The effect of addition of a third component on the behaviour of the lithium doped magnesium catalysts for the oxidative dehydrogenation of ethane

摘要

The oxidative dehydrogenation of ethane was studied with the use of promoted Li/MgO catalysts at temperatures of 600¿650°C. The addition of known promoters, cobalt and tin, gave a slight Increase In activity but a strong decrease in selectivity to ethylene under the conditions used. The addition of sodium improved the selectivity to ethylene and suppressed the formation of carbon monoxide. Using a feed of 12 vol% ethane and 6 vol% oxygen, the U/Na/MgO catalyst with 3.2wt% sodium showed a selectivity of 86 % to ethylene at 38 % conversion of ethane; the Li/MgO catalyst showed a selectivity of 80 % at similar conversions Thermal Investigations of the Li/Na/MgO catalyst showed that an eutectic melt of LINaCO3 is formed at 490°C; the existence of this molten phase is probably the cause of the Increased selectivity.