Olefin oxidation, liquid-phase

The literature on liquid-phase olefin oxidation has been well reviewed (1, 2, 3, 5, 6, 8,12,14,15, 16,17, 18,19,20). Recent attention has been focused on the effects of structure and reaction conditions on the proportions of alkenyl hydroperoxy radical reaction by the abstraction and addition mechanisms at lower temperatures and conversions. The lower molecular weight cyclic and acyclic olefins have been extensively studied by Van Sickle and co-workers (17, 18, 19, 20). These studies have recently been extended to include higher molecular weight alkenes (16). 

J. H. Knox In liquid-phase olefin oxidation, epoxides increase with temperature relative to cleavage products and soon exceed them in yield. In gas phase oxidation at about 300°C. epoxides are minor products... 

The reaction according to eq. (4) seems to proceed via a mechanism which is common for the homogeneous Pd-catalyzed reactions that are often referred to as Wacker oxidations (cf. Section 2.4.1, [4, 8, 9]). In fact, there are several liquid-phase olefin oxidations that are catalyzed by Pd complexes, and the nature of the reaction products depends on the solvent used (Scheme 3). 

Moiseev, n-Complexes in Liquid-Phase Olefin Oxidation, Nauka, Moscow, 1970 (in Russian). 

Vreugdenhil AD, Reit H. Liquid-phase co-oxidation of aldehydes and olefins— radical versus non-radical epoxidation. Rec Trav Chim 1972 91 237-245. 

Choi, K.-M., Mizugaki, T., Ebitani, K., Kaneda, K. Nanoscale palladium cluster immobilized on a Ti02 surface as an efficient catalyst for liquid-phase Wacker oxidation of higher terminal olefins. Chem. Lett. 2003, 32, 180-181. 

Arsenic-Catalyzed Liquid-Phase Process. An arsenic catalyst Liquid-phase process for olefin oxides has been patented by Union Carbide... 

Epoxides such as ethylene oxide and higher olefin oxides may be produced by the catalytic oxidation of olefins in gas-liquid-particle operations of the slurry type (S7). The finely divided catalyst (for example, silver oxide on silica gel carrier) is suspended in a chemically inactive liquid, such as dibutyl-phthalate. The liquid functions as a heat sink and a heat-transfer medium, as in the three-phase Fischer-Tropsch processes. It is claimed that the process, because of the superior heat-transfer properties of the slurry reactor, may be operated at high olefin concentrations in the gaseous process stream without loss with respect to yield and selectivity, and that propylene oxide and higher... 

The present economic and environmental incentives for the development of a viable one-step process for MIBK production provide an excellent opportunity for the application of catalytic distillation (CD) technology. Here, the use of CD technology for the synthesis of MIBK from acetone is described and recent progress on this process development is reported. Specifically, the results of a study on the liquid phase kinetics of the liquid phase hydrogenation of mesityl oxide (MO) in acetone are presented. Our preliminary spectroscopic results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups coordinated to the catalyst. An empirical kinetic model was developed which will be incorporated into our three-phase non-equilibrium rate-based model for the simulation of yield and selectivity for the one step synthesis of MIBK via CD. 

Under conditions of liquid-phase oxidation, alkylperoxyl radicals are stable and react rapidly with RH. They do not decompose into olefin and hydroperoxyl radical. However, some peroxyl radicals have a weak C—OO bond and decompose back to R and dioxygen ... 

Phillips (1) A process for polymerizing ethylene and other linear olefins and di-olefins to make linear polymers. This is a liquid-phase process, operated in a hydrocarbon solvent at an intermediate pressure, using a heterogeneous oxide catalyst such as chromia on silica/ alumina. Developed in the 1950s by the Phillips Petroleum Company, Bartlesville, OK, and first commercialized at its plant in Pasadena, TX. In 1991, 77 reaction fines were either operating or under construction worldwide, accounting for 34 percent of worldwide capacity for linear polyethylene. 

More recently Hartog and Zwietering (103) used a bromometric technique to measure the small concentrations of olefins formed in the hydrogenation of aromatic hydrocarbons on several catalysts in the liquid phase. The maximum concentration of olefin is a function of both the catalyst and the substrate for example, at 25° o-xylene yields 0.04, 1.4, and 3.4 mole % of 1,2-dimethylcyclohexene on Raney nickel, 5% rhodium on carbon, and 5% ruthenium on carbon, respectively, and benzene yields 0.2 mole % of cyclohexene on ruthenium black. Although the cyclohexene derivatives could not be detected by this method in reactions catalyzed by platinum or palladium, a sensitive gas chromatographic technique permitted Siegel et al. (104) to observe 1,4-dimethyl-cyclohexene (0.002 mole %) from p-xylene and the same concentrations of 1,3- and 2,4-dimethylcyclohexene from wi-xylene in reductions catalyzed by reduced platinum oxide. 

Cotton, effect of oxidants on, 462,687 Cotton fiber, ozone damage to, 665 Coulombmetry. See Amperometric analyzers <>i ee mechanism, for liquid-phase ozone-olefin reaction, 72-74, 76 Cydic olefins, 4,60,76 aerosols from, 70-72,83,88 importance of, 104... 

It is generally agreed that alkenyl hydroperoxides are primary products in the liquid-phase oxidation of olefins. Kamneva and Panfilova (8) believe the dimeric and trimeric dialkyl peroxides they obtained from the oxidation of cyclohexene at 35° to 40° to be secondary products resulting from cyclohexene hydroperoxide. But Van Sickle and co-workers (20) report that, The abstraction/addition ratio is nearly independent of temperature in oxidation of isobutylene and cycloheptene and of solvent changes in oxidations of cyclopentene, tetramethylethylene, and cyclooctene. They interpret these results to support a branching mechanism which gives rise to alkenyl hydroperoxide and polymeric dialkyl peroxide, both as primary oxidation products. This interpretation has been well accepted (7, 13). Brill s (4) and our results show that acyclic alkenyl hydroperoxides decompose extensively at temperatures above 100°C. to complicate the reaction kinetics and mechanistic interpretations. A simplified reaction scheme is outlined below. 

