Amine modified silica xerogel for H2S removal at low temperature

High porosity and adsorbent silica xerogels modified by the addition of amine groups, triamine (TRI) or polyethyleneimine (PEI), were developed for the low temperature removal of H2S from biogas. The H2S adsorption and desorption abilities were characterized in a fixed-bed system with respect to the effect of the amine type, loading amount, operating temperature and gas flow rate. Decreasing the temperature and increasing the amine loading level enhanced the H2S removal efficiency. At a temperature of 30 °C, the silica xerogel loaded with 50 wt.% PEI (Si-PEI800-50) showed the highest breakthrough time and breakthrough and saturation capacities. Two PEI layers (the exposed layer and the inner bulk layer) may present in the Si-PEI800-50. The amine efficiency, the ratio of bound H2S/amine was also affected by the amine loading amount, and increased up to a maximum at a 50 wt.% amine loading level for both TRI and PEI800. The performance also depended upon the gas flow rate, the efficiency being decreased as the flow rate was increased. The optimal adsorbent, Si-PEI800-50, was regenerated easily at a mild temperature (optimal of 50 °C) for at least ten successive adsorption-desorption cycles without any detectable loss of adsorption performance or regeneration ability.