Study On Preparation And Catalytic Performance Of Supported Platinum-based Catalyst For Selective Hydrogenation Of Chloronitrobenzene

Chloroanilines are an important class of chemical raw materials and organic intermediates,which have been widely used in the fields of medicine,pesticides,dyes and household chemicals,etc.The chloroanilines are mainly obtained by reduction of chloronitrobenzenes.The catalytic hydrogenation reduction method is received much attention because of its advanced technology,high yield of target products,low energy consumption and small environmental pollution,etc.However,catalytic hydrogenation of chloronitrobenzens is a competitive reaction of nitro hydrogenation and the carbon-chlorine bond hydrogenation.The catalytic hydrodechlorination reaction of the substrates not only limits the selectivity to chloroanilines,but also the hydrogen chloride produced from the hydrodechlorination is also corrosive to the reactor.At present,the gold catalyst in the reported catalysts offers the highest selectivity of chloroanilines for chloronitrobenzens catalytic hydrogenation and can avoid the hydrodechlorination completely,but the application of gold is limitted due to poor stability.Therefore,there is an urgent need to develop a new catalyst of high performance.In this paper,Fe modified Pt/AC catalyst?Pt-Fe/AC?was prepared by impregnation reduction method with activated carbon?AC?as the supporter,and its catalytic performance for chloronitrobenzenes hydrogenation to chloroanilines was investigated.It was found that the addition of an appropriate amount of Fe can improve the Pt/AC catalytic activity and selectivity to chloroanilines,and completely inhibited dechlorination.The conditions of preparation have a great influence on the performance of the catalyst.The experimental results show that the 0.3%Pt-4%Fe/AC calcined at 473 K in flowing air showed excellent catalytic performance for chemoselective hydrogenation of chloronitrobenzenes to chloroanilines.The XRD and TEM characterize results revealed that the Fe and Pt species on AC support are in ahomogenous dispersion without any obvious aggregation.X-ray photoelectron spectroscopy?XPS?revealed the electron transfer from Pt nanoparticles to Fe₂O₃,leading to the electron-deficient state of the Pt nanoparticles in the 0.3%Pt-4%Fe/AC catalyst,which not only can enhance the ability of N=O activation,improve the catalytic activity,but also can weak electronic feedback between Pt and the benzene ring of p-chloroaniline.This may be responsible for the excellent catalytic performance of Pt-Fe/AC-A catalyst for chloronitrobenzenes selective hydrogenation to chloroanilines.In this paper,the catalytic performance of chloronitrobenzenes selective hydrogenation to chloroanilines over the nitrogen-doped activated carbon supported platinum and iron?0.3%Pt-4%Fe?catalysts were investigated.The experimental results show that the catalytic activity of the N-functionalized activated carbon?NAC?supported 0.3%Pt-4%Fe for catalytic hydrogenation of p-chloronitrobenzene is lower than that of activated carbon as support,but the stability is obviously enhanced.