A comparison between yttrium and scandium in improving the properties of nickel and ruthenium-based catalysts for dry reforming

MARIA DO CARMO RANGEL; JASON DE LOS SANTOS; ADRIANA D. BALLARINI; SILVIA C.P. MAINA

Tromsø

Simposio; 11th Natural Gas Conversion Symposium; 2016

In recent decades, the climate changes caused by global warming as well as the growing energy demand have increased the research for new sources of cleaner and more efficient energy. These requirements are largely met by the use of fuel cells, a promising technology able to generate electricity with high efficiency and no pollution. In spite of these advantages, only PEMFC (proton exchange membrane fuel cell) and SOFC (solid oxide fuel cell) have captured the most part of the market share, among the six different kinds available in the market. The high operation temperature (700?1100 oC) of the SOFCs provides several advantages such as the use of different fuels, including natural gas, which can be reformed both internally and externally the cell to produce hydrogen. For most economical operations, the fuel reforming is performed directly on the nickel anode at the same time that the electrochemical reaction in the SOFC. Various types of reforming processes can be used but the dry reforming is especially suitable, since it consumes methane and carbon dioxide, two gases responsible for the greenhouse effect. For most SOFCs, nickel supported on yttrium-stabilized zirconia is the common anode used today. However, its ionic conductivity is decreased at lower temperatures (650-750 oC), hindering the development of fuel cells at intermediate temperatures (IT-SOFC), a promising option to reduce the costs of these devices. To overcome this drawback, the replacement of yttrium by scandium has been proposed. However, the materials used for anodes of SOFC have been selected on basis on the electrochemical properties rather than on the catalytic properties. Moreover, most studies on SOFCs have been addressed to the steam reforming of natural gas. Therefore, a comparison between yttrium and scandium as promotors of zirconia-supported nickel and ruthenium was carried out in this work, aiming to find efficient catalysts for dry reforming of natural gas on nickel anodes of SOFCs.