Effect of ultramicropores on the mechanisms of H2S retention from biogas.

• Ultramicropores exert a strong influence on the adsorption capacity of the materials. • A method to block ultramicropores has been proposed based on molecular simulation. • The ultramicropore blockage causes a drastic drop in H 2 S retention. • The ultramicropore blockage affects not only physisorption, but also chemisorption. • Ultramicropores immobilize and then redistribute molecules to the pore network. The pore distribution in activated carbon is crucial for its performance on adsorption processes. In desulfurization applications, the literature highlights the importance of pores from 5 to 10 Å. However, little is known and reported about the range of ultramicropores smaller than 4 Å, which has been found in commercial samples used for H 2 S retention. In order to clarify the influence of this fraction of pores on the H 2 S retention of typical biogas mixtures, measurements of multicomponent adsorption of hydrogen sulfide in the presence of carbon dioxide for activated carbon samples further impregnated with potassium hydroxide have been performed in column dynamics. Molecular simulation, XRF analysis and textural characterization were applied to aid the study. Results have shown that the H 2 S retention capacity in the presence of CO 2 decreased significantly mainly in the impregnated samples. The degree of reduction in H 2 S retention indicates that ultramicropores can be of substantial importance through a synergistic immobilizing effect of H 2 S molecules. The better understanding of such an effect could improve the development of more efficient adsorbents for chemical industries. [ABSTRACT FROM AUTHOR]