Designer Amines for Post Combustion CO2 Capture Processes

Abstract New amines with characteristics which counteract and contrast underlying issues with current solvents including chemical efficiency, chemical stability, and the ability to be operated over extended periods, will no doubt reduce the cost and environmental impact of CO 2 capture processes via their lower upfront investment in infrastructure and ongoing operational costs. Based on the superior absorption rate and performance of piperazine and the extended family of cyclic piperidine derivatives for CO 2 capture processes, a suite of structurally modified cyclic di-amine/tri-amine solvents utilizing the cyclic structure was proposed. The work presented here aims to provide higher efficiency solvents based on single molecule designer amines in comparison with MEA for post combustion capture of CO 2 . This work details the comprehensive laboratory and modelling investigation of the structurally modified amines series for CO 2 capture processes and a comparison to the capture performance of monoethanolamine (MEA). Thirty designer amines have been synthesised here and their CO 2 cyclic capacities measured using quantitative 13 C NMR spectroscopy. Cyclic capacity results indicated the majority of the designer amines showed improved cyclic capacity (when expressed on molar or mass ratios) compared to MEA. Twelve amines achieved greater than 80% improvement in cyclic capacity over MEA (expressed as moles of CO 2 /mol of nitrogen) with the largest improvement achieving a 158% increase. Estimations of the energy requirements for CO 2 capture for each of the amines was performed here. Ten of the amines synthesised here demonstrated improvements of 27% or greater than the energy performance of MEA, with the largest improvement being 32%. Following this, a selection of designer amines was progressively synthesized at larger scales allowing measurements of CO 2 absorption rates using a wetted wall column at 40oC. Comparable mass transfer rates were observed for two amines, which in combination with the cyclic capacity data and energy estimates places them firmly as promising candidates for CO 2 capture.