Reaction methanation

In the Sabatier reaction, methane and water are formed over a nickel— nickel oxide catalyst at 250°C. The methane is recovered and cracked to carbon and hydrogen, which is then recycled ... 

The amount of energy required to carry out this process depends on the nature of the hydrocarbon it is the highest for saturated hydrocarbons (alkanes, cycloalkanes) and low for unsaturated and aromatic hydrocarbons (in fact, decomposition of acetylene and benzene are exothermic reactions). Methane is one of the most thermally stable organic molecules. 

Methanation Reactions While carrying out the WGS reaction, methane can be formed in the reactor through the methanation reaction, which is the reverse methane SR reaction and is highly exothermal. 

These reactions can be used to estimate the effect of changes in operating parameters on gas composition. As temperature increases, endothermic reactions are favored over exothermic reactions. Methane production will decrease, and CO production will be favored as reactions are shifted in the direction in which heat absorption takes place. An increase in pressure favors reactions in which the number of moles of products is less than the number of moles of reactants. At higher pressure, production of CO2 and CH4 will be favored. 

Hydrogenolysis of butane was performed using Pt and PtRh nanowires and particles/FSM-16 [23, 32] Table 15.6 summarizes the results. In this reaction, methane, ethane and propane were formed from hydrogenolysis of butane, and isobutane from isomerization (15.1) ... 

Figure 3 Schematic of the experimental set-up employed to study the methane decomposition reaction methanizer coupled with the FID was used to quantify ppm levels of CO in the hydrogen stream ...

The differences in reactions at different reactor positions was studied by Springmann et al. who reported product compositions for ATR of model compounds as a function of reactor length in a metal monolith coated with a proprietary noble metal containing Rh. As expected, the oxidation reactions take place at the reactor inlet, followed by the SR, shift, and methanation reactions. Figure 32 shows the product concentration profiles for a 1-hexene feed, which are typical results for all the fuels tested. These results show that steam, formed from the oxidation reactions, reaches a maximum shortly after the reactor inlet, after which it is consumed in the shift and reforming reactions. H2, CO and CO2 concentrations increase with reactor length and temperature. In this reactor, shift equilibrium is not reached, and the increase in CO with distance from the inlet is the net result of the shift and SR reactions. Methane is... 

Irreversible and endothermic SR (reaction (29)) is followed by two equilibrium driven exothermic reactions, methanation (reaction (30)) and WGS (reaction (31)). The prereforming is carried out at a relatively low temperature range, 400 to 550°C, with the overall reaction being close to autothermal. Prereforming provides the following advantages ... 

Tonkovich et al. [81] compared the performance ofa commercial ruthenium/zirconia powder catalyst from Degussa with a laboratory-made ruthenium/zirconia catalyst prepared on a nickel foam monolith for the water-gas shift reaction. Methane formation occurred for the powder catalyst, which was much less pronounced for the monolith. The selectivity towards methane could be reduced at shorter residence times. However, the activity of the laboratory-made catalyst was lower, which was partially attributed to the lower catalyst mass (modified residence time). 

As an illustration, the results of the application of the ESYCAD program to the oxidative coupling of methane are explained. For this reaction, methane may by activated at strong basic sites of the catalyst by hcterolytic chemisorption, resulting in methyl anions which may be oxidized to radicals. In the selective reaction, these radicals dimerize to ethane as the primary product. Acid sites or /j-conductivity should be avoided because they lead to total oxidation. Under reaction conditions the catalyst should be stable, i.e. not be oxidized or reduced or volatize, which can be checked by thermodynamics. 

Metal-support interactions have been recently reviewed by Bond (93), who drew special attention to catalysts that gave evidence for strong metal-support interactions (SMSI). This condition was first observed in 1978 by Tauster et al. (94) for Pt on titania catalysts. The catalysts seemed to lose their capacity for H2 and CO chemisorption but nevertheless retained and enhanced their activity for only two types of reaction methanation and Fischer-Tropsch synthesis. Since then a considerable number of papers devoted to SMSI studies have been published all over the world. 

Thus the lifetime of a constituent with a first order removal process is equal to the inverse of the first order rate constant for its removal. Taking an example from atmospheric chemistry, the major removal mechanism for many trace gases is reaction with hydroxyl radical, OH. Considering two substances with very different rate constants for this reaction, methane and nitrogen dioxide... 

Methane and oxygen react in the presence of a catalyst to form formaldehyde. In a parallel reaction, methane is oxidized to carbon dioxide and water ... 

A dynamic one-dimensional model of char gasification in a fixed-bed reactor has been developed. The model is based on conservation of mass and energy together with chemical equilibrium in the gas phase between H2O, H2, CO2, CO, using the water-gas shift reaction. Methane is assumed inactive in the char bed. The basic equations are ... 

CuO (or other metal oxides) Chemical reaction methane cone. SO2... 

Methane accounts for approximately 85 percent of the composition of natural gas with heavier hydrocarbons, nitrogen, and, in some regions, helium accounting for the other 15 percent [1]. Purification of methane is carried out at ambient or low temperature absorption (5—10 thousand ppm and 1—2 thousand ppm, respectively) and low-temperature fractionation (100 ppm) [2]. Impurities in the methane, such as heavier hydrocarbons, promote undesirable side reaction. Methane is also produced in an increasing number of organic waste-disposal plants [3]. Methane is used as feedstock to produce many chemicals, including hydrogen cyanide, carbon disulfide, and chlorinated methanes. 

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