Effects of various anions and cations in ionic liquids on CO2 capture

Optimization of novel nonaqueous hexanol‐based monoethanolamine/methyl diethanolamine solvent forCO2absorption

“…The inlet and outlet CO 2 flow rates, temperature and pressure variation in the stirred reactor were recorded by a data logger every 10 s. The absorption process was continued until the inlet mass flow rate approached the outlet mass flow rate which means that the alkanolamine solvent reached equilibrium with CO 2 . Then, the absorption curves (flow rate CO 2 [cm 3 /min] vs time [s]) were plotted, and CO 2 absorption capacity (in mole) was determined through difference between flow rates as reported in our previous works 56,57 . The absorption capacity was presented in terms of CO 2 loading ().…”

Reactive Capture of CO2: Opportunities and Challenges

“…Ion pairing with added cations should tune the properties of the anions and should be considered in reaction design. Weaker binding of CO 2 may be described by the activated CO 2 shown in Chart ; with weaker binding, such an interaction would eventually be described by a physisorption mechanism, as observed in ILs , and MOFs, rather than the chemical capture of CO 2. The chemistry of capture agents that are weaker nucleophiles or physisorption agents will likely be closer to that of well-explored CO 2 reaction chemistry; under these conditions, it is more likely that established (electro)­catalysts for CO 2 reduction will work for RCC.…”

“…The scope of Section will be on the chemical capture of CO 2 using solution-phase sorbents, which are relevant to the selected catalysis examples of the following sections; however, other types of capture agents do exist. For example, ionic liquids (ILs) can act as physisorption capture agents, and solid-state materials such as solid adsorbents or metal–organic frameworks (MOFs) are also promising capture agents …”

“…When primary and secondary amines are used as the capture solvents, the CO 2 can bind directly with nitrogen to form a C–N bond, forming a carbamate ion; the mechanism requires a second equivalent of amine to act as the Lewis base, which is protonated to form the ammonium counterion (Scheme ). The carbamate ions are stable enough that the CO 2 remains in the bound state until the solution is heated to temperatures around 393 K (120 °C); the regeneration process can take as much as 3.5 GJ of energy for each ton of CO 2 that is released. , Thus, one key feature of alkanol amines is their stability at the temperatures that are required to release the CO 2 .…”

“…Water has a high heat capacity, so additional thermal energy is required to heat aqueous solutions relative to the energy needed to heat a nonaqueous solution to promote CO 2 release (if that is desirable). ILs such as 1-butyl-3-methylimidazolium acetate, namely, [bmim]­[Ac] (Chart , middle), are predicted to lower the energy needs of CO 2 capture by 16% compared to traditional MEA solutions . We recognize that the RCC process does not require release of CO 2 , but modest heating may weaken the capture agent–CO 2 interaction to promote RCC.…”