Methane continued oxidation

Table II. Methane Partial Oxidation over Si02 Catalyst in Batch and Continuous Flow Reactors...

In a 1999 letter to Nature (Perry Murray etal., 1999), from North Western University, Illinois, the authors record the first laboratory achievement of useful oxidation rates for direct methane electrochemical oxidation, using an IT/SOFC. The cathode structures were porous lanthanum strontium manganite (LSM) on porous ( 203)0.15 (Ce02)o,85 or YDC. The anodes were cermets, porous YSZ with nickel in the pores. The laboratory operating temperatures were in the range 500-700 °C. The account of the North Western work, reporting on new anode types, continues on pp. 921-924 of Williams (2002). 

Methane is oxidized with air to produce formaldehyde in a continuous reactor. A competing reaction is the combustion of methane to form CO2. 

Methanesulfonic acid is primarily manufactured by the batch or continuous oxidation of the methyl mercaptan or dimethyl disulfide with chlorine in saturated aqueous hydrochloric acidJ This chemistry is also the basis for much of the worldwide production of MSC, with photochlorination of methane (vide infra) being the most significant commercial alternative. Other alkanesulfonyl chlorides and sulfonic acids have also been produced in lesser quantities by the CI2/H2O oxidation. Reaction yields are typically 92-100%. The HCl by-product separates as vapor from the saturated reaction mixture. It is absorbed into water to afford a... 

Earlier and continuing work from our laboratories has shown that the introduction of small quantities of tetrachloromethane (TCM) into the feedstream for methane partial oxidation or oxidative coupling produces benefrcial increases in the selectivides to hydrocarbons, particularly ethylene, with many heterogeneous catalysts [19]. Consequently it is of interest to examine the effect of this additive with other oxidation processes, such as the conversion of CO to COj. 

Methane Methanol Oxides of Mn, Co, Pd, Mo, Cr, V, Cu 25-250 1-69 Continuous, homogeneous or heterogeneous catalyst CO2 mixed with perfluorinated compounds (expanded liquid) 139... 

Although studies on methane partial oxidation have never stopped and continued beyond this period, and even attempts to introduce new industrial processes have been made (see, e.g., [29]), none of them found practical implementation. At the same time, under the influence of the theory of branched-chain reactions, developed by Semenov and his co-workers [30], a new understanding of mechanism of the oxidation of hydrocarbons began to take shape. Results of more than half a century of research in the oxidation of hydrocarbons and new concepts of hydrocarbon oxidation mechanism were summarized in a fundamental monograph by Shtern [13]. 

Historically, formaldehyde has been and continues to be manufactured from methanol. EoUowing World War II, however, as much as 20% of the formaldehyde produced in the United States was made by the vapor-phase, noncatalytic oxidation of propane and butanes (72). This nonselective oxidation process produces a broad spectmm of coproducts (73) which requites a complex cosdy separation system (74). Hence, the methanol process is preferred. The methanol raw material is normally produced from synthesis gas that is produced from methane. 

Girguis PR, AE Cozen, EF Delong (2005) Growth and population dynamics of anaerobic methane-oxidizing archaea and sulfate-reducing bacteria in a continuous-flow reactor. Appl Environ Microbiol 71 3725-3733. 

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

Ethylene oxide is produced by adding ethylene, oxygen, a methane diluent, and recycled carbon dioxide to a continuous reactor. Gaseous compositions are controlled carefully to keep the concentrations outside the explosion limits. 

For the measurement of the hydrocarbon precursors of photochemical oxidants, the naturally occurring methane must be separated from the other so-called nonmethane hydrocarbons. Only one procedure, gas chromatography coupled with flame ionization detection, is available for this separation and measurement. Although instrumentation for routinely accomplishing this process is commercially available, its maintenance (continued operation) requires a degree of operational know-how that may be too costly for most public agencies in the United States to support. Consequently, the data currently are insufficient to relate the occurrence of photochemical oxidants and ozone accurately to some of their most important precursors, the nonmethane hydrocarbons. 

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