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Peroxo-heteropoly compound PO4[W(O)(O2)2] was synthesized on calcium-deficient hydroxyapatite using a reaction of surface [HPO4]2− groups on hydroxyapatite with a Na2[W2O3(O2)4] aqueous solution. The vibration of [HPO4]2− at 875 cm−1 became very weak, and the vibration of the peroxo-oxygen bond [O–O]2− at 845 cm−1 appeared in the FT-IR spectrum of the solid product, indicating that PO4[W(O)(O2)2] was formed on the surface of hydroxyapatite. The formed solid sample was further reacted with PdCl2(PhCN)2 in an acetone solution to fix PdCl2 between the O sites on the hydroxyapatite. Elemental analyses proved that the resultant solid contained 1.2 wt.% Pd, implying that PdCl2 molecules were immobilized on the surface of hydroxyapatite. The hydroxyapatite-based hybrid compound containing Pd and PO4[W(O)(O2)2] was used as a heterogeneous catalyst in a methanol solvent for propylene epoxidation by molecular oxygen in an autoclave batch reaction system. A propylene conversion of 53.4% and a selectivity for propylene oxide of 88.7% were obtained over the solid catalyst after reaction at 363 K for 8 h. The novel catalyst could be reused by a simple centrifugal separation, and the yield of propylene oxide did not decrease after the reaction for five runs. By prolonging the reaction time to 13 h, the highest yield of propylene oxide at 363 K over the solid catalyst was obtained as 53.8%, which was almost the same as that of the homogeneous catalyst containing PdCl2(PhCN)2 and [(C6H13)4N]2{HPO4[W(O)(O2)2]2} for the propylene epoxidation. Methanol was used as a solvent as well as a reducing agent in the propylene epoxidation by molecular oxygen. Small particles of Pd metal were formed on the surface of the hybrid solid catalyst during the reaction, and acted as active species to achieve the catalytic turnover of PO4[W(O)(O2)2] in the propylene epoxidation by molecular oxygen in methanol. [ABSTRACT FROM AUTHOR]

Ti- and Al-containing MCM-41 (Al-c-MCM-41 and Al–Ti-c-MCM-41) have been synthesized and tested for direct oxidation of propylene with molecular oxygen. The reaction occurred over Al- and Ti-containing MCM-41 like materials. Al–Ti-c-MCM-41 was found to be more effective than Al-c-MCM-41, while no product was formed for MCM-41 alone. The catalyst performances of Al–Ti-c-MCM-41 at 523 K were dependent on the Si/Al2 and Si/Ti ratios and the highest PO yield was 3% when Si/Al2 of 150 and Si/Ti ratios of 100 were used. A postulated scheme containing Al and Ti species is proposed. [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]

Ti and Al containing MCM-41 (Al-c-MCM-41 and Al-Ti-c-MCM-41) have been synthesized and tested for direct oxidation of propylene with molecular oxygen. Al-Ti-c-MCM-41 is more effective than Al-c-MCM-41, while no product was formed for MCM-41 alone. It is also found that MCM-22 with Si/Al2 ratio of 30 and Na/SiO2 ratio of 0.18 is active for the reaction and a highest PO yield of 11.3% was obtained at 573 K. [Copyright &y& Elsevier]

The transition metal salts (Cu2+, Co2+ and Ni2+) of 10-molybdo-2-vanadophosphoric acid (H5[PMo10V2O40]) were supported on hexagonal mesoporous silica (HMS), and the resultant materials were used as catalysts for the selective oxidation of propylene to acetone by molecular oxygen. CuH3[PMo10V2O40]/HMS showed a high selectivity for acetone of 84.2% at 17.8% propylene conversion in a tubular fixed-bed reactor system under atmospheric pressure at 423 K. The high yield of acetone over CuH3[PMo10V2O40]/HMS at 423 K resulted from the proper acidity and oxidation ability of the heteropoly compound, the nature (acid property, redox property, etc.) of the Cu2+ counter-ion, the high surface area of the HMS support and the proper reaction temperature for the propylene oxidation. [Copyright &y& Elsevier]

Niobium-containing hexagonal mesoporous silica has been synthesized using n-dodecylamine as a template; the novel material is very active as a catalyst in the epoxidation of propylene with hydrogen peroxide and alkyl peroxides as oxidants. [ABSTRACT FROM AUTHOR]

Peroxo-polyoxometalates pillared hydrotalcite has been synthesized by decomposing [PW11O39]7- pillared MgPdAl-type hydrotalcite with 30% H2O2; the novel heterogeneous catalyst showed 91.5% selectivity for propylene oxide at 47.5% propylene conversion for propylene epoxidation by O2 in methanol at 353 K for 10 h. [ABSTRACT FROM AUTHOR]