Catalytic Properties of Ni3Al Powder for Hydrogen Generation by Methane Steam Reforming
Yan Ma1, Ya Xu2, Masahiko Demura2, Dong Hyun Chun3, and Toshiyuki Hirano2. (1) Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-2-1 Sengen, Tsukuba-shi, Ibaraki 305-0047, Japan, (2) Center of Fuel Cell Materials, National Insitute for materials science, 1-2-1 Sengen, Tsukuba-shi, Ibaraki 305-0047, Japan, (3) Materials Science and Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea
Intermetallic compound Ni3Al is well-known as an excellent structural material with its high-temperature strength and good corrosion/oxidation resistance, but its catalytic properties have been rarely investigated so far. Very recently, our group for the first time found high catalytic activity over alkali-leached Ni3Al powder for methanol decomposition, leading to hydrogen generation. The results are promising in fuel cell technologies since development of excellent catalysts for hydrogen production is essential. Following this finding, we found that Ni3Al powder also possesses high catalytic activity for methane steam reforming. The key to the high catalytic activity is chemical pretreatments of the powder. In this presentation we report the chemical pretreatment process of Ni3Al powder and the characteristic behavior of the catalytic properties. In the present study, we used atomized Ni3Al powder as precursor of catalysts for hydrogen generation from methane steam reforming (CH4 + H2O→3H2+CO). Catalytic experiments were performed by isochronal and isothermal tests in the temperature range from 873 to 1223 K. The catalytic activity of the as-received powder was quite low below 1173K. After chemical pretreatment by acid and following alkali leaching, the powder showed a significant enhancement in the activity even below 873 K. Isothermal tests revealed that the chemically pretreated powder shows the best performance at 973 K under the condition of stoichiometric steam/carbon ratio of 1 with no deactivation for over 20 h. Surface characterization by XRD, SEM, TEM and TPR showed that the enhancement by the chemical pretreatment attributes to a formation of nanoscale structure composed of Ni particles on the outmost surface.