Adsorption-enhanced steam-methane reforming

Abstract

Experimental and theoretical studies of steam-methane reforming in the presence of a hydrotalcite-based CO2 adsorbent are presented. Attention is given to the analysis of the transient behaviour of a tubular (integral) reactor when an Ni-based catalyst is admixed with the adsorbent. Considerable enhancement of the methane conversion is experimentally demonstrated. Enhancement arises from the favourable shifts in the reaction equilibria of the reforming and water-gas shift reactions towards further CO2 production. As predicted, the potential for conversion enhancement is shown to increase under the conditions of a high reactor space time, high operating pressure, or a low steam-to-methane feed ratio, i.e. when reaction equilibrium limitations are important. A mathematical model, accounting for mass transfer limited adsorption kinetics, non-linear (Langmuirian) adsorption equilibria and a general reaction kinetic model, is shown to accurately predict the observed elution profiles from the reactor, and thus the degree of conversion enhancement. (C) 2000 Elsevier Science Ltd. All rights reserved.