Controllable preparation of highly dispersed Ni/γ-Al2O3 catalyst for lipids hydrodeoxygenation to biofuel

Abstract

Lipids, which derived from waste cooking oil and produced in large quantities, have a naturally intact long carbon chain structure and can be hydrodeoxygenated to prepare second-generation biodiesel. In order to further improve the hydrodeoxygenation (HDO) performances of the Ni-based catalysts, citric acid additive is used to form chelates with Ni^2 + , thereby weakening the strong interaction between metal Ni and the Al₂O₃ support, forming small Ni nanoparticles and improving the dispersion of metal Ni. Characterization and DFT calculations indicate that the interfacial structure formed by Ni and Al₂O₃ is critical for lipid HDO, and that metallic Ni enables lipid activation and hydrogenation of key intermediates through efficient H₂ dissociation. The effects of metal Ni dispersion, metal-support interactions, and metal Ni content on the lipids HDO performances of the Ni/γ-Al₂O₃ catalysts are investigated in detail. The lipids HDO performances are greatly improved by balancing the metal Ni content and dispersion. The 2CA-6wt% NiAl catalyst has the highest methyl laurate conversion (82.87 %) and alkane selectivity (77.0 %), including the main C₁₁ alkane product with a selectivity of 60.02 %. This work provides a new design method for developing highly efficient lipids HDO catalysts by controlling dispersion.