Catalysts For Oxidation Of Cyclohexane Research Articles

Molecular design of catalysts on the basis of functionalized poly(ethylene oxide) and block copolymers of ethylene oxide and propylene oxide

AbstractTransition metal complexes based on polyethylene oxide and copolymers of ethylene oxide and propylene oxide functionalized by dipyridyl, acetylacetone and catechol have been prepared. Macrocomplexes showed high activity and selectivity as catalysts in oxidation of cyclohexane, hydroxylation of benzene, epoxidation of hexene and allylic alcohol bound by hydrogen peroxide, oxidation of ethylbenzene by dioxygen.

Cationic iroporphyrins as catalyst in comparative oxidation of hydrocarbons: homogeneous and supported on inorganic matrices systems

Cationic ironporphyrins in solution and supported on imidazole propyl gel (IPG) and silica gel (SG) as catalyst in cyclohexane hydroxylation using iodosylarene as oxygen donor were studied. FeTM4PyP 5+, 1 as homogeneous catalyst for cyclohexane hydroxylation, in acetonitrile (CH 3CN) and ultrasound stirring, gives cyclohexanol (C-ol) yields of 20%. The FeTM2PyP 5+, 2 as catalyst for cyclohexene oxidation in CH 3CN and ultrasound stirring is a very efficient system, giving 93% of total yield, with an epoxide:alcohol:ketone selectivity of 77:12:11. The supported systems, 1-IPG and 1-SG are particularly efficient in dichloromethane (CH 2Cl 2), giving C-ol yields of 37% and 53%, respectively. These systems consist of polar hemin in isolated sites, which selectively catalyze cyclohexane oxidation in apolar solvent. They represent good cytochrome P-450 model systems. In the same way, the active site of P-450 consists of a polar protohemin in a hydrophobic pocket, promoting selective cyclohexane oxidation. These rigid cationic 1-IPG, 1-SG, 2-IPG, 2-SG, 3-IPG and 3-SG systems can catalyze with very small amounts of ironporphyrins, which correspond to about 30–80 times fewer numbers than the hemin in P-450 catalytic site.

AlPO4 Molecular Sieves Modified with Metal Chelate Complexes

A new method for modification AlPO4 molecular sieves has been presented. Lack of ion-exchange properties makes the modification of aluminium phosphates for catalytic applications difficult. We have developed a method that involves the crystallization of AlPO4 molecular sieves around metal complexes. This results in encapsulation of the complexes within the intracrystalline pore system. Several metallophthalocyanines have been successfully encapsulated into AlPO4-5 and subsequently tested as catalysts for cyclohexene oxidation. Significant differences in activity result from the presence of different metallophthalocyanines.

Mechanism of the catalytic action of penta(dimethylsulfoxido)vanadyl hexathiocyanatoplatinate in the liquid-phase oxidation of cyclohexene

1. The complex studied — penta (dimethylsulfoxido) vanadyl hexathiocyanatoplatinate (I) is an effective catalyst for the low-temperature oxidation of cyclohexene in alcoholic media, ensuring a high reaction rate up to a high degree of conversion. 2. It has been established that there is a synergism between the component parts of the catalyst, the maximum rate of oxidation of cyclohexene being observed with V/Pt=2. 3. In the initial stages of the oxidation of cyclohexene in the presence of (I), the reaction rate is described by the kinetics of a chain growth-chain breaking process.

Physico-chemical properties of iron-tin mixed oxide catalysts in cyclohexane oxidation

The state of mixed iron-tin oxide catalysts with a variable ratio of their metallic components has been studied by Mossbauer and ESCA spectroscopy. The results are compared with the activity of these catalysts in cyclohexane oxidation.

Heterogeneous Catalysis in Liquid-Phase Oxidation of Olefin. II. Dependence of the Structure of Vanadium–Chromium Binary Oxide Catalyst for Oxidation of Cyclohexene on the Method of Preparation

Abstract The influence of preparative conditions on the structure and catalytic activity of V–Cr oxide catalyst for the liquid-phase oxidation of cyclohexene has been investigated. Three series of binary oxide, V–Cr-D, V–Cr-E, and V–Cr-F, were prepared from acidic, neutral, and alkaline media, respectively. The specific activity of the catalyst was found to be in the order: V–Cr-D>V–Cr-E>V–Cr-F, the catalyst prepared from acidic medium showing the highest activity. The results of structure analysis showed the formation of several chromium isopolyvanadates, i.e., chromium pyrovanadate, chromium metavanadate, and unknown phase (probably chromium polyvanadates), together with V2O5, Cr2O3, and solid solution of Cr6+ in V2O5 lattice. The formation of chromium isopolyvanadate having a higher degree of condensation of the vanadate anion was promoted by use of a more acidic medium in the catalyst preparation. The higher activity for autoxidation was obtained with the catalyst containing the more condensed isopolyvanadate. Epoxidation seems to proceed by the hydroperoxide intermediate mechanism on the active site differing from that for autoxidation.

Heterogeneous Catalysis in Liquid-Phase Oxidation of Olefin. I. Activity of Vanadium System Catalysts for Oxidation of Cyclohexene

Abstract The catalytic activities of various binary oxides containing vanadium for the liquid-phase oxidation of cyclohexene have been studied, in comparison with those of one component oxides and soluble metal acetylacetonates. The reaction was carried out at 60 °C in benzene solvent. The distribution of reaction products suggests the occurrence of autoxidation and epoxidation when vanadium system catalysts are used. Among the binary catalysts, V–Cr and V–Mo systems showed relatively high specific activities, especially high activity being obtained by the former systems calcined at a low temperature. It seems that cyclohexene oxide is formed mainly by two successive catalytic processes, i.e., the formation of cyclohexenyl hydroperoxide by autoxidation and the selective oxidation of cyclohexene with the hydroperoxide. The machanism of epoxidation was confirmed by the reaction of cyclohexene with t-butyl hydroperoxide in the presence of V–Cr catalyst.