Preparation of Vicinally fixed Pd-Heteropoly Acid

用硅烷偶联剂对不同载体（SiO2、TiO2、Al2O3等）进行化学修饰，使钯和杂多酸在载体上固定。将14-磷酸钒（PV14）中的(Pd) / (PV14)原子比调整为等于2时，可有效地获得较高的醇类对醛的活性和选择性。另一方面，利用FT-IR和XPS分析了12-磷钨酸盐和12-磷钼酸盐与含氨基硅烷偶联剂改性载体表面的相互作用。结果表明，通过酸碱相互作用，HPA具有很强的固定性和均匀性，几乎达到单层。此外，通过ESR发现，电子从苯胺基转移到HPA，从而稳定了PMo12的还原态。事实上，在改性的PMo12催化剂上，异丁酸被非常有效地氧化为甲基丙烯酸。

Various carriers (SiO2, TiO2, Al2O3, etc.) were chemically modified with silane coupling agents to fix vicinally Pd and heteropolyacids on the carriers. When the atomic ratio of (Pd) / (PV14) in 14-vanado-phosphate (PV14) as HPA was adjusted to be equal 2, quite high activities and selectivities of alcohols to aldehydes were effectively obtained. On the other hand, the interaction of 12-phosphotungstate and 12-phosphomolybdate with the modifed carrier surfaces with silane coupling agents having amino group were analyzed in detail by FT-IR and XPS.As the results, the HPA were clarified to be fixed strongly and homogeneously up to almost monolayr through an acid-base interaction. By ESR,furthemore, it was recognized that an electron transfer from anilino group to HPA so as to stabilize a reduced state of PMo12. In fact, isobutylic acid was quite effectively oxidaized to methacrylic acid on the modified PMo12 catalysts.