Supported Ni And Pt Catalysts For Hydrogenation Of Nitrobenzene

Aniline (AN) is one of the most important chemicals and intermediates in the production of pharmaceuticals, dyes, pigments and pesticides. Nowadays, AN is produced mainly via hydrogenation of nitrobenzene over Cu, Ni and noble metals (Pt, Pd). Meanwhile, the hydrogenation of nitrobenzene (NB) to AN is one of the typical model reaction to test the catalytic activity for hydrogenation. Compared to metals in bulk, supported metal catalysts can increase the specific surface greatly of metals and support metarials can also stabilize the nano-sized metal particles. Thus, investigation of highly active supported nano-metal catalyst for hydrogenation of NB always is an important and interesting subject.In published papers, supported Ni catalysts were prepared mainly with inorganic nickel salt such as Ni(NO3)2, Ni(CH3COO)2 and NiCl2 as precursors, in which the Ni particles were bigger than 10 nm. In this work, a series of silica gel (ca.200-300 mesh) supported Ni catalysts that have average Ni particle size of 3.7,11.4 and 11.8 nm were prepared by facile impregnation of [Ni(en)3]2+, Ni(NO3)2 and Ni(CH3COO)2. On the 3.7 nm sized Ni catalyst, the selectivity of aniline (AN) reached 99%with a 100% conversion of NB in 5.5 h at 90℃, 1.0MPa, NB:Ni=305 (mol ratio). But the activities of 11.8 nm sized Ni catalysts and commercial Raney Ni catalyst are quite lower.Another part of this thesis is graphene supported Pt catalysts. Graphene is two-dimensional single-layer carbon sheet, having unique performance on the field such as electricity and optics. As a new kind of carbon materials, its application as catalyst support is rarely reported. This work is intent to investigate a simple way to produce the graphene supported Pt catalyst. The activity of graphene supported Pt for hydrogenation of NB to AN was tested. When a mixture of graphite oxide and H2PtCl4 was reduced by ethylene glycol (EG), Pt dispersed highly on the chemically converted graphene (CCG), with mean grain size 3.1 nm. At 20℃,1.0 MPa, the detected TOF of Pt atoms on CCG.EG reached 1,200 min-1, which is 12 times higher than those Pt atoms on MWNTs and active carbon. Moreover, On the Pt/CCG.EG catalyst, the selectivity of AN reached 94.3% with a 100% conversion of NB in 3 h at 0℃,1.0MPa, NB:Ni=13,900. The extremely high activity will make the graphene material be a novel support material in future.