Indirect partial oxidation of methane in a catalytic tubular reactor

1 Indirect partial oxidation of methane in a catalytic tubular reactor 

Hydrogen production is conventionally carried out by steam reforming (SR) of natural gas over Ni-based catalysts. Since most of the natural gas is composed of methane, SR can be described by the following reaction  

The reaction is carried out in packed-bed tubular reactors which are heated externally due to the strong endothermic nature of the reaction. External energy demand can he minimized by coupling SR with catalytic total oxidation (TOX) of part of the fuel fed to the reactor over a Pt-based catalyst  

Combination of SR and TOX is known as indirect partial oxidation (IPOX). Due to the fast nature of TOX, it occurs earlier than SR and elevates the reactor temperature via exothermic heat release. In IPOX, oxygen is always used as the limiting reactant, and once it is completely consumed, the remaining methane is converted to hydrogen via Reaction 11.32. While SR and TOX are the main reactions, product distribution is strongly affected by the water-gas shift (WGS)  

In IPOX it is essential to operate the reactor in adiabatic mode as the exothermal heat has to be kept within the reactor for use in the reforming step. As the adiabatic operation hinders the radial heat transfer, gradients in this direction can be considered as negligible compared to the ones in the axial (z)-direction. Assuming that the convective effects are dominant over the diffusive ones in the z-direction, the spatial changes in the molar 

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