Sodium-Induced Modulation of Hexadecanol Adsorption on Cu-Based Catalysts for Selective Hydrodeoxygenation of Palmitic Acid

Developing catalysts to achieve high selectivity in the production of specific products for the hydrodeoxygenation of fatty acids into high-value chemicals is crucial for industrial and sustainable chemistry. Herein, Cu catalysts supported on γ-alumina (Cu 8.0 Na x /γ-Al 2 O 3 ) were modified with Na + to tailor product distribution in the hydrodeoxygenation of palmitic acid. The unmodified Cu 8.0 /γ-Al 2 O 3 catalyst exhibited higher intrinsic activity ( r obs, 4.1 × 10 −4 mol·g −1 ·h −1 ) than the Na-modified counterparts ( 1.0−3.0 × 10 −4 mol·g −1 ·h −1 ). Notably, the primary hydrodeoxygenation product shifted from n -hexadecane (97.1%) on the Cu 8.0 /γ-Al 2 O 3 catalyst to hexadecanol (93.2%) on the Na-modified catalysts. This change was primarily attributed to differences in palmitic acid adsorption conformation and intermediate hexadecanol adsorption energy. FT-IR spectra revealed that palmitic acid adsorbed in a bidentate bridging mode on Cu 8.0 /γ-Al 2 O 3 but in a monodentate mode on Cu 8.0 Na x /γ-Al 2 O 3 . Density functional theory calculations further confirmed that the Cu 8.0 /γ-Al 2 O 3 catalyst strengthens the adsorption of acid and alcohol, promoting efficient hydrogenation and improving catalytic performance for the conversion of alcohol to n -alkane. In comparison, the Na-doped Cu 8.0 Na x /γ-Al 2 O 3 catalysts display reduced adsorption of acid and alcohol, resulting in a shift toward alcohol as the primary product. This strategic tuning of Cu-based catalysts provides a versatile approach to controlling product distribution in fatty-acid-selective hydrodeoxygenation.