Abstract
The hydrodeoxygenation of amide to amine is one of the most important amine synthetic approaches in chemical engineering. However, low amide reactivity and poor amine selectivity remain big challenges for catalytic hydrodeoxygenation of amides. Here, Ru-VOx/TiO2 catalysts with different V/Ru atomic ratios were prepared with the sequential impregnation method. The physicochemical properties of catalysts were characterized by using XRD, Raman, TEM, CO chemisorption, NH3-TPD, H2-TPR, XPS, and Formamide-DRIFTS. The hydrogenation of butyramide as a model reaction was used to evaluate the catalytic performance. The butyramide conversion and butylamine selectivity varied with V/Ru atomic ratio in a volcano-type relationship, and the 2V-4Ru/TiO2 catalyst (V/Ru atomic ratio = 1) presented the best catalytic performance (96% conversion and 82% butylamine selectivity) at 423 K with 5 MPa H2. The catalyst was also reused five successive times without an obvious decline in either activity or selectivity, showing excellent stability. Based on characterization and evaluation results, the interaction between Ru nanoparticles (∼2 nm) and VOx species promoter generated abundant Ru-VOx boundary with V4+ species adjacent to oxygen vacancies (Ru-Vo-V4+). As the V/Ru atomic ratio was 1, the 2V-4Ru/TiO2 catalyst, with monolayer dispersed VOx species, presented the maximum Ru-VOx boundary and showed the best catalytic activity and selectivity to amine. The monolayer dispersed VOx species also minimized the catalyst surface acidity and suppressed the secondary side reaction. Moreover, the hydrodeoxygenation reaction evaluations of various amides including aliphatic primary amides and cyclic amides showed 90-99% conversion and 78-99% selectivity to corresponding amines, suggesting wide applicability of 2V-4Ru/TiO2 catalyst. The study provides a highly efficient strategy to improve amine selectivity in the hydrodeoxygenation of amides by optimizing the interaction between metal and metal oxide promoters.
Published Version
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