Preparation Of Hydroxyapatite Based Nano-catalyst And Its Oxidation Performance Of Toluene

Volatile organic pollutants（VOCs）are one of the main sources of air pollution at present.This kind of compounds have a great negative impact on human production and life as well as the growth and health of animals and plants.Among many elimination methods,the catalytic oxidation method of end-treatment control is considered to be one of the most effective methods because of its advantages of high efficiency,low energy consumption and no secondary pollution.The key to selecting this method lies in the catalyst.Hydroxyapatite based materials are favored in the field of catalysis because of their strong ion exchange ability,high temperature stability and low price.It has been reported that they can be used for CO catalytic oxidation,heavy metal contaminated soil treatment,and catalytic N₂O reaction.Therefore,we mainly constructed a series of noble metal catalysts supported by hydroxyapatite.Through the"confine effect"of noble metal nanoparticles on HAP carrier,we hope to obtain a catalytic oxidation catalyst with good catalytic performance of toluene at high space velocity and low temperature.The effects of HAP on catalytic oxidation of toluene with different morphologies and preparation methods were studied.The structure-activity relationship between the structure and catalytic activity of the catalyst was elucidated by XRD,N₂ adsorption desorption test,TEM,FT-IR,H₂-TPR and other characterization techniques.（1）HAP samples with rod,flake and flower morphology were prepared by different synthesis methods and adding different structure guides.The samples obtained by hydrothermal method had higher crystallinity and lower specific surface area.The Pt/HAP-H catalyst with flower-like structure showed high catalytic activity in the catalytic oxidation of toluene,and the toluene was completely transformed at 230℃at 30,000 m L·g^-1·h^-1.Compared with Ag,Pt has a small particle size and good dispersion on the surface of the supporter,which makes Pt/HAP catalyst show excellent catalytic performance.（2）HAP supporter prepared by sol-gel method was used to adjust the p H value of the reaction process with NH₃·H₂O.It was found that the purity of HAP supporter was higher when the p H of precursor solution was 10.6.When the calcination temperature of the carrier was 800℃,the pore volume and pore size of the supporter were the largest,which were 0.2 m L·g^-1 and 183.3 nm,respectively,which were conducive to the adsorption of reactant molecules and desorption of products.The Pt/HA-01-800 catalyst had the best performance,and toluene was completely transformed at 243℃.Increasing the calcination temperature of HAP supporter is beneficial to increase the pore volume and pore size of HAP supporter surface,provide more active sites,and promote the conversion of toluene.（3）The solid phase method was used to prepare HAP supporter,and the samples with higher specific surface area,pore volume and pore size were obtained.The catalysts supported with Pt showed good catalytic activity.In addition,it was found that the Pt-Co/HAP bimetallic catalyst prepared by the introduction of transition metal Co significantly improved the catalytic performance.When the Co loading was 15%,the catalyst had the best activity,and the toluene was completely transformed at 209℃.The characterization results showed that Co₃O₄ formed strong interaction with HAP,increased the active site on the catalyst surface,promoted the release of oxygen species,and improved the catalytic performance of the catalyst.