| Cyclohexene,with active C=C andα-H,is found to be an important intermediate in organic synthesis and has been widely used in production of pharmaceutical,pesticide and feed additive.Selective hydrogenation of benzene is an important way to synthesize cyclohexene,which is catalyzed by unsupported Ru-based catalyst.However,due to the high loading and cost of noble metal Ru,it is of the urgent need to develop a catalyst with low Ru loading and highly catalytic performance.In this thesis,Ru/TiO2 catalyst was prepared by impregnation–chemical reduction method.The catalyst was characterized by X-ray powder diffraction,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,Transmission electron microscopy and H2-programmed desorption techniques,etc.The structure-property relationship is discussed.The details are as follows:（1）Ru precursor is supposed to have great impact on Ru particle size and ability in hydrogen adsorption.Herein,P25 type TiO2 was chosen as support,and Ruthenium chloride,Ruthenium acetate and Ruthenium nitrate were selected as Ru precursors.Ru B/P25-Cl,Ru B/P25-OA and Ru B/P25-NO3 catalysts were prepared and their catalytic performances in selective hydrogenation of benzene to cyclohexene were tested.The results show that the Ru B/P25-OA catalyst shows the highest ability in hydrogen adsorption;Ru B/P25-Cl possesses moderate sizes of Ru particles and the highest yield of cyclohexene.Ruthenium chloride is found to be best precursor.（2）TiO2 is rich in surface hydroxyl groups and hydrogen spillover between TiO2 and metal is facile to happen.In this chapter,Ru/TiO2 catalysts were prepared by supporting Ru on commercial anatase,rutile TiO2 without pretreatment or after thermal treatment.It is found that the support and catalyst hydrophilicity is positively correlated with their specific surface area.Ru/Anatase catalyst shows strong hydrogen spillover effect,while no spillover hydrogen is detected in Ru/Rutile.Hydrogen spillover from anatase TiO2 support can be served as secondary active sites in hydrogenation of benzene.So the Ru/Anatase shows higher catalytic activity and larger TOF compared with Ru/Anatase-750 and Ru/Rutile.TiO2 with large specific surface area,high hydrophilicity and more spillover hydrogen,which is favor for preparing Ru/TiO2 catalyst showing high selective hydrogenation activity and cyclohexene selectivity.（3）Anatase TiO2 supports with distinguished specific surface areas were obtained by calcining commercial one at different temperatures,and the thus prepared Ru/Anatase-T（T=600°C,650°C,680°C and 700°C）catalyst were carefully investigated.The specific surface area of the Ru/Anatase-T catalyst decreases,while its crystal size increased,with increasing the calcination temperature of the TiO2 support.The one calcined at 680°C shows a moderate specific surface area,and the supported Ru is electron deficient,which is favor for cyclohexene desorption and improving the catalytic selectivity. |
