On the adsorption behaviour and kinetics of a hydrotalcite-based adsorbent for sorption-enhanced water-gas-shift

Kai T. Coenen (Spreker), Gallucci, F. (Deelnemer), van Sint Annaland, M. (Deelnemer)

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The sorption-enhanced water-gas-shift reaction (SEWGS) combines the water-gas-shift reaction with in-situ adsorption of CO2, which results in hydrogen production combined with carbon capture. Hydrotalcite-based sorbents showed high stability, fast kinetics and high CO2 capacity. However, the interactions between small gas molecules such as H2O, CO2 and H2S and the sorbent are still not fully understood. In order to better understand and quantify these interactions, the adsorption of CO2 and H2O on K-promoted hydrotalcites were studied in detail using TGA (Thermogravimetric Analysis), PBR (packed bed reactor) and in-situ Infrared.
It was found that slow desorption kinetics determine the cyclic working capacity for CO2 and H2O. Furthermore, four different adsorption sites are required to describe the observed complex adsorption behaviour of CO2 and H2O and their cyclic working capacity was determined based on many different carefully designed TGA and PBR breakthrough experiments. The sorption model includes two independent adsorption sites for H2O and CO2 (sites A and B resp.) and another site which can be occupied by both CO2 and H2O, where one component replaces the other (site C). A fourth site (site D) describes the general higher adsorption capacity of the sorbent if H2O and CO2 are fed together to the sorbent.
In-situ IR experiments showed that basic sites with different strength are responsible for the adsorption of CO2. It was concluded that the CO2 desorption rate decreases because of stronger bond CO2 remaining on the sorbent. To describe the desorption kinetics of CO2 and H2O on the sorbent, an Elovich type of equation is used, where the activation energy is changing linearly as a function of the CO2 surface coverage.
Adsorption and desorption of H2O on site A could be described for different operating temperatures.
Periode1 okt 20175 okt 2017
LocatieBarcelona, Spanje
Mate van erkenningInternationaal