Kinetic performance of CO₂ absorption into a potassium carbonate solution promoted with the enzyme carbonic anhydrase: Comparison with a monoethanolamine solution

Development of enzyme-mediated solvents are regarded as a potential option to overcome the energy use disadvantages associated with the benchmark monoethanolamine (MEA) solvent for post-combustion CO₂ capture. In this work, the kinetics of CO₂ absorption into a 20wt% potassium carbonate (PC) solution promoted with the enzyme carbonic anhydrase (CA) was investigated using a stirred tank reactor. Experimental results showed no noticeable change in the intrinsic activity of the CA enzyme with increasing CO₂ loading in PC solution. A rate-based mass transfer analysis was conducted using the enzymatic kinetics measured, and results revealed that in a packed-bed column, the CO₂ absorption rates into a lean and rich PC solution with 3gL^-1 CA were 50% lower and 2.2 times higher, respectively, than those into their 5M MEA counterparts. The liquid-phase mass transfer resistance was dominant for both PC- and MEA-based systems. Modeling results revealed the effective packing volume of the absorber with PC in the presence of 10gL^-1 CA was only slightly larger than that with MEA for post-combustion CO₂ capture.