Low-Temperature Desorption of CO2 from Carbamic Acid for CO2 Condensation by Direct Air Capture.

Abstract

The high temperature requirement for the desorption of absorbed CO2 is one of the issues for the widespread use of direct air capture (DAC), which is a promising technology to reduce atmospheric CO2 concentration. This work realized a liquid diamine absorbent-solid carbamic acid (CA) phase-change DAC system with CO2 desorption at a low temperature by using a MeOH solvent. The CA of isophoronediamine [3-(aminomethyl)-3,5,5-trimethylcyclohexylamine, CA-IPDA] readily desorbed CO2 in MeOH at 50 °C, while IPDA showed the capacity to absorb low-concentration CO2 from air with an IPDA/CO2 ratio of 1:1. The CA-IPDA desorbed more than half of the absorbed CO2 at 60 °C without any gas flow, proving that this system can condense low-concentration CO2 in air to pure CO2 with low energy requirements. The low-temperature desorption of CO2 from CA-IPDA was owing to the high solubility of CA-IPDA in MeOH and the easy CO2 transfer between carbamic acid and MeOH to form methyl carbonate ions. This solubility control in the liquid-solid phase-change system opens up the low-energy DAC systems.