载体钒氧化物中钒-吸附物分子相互作用的ESR研究

AN ESR STUDY OF VANADIUM-ADSORBATE INTERACTION ON SUPPORTED VANADIUM OXIDE CATALYST

电子自旋共振技术已经用来研究还原态V_2O_5/SiO_2催化剂和各种吸附分子的相互作用。实验指出:具有四面体配位结构的V^(4+)离子是活性中心,V^(4+)和CH_2OH,HCl,CH_3CN分子的相互作用导致形成八面体配位结构的表面VO^(2+)络合物,它们的ESR和成键参数计算指出不成对电子主要定位在钒离子的d轨道上。77 K下吸附O_2分子已经观察到氧自由基的ESR信号,但吸附乙烯和丙烯不能改变V^(4+)离子的配位结构。

ESR technique has been used to study the interaction of reduced V2O3,/SO2 catalyst with a variety of adsorbed molecules. It has been shown that the V4+ ions with tetrahedral coordination are active centers. Their interaction with adsorbed molecules, such as CH3OH, HCl, and CH3CN etc, leads to the formation of octahedrally coordinated VO2+complexes on the surface of the catalyst. The calculation of bonding parameters of surface complexes formed indicates that the unpaired electron is mostly confined to the vanadium ions d-orbital. The adsorption of oxygen at 77 K leads to the formation of various oxygen radicals. But no change had been found for the coordinated state of V4+ ions after adsorption of ethylene or propylene molecules.