Study On Selective Hydrogenation Of Chloronitrobenzene To Chloroaniline On Supported Ni Catalyst

Chloroanilines,being regarded as one of the most important kind of organic intermediates,have been wildly applied in the synthesis of dyes,herbicides,flame retardants,plasticizers,organic fine chemicals and other chemical industries.In the synthesis of chloroanilines,the catalytic hydrogenation of chloronitrobenzenes in liquid phase is regarded as one of the most promising rote in term of its atomic economy and environmentally benign concern.Therefore,it is practically significant to develop a new catalyst with high catalytic property and less pollution to environment for chloronitrobenzenes hydrogenation.The supported nickel catalyst is considered to be one of the most indutrial development prospects of liquid phase hydrogenation catalyst due to lower cost,easy availability and ideal catalytic activity.Up to now,however,few studies about hydrogenation of chloronitrobenzenes over the supported nickel catalysts have been reported.Therefore,the supported nickel catalyat has been attempted to use for the hydrogenation of chloronitrobenzenes in order to find an effective catalyst with high activity and selectivity in this thesis.A series of supported nickel catalysts were fabricated via a deposition-precipitation method,which were used as a promising heterogeneous catalyst towards catalytic hydrogenation of chloronitrobenzenes to chloroanilines.The effect of preparation methods(such as calcination and reduction temperatures,precipitation agent and pH value)on the physico-chemical properties of catalysts and the catalytic hydrogenation of chloronitrobenzenes were discussed.In addition,the physico-chemical properties of catalysts were also investigated by the characterization technologies of Brunauer-Emmett-Teller(BET),powder X-ray diffraction(XRD),H2-temperature-programmed reduction(H2-TPR),high-resolution transmission electron microscope(HR-TEM)and scanning electron microscope(SEM).It has been found that the average particle size of Ni and the interactions between NiO and ?-Al2O3 support are the key parameters in determining the catalytic activity and selectivity for the Ni/?-Al2O3 catalyst.Up to 99.27%selectivity to o-chloroaniline(o-CAN)was achieved for o-chloronitrobenzene(o-CNB)with full conversion over Ni/?-Al2O3 with the average particle size of 23.7nm.For the Ni/TiO2 catalyst with a weak interactions between NiO and TiO2 support,the catalytic activity and the selectivity were strongly affected by the proportion of rutile/anatase in titanium dioxide.Experimental results indicated that the present of 4.71%rutile phase in titanium dioxide for Ni/Ti02 exhibited excellent catalytic behavior towards the o-chloronitrobenzene(o-CNB)hydrogenation,99.66%selectivity to o-chloroaniline(o-CAN)was achieved for o-chloronitrobenzene(o-CNB)with full conversion.