Comparative Kinetic Studies of Solid Absorber Catalyst (K/MgO) and Solid Desorber Catalyst (HZSM-5)-Aided CO2 Absorption and Desorption from Aqueous Solutions of MEA and Blended Solutions of BEA-AMP and MEA-MDEA

The kinetic performance of a novel amine solvent blend BEA-AMP was compared with MEA and blended MEA-MDEA in the presence and absence of a solid acid catalyst (HZSM-5) in the desorber column of a bench-scale pilot plant. In addition, a total of seven solid base catalysts were screened using a semibatch reactor to select the one that is most suitable as catalyst for amine-based CO2 absorption. The selected solid base catalyst, K/MgO, was placed in the absorber of the pilot plant. Overall, three absorber-desorber catalytic scenarios were evaluated: blank-blank, blank-HZSM-5, and K/MgO-HZSM-5. For the blank-blank and blank-HZSM-5 scenarios, the novel solvent (4 M BEA-AMP) outperformed 5 M MEA and 7 M MEA-MDEA blend despite BEA-AMP having the lowest molarity. The rates of absorption and desorption for the blank-blank (noncatalytic) scenario for BEA-AMP were 14.8 and 38.4 mol/m(3) min, respectively. For the blank-HZSM-5 system, the rates were 18.1 and 45.6 mol/m(3) min, respectively. Absorption and desorption rates of 29.7 and 62.4 mol/m(3) min, respectively, were obtained for the K/MgO-HZSM-5 system. These results reveal higher rates of absorption and desorption with the inclusion of solid base and solid acid catalysts to the amine-based CO2 capture process. The results show that in the presence of the amine, the electron-rich anion species in K/MgO easily attack the dissolved CO2. This interaction ties the CO2 molecules to the surface of the catalyst, making them readily available for nitrogen atom of the amine in the CO2 absorption process. This process is facilitated because of the large pore size of K/MgO. With the desorber catalyst, easier proton donation by HZSM-5 results in weakening the N-C bond in carbamate, which thereby causes CO2 to break away.