Selective Methanation of Carbon Monoxide

Selective methanation of CO, although basically simpler than preferential oxidation, because no air addition to the reformate is required, suffers not only from the critical issue of competing CO2-methanation [66] but also from temperature management problems [67], which can be solved by multistaged operation when conventional adiabatic fixed beds or monoHths are applied. 

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Another purification method is the selective methanation of carbon monoxide where no additional air is required however, the yield of hydrogen is decreased as three molecules of hydrogen are consumed per molecule of CO. Furthermore, it is... 

Selective methanation of carbon monoxide does not require air addition to the reformate but suffers not only from competing CO2 methanation [148],... 

Nickel and ruthenium [342,343] catalysts are those most frequently under investigation for the selective methanation of carbon monoxide. The main issue of concern is that the concentration of carbon dioxide is much higher in the reformate compared with carbon monoxide and thus the catalyst used for carbon monoxide methanation has to be very selective. Normally, the operating window of methanation catalysts is relatively small, around 250 °C, because a trade-off is required between sufficient activity and selectivity. Well above 250 °C all methanation catalysts tend to be selective for carbon dioxide methanation. 

The plant consists of a pre-reforming step which converts C2+ into methane, which also reduces the coking risk downstream (Figure 4.50). The actual reforming step, the water gas shift reaction, follows and also a step for the selective oxidation of carbon monoxide before the hydrogen-rich gas enters the fuel cell. A steam evaporator is also included in the set-up. 

Selective transformations Selective styrene ring opening [103] One-pot domino process for regioselective synthesis of a-carbonyl furans [104] Tandem process for synthesis of quinoxalines [105] Atmospheric oxidation of toluene [106] Cyclohexane oxidation [107] Synthesis of imines from alcohols [108] Synthesis of 2-aminodiphenylamine [109] 9H-Fluorene oxidation [110] Dehydrogenation of ethane in the presence of C02 [111] Decomposition of methane [112] Carbon monoxide oxidation [113]... 

Another way to eliminate the oxygen plant is to react a metal oxide with methane to yield the synthesis gas in a fluidized-bed reactor (83-86). Experiments have shown that copper oxide readily oxidizes methane to carbon monoxide and hydrogen with high selectivity at a temperature of about 1200 K and that the reduced CuO can be reoxidized with air. Lewis et al. (83-86)... 

Coke oven gas consists mainly of a mixture of carbon monoxide, hydrogen, methane, and carbon dioxide. It is contaminated with a variety of organic and inorganic compounds that have to be separated in absorption columns before its further use as a synthesis gas. The selective absorption of coke plant gas contamination results from a complex system of parallel liquid-phase reactions. Instantaneous reversible reactions ... 

Solid oxide fuel cell (SOFC) uses solid ceramic material, such as Y2O3 stabilized Zr02 (YSZ), as an electrolyte. As SOFC operates at high temperature (600-1000° C), a variety of fuels, e.g., hydrogen, methane, and carbon monoxide, can directly be utilized. The high temperature places severe constraints on material selection and results in difficult fabrication process. Co-ZrO (or Ni-ZrO) and SrO doped LaMn03 have often been used for anode and cathode materials, respectively. 

At these temperature levels, however, and especially with low HJCO ratios, the side reactions producing methane and carbon also develop substantially. To minimize their effects, the catalysts employed must be both active and selective This double requirement raises a number of difficulties, which are circumvented in practice by carrying out the conversion of carbon monoxide in two steps, with intermediate cooling and possibly the injection of additional water at the inlet to the second stage ... 

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