水相加氢脱氧 (HDO) 是将生物质及其衍生物转化为高附加值化学品和可再生燃料的绿色高效方法。然而,合成具有优异加氢脱氧性能的催化剂仍然是一个巨大的挑战。制备了三种不同晶体结构的Ni/Nb2O5催化剂(Ni/TT-Nb2O5、Ni/T-Nb2O5、Ni/H-Nb2O5)用于香兰素加氢脱氧。与 Ni/TT-Nb2O5 和 Ni/H-Nb2O5 催化剂相比,Ni/T-Nb2O5 催化剂具有最高浓度的氧空位 (Ov),从而获得了优异的加氢脱氧性能。在 180 °C、1 MPa H2 和水/乙醇比例为 8/12 时,香兰素转化率为 96.1%,2-甲氧基-4-甲基苯酚 (MMP) 选择性为 79.2%。丰富的 Ni/T-Nb2O5 Ov 吸附并激活了香草醇 (VA) 的 C-OH 键,而水与 VA 形成更强的过渡态,进一步降低了 C-OH 键的解离能。Ov 与水的协同作用促进了香兰素在水相中的加氢脱氧,实现了 MMP 的高产率。这项工作为制备水相中具有高催化性能的催化剂提供了新思路。
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Insights into the catalytic performance of Ni/Nb2O5 catalysts for vanillin hydrodeoxygenation in aqueous phase: The role of Nb2O5 crystal structures
Hydrodeoxygenation (HDO) in aqueous phase is green and efficient approaches to convert the biomass and its derivative to high value-added chemicals and renewable fuels. However, it remains a great challenge for synthesizing catalysts with the excellent hydrodeoxygenation performance. Three kinds of Ni/Nb2O5 catalyst with different crystal structures (Ni/TT-Nb2O5, Ni/T-Nb2O5, Ni/H-Nb2O5) were prepared for vanillin hydrodeoxygenation. Compared with the Ni/TT-Nb2O5 and Ni/H-Nb2O5 catalyst, the Ni/T-Nb2O5 catalyst had the most concentration of oxygen vacancies (Ov), which resulted in the excellent hydrodeoxygenation performance. At 180 ℃, 1 MPa H2, and the water/ethanol ratio of 8/12, 96.1% conversion of vanillin and 79.2% selectivity of 2-methoxy-4-methylphenol (MMP) were obtained. The abundant Ov of Ni/T-Nb2O5 adsorbed and activated the C-OH bonds of vanillyl alcohol (VA), while water formed a stronger transition state with VA to further reduce the disassociation energy of C-OH bonds. The synergistic effect between Ov and water promoted the hydrodeoxygenation of vanillin in aqueous phase, achieving the high yield of MMP. This work provides a new idea for the preparation of catalysts with high catalytic performance in aqueous phase.