Selectivity methanation

As shown on Fig. 8.49 one can influence dramatically both the total CH4 conversion as well as product selectivity by varying the Ag catalyst potential. Thus under open-circuit conditions (Uwr=U r ) the CH4 conversion is near 0.02 with a C2 selectivity (methane molecules reacting to form C2H4 and C2H6 per total reacting CH4 molecules) near 0.5. Increasing Uwr increases the methane conversion to 0.3 and decreases the selectivity to 0.23, while decreasing Uwr decreases the conversion to 0.01 and increases the... 

To further reduce the carbon monoxide, a preferential oxidation reactor or a carbon monoxide selective methanation reactor is used. The term selective oxidation is also used for preferential oxi-... 

The increase in efficiency between the first- and second-generation reactors was attributed to less water in the feed and lower operating temperatures. Reactor models indicated that the major source of heat loss was by thermal conduction. The selective methanation reactor lowered the carbon monoxide levels to below 100 ppm, but at the cost of some efficiency. The lower efficiency was attributed to slightly higher operating temperatures and to hydrogen consumption by the methanation process. Typical methane levels in the product stream were 5-6.2%. ... 

Jeffers, P.M., L. Ward, L. Woytowitch, and N.L. Wolfe. 1989. Homogeneous hydrolysis rate constants for selected methanes, ethanes, ethenes, and propanes. Environ. Sci. Technol. 23 965- 969. 

The possibility of such a condensation sequence has also been demonstrated for rhodium methylene complexes which on thermolysis give selectively methane and propene 54... 

A limited number of uses and some particular reactions of methane have been disclosed in the patent literature, and owing to a relative lack of reactivity in comparison with its functionalized derivatives, it has been shown that the number of sufficiently selective methane reactions is very limited. Besides the useful reactions described above, a set of processes has been described in the patent literature that have, to date, received no practical application. We shall briefly summarize some examples of these reports ... 

Parameter Chain Length Chain Branching Olefin Selectivity Methane Selectivity... 

O. Gorke, P. Pfeifer, K. Schubert, Highly selective methanation by the use of a microchannel reactor, Catal. Today 110 (2005) 132. 

The CO content of the feed to the Proton Exchange Membrane (PEM) fuel cell can not exceed 10-40 ppmv. After the water-gas shift mentioned above, it typically contains in the order of 800-1200 ppmv CO. This CO is most often removed by preferential oxidation (100 °C) or, less practiced, selective methanation (100-300 °C). The gas is then led to the anode of the fuel cell where it is partially converted (70-90 °C). The unconverted gas contains hydrogen and methane and... 

Figure 1. Product selectivity (methane, ethane, propane, isobutane, butane, isopentane, pentane, hexanes, heptanes) in metatheses of ethane, propane, butane, and isobutane.

Thermodynamic Stabilization Energies SE, Bond Separation Energies A ]s, and Anomeric Effect AE for Select Methane Derivatives... 

The Haruta s discovery that nanosized gold particales adsorbed on metal-oxide powders facilitate a wide class of reactions under near-ambient conditions has attracted a worldwide interest [1]. It is known that gold is very inert in bulk phase. However, small gold clusters possess high reactivity in selective methane and alkenes oxidation and hydrogenation of linear alkenes [2]. So, gold nanoparticles have been found to be active catalysts for many reactions of industrial and environmental interest. 

In the Variable page, select Master Comp Molar Flow and in the Variable Speeifies, select Methane. Click OK. 

CI-MS is a powerful tool for steric structure identification that often allows differentiation between isomers. In addition, compound selectivity or sensitivity can be increased by choice of reagent gases with different proton affinities and ion-molecule reaction properties. However, in practice, only few reagent gases are used such as methane or isobutene. Occasionally, ammonia with a higher proton affinity than methane is employed to enhance selectivity. Methane and argon are most frequently used in electron capture negative ionization (ECNI). 

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... 

One of the most recent design approaches for the identification of effective partial oxidation catalysts has considered the activation of reactant and product molecules with catalytically active metal oxide materials (442,443). It is clear that the most effective selective oxidation catalysts are based on metal oxide systems, and it is by this precedent that the activation of methane, oxygen, and methanol has been examined on single metal oxides. The aim of the approach is to search for reactivity factors for catalyst components that when combined in two-component metal oxide catalysts will lead to catalyst formulations with a high degree of synergy for selective methane oxidation. The approach involves the identification of components that... 

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

When oxygen is added to the feed, some catalysts convert carbon monoxide to carbon dioxide with very high selectivity vdiile the methane formation starts not before the oxygen is completely consumed [150]. Therefore preferential oxidation and selective methanation could be operated in a combined manner. Care has to be taken when choosing the catalyst for preferential oxidation of carbon monoxide, because some formulations are very sensitive to light hydrocarbon contained in the reformate as reported by Kraaij et al. [151] who observed rapid deactivation. 

Galletti, C, Specchia, S, Specchia, V. CO selective methanation in H2-rich gas for fuel cell applications MicroChannel reactor performance with Ru-based catalysts. Chem. Eng. J. 2011 167 616-621. 

Men, Y, Kolh, G, Zapf, R, Hessel, V, Lowe, H. Selective methanation of carbon oxides in a microchannel reactor—Primary screening and impact of additives. Catal. Today 2007 125 81-87. 

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. 

Dutronc P, Lucat C, Menil F, Loesch M, Horillo MC, Sayago I, Gutierrez J, De Agapito JA (1993a) A potentially selective methane sensor based on the differential conductivity responses of Pd and Pt-doped tin oxide thick layers. Sens Actuators B 15-16 384-389... 

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