Nb2O5 modified NiAl2O4 catalysts for hydrodeoxygenation of methyl palmitate to long-chain alkane.

The wide-scale application in the bio-fuel area of fatty acid methyl esters (FAME) has been limited because of its high oxygen content, awful low temperature flowability, and low heating value. In this work, the hydrodeoxygenation (HDO) of methyl palmitate as fatty acid methyl ester model compounds for long-chain alkane via Nb₂O₅ modified NiAl₂O₄ catalysts was investigated. The effect of Nb/Ni atomic ratio (0.05:0.30), reaction temperature (260–340 ℃), time (2–10 h), and H₂ pressure (1–5 MPa) on the production of long-chain alkane is exhaustively researched. The results show that the products are mainly pentadecane with a few other alkane hydrocarbons and nickel metal was the main active site. Besides, the added promoter Nb promoted the dispersion of active metal Nickel, increased the acidity, and thus substantially enhanced the HDO activity of methyl palmitate. In response to the best conditions (0.3 g catalyst, 3 g methyl palmitate), the methyl palmitate conversion and pentadecane selectivity over Nb₂O₅-NiAl₂O₄ with 0.20 Nb/Ni atomic ratio reached 91.14% and 80.07%, respectively. However, the methyl palmitate conversion and pentadecane selectivity over pure NiAl₂O₄ catalyst were only 62.53% and 74.67%, respectively. Therefore, Nb₂O₅-NiAl₂O₄ catalysts exhibit remarkable catalytic ability for HDO of methyl palmitate to alkanes. The low cost, easy preparation, high catalytic performance, and recycling stability of Nb₂O₅-NiAl₂O₄ catalyst demonstrate that catalyst Nb₂O₅-NiAl₂O₄ is a promising effective and efficient catalyst for producing long-chain alkane from methyl palmitate. [ABSTRACT FROM AUTHOR]