Carbon-coated Ni/Al2O3 as high-efficiency catalysts for the hydrogenation of furfural to furfuryl alcohol

Abstract

In this study, the catalytic hydrogenation process of furfural to furfuryl alcohol was evaluated over newly designed (Ni/Al₂O₃)@C catalysts. Using Ni₂Al-layered double hydroxide (Ni₂Al-LDH) as the precursor, NiO/Al₂O₃ was obtained via high-temperature calcination. Glucose was used as the carbon source. The (Ni/Al₂O₃)@C catalysts were fabricated through a hydrothermal treatment and calcination under a N₂ atmosphere using different glucose-to-NiO/Al₂O₃ mass ratios. Several characterizations, including XRD, TGA, SEM, BET, TEM, HRTEM and XPS, were employed to characterize the microstructural features and chemical constituents of the prepared catalysts. It was found that the Ni nanoparticle size of Ni/Al₂O₃ was 7.2 nm, whereas that of carbon-coated Ni/Al₂O₃ catalysts was smaller. It was indicated that modification with carbon coating could effectively enhance the dispersibility of Ni active components and inhibit their oxidization. In addition, the performance of the carbon-coated Ni/Al₂O₃ catalysts was affected by the reaction solvent, carbon content and calcination temperature. Under the optimal conditions, the furfural conversion and furfuryl alcohol selectivity reached 96.4% and 89.4%, respectively, over the (Ni/Al₂O₃)@C-2-500 catalyst. The (Ni/Al₂O₃)@C-2-500 catalyst proved to be reusable during multiple recycling runs. The high catalytic performance of (Ni/Al₂O₃)@C-2-500 could be due to the smaller Ni nanoparticles, larger specific surface area, greater surface oxygen vacancies and enriched Ni⁰.