Do we really need Cu in Ni-Cu/aluminosilicate catalysts for hydrodeoxygenation?

Bio-oils obtained from rapid pyrolysis have emerged as a renewable energy source, but their high content of oxygenated molecules gives them unwanted properties for their use as fuels. Hydrodeoxygenation (HDO) is the process used to improve its quality and is commonly studied with model molecules such as guaiacol. Bimetallic NiCu catalysts are highly active in hydrogenation reactions. However, published studies do not allow us to conclude whether the addition of Cu to NiCu catalysts produces the same effect in HDO reactions. For this reason, in this work we study the influence of Cu in NiCu catalysts on the HDO of guaiacol. For the study, the acidity of the Al2O3 was modified by impregnating different amounts of SiO2. Results showed that regardless of the support used, monometallic Ni catalysts were the most active and that the addition of Cu promoted the formation of large Cu-rich alloy particles, which are less active, decreasing the apparent initial reaction rate. On the other hand, the modification of the support promoted the deoxygenation reactions, increasing the formation of cyclohexane, even in monometallic Cu catalysts. It was also established that Ni is responsible for directing the reaction route towards the hydrogenation pathway in the bimetallic catalysts, while the Cu monometallic catalysts followed the deoxygenation route.