Methane reforming and water splitting by zirconia-supported cerium-tungsten composite oxides for cyclic production of syngas and hydrogen

摘要

Redox cycles of methane reforming (MR) and water splitting (WS) of cerium-tungsten composite oxides were investigated at 1223 K for the cyclic production of syngas and hydrogen. Among various composite oxides tested having different Ce/W ratios, the sample with the Ce/W molar ratio of 1, CeW1/Zr, showed the best performance. When the sample was stabilized after several cycles, most of the Ce was present as Ce3+ and thus only W participated in the redox process. Production of CO2 during MR by the cerium tungsten composite sample was much less than that by the WO3-only sample, yielding a H-2/(CO + CO2) ratio much closer to the desired value of 2. The extent of reduction of W by MR remained nearly constant during repeated cycles, but re-oxidation by WS was not complete during the first several cycles. However, the re-oxidation extent increased to full re-oxidation during repeated cycles; the redox system became very stable after the sixth cycle. These are both beneficial effects owing to the presence of Ce. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.