Enzymatic carbon dioxide capture using a thermally stable carbonic anhydrase as a promoter in potassium carbonate solvents

Carbon capture and storage (CCS) is an effective way to reduce CO₂ emissions and to mitigate climate change effects. However, the cost of carbon capture has to be reduced to manageable levels before it can be deployed at an industrial scale. Potassium carbonate solutions (K₂CO₃) are good solvents for CO₂ capture because they have low regeneration energy, low degradation rates and low corrosivity. However, one shortcoming of K₂CO₃ is that it has slow reaction kinetics with CO₂. This limitation can be overcome by the addition of promoters to K₂CO₃ solutions. In this study, the catalysis kinetics of a carbonic anhydrase (NZCA) promoter was tested via the stopped flow technique and a wetted wall column (WWC). The Michaelis-Menten catalysis parameter (k_cat/K_m) was determined to be 2.7 × 10⁷ M⁻¹ s⁻¹ at 298 K, allowing the catalysis reaction activation energy of 51 ± 1 kJ/mol to be obtained at 298–328 K. The catalysis coefficient of the NZCA was determined to be 5.3 × 10⁸ M⁻¹ s⁻¹ using a WWC in 30 wt% potassium carbonate solutions (pH ∼ 11–12) at 323 K. Furthermore, the NZCA maintained more than 70% of its initial catalysis efficiency after continuously running for 8 h in 30 wt% K₂CO₃ solutions at pH of 10.6–10.8 and temperature of 323 K.