Effect of La2O3 addition on Ni/Al2O3 catalysts to produce H2 from glycerol

Biodiesel has been promoted as the only realistic alternative to petro-oil in the transport sector, as it can be mixed in any ratio with standard diesel for use in diesel engines. However, the increase in biodiesel production has been accompanied by increases in glycerol production, which is the main by-product of the process. As hydrogen is a clean energy carrier, conversion of glycerol to hydrogen is one among the most attractive ways to make use of this byproduct. In this study, the catalytic production of hydrogen by steam reforming of glycerol has been experimentally performed in a fixed-bed reactor. The performance of this process was evaluated over nickel (Ni) supported on un-promoted and promoted with La2O3 alumina catalysts. Catalysts were synthesized applying the wet impregnation method at a constant metal loading (8wt%). The synthesized samples, at their calcined or/and reduced form, were characterized by X-Ray Diffraction (XRD) and the N2 adsorption-desorption technique (BET). Their chemical composition was determined by inductively coupled plasma (ICP), while the deposited carbon on the catalytic surface was measured by a CHN analyzer. Morphological examination and elemental analysis was done using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) respectively, for both fresh and used catalysts. The catalytic performance of the catalysts concerning the glycerol steam reforming reaction was studied in order to investigate the effect of the reaction temperature on (i) Glycerol total conversion, (ii) Glycerol conversion to gaseous products, (iii) Hydrogen selectivity and yield, (iv) Selectivity of gaseous products, and (v) Selectivity of liquid products. From the work presented herein, it can be concluded that the addition of lanthanum to Ni catalysts supported on alumina favors the formation of gaseous H2 and CO2, minimizes liquid effluents and inhibits the formation of carbon during the reaction. The fall in carbon formation may be attributed to the lanthanum’s redox properties, which offer alternative routes to the