| Catalysis by polyoxometalates is a field of increasing importance. In applied catalysis,most of the pioneering work has been done since the 1970s mainly by Japanese, eightworld-famous industrial processes of ten thousand products per year based onpolyoxometalates. In the heterogeneous as well as homogenous catalytic system, using polyoxometalates asacid-base, oxide-redox or bifunctional catalysts, there are several advantages such as highcatalytic activity, products selectivity, mild reaction conditions, light atmospherecontaminated. On the other hand several advantages that traditional catalysts has none, whichmake them economically and environmentally attractive especially in selectivetransformations of organic substances, oxidation of unsaturated compounds, hydration ofolefins: 1, the stable structure;2, very high solubility in polar solvents;3, unique"pseudoliquid phase";4, heteropoly acid anions exhibit an extremely high proton mobility.This catalytic oxidation of alicyclic alkene used H2O2 (30 %) as "green" and "friendly"oxidant. This work had four aspects as follows:1,We explored the catalytic activity of vacant polyoxometalate. Oxidation reaction ofcyclohexene in 1,2-dichloroethane solvent was catalyzed by trivacant Keggin-typepolyoxometalate tetra-butylammonium salts [(C4H9)4N]9[A-α-PW9O34] ,[(C4H9)4N]9[(FeШ(OH2)2)3(A-α-PW9O34)2] and [(C4H9)4N]4H3[PW11O39]. The probablemechanisms were discussed in this paper .2, We studied the number of ordinated water of polyoxometalate catalysts how to affect thecatalytic activity. Oxidation of cyclohexene with hydrogenperoxide (30%) solution asoxidant in 1,2-dichloroethane solvent was catalyzed by tri-ordination water Keggin-typesandwich polyoxometalate tetra-butylammonium salts [(MⅢ (H2O))3(BiW9O33)2]12-(M=Co,Mn, Ni ) and double tri-ordination water [(MⅡ(H2O)3)2(WO2)2(BiW9O<sub>33)2]<sub>10(-M=Co, Mn, Ni ).3, We investigated the catalytic activity of the number of transition-metal-iron insandwich-type polyoxometalate catalysts. Oxidation of cyclohexane in acetonitrile solventcatalyzed by two transition-metal-iron sandwich Dawson-type(TBA)16[Fe2(NaOH2)2(P2W<sub>15O56)2 and three or four Keggin-type (TBA)9[(FeⅢ(OH2)2)3(A-a-PW9O34)2] or (TBA)12[(SiW10O37)2Fe4(OH)4].4, We prepared polyoxometate [Ag6(PMo10V2O40)](CH3COO).8H2O nanoparticles inmiremulsions comparing the catalytic activity with [Ag6 (PMo10V2O40)](CH3COO).8H2Oin the catalytic oxidant cyclohexane system in acetonitrile.
|
PDF Full Text Request