| dc.description.abstract | The spherical catalyst was mostly used in industries. In order to use active metal adequately, the metal was supported on the spherical carrier to form the egg-shell catalyst. In this study, egg-shell and powdered catalyst which Cu-Pd bimetals were supported on spherical SiO2 were introduced to carry out the application of p-CNB hydrogenation reaction. All the egg-shell catalysts were characterized by OM, TEM, HRTEM, and XPS. As for the activity test of liquid phase p-CNB hydrogenation reaction, the reaction condition were 298 K of reaction temperature, 0.55 MPa H2 partial pressure, and stirring rate under 300 rpm in a batch reactor.
From the results, thinner metal layer, smaller particle size, better dispersion of metals, and the larger amount of active metals were found in fresh egg-shell catalysts compare with the used ones. The thick metal layer of used egg-shell catalysts was due to the migration of Cu into the inner core. Besides, larger particle size, the agglomeration, and smaller amount of active metals were also observed in used egg-shell catalysts. In the reaction test, both activity and p-CAN selectivity of powdered catalysts were poor in comparison with egg-shell catalysts. Adding small amount of metals could not only achieve good selectivity, but the result of low reaction rate also improved the fast reaction of using powdered catalyst which might lead to the inadequate use of metals. Moreover, the addition of very small amount of Au could enhance the catalysis of Cu-Pd/SiO2 egg-shell catalyst. Therefore, Cu-Pd/SiO2 egg-shell catalyst showed better selectivity of this reaction. Most important of all, catalyst with egg-shell structure was successfully made by ourselves which had almost the same catalytic result. | en_US |