Effect of Additional CeO_2 on Steam Reforming Performance of Ni/ZrO_2 Fuelled by Natural Gas for Application in SOFC

摘要

An alternative method to reform natural gas efficiently for later utilisation in Solid Oxide Fuel Cell (SOFC) is presented. As natural gas consists of some high hydrocarbon elements, an external pre-reforming unit, where some hydrocarbons can be partially reformed before reaching the main reforming unit, is required. In the present work, Ni/ZrO_2 was studied as a reforming catalyst. Without any pre-reforming, TPO experiment indicated the high amount of carbon deposition on the surface of Ni/ZrO_2 after exposure in normal steam reforming conditions fuelled by natural gas. In order to improve the reforming performance of Ni/ZrO_2 such as preventing possible surface carbon formation, CeO_2 was investigated by adding together with Ni/ZrO_2 in the same unit either as an internal pre-reforming or co-reforming element. Although CeO_2 has been reported to have low steam reforming reactivity, this material was proved to provide much higher resistance toward carbon formation than Ni/ZrO_2 under the same conditions. The experimental results support the idea of using CeO_2 as pre-reforming element rather than co-reforming element. By using CeO_2 as the pre-reforming element, less inlet steam/carbon ratio was required to prevent the formation of carbon species on the surface of Ni/ZrO_2. These benefits are mainly due to the redox and high oxygen storage abilities of CeO_2.