Intensified CO<sub>2</sub> Capture in Structured Microreactors\nwith Carbonic Anhydrase Enzyme Immobilized on Open-Cell Foam Packings

To\nmitigate climate change, it is of utmost importance to develop\ninnovative, energy-efficient technologies to capture CO<sub>2</sub>. In this context, this study is envisioned as an exploration of\nopportunities by proposing an intensified CO<sub>2</sub> capture process\nin a novel immobilized enzyme structured packed-bed microreactor (IE-SPBμR)\nwith human carbonic anhydrase II (hCA II) enzyme attached on open-cell\nfoam packings, which constitutes a promising alternative for mass-transfer-limited\nreactions. Enzyme-mediated CO<sub>2</sub> uptake and fluid dynamics\nin IE-SPBμR were analyzed for different microreactor operating\nconditions and enzyme loadings, and using different buffer systems,\nvia a 3D two-phase flow model coupled with governing equations of\nmass transport in gas/liquid phases and diffusion/reaction within\nthe enzymatic catalyst layer. The results showed that IE-SPBμR\ngenerates a remarkable intensification of CO<sub>2</sub> uptake at\nlow hCA II enzyme loadings due to enhanced mass transfer over large\ninterfacial areas that allow greater use of the large hCA II enzyme\nturnover while, at the same time, maintaining low pressure losses.\nThe performance of IE-SPBμR is significantly enhanced by increasing\nliquid flow rate, decreasing pore diameter of foam packing, operating\nwith buffers with low dissociation constant of protonated form and\nwidening packed bed height while preserving pressure drop at low levels.\nAn important advantage is that the pressure drop in IE-SPBμR\nwith selected open-cell foam packings is 1–2 orders of magnitude\nlower, compared to packed-bed microreactors of similar specific surface\narea, thus allowing the process volume to be easily scaled-up by increasing\nthe height of packed bed. The significant process intensification\nhighlights the attractiveness of IE-SPBμRs, connected in modular\nunits, especially for capturing CO<sub>2</sub> from dispersed sources.