Preparation Of Silver-loaded Hydroxyapatite Catalyst And Its CO Catalytic Oxidation Performance

Hydroxyapatite,as a“green”inorganic material,has good chemical and thermal stability.It can be widely used as a catalyst carrier in the field of catalysis.Supported nano-silver（Ag）catalyst has been widely used in heterogeneous catalysis,but its practical application is limited due to poor thermal stability.Therefore,we reported a novel supported nano-Ag/HAP catalyst using the strong metal supported interaction（SMSI）between Ag nanoparticles（NPs）and hydroxyapatite（HAP）.In this paper,the specific morphology of hydroxyapatite was prepared by hydrothermal method and co-precipitation method using tetrahydrate calcium nitrate as calcium source and diammonium hydrogen phosphate as phosphorus source.Taking advantage of the unique confinement effect with different morphology HAP,and protective effect of hydroxyl groups on HAP surface,the highly dispersed Ag NPs was obtained.The morphology and structure of HAP and Ag/HAP catalysts were characterized by XRD,SEM,TEM,FT-IR,UV-vis,H₂-TPR and other characterization methods,and the relationship between the support and catalytic performance of the catalyst was explored,so as to obtain CO oxidation catalysts with good activity:（1）Using sodium citrate as template,a series of two-dimensional lamellar HAP with different sizes were obtained by adjusting the hydrothermal temperature.Ag/HAP catalyst with low loading was prepared by incipient-wetness impregnation method.It is found that the morphology,size and specific surface area of the HAP support all affect its performance.When the hydrothermal temperature is 160 ℃,the support has the largest specific surface area and small size,and the surface-OH vibration peak is stronger,which shows the highest catalytic activity of Ag/H-160,and CO is completely transformed at 180 ℃.（2）The HAP nanosheet was prepared by co-precipitating method.The p H value of the system was controlled by changing the addition amount of Na OH,and HAP with different specific surface area was obtained.The results showed that the H₁₂ sample had a maximum specific surface area of 99 m~2/g at p H=12.The supported Ag/HAP catalyst was prepared using the series of lamellar HAP as carrier,and the catalytic oxidation performance of CO was also studied.The results show that the lamellar Ag/HAP catalyst has better catalytic performance,and the full conversion of CO oxidation can be achieved at 160 ℃.Superior to other catalysts reported in the literature.（3）On the basis of HAP layer structure research,one-dimensional nanometer HAP rod and three-dimensional flower structure HAP were prepared by hydrothermal methods.Furthermore,Ag/HAP（3 wt.%）catalyst was prepared by impregnation method to study the performance of CO oxidation,and the structure of HAP and properties of nanometer Ag catalyst detailed characterization.The results show that the under the same condition of Ag loading,the content of Ag~0on HAP surface with high specific surface area and small particle size is higher,which is more conducive to the dispersion of Ag,and the prepared Ag/HAP catalyst is the best.