Low-energy-consumption and environmentally friendly CO2 capture via blending alcohols into amine solution

Abstract

The conventional regeneration processes for aqueous amine-based sorbents require high regeneration temperature and are very energy intensive. In this work, a low-temperature and energy-saving CO2 capture technology has been successfully developed by using alcohols-amines-water mixtures as sorbents. The addition of certain amounts of alcohols [especially ethanol (EtOH)] to amines can significantly increase the CO2 desorption rates and cyclic CO2 capture capacities in comparison with those of monoethanolamine-water, diethanolamine-water, and methyldiethanolamine-water systems. The sorbent containing 40 wt% EtOH, 20 wt% monoethanolamine (MEA), and 20 wt% H2O can increase cyclic CO2 capture capacity by 6.8 times and a maximum improvement of 236 times in CO2 desorption rate at 75 °C, which makes the use of the low-temperature waste heat in power plants for CO2 capture or self-supported CO2 capture in power plants possible. To the best of authors’ knowledge, this is the first time that Raman and Fourier transform infrared spectroscopy characterizations have been used to confirm that ethanol in EtOH-MEA-H2O can change the reaction pathway by forming C2H5OCO2− instead of HCO3−, which is difficult to decompose. In addition, the experimental results confirm that the new technology can significantly avoid amine degradation – a common challenge of the state-of-the-art CO2 capture technologies. Therefore, the new CO2 capture technology is promising from the perspectives of energy saving and environmental protection.