Solar induced low-temperature phase separation in thermomorphic solvents for CO2 capture

Replacing steam with solar for CO2 regeneration is an incredibly promising approach. However, the high temperature required for solvent regeneration and the less-than-optimal photothermal conversion efficiency that prevents reaching the necessary regeneration temperature are significant limitations to this approach. In this work, thermomorphic solvents containing dimethylcyclohexylamine, N-methylcyclohexylamine and photothermal nanoparticles were prepared for CO2 capture. Nano carbon black, multi-walled carbon nanotube and carboxyl group functionalized multi-walled carbon nanotube were used as promoter for photothermal conversion. The experimental results exhibit the high CO2 absorption capacity of 0.1081 g/g solvent for the carboxyl group functionalized multi-walled carbon nanotube based solvent, and it can be efficiently regenerated under solar irradiation at a low temperature of ∼ 323 K. It is noteworthy that the photothermal material not only raise the solution temperature(∼325 K) during solar irradiation but also boosts the CO2 absorption rate, and leads to a ∼ 20.8 % increase in CO2 absorption capacity during the absorption process. Furthermore, the utilisation of photothermal regeneration for thermomorphic solvents can achieve an efficiency of 78.6 %, with a regeneration heat of 2.35 GJ/t CO2, resulting in an energy consumption reduction of approximately 41.1 % in comparison to 30 wt% monoethanolamine. The photo triggered regeneration of the thermomorphic solvent investigated in this study shows promising potential as an energy-efficient carbon capture technology.