The catalysts calcined at temperatures 900c consist

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Unformatted text preview: al oxide phase with periclase structure and spinel phases, where only the Ni 2+ ions in the divalent metal oxide phase are reducible up to the applied reduction temperatures. The catalyst calcined at 800°C consists of a poorly crystallised divalent metal oxide phase with periclase structure, an amorphous Al2O3 phase and a small amount of spinel phase at their interface. This results in the reduction of almost all Ni2+ ions. Ni10C800 also shows the highest amount of available surface Ni. Nevertheless its dispersion is the lowest, which is attributed to an increase in sintering due to the higher total amount of reduced Ni. The lower Ni dispersion of Ni10C1000 compared to Ni10C900 is attributed to the fact that a higher reduction temperatures had to be applied 99 3. Results and discussion - catalyst preparation and characterisation ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp (1100°C compared to 950°C) leading to an higher mobility of the Ni atoms formed during the reduction, which results in increased sintering. 1m mol H2 / (s·g) reaction rate [m mol H2 / (s·g)] Ni10C1000 Ni10C900 Ni10C800 0 200 400 600 temperature [°C] 800 Fig. 24 TPR profiles of the catalyst Ni10 calcined at 800, 900 and 1000°C 1000 100 3. Results and discussion - catalyst preparation and characterisation 1m mol H2 / (s·g) reaction rate [m mol H2 / (s·g)] Ni10C1000 Ni10C900 Ni10C800 0 100 200 temperature [°C] 300 Fig. 25 TPR profiles after passivation of the catalyst Ni10 calcined at 800, 900 and 1000°C. All catalysts were reduced in TPR run and passivated below 40°C 0.15 Ni dispersion 0.15 0.11 0.1 0.09 0.05 0 Ni10C800 Ni10C900 catalyst Ni10C1000 Fig. 26 Ni dispersion of the catalyst precursor Ni10 calcined at 800, 900 and 1000°C estimated from the TPR results 3. Results and discussion - catalyst preparation and characterisation 101 3.2.8. Basicity measurements For the processes related to the partial oxidation of C3H8 (steam reforming, CO2 reforming, partial oxidation of CH4) it was reported that the basicity can influence the catalytic performance especially the catalyst’s stability and the tendency towards coking. For example in the naphtha steam reforming alkali metal oxides must be added to avoid excessive c...
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