OLEFIN METATHESIS OVER SUPPORTED SILICA-MOLYBDENA CATALYSTS ACTIVATEDBY GAMMA-IRRADIATION AND MECHANOCHEMICAL TREATMENT IN THE PRESENCE OFALKANES

It is found that supported silica-molybdena catalysts (MoO3/SiO2) exhi bit high catalytic activity in propene and l-hexene metathesis at 293 K after gamma-irradiation or mechanochemical treatment (MCT) under an alkane atmosphere (methane, butane). Specific catalytic activities and productivities of the activated catalysts in the metathesis reactions are determined. On the basis of UV-Vis spectra and IR spectra of adso rbed CO, it is shown that gamma-irradiation and MCT of the catalysts i n the presence of alkanes result in the reduction of Mo6+ ions to Mo5 and Mo4+, in the formation of stable pi-complexes of Mo4+ With olefin s, and, probably, in the production of surface carbene complexes Mo=CH -R. The latter are supposed to provide high catalytic activity in olef in metathesis. A scheme of processes occurring under gamma-irradiation and MCT is proposed. A key step in this scheme is the formation of th e Mo-C bond.