Development of catalysts for fast, energy efficient post combustion capture of CO2 into water; an alternative to monoethanolamine (MEA) solvents

The aim is to develop fast catalytic absorption/desorption of CO2 at low temperatures using water as solvent. The naturally occurring zinc metallo -enzyme carbonic anhydrase (CA) can concentrate CO2 using a reversible hydration/dehydration cycle at neutral pH and at ambient temperatures. A number of macrocyclic and tripodal complexes of zinc (II), and other metals that mimic the CA catalytic process, proceed by hydration of CO2 to bicarbonate followed by the reverse dehydration of the bicarbonate to regenerate CO2. This initial study is of the fast catalysis of the reverse reaction (the dehydration of the bicarbonate ion back to CO2) at temperatures in the range 20–55 C. The turnover rate constants for the catalytic desorption have been measured for zinc-1, 4, 7, 10-tetraazacyclo-dodecane, (zinc-cyclen), the zinc tripodal complexes: zinc-nitrilo-tris(2-benzimidazoyl-methyl-6-sulfonic acid), (zinc-L1S), and zinc-tris(2-benzimidazoylmethyl)-amine, (zinc -LI). CA or the zinc complexes are proposed for utilization in a water based capture process, hence avoiding the energy intensive steam stripping steps necessary with amine solvents