Preparation of a Nanostructured Ni/CaO<middle dot>Al2O3 Catalyst for Syngas Production via Glycerol Dry Reforming: Role of the Preparation Method

Four nickel nanostructure catalysts supported on the CaO<middle dot>Al2O3 (CA) support were synthesized with different synthesis procedures (i.e., coprecipitation, evaporation-induced self-assembly, sol-gel, and autocombustion) and have been investigated in a glycerol CO2-reforming reaction. The nitrogen adsorption-desorption, SEM, XRD, TEM, H-2-TPR, O-2-TPO, TGA, and FTIR techniques were used to characterize prepared Ni/CaO<middle dot>Al2O3 catalysts, and their catalytic performances were evaluated at 600-750 degrees C, atmospheric pressure, and a CO2/glycerol ratio of 1. It was demonstrated that the preparation route strongly influenced the structural, textural, and chemical features of the as-prepared samples. The maximal conversion of glycerol (ca. 55% at 750 degrees C) was obtained over the Ni/CA sample prepared by the sol-gel technique. It also exhibited better catalytic stability during the 25 h of the dry reforming reaction. The smaller Ni crystalline size (16.7 nm) and high Ni dispersion with strong interaction with the CaO<middle dot>Al2O3 support for this sample can result in superior catalytic performance and stability compared with other synthesized samples. This synthesis procedure was sensitive to the solvent type, and the physicochemical property was significantly affected by changing the solvent; therefore, it should be noted as a significant parameter for this preparation method. For the investigation of this parameter, three solvents, including methanol, ethanol, and propanol, were applied in the sol-gel method, and the obtained results imply that employing ethanol as a solvent in this method resulted in achieving better structural properties as well as higher catalytic efficiency in the glycerol CO2-reforming reaction. As a result, the simple sol-gel technique was successful for the preparation of the Ni/CaO<middle dot>Al2O3 sample with high potential as a catalyst for glycerol CO2-reforming.