Xiaoyan Liu,Guojun Lan,Panpan Su,Lihua Qian,Tomas Ramirez Reina,Liang Wang,Ying Li,Jian Liu
The hydrogenation of levulinic acid to γ-valerolactone with water as solvent is a crucial reaction for producing fine chemicals. However, the development of highly stable catalysts is still a major challenge. Here, we prepared a Ru nanoparticles incorporated in mesoporous-carbon (Ru-MC) catalyst to achieve high stability in acidic aqueous medium. The Ru-MC showed excellent catalytic performance (12024 h −1 turnover frequency) in the hydrogenation of LA-to-GVL. Compared with Ru supported on mesoporous carbon catalyst (Ru/MC) prepared by conventional wet impregnation method, the Ru-MC showed excellent reusability (more than 6 times) and thermal stability (up to 600 °C). Based on H 2 -TPR-MS characterization, it was proposed that the incorporated structure significantly increased the interaction between Ru nanoparticles and carbon support, which effectively prevent the leaching and sintering of Ru nanoparticles and contributed to increased high reusability and thermal stability of the Ru-MC.
A highly efficient and stable Au–Cu/hydroxyapatite (HAP, Ca10(PO4)6(OH)2) catalyst was reported. HAP was prepared through a deposition–precipitation method. Au–Cu/HAP catalysts were obtained by a two-step impregnation approach. The samples were characterized by XRD, TEM, SEM, UV-Vis, ICP, XPS, H2-TPR, and O2-TPD. CO oxidation reaction was carried out to evaluate the catalytic performance of samples. TEM and UV-Vis results showed that the metallic particles supported on Au–Cu/HAP were smaller than those on Au/HAP, and they were highly dispersed on the HAP support. Patterns of XPS revealed that CuO nanoparticles were formed in the Cu/HAP catalyst, while CuO and Cu2O species coexisted in Au–Cu/HAP catalyst. Based on the O2-TPD data, the addition of copper to Au/HAP gave rise to more new O2 adsorption sites and bigger O2 adsorption capacity. The catalysis results indicated that the Au–Cu/HAP was capable of obtaining higher efficiency and stability compared with Au/HAP and Cu/HAP for CO oxidation. It was likely that the synergistic interaction between gold and CuOx phase created the most active sites on Au–Cu/HAP and was responsible for the enhanced activity and stability in comparison with Au/HAP and Cu/HAP.
Yuanyuan Zheng,Xiaoming Zhang,Yi Yao,Xiaohong Chen,Qihua Yang
Ultra-small Au nanoparticles (<2 nm) supported on hollow silica nanospheres were successfully fabricated with the aid of chemical modification (–SH groups) or through simple immersion method, leading to supported catalysts Au/SH-HNS and Au/HNS. The resulting solid catalysts showed good thermal stability and the small particle sizes could be remained even at high temperature of 350 °C. Such catalysts were catalytically active in the oxidation of styrene using O2 as oxidant under 1 atm pressure. The catalytic results showed that the activity strongly depends on the Au loading amount, and the loading of 4–5 wt% led to the highest activity. Significant rate enhancement was observed with gold nanoparticles supported on pure silica in comparison with thiol modified silica nanospheres, suggesting the negative effects of thiol groups. The solid catalyst could be reused at least 8 reaction cycles without significant decrease in activity and selectivity. This study not only supplies an active, recoverable catalyst for the green transformation of styrene, but also demonstrates that the hollow silica nanosphere material has a superior ability in stabilizing metal nanoparticles against growth.
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