Formation of unsaturated carbonyl compounds catalysed

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Unformatted text preview: he low specific activity of the catalysts relatively high temperatures had to be applied and under such reaction conditions it was found that primary reaction products were not stable and reacted further to higher condensation products [116, 117, 119]. Therefore the reaction was also regarded as not suitable for the determination of the basicity of the catalysts. Neither TPD of CO2 nor the test reactions succeeded in an experimental description of the surface basicity of the catalysts that would be better than simply describing it by the Mg content in the catalysts. 3. Results and discussion - catalyst preparation and characterisation 108 4. Results and discussion - catalytic partial oxidation of propane 109 4. Results and discussion - catalytic partial oxidation of propane 4.1. Catalyst screening All synthesised catalysts were supposed to the standard catalytic tests that were performed for 240 minutes at 700 or 800°C at high space velocity (gas hourly space velocity (GHSV) 900· dm3· h-1· g(catalyst)-1). 25% O2 surplus compared to the stoichiometric reaction was used to suppress excessive coke formation. The same tests were performed employing a conventional steam reforming catalyst Ni/Al2O3 (20 wt% NiO, 2 wt% K2O). The obtained results allowed comparing the catalysts in terms of activity, selectivity, deactivation rate and coking. The results of the catalytic screening at 700°C are shown in Figure 32. The conversion of O2 was found to be almost complete over all catalysts. Although the C3H8 conversion was never complete, it was always high ( •   ,W ZDV IRXQG WR EH KLJKHVW RYHU WKH catalysts with a low to medium Ni/Mg ratio. Over all catalysts CO and H2 were always the main products with yields equal to or above 65 and 47% respectively. The trend in the yield of CO reflected the trend in the C3H8 conversion and was highest over Ni30C900 (85%). For each individual catalyst the yield of H2 was lower than the yield of CO, here the highest yield was achieved over Ni10C900 (68%). The yield of water exhibited the opposite trend to the yield of H2, with exception of Ni1...
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