Concentration profiles, methane steam reforming

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... 

When operating with naphtha as feed, the endothermic reforming reaction is dominant at the top of the bed. As the concentrations of both hydrogen and carbon monoxide increase, the exothermic methanation reaction becomes the dominant reaction so that the overall reaction is exothermic. Gradual catalyst deactivation leads to the temperature profile moving down the bed and catalyst fife can be as long as two years. With natural gas feed any hydrocarbons heavier than methane are reformed, the methane steam equilibrium is established, and the overall reaction is endothermic. Operating details are shown in Table 9.16. 

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