Evaluation of enhanced absorption of carbon dioxide using carbonic anhydrase in aqueous solutions of 2-amino-2-methyl-1-propanol

Abstract

The use of carbonic anhydrase (CA) as a catalyst for bicarbonate formation in amine solutions has shown the potential to increase the absorption rate of CO₂, thus potentially reducing capital cost of a CO₂ capture plant, as the size of equipment can be reduced. On another approach, it could replace part of the amine to offer lower environmental impact. In this work, the catalytic effect of CA on the absorption properties of aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) was evaluated. The CA (DvCA8.0) used is an engineered variant that is more thermostable and tolerant of high pH-values. As a first step, a stability comparison between ultrastable DvCA8.0 and benchmarking commercial Bovine Carbonic Anhydrase (BCA) showed that DvCA8.0 could withstand higher concentrations of AMP at tested conditions and presents an activation in AMP concentrations up to 2.0 M AMP. Addition of DvCA8.0 increased the initial absorption rate of an aqueous 1.05 M AMP solution by 103%in a continuous flow reactor. Detailed equilibrium studies at different temperatures showed that CA had an effect in the CO₂ absorption rate even at very low concentrations (0.565 μg CA/mL), while not affecting the solubility or heat of absorption of CO₂ in the solution. The results highlight the significance of CA as a green and sustainable promoter in post-combustion CO₂ capture. We showcase, for the first time, the application of an ultrastable CA as promoter of sterically hindered amines demonstrating the exciting potential of using ultrastable biocatalysts for enhancing the CO₂ absorption rate under industrially relevant conditions.