(242b) Aqueous Phase Hydrogenation of Amine Captured CO2

Carbon dioxide (CO₂) will become increasingly available as a cheap, renewable, and abundant carbon feedstock as commercialization for the carbon capture and storage (CCS) from power plants is coming into play. Development of highly efficient methods for CO₂ reduction would greatly increase the range of possible products derivable from CO₂. The hydrogenation of CO₂ to formic acid appears to be a straightforward approach to utilize CO₂. This reaction in the gas phase is endergonic (DG^o₂₉₈ = +33 kJ mol^-1), i.e. thermodynamically unfavourable. However, the same reaction in the aqueous phase is exergonic (DG^o₂₉₈ = -4 kJ mol^-1).   Moreover, bases in aqueous solutions, e.g. NH₃, enhance the hydrogenation of CO₂ (DG^o₂₉₈ = -10 kJ mol^-1). Hydrogenation of amine-CO₂ adducts or ammonium carbonates in aqueous solutions are thus thermodynamically favorable to produce formic acid. However, there are only few studies of hydrogenation of CO₂ to formic acid in the presence of amines with homogeneous catalytic systems. And the homogeneous catalysts were not stable or their performance was suppressed when water was present.  Herein, we develop the carbon capture and conversion (CCC) process to convert amine-CO₂ adducts to formic acid with supported metal nano-cluster catalysts in aqueous media. To design the stable heterogeneous catalytic system for this reaction, we aim to directly convert the amine-CO₂ adducts from the CO₂ capture step of CCS process to formic acid, saving the energy and cost for separating, compressing, and transporting CO₂ in the storage step of a CCS process. The effects of the amine structures and the aqueous phase intermediates on the yield of formic acid were also investigated.