THE PRESENCE OF ALKANES

It is found that silica-supported molybdena catalysts (MoO3/SiO2) irra diated with UV light in an alkane (methane, n-butane, and isobutane) a tmosphere gain high activity in the metathesis of propylene and hexene -1 at 293 K. The efficiency of photoactivated catalysts in these react ions is determined. The UV-VIS and IR spectroscopic studies of the MoO 3/SiO2 catalyst showed that under UV irradiation of this system in the presence of alkanes, the reduction of Mo6+ ions to Mo5+ and Mo4+ ions and the formation of stable Mo4+ pi-complexes of olefins and, probabl y, carbene Mo=CH-R surface complexes, which provide high activity of t his catalyst in the olefin metathesis, occur. A scheme of conversions proceeding under UV irradiation via a key stage of Mo-C bond formation is proposed.