Low viscosity alkanolguanidine and alkanolamidine liquids for CO2 capture?

RSC Advances Pub Date: 2012-11-09 DOI: 10.1039/C2RA22801G

Abstract

Global carbon dioxide (CO2) emission is expected to increase tremendously with the shift to coal-powered plants for energy generation. Capture and sequestration of CO2 are needed to mitigate environmental effects. Solvents currently used for this are the energy-intensive aqueous amines. Here we present 10 advanced solvents called alkanolguanidines and alkanolamidines that are potentially energy-efficient CO2-capture solvents. These solvents were synthesized in 1–3 steps from commercially available materials. One alkanolamidine derived from a 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) base core has a low vapor pressure and a high viscosity, resulting in low CO2 uptake capacity at standard temperature and pressure (STP). Three imidazoline base derived alkanolamidines were non-viscous but do not bind CO2 at STP, however, under mild pressure they effectively capture 7–10 wt%, making them suitable for high-pressure CO2 capture. Six novel alkanolguanidine molecules have low vapor pressure and low viscosity (<10 cP) which enable high CO2 uptake at STP. These compounds bind CO2 chemically via the alcohol moiety forming zwitterionic guanidinium and amidinium alkylcarbonate ionic liquids. These materials can be regenerated thermally by heating the alkylcarbonate to 75 °C. CO2 binding capacities of up to 12 wt% were achieved using several of these compounds at STP. Through this study we found that alkanolguanidines have low viscosity, are non-volatile, have high CO2 uptake at STP and are tolerant to water; thus we selected one compound for physical property testing.

Graphical abstract: Low viscosity alkanolguanidine and alkanolamidine liquids for CO2 capture
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