Comparison of adsorbents for H₂S and D4 removal for biogas conversion in a solid oxide fuel cell

Abstract

Biogas contains trace compounds detrimental for solid oxide fuel cell (SOFC) application, especially sulphur-containing compounds and volatile organic silicon compounds (VOSiCs). It is therefore necessary to remove these impurities from the biogas for fuelling an SOFC. In this paper, dynamic lab-scale adsorption tests were performed on synthetic polluted gas to evaluate the performance of a polishing treatment to remove hydrogen sulphide (H2S - sulphur compound) and octamethylcyclotetrasiloxane (D4 - VOSiC). Three kinds of adsorbents were tested: an activated carbon, a silica gel (SG) and a zeolite (Z). Z proved to be the best adsorbent for H2S removal, with an adsorbed quantity higher than [Formula: see text] at the SOFC tolerance limit. However, as concerns D4 removal, SG was the most efficient adsorbent, with an adsorbed quantity of about 184 mgD4/gSG at the SOFC tolerance limit. These results could not be explained by structural characteristics of the adsorbents, but they were partly explained by chemical interactions between the adsorbate and the adsorbent. In these experiments, internal diffusion was the controlling step, Knudsen diffusion being predominant to molecular diffusion. As Z was also a good adsorbent for D4 removal, competition phenomena were investigated with Z for the simultaneous removal of H2S and D4. It was shown that H2S retention was dramatically decreased in the presence of D4, probably due to D4 polymerization resulting in pore blocking.

Physical Activation of Waste-Derived Materials for Biogas Cleaning

“…Ducom et al (2013) showed how fly ash from biomass was able to remove some trace compounds from the biogas [40]. Fly ash from wood waste and char have a lower removal capacity for the desulphurisation of biogas compared to commercially activated carbons [39,[41][42][43][44]. The waste materials adopted for the purpose of cleaning biogas require more research, especially on the improvement of their physical characteristics, such as microporous volume and specific surface area.…”

Adsorptive Biogas Purification from Siloxanes—A Critical Review

“…The usefulness of zeolites for removing VMSs from biogas has been confirmed by numerous studies, e.g., [31,39,40]. Owing to their high thermal resistance they are also suitable for repeated thermal regeneration [25].…”

Green Synthetic Fuels: Renewable Routes for the Conversion of Non-Fossil Feedstocks into Gaseous Fuels and Their End Uses

“…Hydrogen sulfides and halogens are adsorbed on Ni/YSZ active surface inhibiting the catalytic reactions [688]. H 2 S and HCl are removed by adsorption in materials, such as activated carbon, metal oxides (ZnO, MnO, CuO), silica gel and zeolites [689], or chemical absorption in water [690]. The hydrogen sulfide solubility is improved by alkaline compounds or by H 2 S catalytic oxidation [690].…”