γ-Valerolactone (GVL) is a promising bio-based platform molecule with significant potential for energy applications. The production of GVL via biomass-based levulinic acid (LA) is an important reaction. To enhance the conversion and selectivity of non-precious-metal catalysts in the LA-to-GVL process and to better understand the key factors influencing this conversion, we conducted a series of experiments. In this study, supported Cu-Ni bimetallic catalysts (Cu-Ni2/Al2O3) were prepared using layered double hydroxides (LDHs) as a precursor. Compared with Cu-Ni catalysts synthesized via the conventional impregnation method, the Cu-Ni2/Al2O3catalysts exhibit higher catalytic activity and stability. The results demonstrated that efficient conversion was achieved with isopropanol as the hydrogen donor solvent, a reaction temperature of 180 °C, and a reaction time of 1 h. The yield of GVL reached nearly 90%, with a decrease of approximately only 6% after six consecutive cycles. The Cu-Ni2/Al2O3catalyst proved to be effective for converting biomass-derived LA to GVL, offering a route that not only reduces production costs and environmental impact but also enables efficient biomass-to-energy conversion.
The hydrogenation of nitriles is an environmentally friendly and atom-economical route to prepare high-value amines; however, it is still a challenge to control selectivity because of the occurrence of hydrogenation, self-coupling, and hydrogenolysis reactions during the hydrogenation process. It is highly desirable to develop efficient non-noble-metal catalysts for the hydrogenation of nitriles to secondary amines, although several noble metal catalysts have been reported. Herein, we successfully prepared a Cu–Ni/W20O58 catalyst and found that the Cu4.4–Ni0.6/W20O58 catalyst showed a 92.3% yield with initial TOFs of 270.0 h–1 at 373 K and 3 MPa H2 for the hydrogenation of benzonitrile (BN) to dibenzylamine (DBA), which was much superior to that of the monometallic Cu4.4/W20O58 and Ni0.6/W20O58 catalysts. Moreover, the Cu4.4–Ni0.6/W20O58 catalyst could be reused at least 4 times and was effective for the hydrogenation of various nitriles with superior selectivity to secondary amines. Furthermore, the reaction mechanism of BN hydrogenation for the Cu–Ni alloy of Cu4.4–Ni0.6/W20O58 was proposed on the basis of spectroscopic studies such as XRD, TPR, TEM, XAFS, and XPS, kinetic studies such as the effect of BN concentration and H2 pressure, the isotopic effect of hydrogen, and the effect of the reaction temperature and DFT calculations. The rate-determining step was the hydrogenation of benzylidenamine (BI) to the half-hydrogenated intermediate by one H atom over the Cu4.4–Ni0.6/W20O58 catalyst. The Ni–W20O58 interface was responsible for the adsorption and activation of BN, and the electron-rich Cu acted as the site for H2 dissociation; the synergistic effect of Cu and Ni led to the superior catalytic performance of the Cu4.4–Ni0.6/W20O58 catalyst.
The synthesis of unsaturated tertiary amine by the amination of oleyl alcohol and dimethylamine under atmospheric pressure over Cu–Ni catalysts supported on CaCO 3 was studied. The yield of tertiary amine and the retention rate of the unsaturated bond can reach 95.4 and 93.3 %, respectively. The yields of tertiary amine over different Cu/Ni ratios catalysts were close to each other, which meant that Cu/Ni ratios had no obvious influence on the production of tertiary amine, while the retention rate of the unsaturated bond over the catalyst containing only Cu was higher than the catalysts containing Cu–Ni. The major effect of the Cu element was dehydrogenation, and the ability of the hydrogenation was weak. The ability of the Ni element to break the carbon–carbon bonds and hydrogenation was strong. Therefore, the performance of the Cu catalyst was better than the conventional Cu–Ni-based catalyst for the retention of the unsaturated bond in long-chain R of the tertiary amine.
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