Study On Hydrogen Production From Ammonia Decomposition Catalyzed By Cerium Based Oxide Supported Nickel

The development of hydrogen production,transportation,and storage systems is crucial for future social development,as the use of hydrogen neither relies on fossil fuels as energy nor leads to an increase in greenhouse gas emissions such as carbon dioxide and air pollution.Ammonia,as a hydrogen carrier with the advantages of convenient storage and transportation,no CO_X generation,and high hydrogen content,has attracted widespread attention.However,currently,ammonia usually requires a higher reaction temperature for reaction,so it is necessary to find a suitable low-temperature catalyst.This article first finds a suitable Ni loaded catalyst carrier by regulating the carrier metal,and then obtains an efficient and stable ammonia decomposition catalyst by regulating the loading method.The main research content is as follows:（1）Different catalyst supports were successfully synthesized using sedimentation precipitation method,and Ni was loaded on these supports through impregnation method.The experiment showed that the Ni/ALC（Ni/Al₅La₃Ce₇O_x）catalyst was successfully prepared,and the effect of the support on ammonia decomposition activity and the effect of the addition of Al and La on the lattice structure of CeO₂ were studied.Through research,it was found that a uniformly dispersed Ni/ALC catalyst was successfully prepared.Through the analysis of XRD,it is found that La³⁺doped into CeO₂ after La addition form La-Ce-O solid solution,and Al³⁺added after Al lead to the reduction of lattice edge length and lattice distortion.Through chemical adsorption analysis,Ni/ALC catalysts exhibit strong metal support interaction,which enhances the activity of ammonia decomposition.XPS and Raman analysis showed that the doping of La³⁺significantly increased oxygen vacancies,and the incorporation of Al formed Al-O-Ce bonds.The catalyst activity test showed that the conversion rate of Ni/ALC catalyst reached 99.7%at a space velocity of 6000 m L·h^-1·g_cat^-1 and a temperature of550℃.（2）Using the metal carrier ALC from the previous chapter,the loading method was improved by adding surfactants during loading.First of all,the study of adding different surfactants found that the addition of citric acid and cyclodextrin significantly changed the surface structure of the catalyst,significantly increased the specific surface area and improved the ammonia decomposition activity.The addition of citric acid adjusted the weak,and the ammonia adsorption strength of the intermediate acidic sites,thus improving the catalyst reaction activity.By adjusting the content of different citric acids and nitrogen adsorption and desorption,it was found that different concentrations of citric acid regulated the specific surface area and pore size of the catalyst.The increase in citric acid content also promotes the formation of Ni-O-Al（Ce or La）bonds in the catalyst.The CA-60 catalyst achieved an extremely high ammonia decomposition conversion rate of 99.7%at a space velocity of 30000 m L·h^-1·g_cat^-1and a temperature of 600℃.