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In the absence of the catalysts the yield of co2 was

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Unformatted text preview: ved. This points out that in all cases the total combustion is promoted by the catalysts, Ni containing or not, reduced or not reduced. Therefore some limited total combustion activity can be attributed to the metal oxide matrix. 4.3. Influence of the O2/C3H8 ratio The influence of the O2/C3H8 ratio was investigated at 800°C in the range from 0.75 –1.50, were 1.00 corresponds to the stoichiometric value and 1.25 to the generally applied feed composition (25% O2 surplus). The GHSV was kept at the same value as in the other catalytic tests by adjusting the He flow (900 dm3· h-1· g(catalyst)-1). The exact composition of the feed mixture for the different O2/C3H8 ratios is stated in Table 12. 4. Results and discussion - catalytic partial oxidation of propane 125 Tab. 12: Feed composition at different O2/C3H8 ratios O2/C3H8 ratio (1.00 = Feed composition [%] stoichiometric ratio) O2 C3H8 He 0.75 18.30 16.07 65.63 1.00 24.40 16.07 59.53 1.25 30.50 16.07 53.43 1.50 36.60 16.07 47.33 Over the whole range the O2 conversion was complete, the C3H8 conversion increased with increasing O2/C3H8 ratios to 95% at ratio 1.25 and was complete at O2/C3H8 ratio 1.50 (Fig. 39). The yields of CO followed the same trend as the C3H8 conversion. As in the catalytic screening the yield of H2 was always lower than the yield of CO. It increased steadily from O2/C3H8 ratio 0.75 to 1.25 but decreased at 1.50. The yield of H2O increased steadily with increasing O2/C3H8 ratio from 1% to 37%. The yield of CO2 was low up to O2/C3H8 ratio 1.25, but increased at 1.50. CH4 was always the main hydrocarbon product, its yield decreased to 1% at O2/C3H8 ratio 1.50. Other hydrocarbon products, C2H4 (Y ≤ 1%) and C3H6 (Y ≤ 2%), as well as C2H6 (Y < 1%) were observed only up to the stoichiometric O2 content in the feed. Their yield was higher at O2/C3H8 ratio 0.75 than at 1.00. Under all O2/C3H8 ratios the catalyst exhibited very good stability (Fig. 40). The apparent activation at O2/C3H8 ratio 0.75 and 1.00 results again from the fact that under the...
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