Study On The Modification Of Pd-based Catalyst For Anthraquinone Hydrogenation Reaction

Hydrogen peroxide is an environmentally friendly reagent.It has been widely used in many fields,such as environmental protection,papermaking,textile,chemical synthesis,disinfection,electronics,metallurgy,aerospace and etc.Anthraquinone route is the most important method in the production of hydrogen peroxide,in which the key step is the catalytic hydrogenation of anthraquinone.Development of catalysts with superior catalytic performance and low cost have great significance for increasing the hydrogen peroxide production and reducing the production cost.Hence,in the thesis,we made attempts to improve the effect of anthraquinone hydrogenation catalyst through incorporating a second metal as well as modifying the support.Bimetallic PdRu catalysts had been prepared by adding Ru to Pd/Al₂O₃,the superior performance of PdRu/Al₂O₃ is due to the synergistic effect between Pd and Ru.On one hand,addition of Ru to Pd/Al₂O₃ enhanced the adsorption and activation capacity of hydrogen.On the other hand,the Ru⁴⁺in the bimetallic PdRu/Al₂O₃catalysts can act as the electrophilic sites to interact with the lone electron pair of the oxygen atom to adsorb and activate the anthraquinone molecule through the“Electrophilic C=O Activation”effect.That's to say,the addition of Ru to Pd can enhance the adsorption and activation capacity of hydrogen and C=O of anthraquinone molecule in the same time,which attribute to the superior catalytic performance.MgAl Zr-layerd double hydrotalcites?LDHs?were synthesized in situ on Al₂O₃ to modify the support.Then,Pd was introduced to prepare the Pd/MgAlZr-MMO@Al₂O₃catalyst.It was found that the Pd/MgAlZr-MMO@Al₂O₃ showed higher activity and selectivity compared with Pd/Al₂O₃ in the anthraquinone hydrogenation reaction.For MgAl Zr-MMO@Al₂O₃,on one hand,the uniform layer plate of hydrotalcite structure interlaced with each other,which increased the surface area of the support.On the other hand,LDHs had confinement effect.These two factors could improve the dispersion of metal.What's more,Zr confined in the lattices of MgAl-LDHs layers could interact with Pd,which induced the higher dispersion of Pd.Therefore,Pd/MgAl Zr-MMO@Al₂O₃ shown higher activity.Furthermore,the external surface area of the support was enhanced because of the in situ growth of LDHs construction on the Al₂O₃,which shortened the Pd penetration depths and reduced the diffusion distance and residence time of anthraquinone molecule,thus consequently reduced the excessive hydrogenation and increased the selectively.