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Abstract: A new type of layered double hydroxides intercalated by peroxo-polyoxometalates was synthesized by treating PdMAl-[PW11O39] (M = Mg2+ or Zn2+) with 30% H2O2. XRD, FT-IR, and 31P MAS NMR revealed that the interlayer anion [PW11O39]7− was converted mainly to {PO4[WO(O2)2]4}3− and [W2O3(O2)4(H2O)2]2−. 27Al MAS NMR revealed that the brucite-like layers did not collapse during synthesis. PdMgAl-[PW4 + W2] showed 91.5% selectivity for propene oxide at 47.5% conversion during propene epoxidation by O2 in methanol at 353 K for 10 h. The catalytic ability of PdMgAl-[PW4 + W2] can be attributed to the presence of highly active Pd particles in the brucite-like layers that generate H2O2 in situ, the strong epoxidation ability of interlayer peroxo-polyoxometalates with dilute H2O2, and the promotion effect of the basic MgAl-type brucite-like layers toward alkene epoxidation. Moreover, PdMgAl-[PW4 + W2] can be separated and reused by filtration without leaching active components into the solvent. [Copyright &y& Elsevier]

The catalyst system consisting of Pd, Ti-modified MCM-22, and methanol was found to catalyze the epoxidation of propylene with molecular oxygen without hydrogen and PO was formed with a PO yield above 19.5% and 458 turnovers based on palladium. The catalyst performance of Pd is affected by the properties of Ti-modified MCM-22 such as BET surface area and the amount of NH3 adsorption. The catalyst material consisting of palladium and Ti-modified MCM-22 can be recovered and used 3 times without reduction in the PO yield. It is assumed that not only palladium but also peroxy intermediates derived from methanol/oxygen play an important role in the oxidation of propylene. [Copyright &y& Elsevier]