Selective, bifunctional Cu-WOx/Al2O3 catalyst for hydrodeoxygenation of fatty acids
Selective hydrodeoxygenation of oleic acid (OA) forming n-octadecane in yield as high as 93% over a non-noble metal, sulfur-free, bimetallic Cu-WOx/Al2O3 catalyst, in a batch reactor, at 300 °C, 30 bar H2, reaction time of 1 h and reactant to catalyst weight ratio of 2 g OA/0.2 g is reported for the first time. Several Cu-WOx compositions were evaluated. A catalyst with 10 wt% Cu and 4 wt% W enabled the highest activity and selectivity. Upon WOx addition, the amount of moderate and strong acid sites increased and more Cu in the catalyst was in reduced electron-rich metallic (Cu0) state. However, crystallite size and dispersion of Cu were a little affected. WOx promoted the fatty acid hydrodeoxygenation activity of Cu. While a monometallic catalyst (10Cu/Al2O3) yielded both n-octadecane and n-heptadecane along with high amounts of intermediate products (octadecanol and octadecanal), the bimetallic catalyst (10Cu-4WOx/Al2O3) gave mainly n-octadecane. Acidity and high amount of reduced Cu0 species are responsible for the high catalytic hydrodeoxygenation performance of this bimetallic catalyst.