(550c) Hydrogen Sulfide Removal from Biogas on "Molecular Basket" Sorbents

Authors: 
Quan, W., Georgia Institute of Technology
Wang, X., Pennsylvania State University
Song, C., Pennsylvania State University
Biogas is a sustainable energy source which can be used as an alternative fuel. However, hydrogen sulfide (H2S) in biogas (formed from the decomposition of organic materials) limits the application of biogas due to its corrosivity and sulfur-toxicity. Recently, “Molecular basket” sorbents (MBS) for acid gas adsorption developed in our group could achieve H2S sorption/desorption at ambient conditions. Nevertheless, the large amount of CO2 in biogas strongly inhibits H2S sorption on conventional MBS. Therefore, the objective of this work is to selectively remove H2S from biogas which contains a high-level concentration of CO2. In this work, a series of tertiary-amine-based “Molecular Basket” sorbents were prepared and applied in H2S removal from the gas mixture containing a high concentration of CO2. Poly allylamine (PA), polyethylenimine (PEI), and tetramthyl hexanediamine (TMHDA) were loaded on SBA-15 to compare the H2S sorption performance in the absence and presence of CO2. In the presence of CO2, the H2S sorption dropped dramatically on PA/SBA-15 and PEI/SBA-15, whereas the selectivity of TMHDA/SBA-15 for H2S sorption remained stable. The inlet concentration (H2S and CO2), the regenerability, as well as the effects of CH4 and moisture were studied. The H2S sorption capacity was increased with increasing inlet H2S concentration, and the sorption on TMHDA/SBA-15 was fitted to Langmuir adsorption isotherm. However, the H2S sorption capacity was slightly decreased with the increase of inlet CO2 concentration. The regenerability was good under mild regeneration conditions. In addition, other components in biogas, such as CH4 and moisture, showed little effect on the H2S sorption performance over MBS. This work demonstrated that tertiary-amine-based MBS is selective for the H2S removal from biogas.
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