High capacity potassium-promoted hydrotalcite for CO2 capture in H2 production

This paper presents an experimental study for a newly modified K2CO3-promoted hydrotalcite material as a novel high capacity sorbent for in-situ CO2 capture. The sorbent is employed in the sorption enhanced steam reforming process for an efficient H-2 production at low temperature (400-500 degrees C). A new set of adsorption data is reported for CO2 adsorption over K-hydrotalcite at 400 degrees C. The equilibrium sorption data obtained from a column apparatus can be adequately described by a Freundlich isotherm. The sorbent shows fast adsorption rates and attains a relatively high sorption capacity of 0.95 moVkg on the fresh sorbent. CO2 desorption experiments are conducted to examine the effect of humidity content in the gas purge and the regeneration time on CO2 desorption rates. A large portion of CO2 is easily recovered in the first few minutes of a desorption cycle due to a fast desorption step, which is associated with a physi/chemisorption step on the monolayer surface of the fresh sorbent. The complete recovery of CO2 was then achieved in a slower desorption step associated with a reversible chemisorption in a multi-layer surface of the sorbent. The sorbent shows a loss of 8% of its fresh capacity due to an irreversible chemisorption, however, it preserves a stable working capacity of about 0.89 moVkg, suggesting a reversible chemisorption process. The sorbent also presents a good cyclic thermal stability in the temperature range of 400-500 degrees C. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.