Rate enhancement by Cu in Ni_xCu_1-x/ZrO₂ bimetallic catalysts for hydrodeoxygenation of stearic acid

Hydrodeoxygenation of stearic acid on Ni/ZrO₂ to n-heptadecane occurs via the reduction to 1-octadecanal, followed by decarbonylation of the aldehyde to n-heptadecane. Stearic acid binds stronger than 1-octadecanal on Ni, causing decarbonylation to start only once stearic acid is almost fully converted. This first step is enhanced by addition of Cu either in the form of Cu/ZrO₂ or in the form of a ZrO₂ supported Ni_xCu_1-x nano-alloy. Cu has not only a higher activity for the reduction of stearic acid, it also increases the activity of Ni for decarbonylation of 1-octadecanal by increasing the electron density of Ni in the bimetal catalyst. The combination of these two effects leads to high activity of Ni-Cu bimetallic catalysts.