Abstract
The addition of BaBr2(<70 mol%) to Ho2O3could improve considerably both the C2H6conversion and C2H4selectivity of the ODE (oxidative dehydrogenation of ethane) reaction. The use of BaO as a modifier was not suitable because the catalyst degraded rapidly due to BaCO3formation. At 640°C, C2H6:O2:N2=2 : 1 : 4, and space velocity=6000 mL h−1g−1, C2H6conversion of 70.6%, C2H4selectivity of 80.2%, and C2H4yield of 56.6% were observed over the 50 mol% BaBr2/Ho2O3catalyst after a reaction time of 1 h. We conclude that the addition of BaBr2to Ho2O3can (i) enhance oxygen activation, (ii) protect a certain amount of active basic sites from CO2poisoning, and (iii) suppress C2H4deep oxidation. It is possible that the presence of Br−ions could have induced the formation of new active sites suitable for C2H4generation. However, we observed continuous leaching of bromine during the ODE reaction, and the 50 mol% BaBr2/Ho2O3catalyst gradually degenerated to a somewhat aged BaO/Ho2O3catalyst. After 40 h of reaction, the C2H6conversion, C2H4selectivity, and C2H4yield diminished to 51.8, 63.8, and 33.0%, respectively.
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