Three-phase reactor model for the aqueous phase reforming of ethylene glycol

Using both experiments and modeling, it is shown how an optimal reactor design is beneficial for the production of hydrogen via aqueous phase reforming of ethylene glycol. The experiments reveal an inhibiting effect of hydrogen pressure on the reforming rate, while the yield to side products slightly increases with increasing hydrogen pressure. The addition of nitrogen as an inert gas results in a decrease of this inhibiting effect due to a decrease of the hydrogen pressure in the gas phase and to an increase in the liquid-gas mass-transfer rate. We have developed a comprehensive reactor model that successfully predicts the experimental observation at lower residence times (and low hydrogen pressures) but overestimates the actual hydrogen yields at higher residence times. According to this model, a high mass transfer from the active sites to the gas phase aids hydrogen removal from the catalyst surface and results in a remarkable increase of the hydrogen yield. The addition of nitrogen as stripping gas is also beneficial. The model predicts a sharp decrease of the hydrogen yield as the pressure increases, while nitrogen co-feeding reduces such effect. The addition of nitrogen is an effective approach to reduce the inhibiting effect of hydrogen, even though the increase of TOFH₂ levels off as the gas-to-liquid ratio increases. From a reactor engineering point of view, the increase of the mass-transfer rate is an even more attractive approach. This can be achieved, for example, in a microchannel reactor within the Taylor flow regime.