Preparation Of Nano Metallic Catalysts And Its Application In Dehydrogenation And Hydrogenation Reactions

The nano particles have gained more and more attention in recent years due to its special property, such as volume effect, surface effect and macroscopic quantum effect. Nano materials are more and more widely used in catalysis; moreover, dehydrogenation and hydrogenation reactions are important process in industry. The investigation of nano metal catalysts over dehydrogenation and hydrogenation reactions is important in both theoretic studies and industrial applications.Several methods (impregnation, co-precipitation and ultrasonic sol-gel) have been first comparatively examined for the preparation of the nano Cu-Cr-Fe/γ-Al2O3 catalysts. The continuous synthesis of 2-methylpiperazine was systematically studied over the above catalysts, and the results showed that the preparation method significantly affected their catalytic performance. A Cu-Cr-Fe/γ-Al2O3 catalyst prepared by the ultrasonic sol-gel method was proved to be the most active one and showed a good stability for this reaction. The catalysts are characterized by BET, XRD, XPS, TG/DSC, TPR, AAS and TEM. The existence of CuCr2O4 and Fe2O3 were believed to contribute to the dispersion and stabilization of Cu0 in the reduced catalyst. A surprising copper migration during the calcination process was detected by XPS analysis for the Cu-Cr-Fe/γ-Al2O3-USG catalyst, which was correlated with the high activity and stability of this catalyst.A series of nano nickel-based catalysts were prepared by the co-precipitation method and tested in the continuous synthesis of 1, 4-cyclohexanediol from hydroquinone. A Ni-Sr-Al catalyst was found to have the best activity among all the catalysts studied. The addition of Sr significantly increased the selectivity to 1, 4-cyclohexanediol. The conversion of the raw material reached 98.3% and the selectivity to 1, 4-cyclohexanediol was about 93.0% under the optimal reaction conditions. The more dispersed nickel species on the surface of the support and the decrease of the acidity were ascribed to the addition of Sr based on XRD,TPR and SEM characterizations, which in turn improved the selectivity to 1, 4-cyclohexanediol.