The role of Zr in NiZrAl oxides catalyst and the evaluation on steam reforming of glycerol for hydrogen product

The NiZrAl mixed metal oxides catalysts with varied Zr/Al ratio were derived from the layered double hydroxides (LDH) through the thermal decomposition. The different techniques such as TG, XRD, N-2 adsorption/desorption, XPS, TPR, H-2 chemisorption, SEM and TEM etc. were applied to study the thermal decomposition behaviors of the corresponding LDH, crystalline phases changes before and after reaction, the porous structure, chemical state of surface element, reducibility, properties of active phase metallic Ni and the morphology. The results showed that the LDH structure could be kept during the experimental range from 0.1 to 1.0, although high Zr/Al ratio made the structure feature weaken. The porous structure of the calcined catalysts exhibited an significant change when Zr/Al ratio reached 0.5. Both Ni dispersion and surface increased linearly with the increased Zr/Al, however, more amount of surface Ni was reduced and less amount of coke was formed over the sample NiZr0.5Al. It consequently gave the best conversion to gaseous products and the highest selectivity of hydrogen by promoting the water gas shift reaction and suppressing the CO methanation reaction.