Research On The Synergistic Catalytic Hydrogenation Performance Of Ni-Metal Oxide Nanoclusters

Catalytic hydrogenation is considered to be a promising production method with the advantages of environmental protection and high efficiency,and has a very broad application prospect.The application of catalytic hydrogenation in this paper is reflected in the following two parts:First,the carbon dioxide content in the atmosphere has risen sharply after the industrial revolution,the capture and resource utilization of carbon dioxide has become a current research central issue.Carbon dioxide can be converted to formic acid through hydrogenation reduction reaction,then used as chemical raw material,hydrogen storage energy material,liquid fuel,and so on.Second,halogenated arylamine compounds are widely used in organic chemistry,material chemistry,medicinal chemistry and other fields.Catalytic hydrogenation is an important way to prepare halogenated aromatic amine compounds from halogenated aromatic nitro compounds.However,the catalytic reduction of arylnitro compounds containing halogen（Cl,Br,and I）atoms often has poor selectivity,because the reactants are prone to dehalogenation during the reaction process,In this paper,nickel-metal oxide（Ni-MOx）nanoclusters with sizes ranging from 1.5 to3.8 nm were prepared by using three different reverse microemulsion systems,and the active components were loaded onto regular spherical support silica（SiO₂）forming a metal-supported catalyst.In this paper,the structure and morphology of the materials prepared by three different reverse microemulsion systems were compared,and the activity comparison of Ni-based catalysts doped with different metal oxides for the hydrogenation reduction reaction of sodium bicarbonate to formic acid was also explored.Among them,the structure of the material prepared by using Triton X-100 as surfactant is the best,which is a multi-core-shell structure,and there are many active sites distributed on the surface of the carrier and in the pores,the active components have an average size of 1.6 nm and belong to composite nanoclusters.In this paper,different metal oxides were used to dop and modify Ni and applied in the reaction of carbon dioxide catalytic hydrogenation to formic acid,in order to form electron transfer with the main catalyst Ni to improve the catalytic activity of the catalyst.The study found that the catalytic activity of the catalyst was the highest after using Triton X-100 as surfactant and CeO₂doping.The paper also explores the recycling performance of Ni-CeO₂/SiO₂catalyst.Moreover,the effect of reaction conditions was investigated.When the reaction temperature was 200℃ and the H₂pressure was 2 MPa,the catalytic material with the best performance was used to react for 2 h,and the yield of formic acid could reach77.8%.At the same time,the reaction mechanism was explored and proposed with the existing results in the laboratory.The reaction process is that Ni^δ+and MOx^δ-promote the hetero-splitting of H₂into H^δ+and H^δ-,which react with HCO₃^-to obtain the target product HCOO^-.The previously prepared Ni-CeO₂/SiO₂materials can also be used to catalyze the hydrogenation reduction of halogenated arylnitro compounds to halogenated anilines with high selectivity.The doping of CeO₂improves the agglomeration of Ni to a certain extent.Due to the difference in work function between materials,electrons will flow from Ni to CeO₂;in addition,a large number of oxygen vacancies can be generated on the surface of ceria material,which can inhibit the dehalogenation of the halogenated arylnitro compounds during the hydrogenation reduction process,thus improving the selectivity of the target product and the catalytic activity.The catalyst prepared in this paper has high activity in catalyzing the hydrogenation of different halogenated arylnitro compounds.The hydrogenation conversion rate of chlorinated and brominated arylnitro compounds can reach more than 93%,and the hydrogenation of iodo arylnitro compounds conversion rate can reach more than 83%,the selectivity to the target product can reach more than 90%,and it can be recycled more than five times.