Studies On Fabrication And Properties Of The Cerium-based Composite Catalysts

Cerium（Ce）is the most abundant rare earth element on earth,and its content（66.5 ppm）more than copper（60 ppm）in the lithosphere.Its unique external electronic configuration[Xe]4f¹5d¹6s²,Ce³⁺and Ce⁴⁺conversion makes cerium oxide（Ce O₂）have a large number of surface defects,high oxygen storage capacity,excellent chemical and structural stability,and it is used in alloys,phosphors,catalytic,Magnetism,medicine and other fields have a wide range of applications.In recent years,cerium oxide has received a lot of research in the field of catalysis,but there is still need for breakthroughs in its preparation method and actual production catalysis.This thesis is mainly devoted to exploring the potential applications of cerium-based catalysts in the field of industrial catalytic acetylene hydrogenation and photocatalytic degradation of pollutants.Cerium oxide is used as a promoter to improve its catalysis performance by means of doping,in-situ growth,and construction of heterojunctions.This thesis is mainly divided into five segments,the contents of which are as follows:Chapter 1:Briefly explain the structural features and performance advantages of cerium and cerium oxide,and summarize the application and research status of cerium-based materials in the field of catalysis.Aiming at some problems in the catalysis process of cerium-based materials,the research strategy of this paper is proposed.Chapter 2:By doping cerium into hydrotalcite and in situ growing it on industrial-grade spherical alumina,it is used to improve the conversion rate and selectivity of catalytic acetylene hydrogenation.The introduction of hydrotalcite makes the material have a larger surface area,effectively inhibits the agglomeration of the active component palladium,and exposes more active sites.At the same time,cerium doping can adjust the electronic structure of palladium nanoparticles and improve the selectivity of acetylene hydrogenation catalysis.Chapter 3:Using the one-pot method,cerium oxide nanocrystals and aluminum oxyhydroxide are in situ grown on industrial-grade spherical alumina as a carrier for the active component palladium to improve the conversion and selectivity of catalytic acetylene hydrogenation.The lamellar structure of aluminum oxyhydroxide increases the surface area of the composite material and improves the dispersion of cerium oxide nanocrystals and palladium nanoparticles.Cerium oxide can activate hydrogen and interact with palladium to improve the conversion rate and stability of acetylene hydrogenation catalysis.Chapter 4:Under the condition of no additional alkali source,through a simple synthesis method,successfully prepared ZnO/Ce O₂ heterojunction,after light deposition of silver nanoparticles,Ternary composite catalyst showed excellent degradation performance in the application of photocatalytic removal of pollutants.The introduction of cerium oxide nanocrystals and silver nanoparticles acts as a trap for trapping electrons,inhibits the recombination of photogenerated carriers,and improves the efficiency of photocatalytic degradation of pollutants.Chapter 5:Summary and expectations of the research work of this paper.