Study On Hydrogen Release And In-situ Hydrogenation Activity Of Inexpensive Metal-Doped Catalysts

With the rapid development of modern industry,amounts of untreated industrial chemicals that were directly discharged into the environment have led to serious threat to human beings,soil,water resources and the entire ecosystem.Nitroaromatic compounds,as one of the pollutants in water,have high stability and are hardly degraded in water.At present,so reducing nitroaromatics to corresponding aromatic amines by catalytic hydrogenation is one of the most effective strategy.The traditional hydrogenation method involves in some harsh conditions,such as high temperature and high pressure.Moreover,main disadvantages of this method including high cost,low safety factor and low utilization of H2.Therefore,an effective method is developed to construct a tandem hydrogenation of nitroaromatics by replacing H2 with hydrogen-rich compounds.The most critical problem of the tandem hydrogenation reduction is developing much more efficient catalytic systems.In this thesis,a series of inexpensive metal-doped metal composites or supported metal nano-catalysts were successfully prepared by ammonia co-precipitation and calcination method,in which four major transition metals（iron,cobalt,nickel,and copper）are combined in pairs.The species phase,structure and morphology of the as-prepared catalysts were analyzed and characterized.Furthermore,catalytic performance of these catalysts was systematically evaluated for the hydrogenation reaction of halogenated nitroaromatics.The main research contents are listed below.（1）A series of nickel-cobalt nanocomposites were prepared by ammonia-water coprecipitation-calcination method.The experimental results show that the amorphous N0.2CC loaded with some Co SO4 nanoparticles has excellent catalytic performance for hydrogen release of aminoborane（AB）,with a maximum hydrogen generation rate（HGR）of 617 m L min^-1 gcat^-1and an effective hydrogen volume of 148 m L with 2 mmol AB.And N0.2CC has the best catalytic performance for the hydrogenation of m-chloronitrobenzene（m-CNB）,indicating 100%m-CNB conversion and 100%selectivity of m-chloroaniline（m-CAN）.In addition,the catalyst has good recyclability and can be recycled for more than 5 times.（2）A series of copper oxide/titanium dioxide nanocomposites were prepared by the same method mentioned above.Furthermore,their reactivities were investigated towards the hydrogen generation of H2 from the catalytic hydrolysis of AB and the tandem hydrogenation of m-CNB.The observations indicate that the one copper oxide nano-catalyst（Cu0.5Ti0.5）supported on ultra-thin titanium dioxide nanowires has moderate catalytic performance for hydrogen release of AB,with a maximum HGR of 195 m L min^-1 gcat^-1 and 117 m L of hydrogen volume with 2 mmol AB.The Cu0.5Ti0.5 sample displayed remarkable performance in the m-CNB tandem hydrogenation under mild conditions,displaying 100%yield of m-CAN as the aim product.Substrate expansion experiments exhibited that Cu0.5Ti0.5 still possesses excellent activity in the tandem hydrogenation of various halogenated nitrobenzenes,giving approximately 100%of the conversion of the substrate and the selectivity of the target products.（3）Moreover,catalytic performance of varied magnetic copper ferrite nano-catalysts（Cux Fe3-x O4）were investigated for the hydrogen release from the AB hydrolysis and the m-CNB tandem hydrogenation.prepared by ammonia-water coprecipitation-calcination method.The experimental results denote that the selected Cu0.5Fe2.5O4 catalyst has moderate catalytic reactivity for AB dehydrogenation with 375 m L min^-1 gcat^-1 of maximum HGR and 138m L of an effective hydrogen release volume with 2 mmol AB.The current Cu0.5Fe2.5O4 sample also has the best catalytic performance for m-CNB hydrogenation at room temperature and normal pressure.Namely,both the m-CNB conversion and the m-CAN selectivity can reach 100%.Meanwhile,Cu0.5Fe2.5O4 catalyst has excellent stability and magnetic properties,which can be reused for more than 6 times.