Atmospheric hydrodesulfurization of diesel fuel using Pt/Al2O3 catalysts prepared by supercritical deposition for fuel cell applications

Hydrodesulfurization (HDS) of low-sulfur model and commercial diesel fuel (500 ppmw 5) using Pt/Al2O3 catalysts prepared by supercritical carbon dioxide (scCO(2)) deposition method is investigated at atmospheric pressure and in temperature range of 290-350 degrees C. The reactivity of the investigated organosulfur compounds followed the known trend, that is: BT > 2-MDBT > DBT >> 4-MDBT > 4.6-DMDBT, despite the nonconventional operating conditions and catalyst. The HDS of dibenzothiophenes was found to proceed only via the direct desulfurization route (C-S bond scission) under the studied conditions whereas HDS at high H-2 pressure proceeds via both direct desulfurization and hydrogenation routes. This limitation had several consequences. Under atmospheric pressure, the HDS reaction exhibited low reactivity particularly towards the stericly hindered substituted dibenzothiophenes. HDS of commercial diesel at atmospheric pressure using catalyst prepared by supercritical fluid deposition technique was found to be feasible, however, the catalyst had to have high metal loading and the reactor had to be operated under high H-2/fuel ratio with low hourly space velocity. (c) 2009 Elsevier B.V. All rights reserved.