Research On Supported Platinum Catalyst For Catalytic Oxidation Of Low Concentration Formaldehyde At Room Temperature

Formaldehyde is a kind of carcinogenic and teratogenic poisonous gas.With the extensive use of various building materials,indoor formaldehyde has seriously threatened people's health.The catalytic oxidation method has the advantages of high efficiency,complete treatment and extremely effective for low concentration formaldehyde gas treatment without secondary pollution,considered as the most promising and effective method for formaldehyde removal.Pt-supported catalysts have the best performance in the catalytic degradation of formaldehyde.Currently,How to combine carrier selection and preparation conditions optimization,design and manufacture of supported platinum-based catalysts with low platinum loading and high catalytic degradation performance for low concentration formaldehyde has become a subject of extensive concern.Based on the above situation,a series of supported platinum catalysts were prepared by using TiO2,ZSM-5 zeolite,CeO2,Co3O4,ZrO2 as carriers.Under the same preparation methods and conditions,the catalytic decomposition of formaldehyde was investigated.Based on the results of this study,the effects of different preparation methods and conditions on the activity of the catalyst were studied,and the rare earth metals Ce and La were further added to modify the catalyst.The catalysts were characterized by XRD,BET,TEM,CO adsorption and XPS.The specific research results are as follows:1.When the Pt load was 0.5%,the order of formaldehyde oxidation activity of t five catalysts prepared by the same method is Pt/TiO₂>Pt/ZSM-5>Pt/CeO₂>Pt/Co₃O₄>Pt/ZrO2.The specific surface area of the carrier is not the main factor affecting the activity of the catalyst,but too low specific surface area affects the nucleation of platinum particles,and the reaction activity of the catalyst is related to the size and dispersion of platinum particles.2.Based on the Pt/TiO2 catalyst with the best formaldehyde oxidation activity,the effects of different preparation methods and reaction conditions on the activity of the catalyst were investigated.The results showed that the order of Pt/TiO₂ catalyst prepared by impregnation method,direct reduction method and precipitation deposition method was Pt/TiO₂?DP?>Pt/TiO₂?R?>Pt/TiO₂?IMP?.In addition,the optimum reaction conditions for the preparation of the Pt/TiO₂ catalyst by the precipitation deposition method are as follows:NaBH₄ is used as a reducing agent,pH=9.3.The activity of Pt/TiO2 catalyst was directly proportional to the Pt load,but the catalyst activity decreased when the Pt load was 2%.Based on the comprehensive consideration of catalytic activity and economy,0.5%Pt/TiO₂ catalyst is the most ideal.It can completely degrade formaldehyde within 85min,which can be further studied.4.The Pt/TiO₂ catalyst was modified by the introduction of lanthanum and cerium by impregnation method.The addition of lanthanum and cerium can improve the reactivity of the catalyst.Pt-5%Ce/TiO₂ catalyst has the best reactivity,Under the action of Pt-5%Ce/TiO₂ catalyst,the formaldehyde of 20mg·m^-33 can be completely degraded in 55min.In 15 reaction cycles,Pt-5%Ce/TiO₂ catalyst did not deactivate,and could completely degrade formaldehyde.BET,XRD,TEM,STEM,XPS and CO adsorption characterization results showed that the addition of Ce increased the dispersion of Pt particles to 2.21nm and reduced the Pt particle size from 2.9nm to2.21nm.In addition,XPS results showed that the addition of Ce provided abundant oxygen vacancy,increased the ratio of chemically adsorbed oxygen atoms to lattice oxygen atoms,and was conducive to the adsorption of oxygen atoms,so as to generate adsorbed oxygen atoms and improve catalytic activity.