Preparation Of Noble Metal-based Catalysts By Reverse Microemulsion And Study On Its Hydrogenation Activity

Recently, the principle of microemulsion with nano particles prepared is a hotspot ofstudy in preparing solid catalysts. It has many characteristics,such as simple device, easyoperation. And the controlled growth and shape of nanometer particles can be achieved bychanging the composition of microemulsion.By combination of conductivity with the visual, the microemulsion system ofCTAB/n-butarol/cyclohexane/H2PtCl6was determined.A series of Pt/TiO₂catalysts wereprepared with the different composition ratio of microemulsion and adding metal additives.Using o-,m-,p-chloronitrobenzene selective hydrogenation as a probe reaction. Effect ofthe composition of microemulsion, type of carriers, and mixing different metal additives onthe activity for selective hydrogenation over Pt-based catalysts were studied.And it also wascompared with impregnation methods.The results showed:（1） In the microemulsion system ofCTAB/n-butarol/cyclohexane/H2PtCl6, when mCTAB:mbutarol=3:7,（mCTAB+mbutarol）:mcyclohexane=3:7,H2PtCl6solution of3.6wt%, whose preparation temperature is30℃and using anataseas carriers,Pt/TiO₂catalyst exhibited the highest activity.（2） Pt/TiO₂catalyst made frommicroemulsion shows higher activity. The yield of o, m, p-chloronitrobenzene were95.8%、97.1%、77.7%. The corresponding to TOF valuaes were20.7×10^-2s^-1、21.1×10^-2s^-1、16.8×10^-2s^-1.While Pt/TiO₂is prepared by the impregnation method, the yield of the o, m,p-chloronitrobenzene were13.3%、25.2%、17.0%.The corresponding to TOF valuaes were1.9×10^-2s^-1、3.6×10^-2s^-1、2.5×10^-2s^-1.And metal alkoxides method is worse.（3） The selectivehydrogenation of p-CNB was significantly enhanced by adding Sn2+.better onversion rate andselectivity of corresponding chloroaniline. When with a Pt:Sn molar ratio of3:1,the result wasbest.The yield of p-CNB is92.3%and TOF is20.0×10^-2s^-1.