Methane coupling reactions

The lithium oxide-promoted barium oxide also functions as a catalyst for the methane coupling reaction, but the mechanism is not clearly understood at the present time. The only comment that might be offered here is that the presence of ions on the surface of this material might etdrance the formation of methyl radicals drrough the formation of hydroxyl groups thus... 

Methane-coupling reaction conversions and yields less than 25 percent initially were—and still are—below those acceptable for commercial fuel and chemical feedstock production. But worldwide research and development in more recent years continue to suggest that variations in process parameters, reactor design, and catalyst composition and structure may bridge this gap. Lower reaction temperatures—in the 300-400°C range may... 

The model describes the methane coupling reaction over Li/MgO quite well. The predicted reaction rates, conversions, and selectivity are plotted with experimental results in the previous figures. Rates and selectivities are also calculated over a wide range of conditions. According to the model, the decrease in the methane conversion rate with increasing CO2 partial pressure is due to the strong adsorption of CO2, reflected in the large values of Kc. ... 

Under steady state reaction conditions, the effects of CO2 on the methane coupling reaction over Li/MgO catalyst were quantitatively determined. Poisoning effects of CO2 on carbon oxide formation rate, C2 formation rate, and methane conversion were observed for all methane to oxygen ratios and all temperatures. However, C2 selectivity is relatively unaffected by CO2 partial pressure. The mechanism described here accounts for important elementary steps, especially the effects of carbon dioxide. Under the low conversion conditions used in this study, further oxidation of C2 products to CO and CO2 is assumed negligible. These reactions will become more important at high conversions. Rate expressions derived from the mechanism match well the experimental conversions and selectivities. 

Tested samples of the catalysts were exposed to various pretreatments at air temperatures up to 1073 K without steam and at 1023 K with 100 % steam. Methane coupling reaction in the absence of oxidants in feed was carried out in an impulse microreactor the charge was 0.1 g of the catalyst one pulse of methane was 1.17 ml. 

Catalysis Considerations for Promoting Methane Coupling Reactions... 

Our studies turned from the methane coupling reaction to the investigation of higher temperature methane reactions. Using tubular electrocatalytic cells with Pt anodes, the conversion of methane becomes more selective with CO as the major product at high temperatures. As summarized in Table 6 methane conversions can approach 100% with CO selectivities up to 97% at 1100 C. This suggested that the electrochemical cells could be used for the partial oxidation of methane to synthesis gas. We call this process Electropox, for electrocatalytic partial oxidation. 

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