Preparation Of Immobilized Noble Metal Pd Catalysts And Their Application Research

The ideal orgnic synthesis should produce the desired product in 100% yield and selectivity. Noble metal catalyst can maximize reaching mis aim, but the high price of the noble metal limited its apply. The search for recyclable catalysts with low teaching level of metals has been constantly recognized as one of the prime concerns from both academic and industrial perspectives.Immobilized noble metal catalysts can facilitate the catalyst separation from the reaction mixture, simplify catalysts recovery and recycling, and eventually be prospective to meet the tendency of green chemistry.The metal particle size of supported catalysts is an important factor affecting catalytic reactions. The catalytic behavior of small particles has become of interest. Microemulsion is a novel method of controlling the metal particle size, the catalysts prepared by microemulsion exhibited a much higher activity as compared to catalysts prepared from impregnation.In this thesis, we mainly discuss these kinds of work:Impregnation method was employed to prepare a series of supported 3% paladium catalysts,which were characterized by XRD, SEM and specific surface area analysis, and their catalytic behavior was investigated in the dehalogeno-dimerization of monosodium 4-chlorophthalate. And then the effects of preparation conditions of catalysts on the dehalogeno-dimerization of monosodium 4-CPA performance were studied. The results of experiment indicate that: the convertion of 4-CPA is nearly reaching 100% and the selectivity of BPTA is 87.6% on this kind of catalyst The reaction conditions described as follows: reaction temperature of 75℃, catalyst amount of 0.5 g and reaction time of 8h, glycerin was reducing agent. Microemulsion method was employed to prepare a series of immobilized Pd nanoparticle catalysts, Pd-SiO₂, which were characterized by XRD, SEM and specific surface area analysis, the average Pd particle size is rather small and the size distribution is considerably narrow. And the Pd particles exist nearly in spherical shape and have a uniform distribution in the matrix of SiO₂. Then the effects of some preparation conditions such as preparation temperature, Pd content , amount of NH₃. H₂O aqueous solution, different surfactants and water/surfactant molar ratio ω were investigated, then "tween-80/l-hexanol/PdCl₂" aqueous solution was found to be a suitable preparation system. Their catalytic behavior was investigated in the dehalogeno-dimerization of monosodium 4-chlorophthalate. The optimal loading of Pd was 3wt%, and the weight ratio of the catalyst to 4-CPA was l:60(weight). The optimal reaction conditions were as follows: reaction temperature of 75°C, reactiontime of 8h,glycerin is reducing agent. Under the above-mentioned conditions, the selectivity of BPTA is 92.7%, which is higher than that over the catalyst prepared by impregnation method.The catalyst showed a partial deactivation after reaction. The characterisation results showed that the reason for deactivation might attribute to the active centers on the surface of the catalyst being partially encapsulated by organic substances in the course of reaction. However the activity of the catalyst which had been regenerated did not drop after employed for five runs.