Zirconia supported nickel catalysts for glycerol steam reforming: Effect of zirconia structure on the catalytic performance

The effect of the zirconia structure in Ni/ZrO2 catalysts on the glycerol steam reforming (GSR) reaction was studied. A tetragonal zirconia support was synthesized via a hydrolysis technique and loaded with 5 wt% Ni via a wet-impregnation method. Similarly, a commercial monoclinic zirconia support was also impregnated with 5 wt% Ni. Following calcination at 600 degrees C, physico-chemical properties of the prepared catalysts were investigated by X-Ray Diffraction (XRD), H-2-Temperature Programmed Reduction (H-2-TPR) and CO2-Temperature Programmed Desorption (CO2-TPD) techniques. The catalysts were then tested in the GSR reaction in the 400-700 degrees C range with a steam to glycerol molar ratio of 9:1 and a flow rate of 0.025 mL/min. The monoclinic catalyst exhibited a better performance giving higher hydrogen yields and glycerol conversions. This was attributed to an improved reducibility of Ni in this catalyst. Stability tests at 600 degrees C revealed the deactivation of the tetragonal catalyst during 6 h as a result of the formation of encapsulating coke which blocked active Ni metal sites. The monoclinic catalyst, exhibiting the formation of only filamentous coke, remained relatively stable for 24 h. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.