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Since several factors characterising the catalysts

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Unformatted text preview: an approximate metal composition Ni10Mg62Al28 calcined at 900°C exhibited the best catalytic performance, a good stability with time-on-stream and a high resistance against coking (the highest at 800°C). The partial oxidation of C3H8 performed over this catalyst compared with the results of the non-catalytic reaction showed at least two-fold increase in the yield of CO and eightfold increase of the H2 yield. At lower temperatures these differences were even greater. Calcination of the catalyst Ni10 at 1000°C did not improve the catalytic performance, but resulted in a lower stability and higher coking. Calcination at 800°C lead to a decrease of the catalytic performance and to not reproducible results attributed to the partial reconstruction of the former hydrotalcite-type structure. Therefore Ni10 calcined at 900°C was used for further investigations of the influence of the O2/C3H8 ratio and 5. Conclusions 144 ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp the space velocity on its performance at 800°C. These studies revealed that the total C3H8 conversion was only achieved in excess of O2 because even under O2 deficient conditions part of the O2 lead to the total oxidation products CO2 and especially H2O. When all C3H8 was converted excess O2 lead not to the catalyst oxidation, but to an increase in the yield of total oxidation products. The highest yields of CO and H2 are achieved at total C3H8 conversion. Under O2 deficient conditions only small amounts of unsaturated hydrocarbons were formed. Not reacted C3H8 did not result in a decrease of the stability of the catalysts or an increase of coking. It was also found that the catalytic partial oxidation of C3H8 could be performed at gas hourly space velocities as high as 1200 dm3· h-1· g(catalyst)-1. The observed decrease in coke formation with increasing space velocity may be attributed to an increase in the local catalyst temperature resulting from the higher turnover frequency. All the findings of this work indicate that Ni catalysts derived from hydrotalcite-type precursors are promising catalyst for the par...
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