In the blank experiments c3h8 and o2 are only

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Unformatted text preview: as 565°C the C3H8 conversion is still above 60%. With exception of the reduced Ni catalyst considerable amounts of CH4 and unsaturated hydrocarbons, especially C2H4, were observed. This indicates the occurrence of cracking, according to Equation 9 [22]. C3H8 → CH4 + C2H4 (Eq. 9) This point is not undermined by the fact that at high temperatures the yield of CH4 is too high for pure cracking. CH4 is more stable and therefore less likely to react further. CH4 can also be produced by the hydrogenation of reactive carbon deposits [127]. The considerable amounts of C3H6 may be attributed to either oxidative or thermal dehydrogenation of C3H8 (Eq. 10 and 11) [22]. C3H8 + 0.5 O2 → C3H6 + H2O (Eq. 10) C3H8 → C3H6 + H2 (Eq. 11) The absence of considerable yields of alkyne products may result from their greater reactivity compared to alkenes, e.g. towards coking. The low yield of CH4 (≤ 3%) and the absence of unsaturated hydrocarbon over the reduced catalyst do not necessarily 4. Results and discussion - catalytic partial oxidation of propane 124 ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp exclude the possibility of considerable dehydrogenation or cracking. As unsaturated hydrocarbons are more reactive than C3H8, which is converted to more than 60% even at 565°C over the reduced Ni catalyst, they are expected to react completely over the active catalyst. Furthermore the reduced Ni containing catalysts are active in the partial oxidation of CH4. H2O and CO2 were next to CO the only detected oxygen containing products in all experiments. H2O was the main oxygen side product in all experiments, whereas CO2 was only a minor product. However, different trends were observed in the yields of H2O and CO2. In the absence of any of the catalysts the yield of H2O reflected the conversion, whereas over the different catalysts, H2O was still observed in considerable amounts even at low C3H8 conversions (Y •   7KH GLIIHUHQFHV DUH even more obvious for CO2. In the absence of the catalysts the yield of CO2 was always below 2% and decreased to zero at low conversion. In the presence of a catalyst, however, the yield was above 3% even at 600°C, where rather low conversions were achie...
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