CO2 Desorption Kinetics for Immobilized Polyethylenimine (PEI)

The CO2 desorption rate from CO2-loaded immobilized polyethylenimine (PEI) on mesoporous silica was investigated in a fluidized bed unit. Nonisothermal studies were carried in the temperature range of 340-380 K and different heating rate (1.0-2.7 K/min). The tests were performed using two different inlet CO2 concentrations, mainly 16.5% and 33%. The kinetics involved in CO2 desorption was studied by applying various analytical techniques (model-free and model-fitting) to the nonisothermal data. The model-free approach represented by the nonisothermal isoconversional methods revealed that the apparent Arrhenius parameters (A and E-a) increased with extent of conversion for 0 <= X <= 0.3, followed by an approximately nearly constant value at the higher CO2 desorption levels. In the constant-E-a region, the nonisothermal CO2 desorption follows a two-dimensional diffusion model. The apparent Arrhenius parameters (In A and E-a) evaluated were 71.3 +/- 3.6 and 230.5 +/- 13.0 kJ/mol, respectively.