Enhanced selective adsorption of H2S from CO2 by incorporating methylated polyethyleneimine into a porous carbon matrix

Abstract

In this study, a series of hybrid adsorbent materials (AC@mPEI) with superior selective separation properties of H2S and CO2 are prepared by taking advantage of the differences in reaction mechanisms between H2S and CO2, as well as tertiary amines. Using a straightforward impregnation method, the methylated polyethyleneimine (mPEI) is successfully introduced into the pores of the porous carbon to create the desired hybrid adsorbents. The strong interaction between the tertiary amine groups and H2S facilitates the selective separation of H2S and CO2 gases. Remarkably, the adsorbent (1:1)AC@mPEI exhibits a substantial H2S adsorption capacity of 5.83 mmol·g−1 at 298 K and 1.0 bar and a high separation selectivity of H2S to CO2 (133), which is approximately 16.6 times higher than that of the porous carbon supporter. Further investigations, involving adsorption thermodynamics, breakthrough experiments, and spectroscopy, confirm that the strong interaction between the hybrid materials and H2S plays a pivotal role in enhancing the separation selectivity of H2S. Additionally, the adsorbed H2S can be well desorbed through vacuum degassing, allowing for multiple cycles of the adsorbent. This strategy, which leverages differences in gas adsorption mechanisms to fabricate hybrid adsorbents, presents novel concepts for the development of functional adsorbent materials for selective separation of gases.