W promoted Ni-Al2O3 co-precipitated catalysts for green diesel production

Abstract

The promoting action of W in the Ni-Al2O3 co-precipitated catalysts with high nickel loading (31–46 wt% Ni) has been investigated in the selective deoxygenation of sunflower oil and waste cooking oil towards green diesel production. A WNi-Al2O3 catalyst containing 8 wt% W and 35 wt% Ni (NiNi+W=0.9 atomic ratio) proven the most efficient. The detailed characterization of the catalysts allowed an insight concerning the tungsten promoting action. It was attributed to the increase in the catalyst specific surface area and metallic nickel surface area, the acidity regulation, the decrease of the amount of catalytically inactive nickel aluminate formed and to the participation of W5+-oxo species via their defect oxygen sites in the selective deoxygenation network. The optimum reduction – activation temperature was found at 500 °C, where a good compromise between the increase of metallic Ni relative amount, the decrease of the specific surface area and the increase of Ni mean crystal size is achieved.