The differences in the catalyst deactivation and the

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Unformatted text preview: n homogeneous reactions at increasing GHSV less unsaturated hydrocarbons are formed, which are more likely to form coke, which can depending on its form lead to catalyst deactivation. 4. Results and discussion - catalytic partial oxidation of propane 133 4.5. Influence of the calcination temperature In order to investigate the influence of the calcination temperature on the catalytic behaviour the precursor Ni10 was calcined at 700, 800, 900 and 1000°C. The step from 900 to 1000°C was chosen to investigate how a higher degree of crystallinity influences the catalytic behaviour. Another reason was to perform the reaction at 900°C while fulfilling the set criteria that the maximal reaction temperature should be 100°C lower than the calcination temperature. Calcination at 700 and 800°C was performed especially to investigate the difference in the catalyst behaviour due to the change of the structure. As discussed earlier the catalysts calcined at 700 and 800°C consist of a poorly crystallised divalent metal oxide phases with periclase structure, an amorphous Al2O3 and a spinel phase at their interfaces, whereas after calcination at 900°C well crystallised divalent metal oxide phases with periclase structure and spinel phases are present. Furthermore, it is also possible for the catalyst calcined at 800°C to reconstruct the HT structure, it is but far less likely for the catalysts calcined at higher temperatures. It must be pointed out that only over the catalyst calcined at 800°C no reproducible results could be obtained. It can only be speculated about the reason, but it might be due to the (partial) reconstruction of the former HT structure as the reaction was carried out at high temperatures and considerable amounts of water were formed. The catalysts at temperature ≤ 800°C exhibited partial reconstruction already after calcination. Even though the results for the catalyst Ni10C800 were not reproducible, for a comparison the best results are presented. Due to this problem no catalytic tests were performed for the catalyst Ni10C700. However...
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This document was uploaded on 10/07/2013.

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