Regeneration of Alumina-supported Nickel Oxide Catalyst Covered with Large Amounts of Carbon Deposits during the Dehydrogenations of Ethane, Propane, and Isobutane

Improvement in the dehydrogenations of ethane, propane, and isobutane over alumina-supported nickel oxides occurs together with the formation of large amounts of carbon deposits with time-on-stream, but catalyst activity is decreased with an additional increase in time-on-stream. This improvement in activity is due to metallic nickel formation that is highly dispersed over carbon nanotube-like deposits. However, the activity decreases as this highly dispersed metallic nickel is further covered with carbon deposits. We describe the use of oxygen treatment to regenerate the catalyst. Oxygen treatment to remove carbon deposits generally results in a less active catalyst due to sintering of the active species. However, we speculated that sintered nickel oxide could form carbon nanotubes in the proposed system, and that the formation of highly dispersed nickel over the nanotubes would regenerate the catalyst. To prove this hypothesis, dehydrogenations of ethane, propane, and isobutane were investigated using 18, 15, and 20 % nickel oxide supported on y-alumina, respectively. We confirmed regeneration of the catalytic activity via oxygen treatment during subsequent dehydrogenations.