Polyoxometalate catalyst

Marchal-Roch, C. Bayer, R. Moisan, J.F. Teze, A. Herve, G. Oxidative dehydrogenation of isobu-tyric acid Characterization and modeling of vanadium containing polyoxometalate catalysts. Top. Catal. 1996, 5,407-419. 

M. Fournier, C. Fuemi-Jantou, C. Rabia, G. Herve, and S. Launay, Polyoxometalates Catalyst Materials X-Ray Thermal Stability Study of Phosphorus-containing Heteropolyacids Hj xPMi2. xVx04o13-14H20 (M = Mo, W x = 0-1), J. Mater. Chem., 2, 971-978 (1992). 

SCHEME 85. Epoxidation of alkenes and alkenols with a perfluorinated quaternary ammonium salt of a polyoxometalate catalyst... 

Several functional ligninase models that do not contain key structural elements of LiP or MnP are worth mentioning since they do not use dihydrogen peroxide in the delignification process. Among them, robust polyoxometallate catalysts have been shown [64] to work well with dioxygen, thus making this chemistry commercially attractive. 

Figure 2.64 Structure of polyoxometalate catalysts used for the conversion of isobutane into methacrylic acid.

Besides hydrogen, other reductants for O2 in the liquid-phase epoxidation of propene include carbon monoxide, aldehydes, alcohols and other organic compounds. The reaction proceeds very efficiently with methanol as the reductant, in the presence of Pd and the Ti-Al-MCM-22 catalyst or Pd and peroxo-polyoxometalate catalysts the latter have been intercalated inside layered double hydroxides to make them heterogeneous [29e,h]. A propene conversion of 47%, with 91.5% selectivity for PO, was obtained at 80°C [29h]. 

D. Sloboda-Rozner, P. Witte, P. L. Alsters, R. Neumann, Aqueous biphasic oxidation A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide, Adv. Synth. Catal. 346 (2004) 339. 

T. Sakamoto, C. Pac, Selective epoxidation of olefins by hydrogen peroxide in water using a polyoxometalate catalyst supported on chemically modified hydrophobic mesoporous silica gel. Tetrahedron Lett. 41 (2000) 10009. 

S. Roy Chowdhury, P. T. Witte, D. H. A. Blank, P. L. Alsters, J. E. ten Elshof, Recovery of homogeneous polyoxometalate catalysts from aqueous and organic media by a mesoporous ceramic membrane without loss of catalytic activity, Chem. Eur.. 12 (2006) 3061. 

Polyoxometalate Catalysts on Benzene Hydroxylation with Hydrogen-Peroxide and 2 Reaction Types with and Without an Induction Period J. Mol. Catal. A. 152, 55 (2000). 

Kozhevnikov, I.V. 2002. Catalysis by Polyoxometalates Catalysts for Fine Chemical Synthesis. New York WUey. 

An example of a system for photocatalytic water oxidation with a molecular catalyst based on abundant metals is shown in Fig. Id. The Cobalt polyoxometalate catalyst is oxidized with Ru —trisbipyridine that is generated by quenching of the photo-excited Ru —trisbipyridine sensitizer with peroxodisulfate as sacrificial electron acceptor. The system operates at pH 8 and exhibits a high (30 %) photon-to-02 yield while the stability of the catalyst allowed for turnover numbers >220 that were limited by depletion of electron acceptor only [7]. This performance of the abundant-metal-based catalyst is superior to that of an analogue ruthenium polyoxometalate water oxidation catalyst. 

NomiyaK, Nemoto Y, HasegawaT, Matsuoka S (2000) Multicenter active sites of vanadium-substituted polyoxometalate catalysts on benzene hydroxylation with hydrogen peroxide and two reaction types with and without an induction period. J Mol Catal A Chem 152 55-68 Ono Y (1992) Perspectives in catalysis. In Thomas JM, Zamaraev KI (eds). Blackwell scientific publications, Oxford... 

As a consequence of showing that alkylated polyethyleneimines can facilitate aqueous biphasic catalysis, we extended the concept by the preparation of a cross-linked polyethyleneimine assembly that encapsulated a polyoxometalate catalyst, which resulted in the Upophiloselective oxidation of secondary alcohols (Scheme 9.17) [152]. Thus, even though reactions were carried out in water, competitive oxidation of a more hydrophobic alcohol in the presence of a hydrophilic alcohol significantly favored the former. The lipophiloselectivity was proportional to the relative partition coefficient of the substrates. 

Methacryhc acid is a major chemical conunodity produced annually via a multistep route that does, unfortunately, produce many environmentally undesirable by-products.Methacrylic acid, however, can also be direcily formed by oxidation of isobutane over polyoxometalate Keggin catalysts (e.g. H3PM012O40 and its vanadium-substituted analogs H3+xPMoi2-xVx04o) and such a green process has been investigated by several researchers. This possibility has resulted in many oxidation studies with polyoxometalate catalysts over the past two decades. 

Polyoxometalates Catalysts for Sustainable Oxidations and Energy Applications... 

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