Mingheng Li, PhD, California State Polytechnic University
Utilizing thermogravimetric analysis (TGA), the CO2 adsorption capacities at various partial pressures of CO2 were measured. The CO2 adsorption capacities of various sol-gel synthesized MgO were compared to commercially available adsorbents (Figure 1). The increase in CO2 adsorption correlated directly with surface area. It was also observed that MgO aerogel has faster CO2 adsorption kinetics and is less prone to N2 adsorption as compared to alumina. A mathematical model was developed to describe the kinetics and equilibrium of CO2 adsorption by correlating TGA data.
MgO aerogel 250C = amorphous, sol-gel derived MgO with surface area above 200 m2/g
MgO xerogel 250C = amorphous, sol-gel derived MgO with surface area below 200 m2/g
MgO aerogel 450C = crystalline, sol-gel derived MgO with surface area below 100 m2/g
Commercial MgO 450 = crystalline MgO with surface area below 50 m2/g
Na doped Alumina = crystalline, commercially obtained
Alumina = crystalline, commercially obtained
Figure 1: Isotherms derived from TGA measurement.
An automated packed-bed reactor was constructed to study multi-cycle adsorption/desorption of CO2 under more realistic conditions using commercially available sodium oxide impregnated alumina particles. A dynamic mathematical model was developed to study CO2 adsorption/desorption as well as adsorption enhanced reforming of methanol to produce hydrogen in packed-bed reactors around 250 ˚C.
Figure 2: Normalized CO2 concentration measured at the exit during adsorption and desorption cycles in a packed-bed reactor.