(440g) Reversible Chemisorption of Carbon Dioxide

The advent of hydrogen economy has renewed interest in novel ways of producing hydrogen by reforming of natural gas and by gasification of coal. Sorption Enhanced Reaction Processes (SERP) can have large impacts in achieving these goals. The SERP concepts use a reversible chemisorbent for selective removal of CO₂ from a hot gas (350-450 ^oC).

Hydrotalcites promoted by K₂CO₃ is a found to be an acceptable chemisorbent for this purpose. This paper reports the results of detailed column dynamic and TGA studies of high temperature sorption and desorption of CO₂ from N₂ on such a material. The chemisorption isotherms of CO₂ are Type I and the rate of chemisorption is fast. The desorption of chemisorbed CO₂ is governed essentially by local equilibrium. Thermodynamic models are proposed to describe the chemisorption process. Possible mechanisms of the surface reactions underlying the chemisorption process are discussed.