Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Adsorptive on-board desulfurization over multiple cycles for fuel-cell-based auxiliary power units operated by different types of fuels Raphael Neubauer a,* , Christof Weinlaender a , Norbert Kienzl b , Brigitte Bitschnau c , Hartmuth Schroettner d , Christoph Hochenauer a a Institute of Thermal Engineering, Graz University of Technology, Inffeldgasse 25/B, 8010 Graz, Austria b Bioenergy2020 + GmbH, Inffeldgasse 21/B, 8010 Graz, Austria c Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9/I, 8010 Graz, Austria d Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria HIGHLIGHTS • Efficient adsorptive desulfurization at -10 to < 60 °C using Ag-Al 2 O 3 as adsorbent. • In situ adsorbent regeneration via hot APU off-gas. • Thermal and chemical stability of Ag- Al 2 O 3 under APU off-gas conditions. • Constant desulfurization and re- generation performance over multiple cycles. GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Adsorption Desulfurization Dibenzothiophene Regeneration Fuel cell Cyclic operation ABSTRACT 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-Al 2 O 3 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-Al 2 O 3 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 ca- pacity 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. 1. Introduction On-board desulfurization is mandatory to operate highly efficient but sulfur sensitive fuel cell systems with commercial hydrocarbon- based fuels in mobile applications. The total sulfur content in com- mercial fuels is in the range of 10–5000 ppm and depends on the type of https://doi.org/10.1016/j.jpowsour.2018.02.083 Received 12 October 2017; Received in revised form 7 February 2018; Accepted 26 February 2018 * Corresponding author. E-mail address: raphael.neubauer@tugraz.at (R. Neubauer). Journal of Power Sources 385 (2018) 45–54 Available online 15 March 2018 0378-7753/ © 2018 Elsevier B.V. All rights reserved. T