Effect of preparation methods on structure and catalytic activity of Ni loaded Ce x Zr1−x O2 catalysts for hydrogen production via autothermal reforming of ethane

Abstract

Ni/Ce0.75Zr0.25O2 catalysts were prepared using a variety of methods with water medium (Ni/CZW), urea-water medium (Ni/CZUW) and urea-water–alcohol medium (Ni/CZUWA). All of the catalysts were characterized by XRD, BET surface area, SEM, TEM, TPR and TGA analysis, respectively. The effect of the support composition as well as the metal loading on the autothermal reforming (ATR) of ethane was evaluated in a fixed-bed flow reactor at temperatures ranging from 300 to 700 °C. In the activity test, the Ni/CZUWA catalyst exhibited enhanced activity, which may be attributable to low levels of carbon deposition. The principal drawback—the decrease in the catalyst activity as the result of carbon deposition—was overcome by optimizing the catalyst preparation technique. From SEM analysis, Ni/CZUWA depicted nano-fiber morphology, whereas the other Ni/CZW and Ni/CZUW catalysts evidenced carbon clusters on its surface, which demonstrates clearly that the former is better than the latter for ethane reforming. The TPR results show that the Ni particles were more thoroughly dispersed in Ni/CZUWA catalyst than in the other catalysts. Depending on the composition and metal loading, a solid solution and/or a highly dispersed nickel oxide in ceria (or ceria–zirconia) can be obtained. The TGA data also supported the SEM observations, which illustrated approximately 5% less carbon deposition for the Ni/CZUWA catalyst.