The liquid-phase oxidation of olefinic compounds initiated by azo-Ws-isobutyronitrile has been studied by Bateman (B6, B7). A mechanism similar to that presented above is invoked to explain the data. Gas-phase... 

Of the technological modifications, Fischer-Tropsch synthesis in the liquid phase (slurry process) may be used to produce either gasoline or light alkenes under appropriate conditions249,251 in a very efficient and economical way.267 The slurry reactor conditions appear to establish appropriate redox (reduction-oxidation) conditions throughout the catalyst sample. The favorable surface composition of the catalyst (oxide and carbide phases) suppresses secondary transformations (alkene hydrogenation, isomerization), thus ensuring selective a-olefin formation.268... 

Two selective processes are important in the oxidation of ethylene the production of ethylene oxide and acetaldehyde. The first process is specifically catalyzed by silver, the second one by palladium-based catalysts. Silver catalysts are unique and selective for the oxidation of ethylene. No similar situation exists for higher olefins. The effect of palladium catalysts shows a resemblance to the liquid phase oxidation of ethylene in the Wacker process, in which Pd—C2H4 coordination complexes are involved. The high selectivity of the liquid phase process (95%), however, is not matched by the gas phase route at present. 

Reaction 1 has been postulated both in oxidations of alkanes in the vapor phase (29) and in the anti-Markovnikov addition of hydrogen bromide to olefins in the liquid phase (14). Reaction 2 involves the established mechanism for free-radical bromination of aromatic side chains (2). Reaction 4 as part of the propagation step, established in earlier work without bromine radicals (26), was not invoked by Ravens, because of the absence of [RCH3] in the rate equation. Equations 4 to 6, in which Reaction 6 was rate-determining, were replaced by Ravens by the reaction of peroxy radical with Co2+ ... 

The preceding discussion has been restricted to oxidation of gaseous ethylene at elevated temperatures, little mention having been made of other olefins or other reaction conditions. The fact ia, however, that few illustrations of liquid phase ostoiytic epoxidation are known. 

Calvert and McQuigg suggest that yet unknown radicals, such as 0CH20 or those derived from it, formed in the 03-olefin-air mixtures may oxidize S02 in the homogeneous reaction. It is known that OH and H02 radicals combine rapidly with S02. The addition products may eventually be transformed into sulfuric acid, peroxysulfuric acid, sulfates, and nitrates in a polluted atmosphere probably in a liquid phase of aerosol particles, although the detailed steps are still unknown. Finlayson and Pitts (357) believe that the oxidation of aromatic compounds by such species as OH, H02, 03, and 0(3P) may also be significant for the formation of organic aerosol. 

Catalytic oxidation is the most important technology for the conversion of hydrocarbon feedstocks (olefins, aromatics and alkanes) to a variety of bulk industrial chemicals.1 In general, two types of processes are used heterogeneous, gas phase oxidation and homogeneous liquid phase oxidation. The former tend to involve supported metal or metal oxide catalysts e.g. in tne manufacture of ethylene oxide, acrylonitrile and maleic anhydride whilst the latter generally employ dissolved metal salts, e.g. in the production of terephthalic acid, benzoic acid, acetic acid, phenol and propylene oxide. 

Finally, selective hydrogenation of the olefinic bond in mesityl oxide is conducted over a fixed-bed catalyst in either the liquid or vapor phase. In the liquid phase the reaction takes place at 150°C and 0.69 MPa, in the vapor phase the reaction can be conducted at atmospheric pressure and temperatures of 150—170°C. The reaction is highly exothermic and yields 8.37 kJ/mol (65). To prevent temperature runaways and obtain high selectivity, the conversion per pass is limited in the liquid phase, and in the vapor phase inert gases often are used to dilute the reactants. The catalysts employed in both vapor- and liquid-phase processes include nickel (66—76), palladium (77—79), copper (80,81), and rhodium hydride complexes (82). Complete conversion of mesityl oxide can be obtained at selectivities of 95—98%. 

The search for new environmentally-friendly epoxidation methods using 02 as a sole oxidant has attracted much interest. Although there has been some success with 02 and homogeneous catalyst systems in the liquid phase without the use of reducing reagents, there have been few reports concerning heterogeneous epoxidation of olefins [45, 46]. 

Some other catalytic events prompted by rhodium or ruthenium porphyrins are the following 1. Activation and catalytic aldol condensation of ketones with Rh(OEP)C104 under neutral and mild conditions [372], 2. Anti-Markovnikov hydration of olefins with NaBH4 and 02 in THF, a catalytic modification of hydroboration-oxidation of olefins, as exemplified by the one-pot conversion of 1-methylcyclohexene to ( )-2-methylcycIohexanol with 100% regioselectivity and up to 90% stereoselectivity [373]. 3. Photocatalytic liquid-phase dehydrogenation of cyclohexanol in the presence of RhCl(TPP) [374]. 4. Catalysis of the water gas shift reaction in water at 100 °C and 1 atm CO by [RuCO(TPPS4)H20]4 [375]. 5. Oxygen reduction catalyzed by carbon supported iridium chelates [376]. - Certainly these notes can only be hints of what can be expected from new noble metal porphyrin catalysts in the near future. 

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