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Acid base interaction and its influence on the adsorption kinetics and selectivity order of aromatic sulfur heterocycles adsorbing on Ag-Al2O3

Neubauer R, Husmann M, Weinlaender C, Kienzl N, Leitner E, Hochenauer C

Published 1 February 2017

Citation: Neubauer R, Husmann M, Weinlaender C, Kienzl N, Leitner E, Hochenauer C. Acid base interaction and its influence on the adsorption kinetics and selectivity order of aromatic sulfur heterocycles adsorbing on Ag-Al2O3. Chemical Engineering Journal. 1 February 2017;309: 840-849.

Abstract

Adsorptive desulfurization is a promising technology to provide sulfur free fuels for fuel cell based power units. In this work the adsorption kinetics of three different aromatic sulfur heterocycles was studied for Ag-Al2O3. The influence of individual as well as competitive adsorption on the selectivity order was investigated by equilibrium and breakthrough experiments. In these experiments a jet-A1 fuel enriched with benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used. The adsorption of aromatic sulfur heterocycles on Ag-Al2O3 proceeds via three different adsorption mechanisms. Within these mechanisms the π-interaction (π-Ag) and the direct sulfur-silver interaction (S-Ag) are significantly stronger in comparison to the acid base interaction (S-H). The results showed that the π-Ag and S-Ag interactions are the major adsorption mechanisms in the first stage, where film-diffusion limits the adsorption rate. In the second stage, the S-H interaction plays only an important role for BT, where intraparticle diffusion is the rate controlling step. The overall selectivity order was found to be BT > DBT > 4,6-DMDBT in the case of competitive adsorption for both equilibrium and breakthrough performance. The S-H contribution was related to incorporation of silver into blank γ-alumina, which significantly increased the overall acidity of the adsorbent.

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