Post Combustion Capture (PCC) of CO₂ generated from coal-fired power stations has been identified as a crucial part of the global solution to climate change. This process is industrially proven for absorbents such as monethanolamine (MEA), and has been used to remove CO₂ from gas streams in commercial processes.
When applied on a large scale to existing coal-fired power stations PCC has high energy and cost penalties. One approach to reducing the energy requirements and cost of the process is through the development of better absorbents.
When CO₂ reacts with amines in aqueous solution, carbamate, bicarbonate and protonated amine are generated. Amines that form more bicarbonate than carbamate have higher absorption capacities and require less energy for regeneration. In this paper, we present results that combine CO₂ absorption experiments with in situ FT-IR spectroscopy to analyse the reactivity of functionalised amines towards CO₂. The results were rationalised according to measured absorption capacity and IR-identifiable reaction products, i.e. carbamate versus bicarbonate formation. IR spectral analysis demonstrated the presence of free amine, carbamate, protonated amine and bicarbonate species in the amine/CO₂/H₂O systems. A relationship between the measured absorption capacity of each amine and the evolution of the carbamate, bicarbonate and protonated amine absorbance peaks was observed. Amines that formed bicarbonate to a greater extent than MEA were also identified. FT-IR spectroscopy was found to be a relatively simple method for distinguishing carbamate from bicarbonate formation in the screening of potential amine absorbents.