New equilibrium and column dynamic data for chemisorption of carbon dioxide from inert nitrogen at 250, 350, and 450°C were measured on a sample of sodium oxide promoted alumina, which was found to be a reversible chemisorbent for CO 2. The equilibrium chemisorption isotherms were Langmuirian in the low pressure region (P CO2 <2.0 kPa) with a large gas-solid interaction parameter. The isotherms deviated from the Langmuirian behavior in the higher pressure region. A new analytical model which simultaneously accounted for Langmuirian chemisorption of CO 2 on the adsorbent surface and additional reaction between the gaseous and sorbed CO 2 molecules was used to describe the measured equilibrium data. The heats of CO 2 chemisorption and the additional surface reaction were, respectively, 64.9 and 37.5 kJ/mol. The column breakthrough curves for CO 2 sorption from inert N 2 on the chemisorbent as well as the desorption of CO 2 from the chemisorbent by N 2 purge at 350°C could be described by the linear driving force (LDF) model in conjunction with the new sorption isotherm. The same LDF mass transfer coefficients can be used to describe both sorption and desorption processes. The CO 2 mass transfer coefficients were (i) independent of feed gas CO 2 concentration in the range of the data at a given temperature, and (ii) a weak function of temperature. The ratio of the mass transfer zone length to the column length was very small due to highly favorable CO 2 sorption equilibrium. Several sequential cyclic CO 2 sorption-desorption column dynamic tests were conducted to demonstrate the apparent stability of the material.
- Carbon dioxide
- Chemisorption-surface reaction model
- Cyclic stability
- Sodium oxide promoted alumina
ASJC Scopus subject areas
- Environmental Engineering
- General Chemical Engineering