Effect of Amines on MIL-101(Cr) for Simultaneous H2S/CO2 Removal from Biogas

Abstract

Production of biomethane from raw biogas requires the removal of impurities, such as CO2 and H2S. To accommodate the variety of biogas sources, a modular separation design with a small footprint is desired. In this work, we report three diamine-impregnated metal-organic frameworks (MOFs), MIL-101(Cr) (diamines: diethylethylenediamine, ee-2; 2,2-dimethyl-1,3-propanediamine, dmpn; N-methylethylenediamine, m-2) for simultaneous removal of H2S and CO2 from simulated binary and ternary biogas mixtures. The H2S and CO2 separation performance and regeneration conditions were investigated by dynamic column breakthrough and temperature-programmed desorption experiments. While all three diamine-impregnated MIL-101(Cr) samples were H2S-selective over CO2 in the mixture compositions studied, MIL-101(Cr)-ee-2 displayed the highest H2S/CO2 adsorption selectivity of ∼7. Also, it showed distinct desorption temperatures for H2S and CO2 that allows for concentrated H2S collection during adsorbent regeneration, which can potentially simplify the biogas separation process to achieve concentrated biomethane and H2S collection using the same adsorption module.