Continuous catalytic deoxygenation of model and algal lipids to fuel-like hydrocarbons over Ni-Al layered double hydroxide

The deoxygenation of lipid-based feeds to diesel-like hydrocarbons was investigated over a series of oxide-supported Ni catalysts. Catalyst screening in a semi-batch reactor revealed that a Ni-Al layered double hydroxide formulation afforded a higher yield of hydrocarbons in the diesel range than 20 wt% Ni/Al₂O₃, 20 wt% Ni/ZrO₂, 20 wt% and Ni/La-CeO₂ (lanthanum-stabilized ceria). Through a series of fixed bed reactor experiments involving model lipids in which reaction conditions - including temperature, hydrogen partial pressure and feed to catalyst ratio - were systematically changed, the effects of these variables on catalyst performance were elucidated. Based on the results of these experiments the optimum set of conditions was identified and applied to the conversion of realistic feeds, including the oil extracted from algae cultured using flue gas from a coal-fired power plant. Catalyst stability studies showed Ni-Al layered double hydroxide to be a stable formulation, no significant loss of activity being observed between 6 and 72 h on stream under conditions known to promote catalyst deactivation, namely the use of an unsaturated feed - comprising both a triglyceride and a considerable amount of free fatty acids - in high concentration.