A comparative analysis of the effect of amines on CO2 absorption of type III porous liquids

Porous liquids are promising absorbents for CO 2 capture due to porosity and liquidity. In this paper, three amines, TEPA, PEI, and MEA, were used to reinforce CO 2 capture in type III porous liquids, and the influences of these amines on the CO 2 uptake of the porous liquids were discussed. First, determining the optimal TEPA, PEI, and MEA loadings were 30 wt%, 30 wt%, and 50 wt%, respectively. Then, the amine-modified type III porous liquids, TEPA@ZIF-8/[EMIm]/[NTf 2 ], PEI@ZIF-8/[EMIm]/[NTf 2 ], and MEA@ZIF-8/[EMIm]/[NTf 2 ] were prepared. The effects of different parameters on the CO 2 absorption characteristics were systematically investigated. It was found that amines-modification could significantly reinforce CO 2 absorption of type III porous liquids at low CO 2 partial pressures. The CO 2 uptake capacity of 5-30TEPA@ZIF-8/[EMIm][NTf 2 ], 5-30PEI@ZIF-8/[EMIm][NTf 2 ], 5-50MEA@ ZIF-8/[EMIm][NTf 2 ] was 4.43, 2.28, and 3.96 times higher and the corresponding absorption rates were 8.45, 2.25, and 26.3 times higher than that of 5-ZIF-8/[EMIm][NTf 2 ]. The CO 2 absorption kinetic properties were revealed, and the results showed the fractional-order kinetic model best fitted the CO 2 absorption process, suggesting the CO 2 absorption coupled with the CO 2 diffusion inside the main units and the chemical reaction at the active sites. Finally, the cyclic regeneration performance results displayed that TEPA@ZIF-8/[EMIm][NTf 2 ] exhibited a good cyclic regeneration performance and has the potential for CO 2 capture.