Adsorptive absorption: A preliminary experimental and modeling study on CO2 solubility

A new unit operation in chemical engineering, adsorptive absorption (i.e., the coupling of adsorption and absorption), was first proposed conceptually in this work for carbon dioxide (CO2) capture. The separating agent is the mixture of an ionic liquid (IL) that provides the absorption function and a zeolitic imidazolate framework (ZIF) that provides the adsorption function. To better understand the coupling effect, we measured the total CO2 solubility in the mixed separating agent by uniformly suspending ZIF powder in IL at temperatures from 298.2 to 243.2 K and pressures from 4.0 to 30.0 bar. It was verified that CO2 solubility in ILs can apparently be enhanced via the addition of ZIF-8 over wide temperature and pressure ranges. Both total CO2 solubility and total working capacity in the mixed separating agent can be well described by the lever rule with the ARDs being less than 6.02%, when the predictive UNIFAC model and GCMC (grand canonical Monte Carlo) simulation were used together. Preliminary experimental and modeling results show that adsorptive absorption is a promising technology for CO2 capture, which should be further addressed in future work.