Ethylene oxide synthesis

The synthesis of ethylene oxide by direct oxidation with air/oxygen over a supported (a-Al203) silver catalyst is a well-established process. Kestenbaum et al. demonstrated the potential of a MSR of 126 channels (9 mm length, 50 pm height, and 500 pm width) as the catalytically active component (microstruc-tured silver foils in parallel-flow geometry), within explosion limits [19], compared with the industrial process. 

Oxidative coupling of methane (OCM) to C2 hydrocarbons is one of the promising potential routes for direct conversion of natural gas to higher hydrocarbons. 

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Fig. 9. Schematic representation of a catalyst for ethylene oxide synthesis (not to scale). The porous support particle consists of microparticles held together...

Partial Oxidation of Ethylene to Ethylene Oxide. About 3.3 million metric tons of ethylene oxide were produced worldwide in 1988. Of this, about 70% was converted into ethylene glycol, and the balance went into detergents and other appHcations. An excellent review of ethylene oxide synthesis has been written (66). 

Berty, J.M., 1983, Ethylene Oxide Synthesis, chapter 8 in. / Applied Industrial Catalysis I, B.E. Leach, ed., pp. 207-238, Academic Press, New York. 

Often the micro-reactor data were able to confirm literature values for true reaction rates. For ethylene oxide synthesis, a reaction rate of 4.8 10 mol s m was observed [159]. This figure, when corrected to compensate different experimental conditions, compares with a literature value of 1.7 10 mol s m then, a value... 

Heat management is of crucial importance for ethylene oxide synthesis (see original citahons in [4]). The reachon enthalpy of the total oxidation to carbon dioxide (AH = -1327 kj/mol) is more than 10 times larger than that of the partial oxidahon (AH = -105 kJ/mol), which induces locally very hot temperatures (hot spots) with corresponding negative consequences on the reaction course. 

Ethylene oxide synthesis is one of the largest-volume industrial processes with a produchon rate of some plants of several 100 0001 a (see original citahons in [4]). In 1995, the world capacity for ethylene oxide was approximately 11 200 0001 a. As industrial catalyst silver on alumina is employed. In addihon to large produc-... 

GP 2] [R 2] The smooth surface of the laser-LIGA OAOR silver is roughened and pitted after OAOR treatment and used during more than 1000 h of ethylene oxide synthesis [4]. The etched OAOR silver shows pronounced sintering and agglomeration for the same type of treatment. 

The very promising results for ethylene oxide synthesis by micro-channel processing given above shll await industrial implementation. Selechvity needs to be further improved above 80%, as the costs for ethylene contribute 80% to the overall process costs ]4]. In addihon to the costs argument, the usual requirements for transfer from laboratory to industrial scale will face the micro reactor reliability, proper process control and much more. 

Nagasaki Y, Kutsuna T, Iijima M, Kato M, Kataoka K, Kitano S, Kadoma Y (1995) Formyl-ended heterobifunctional poly(ethylene oxide) synthesis of poly(ethylene oxide) with a formyl group at one end and a hydroxyl group at the other end. Bioconjug Chem 6 231-233... 

This will give a limiting selectivity of 4/5, or 80%. The idea of coupled reactions in the ethylene oxide synthesis goes back to at least 1942, when it was published by Worbs (19). Other combinations can be devised, as listed in Table II. In each case the complex M02 is the starting species, and one oxygen atom of this complex is assumed to react with... 

Together with oxidation of olefins with peroxy acids, cyclodehydro-Uulogenatione constitute the bulk of epoxide syntheses known at the present time. In addition the latter reactions possess the eminence of antiquity, since Wurtt himself18 4 made use of cyclodehydzohalo- cootion in the very first recorded ethylene oxide synthesis. 

Conversely, vaporizing heat transfer media are used exclusively to remove heat from exothermic reactions. Whereas formerly petroleum fractions such as kerosene (e.g. in ethylene oxide synthesis) were more widely... 

In both the liquid-phase and the gas-phase reactions, the STYs of PO have reached a level of 100 gpo kgcaJ, h which is comparable to that of ethylene oxide synthesis in industrial processes. However, there still remain some barriers against commercialization, namely catalyst life and hydrogen utilization efficiency. 

Hydrogenation of aromatic nitro compounds to aromatic amines Hydrogenation of aldehydes and ketortes to alcohols Hydrogenation of atomic olehnic groups Hydrogenation of unsaturatcd nitriles to unsaturated amines Hydrogenation of diolefins artd alkynes to monoolehns Hydration of ethylene oxide alkylation of aromatics with olehns oxidation of alcohols to aldehydes Oxidation of ethylene to ethylene oxide Synthesis of HCN from NH, and CH4 Oxidation of CH3OH to HCHO... 

All these reactions and especially the latter two. which correspond to the complete combustion of ethylene and of its oxide, are highly exothermic and complete. in the operating conditions of ethylene oxide synthesis. To guide the transformation in the direction of the first reaction, the operations require the presence of a metallic catalyst. The catalyst is generally considered to act according to the foliowring reaction mechanism ... 

As a rule, industrial plants operate with a silver-based catalyst in a fixed bed, with recycle of unconverted ethylene. They comprise two main sections, ethylene oxide synthesis and purification. 

This process is similar in priociple to the ethylene oxide synthesis process. The main reactions involved are the following ... 

Impurities in the starting material stream can have positive effects (e.g., addition of halogen-containing compounds in silver-catalyzed ethylene oxide synthesis, but mostly their effects on catalyst performance are negative. In each case the catalyst must be tested with the original feed (e.g., from an integrated pilot plant). 

Ethylene oxide synthesis Ag halogenated hydrocarbons inhibitor increase selectivity... 

Another example is industrial ethylene oxide synthesis. Here, too, it was shown that a decrease in the Ag surface area due to sintering is responsible for the deactivation of the catalyst. 

Comparing the ISS spectra of an unused and a used silver catalyst for ethylene oxide synthesis shows how the alkali metal promoter on the catalyst behaves during the process (Fig. 5-50). In time, the alkali metal promoter spreads across the surface of the catalyst [25]. 

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