Characterizations of nanostructured nickel aluminates as catalysts for conversion of glycerol: Influence of the preparation methods

- Nickel aluminate catalysts screened for glycerol transformation.
- The coprecipitated and nanocasted catalysts having NiO and NiAl2O4 phases.
- NiAl2O4 phase improved dehydrogenation-hydrogenolysis reactions.
- Nanosized NiAlxOy active phase led to high glycerol conversions.
- Sintering and coking effects caused the deactivation of the solids.

Three different preparation methods were applied to prepare nickel aluminates (i.e. nanocasting (NiAlN), coprecipitation (NiAlC) and wet impregnation (NiAlW) methods). All catalysts exhibited the NiAl2O4 phase besides that of NiO and γ-Al2O3. The NiAlN catalyst showed nanoparticles of the aforesaid oxides whereas NiAlxOy was the predominant phase found over NiAlW catalyst. The performances of the nickel aluminate-based catalysts were evaluated in glycerol dehydration to produce valuable chemical compounds through the dehydration of glycerol. The sintering effects were responsible for the decreased performance of NiAlC in glycerol dehydration. On the contrary, NiAlN is found to be deactivated due to the lesser stability of its supported nanoparticles, being the glycerol conversion of ca. 3.3% at the end of the reaction. Besides, the reaction efficiently proceeded on NiAlW, which had a high catalytic performance with 19.7% glycerol conversion to acetol and others products and no deactivation along of the time for 25 h of time on stream was observed. This was due to the stability of the NiAlxOy phase, which impeded phase transformation and was resistant to heavy coking.

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