Influence of the synthesis method parameters used to prepare nickel-based catalysts on the catalytic performance for the glycerol steam reforming reaction

Abstract

The influence of the synthesis method parameters used to prepare nickel-based catalysts on the catalytic performance for the glycerol steam reforming reaction was studied. A series of Al2O3-supported Ni catalysts were synthesized, with nickel loading of 8 wt%, using the incipient wetness, wet impregnation, and modified equilibrium deposition filtration methods. The catalysts' surface and bulk properties were determined by inductively coupled plasma (ICP), N2 adsorption-desorption isotherms (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and temperature-programmed reduction (TPR). Used catalysts were characterized by techniques such as elemental analysis and SEM in order to determine the level of carbon that was deposited and catalyst morphology. The results indicated that the synthesis method affected the textural, structural and surface properties of the catalysts, differentiating the dispersion and the kind of nickel species on alumina's surface. The formation of nickel aluminate phases was confirmed by the XRD and TPR analysis and the β-peak of the Ni/Al-edf catalyst was higher than in the other two catalysts, indicating that the nickel aluminate species of this catalyst were more reducible. Both Ni/Al-wet and Ni/Al-edf catalysts showed increasing CO2 selectivities and approximately constant CO selectivities for temperatures above 550 °C, indicating that these catalysts successfully catalyze the water gas shift reaction. It was also confirmed that the Ni/Al-edf catalyst had the highest values for glycerol to gaseous products conversion, hydrogen yield, allyl alcohol, acetaldehyde, and acetic acid selectivities at 650 °C and the lowest carbon deposition of the catalysts tested. The correlation of the catalysts' structural properties, dispersion and reducibility with catalytic performance reveals that the EDF method can provide catalysts with higher specific surface area and active phase's dispersion, that are easier to reduce, more active and selective to hydrogen production, and more resistant to carbon deposition.