Preparation And Regulation Of Ru-based Catalysts For Phthalates Hydrogenation

Phthalates are widely used as plasticizer,however phthalate may migrate into the human body in the process of using,thereby endangering human health.As the product of phthalates hydrogenation,cyclohexanedicarboxylic acid ester is considered as an environmental friendly plasticizer,which could replace traditional phthalate-based plasticizer.Therefore,it is of great significance to develop efficient catalyst for hydrogenation of phthalates.In the present study,activated carbon with different structure properties were used to prepare a series of Ru/AC catalysts for the hydrogenation of dioctyl phthalate(DOP)to dioctyl 1,2-cyclohexanedicarboxylate(DOCH).It showed that DOP hydrogenation firstly produced di(2-ethylhexyl)tetrahydrophthalate(DOTP),and then DOTP was further hydrogenated to DOCH over the Ru-based catalyst.The characterization results indicated that the dispersion of Ru was significantly improved by increasing the microporous surface area.However,extra high microporous surface area will enhance the encapsulation of ultra-fine Ru nanoparticle in these micropores.As the molecular dynamics diameter of DOP(2.15 nm)is larger than the diameter of micropores(0.6nm),Ru nanoparticles encapsulated in micropores cannot fully contact with DOP molecules.Therefore,the apparent activity of the catalyst did not linearly increased with the the Ru dispersion.An appropriate micro-mesoporous structure of the support should be crucial important for the preparation of a highly efficient Ru catalyst.In conclution,the coupling effect between the surface reaction and pore diffusion in Ru/AC catalyst system was proposed.In addition,the as-prepared Ru/AC catalyst also exhibited excellent activity in the hydrogenation of various phthalates(DBP,DAP),and the yield can reach 100%,indicating that the catalyst has wide application prospect.To improve the hydrogenation performance of the catalyst,Ru Ni bimetallic catalyst was prepared by modifying Ru/AC catalyst with Ni additive.Ru can promote the reduction of Ni Ox species on the surface of Ni doped bimetallic catalysts.It have shown that Ni can greatly accelerate the hydrogenation rate of C=C bond on DOTP and improve the selectivity of DOCH.The synergistic effect between Ru and Ni significantly enhanced the activity and selectivity in the hydrogenation of DOP.Ru Ni bimetallic catalysts with different Ru Ni distributions were prepared by co-impregnation and stepwise impregnation.The impregnation sequence of Ru and then Ni led to the partial coverage of Ru nanoparticles by Ni species,resulting in lower catalytic activity.The post impregnation sequence of Ru exhibited hightest dispertion of Ru,giving the highest activity as well in the hydrogenation of DOP.These findings could provide a meaningful instruction for developing efficiently industrial catalyst for phthalates hydrogenation.