Carbon Dioxide as Hydrogen Acceptor in Dehydrogenation of Alkanes

Reactions [formula omitted] and C + CO₂ ⇋ 2CO (2) were applicable in generating a product mixture containing olefins and CO from a paraffin-CO₂ feed, by use of conventional dehydrogenation catalysts. Conversion to olefins was limited because Reaction 1 was endothermic and equilibrium-controlled. Under favorable conditions for Reaction 1, Reaction 2 was too slow in the presence of the hydrocarbons to prevent coking and catalyst deactivation. However, alternate feeding of paraffin and CO₂ allowed Reaction 2 to proceed to the right at a reasonable rate and retard catalyst deactivation. Zoned feed of paraffin and CO2 in a fluidized-bed reactor also helped Reaction 2 to proceed at a reasonable rate. Continuous addition of air to the paraffin feed gave low conversion and selectivity, but air fed alternately with hydrocarbon or zoned air in a fluidized bed gave satisfactory results.