Preparation Of Carbon Supported Pt Single-atom Catalyst And Its Application For Catalytic Hydrogenation Reaction

Functionalized aromatic amines are very important organic intermediates widely used in medicine,pesticides,fuels and chemicals and so on.Currently,aromatic amines and functionalized aromatic amines are mainly produced by catalytic hydrogenation of aromatic nitro compounds,and the catalytic hydrogenation reaction is mainly affected by catalyst catalysis.It was found that the supported metal catalysts exhibitted excellent catalytic performance in the selective catalytic hydrogenation,but the catalytic activity of the supported metal catalyst was mainly affected by the metal active components.The researchers found that the reactive metal could not react completely in the reaction process due to the reduction of the dehalogenation or the unsaturated group.It was found that the catalytic performance of the supported metal catalyst was mainly affected by the size of the metal.The researchers tried to decrease the size of the active metal to atomic level,each metal atom showed optimal catalytic performance.The latest results show that single-atom catalysts had very excellent catalytic performance in the chemoselective hydrogenation,thus preparation of single atom catalyst was very important.Recently,the methods used to prepare single-atom catalysts included: atomic layer deposition method,coprecipitation method,impregnation reduction method,stepwise reduction method and quality soft landing method and so on.Among them the methods of the successful preparation of the Pt single atomic catalysts included: atomic layer deposition,coprecipitation,and impregnation reduction method etc.However,these methods required the preparation of the support in advance,and then the single atoms were supported on the surface of the support,the single atoms on the surface of the support agglomerated easily during the reaction the activity of the catalyst was decreased.In this paper,a simple and rapid synthesis method-liquid plasma discharge method was used to incorporate Pt atoms in carbon onion layers during the growth of carbon onion,which improved the stability of Pt single atom catalyst.In this paper,we firstly explored the effects of discharge current and electrode rod on the morphology and structure of the product.And the carbon form,the size of Pt particles and the dispersion of Pt particles were investigated by HRTEM,STEM,EDS,Raman,XRD and XPS.Furthermore,the discharge parameters were optimized,and the catalyst of Pt single atom supported on the graphitic layers was successfully prepared.It was the first time that the single atom catalysts were successfully prepared by the plasma discharge in liquid.The Pt single atom catalyst has high dispersibility and high stability,and the loading of the metal is only 0.298 wt.%.The prepared Pt single-atom catalysts were used for the chemoselective hydrogenation of aromatic nitro compounds.And compared with other solutions,the Pt single-atom catalysts present the best performance in EtOH solution,which is the optimal condition.In addition,the home-maded Pt single-atom catalysts can not only show excellent performance in the catalytic hydrogenation of different aromatic nitro compounds,but also can help halonitrobenzenes to highly selective transform into corresponding haloanilines without any dehalogenation phenomenon.The Pt single-atom catalysts prepared in this study have good stability,and the Pt single-atom catalysts present excellent performance at least 10 cycles and without any loss in its activity and selectivity(all>99.6%)in the reaction of p-chloronitrobenzene catalyzed hydrogenation.More importantly,the Pt content almost has no loss even after 5 cycles(5 cycles the Pt content was 0.286 wt.%).