The effect of adsorbent characteristics on the performance of a continuous sorption-enhanced steam methane reforming process

The steam methane reforming (SMR) process for hydrogen production with in situ CO2 capture on adsorbent particles pneumatically conveyed through a monolithic catalytic reactor and subsequently regenerated ex situ, was considered. A mathematical model has been formulated, based on differential mass and energy balances in the reactor and the regenerator, Langmuir isotherm for CO2 sorption equilibrium, the linear driving force approximation for sorption kinetics, and literature values for the kinetics of the three main SMR reactions. The effect of the adsorbent characteristics-the maximum CO2 capacity and the sorption kinetics-on the overall process performance in terms of methane conversion and CO2 separation has been systematically investigated in a parametric study. The main conclusions of the study are that: (i) conversion enhancement and CO2 recovery show a strongly non-linear dependence on both sorption capacity and kinetics; (ii) comparable conversion enhancement and CO2 recovery can be achieved by means of both lithium zirconite-like (high capacity, slow kinetics) and hydrotalcite-like (low capacity, fast kinetics) adsorbents; (iii) if an ideal adsorbent possessing hydrotalcite-like sorption kinetics and zirconite-like capacity were developed, the conversion enhancement factor could be more than doubled and a nearly 100% CO2 recovery could be achieved under otherwise identical conditions.