Scientific Journals | 2018
Adsorptive on-board desulfurization over multiple cycles for fuel-cell-based auxiliary power units operated by different types of fuels
Neubauer, R, Weinlaender C, Kienzl N, Bitschnau B, Schroettner H, Hochenauer C. Adsorptive on-board desulfurization over multiple cycles for fuel-cell-based auxiliary power units operated by different types of fuels. Journal of Power Sources. 1 May 2018, 385: 45-54.
On-board desulfurization is essential to operate fuel-cell-based auxiliary power units (APU) with commercial fuels. In this work, both (i) on-board desulfurization and (ii) on-board regeneration performance of Ag-Al2O3 adsorbent is investigated in a comprehensive manner. The herein investigated regeneration strategy uses hot APU off-gas as the regeneration medium and requires no additional reagents, tanks, nor heat exchangers and thus has remarkable advantages in comparison to state-of-the-art regeneration strategies. The results for (i) show high desulfurization performance of Ag-Al2O3 under all relevant operating conditions and specify the influence of individual operation parameters and the combination of them, which have not yet been quantified. The system integrated regeneration strategy (ii) shows excellent regeneration performance recovering 100% of the initial adsorption capacity for all investigated types of fuels and sulfur heterocycles. Even the adsorption capacity of the most challenging dibenzothiophene in terms of regeneration is restored to 100% over 14 cycles of operation. Subsequent material analyses proved the thermal and chemical stability of all relevant adsorption sites under APU off-gas conditions. To the best of our knowledge, this is the first time 100% regeneration after adsorption of dibenzothiophene is reported over 14 cycles of operation for thermal regeneration in oxidizing atmospheres.
Peer Reviewed Scientific Journals | 2017
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. 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.
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.
Peer Reviewed Scientific Journals | 2016
Adsorptive Desulfurization: Fast On-Board Regeneration and the Influence of Fatty Acid Methyl Ester on Desulfurization and in Situ Regeneration Performance of a Silver-Based Adsorbent
Neubauer R, Weinlaender C, Kienzl N, Schroettner H, Hochenauer C. Adsorptive Desulfurization: Fast On-Board Regeneration and the Influence of Fatty Acid Methyl Ester on Desulfurization and in Situ Regeneration Performance of a Silver-Based Adsorbent. Energy and Fuels. 16 June 2016;30(6): 5174-5182.
Adsorptive on-board desulfurization units require a high desulfurization and regeneration performance for a wide range of fuels to keep them small and ensure long maintenance intervals. A novel thermal regeneration strategy was investigated in this work, fulfilling all requirements for in situ on-board regeneration. In this strategy, a temperature-controlled flow rate (TCFR) of air was used to control the temperature inside the adsorber. With this dynamic approach, the regeneration time was reduced significantly in comparison to other thermal regeneration strategies. The novel regeneration strategy was tested using Ag–Al2O3 as an adsorbent to desulfurize a benzothiophen (BT)-enriched road diesel (300 ppmw of total sulfur). A commercial diesel containing fatty acid methyl ester (FAME) was used to evaluate the fuel flexibility regarding desulfurization and regeneration performance. In the case of 6.63 wt % FAME and 300 ppmw of sulfur, the breakthrough adsorption capacity of sulfur decreased from 1.04 to 0.17 mg/g. In TCFR regeneration experiments, the breakthrough adsorption capacity was restored to over 94% in the case of both fuels. Thereby, the Brunauer–Emmett–Teller (BET) surface area of the regenerated adsorbent decreased by only 1.5%, and negligible carbon deposits were detected.