Research On Efficient Catalytic Oxidation Of Methanol At Normal Temperature

Volatile organic compounds?VOCs?pollution has become the focus of attention in the world,and alcohol is an important component of VOCs.The normal temperature catalytic oxidation?NTCO?method has the characteristics of low reaction temperature and safety operation.At present,NTCO of VOCs has gradually become one of the important technologies for controlling atmospheric pollutants.This paper explores the catalytic ozonation behavior of methanol at normol temperature,and provides important theoretical support for the study of VOCs.In this paper,normal temperature catalytic ozonation of methanol was used as a probe reaction.Preparing a series of catalysts which metal oxides were used as supporters and noble metals were active site,besides supporters and the species of noble metal were studied.The results showed that the Pt/FeO_x catalysts which prepared by coprecipitation method and used Fe?NO₃?₃ as precursor had the the best performance on NTCO of methanol.Then the preparation pH,Pt loading rate and calcination temperature of Pt/FeO_x catalysts were optimized,and the results showed that the optimum preparation pH of Pt/FeOx catalysts was 8,the optimum loading of Pt was 0.2wt%and the optimum calcination temperature was 400?.The Pt/FeO_x with different Pt content was characterized by ICP-OES,and the results showed that the actual loading value of Pt is consistent with the theoretical load value.The XRD,SEM,TEM and XPS characterization of the catalysts with different calcination temperatures were studied.SEM and TEM results showed that Pt particles are very small and dispersed on the surface of the supported FeO_x,XRD results showed that the crystal form of FeO_x changes with the increase of calcination temperature and the particles of Pt in the catalysts were very small and highly dispersed to the surface of FeO_x which is consistent with the SEM and TEM results.XPS results showed that the calcination temperature affected the valence state of Pt,and when calcination temperature was 400?,the Pt⁰/Pt²⁺in the catalyst is about 1 and Pt/FeO_x catalyst has highest activity during NTCO of methanol.The effects of reaction conditions on NTCO of methanol were investigated,and the reaction temperature,space velocity,initial concentration of methanol and initial concentration of ozone on the NTCO of methanol were investigated.The experimental results showed that when the reaction temperature was 30?,the space velocity was24000 h^-1,the initial concentration of methanol was 350 mg/m³ and the initial concentration of ozone was 300 mg/m³,methanol could be completely degraded.The catalytic activity was not reduced after 6 times cycles,indicating that the Pt/FeO_x catalysts have a certain ability of recycling.The off-gas was treated with commercially ozone treatment catalyst,and when the treatment space velocity was 8000 h^-1,the time for ozone to be completely removed can reach up to 312 h.The power-rate law was applied to fit the reaction kinetic data with the apparent activation energy was 14.66 kJ mol^-1,which was much lower than the activation energy of ozonation of methanol alone,indicating that the addition of catalyst greatly reduced the activation energy of the reaction.·OH was detected by EPR which indicated that·OH was formed during the reaction.Subsequently,the amount which was4.20×1012?unit/cm³?of gaseous·OH produced in the experiment was determined by high performance liquid chromatography with salicylic acid impregnation membrane capture.Finally,the reaction products were detected by FTIR,and the results showed that methanol was completely oxidated to CO₂ and H₂O under the experimental conditions.The NTCO technology has the characteristics of good treatment effect and low operating cost,which can be used in the field of VOCs treatment,and it will have broad application value.