OXIDATIVE DEHYDROGENATION OF ETHANE TO ETHENE OVER BAO-MODIFIED AND BABR2-MODIFIED HO2O3 CATALYSTS

The addition of BaBr2 (<70 mol%) to Ho2O3 could improve considerably b oth the C2H6 conversion and C2H4 selectivity of the ODE (oxidative deh ydrogenation of ethane) reaction. The use of BaO as a modifier was not suitable because the catalyst degraded rapidly due to BaCO3 formation . At 640 degrees C, C2H6:O-2:N-2 = 2:1:4, and space velocity = 6000 mL h(-1) g(-1), C2H6 conversion of 70.6%, C2H4 selectivity of 80.2%, and C2H4 yield of 56.6% were observed over the 50 mol% BaBr2/Ho2O3 cataly st after a reaction time of 1 h. We conclude that the addition of BaBr 2 to Ho2O3 can (i) enhance oxygen activation, (ii) protect a certain a mount of active basic sites from CO2 poisoning, and (iii) suppress C2H 4 deep oxidation. It is possible that the presence of Br- ions could h ave induced the formation of new active sites suitable for C2H4 genera tion. However, we observed continuous leaching of bromine during the O DE reaction, and the 50 mol% BaBr2/Ho2O3 catalyst gradually degenerate d to a somewhat aged BaO/Ho2O3 catalyst. After 40 h of reaction, the C 2H6 conversion, C2H4 selectivity, and C2H4 yield diminished to 51.8, 6 3.8, and 33.0%, respectively. (C) 1998 Academic Press.