Effect Study Of Natural Minerals As Support In The Process Of Catalytic Combustion Of VOCs

Volatile organic compounds?VOCs?is a kind of important air pollutants,and it has been included in the key atmospheric pollution as the increase of the phenomenon of air pollution in recent years.This study made the perovskite oxide La_0.8Ce_0.2MnO₃ the active component and made the natural mineral material palygorskite?hereafter referred to PG?and kaolin?hereafter referred to K?the supports,and then prepared the loaded catalysts.The modified conditions of PG and K,the catalytic combustion activity of toluene when La_0.8Ce_0.2MnO₃ which was loaded on PG and K and the conditions of catalysts preparation were studied.The catalysts were characterized by means of the microscopic analysis for example XRD,SEM,TEM,H₂-TPR,BET and NH₃-TPD and so on simultaneously.The best way to modify palygorskite was determined by orthogonal experiments firstly:hydrochloric acid concentration was 3mol/L,hydrochloric-palygorskite ratio?g:ml?was 1:5,pickling time was 6 h.Then La_0.8Ce_0.2MnO₃ was supported on palygorskite modified by hydrochloric acid with the coprecipitation method.It was found that the specific surface area of La_0.8Ce_0.2MnO₃/PG could reach 90m²/g,and the catalyst exhibited better activity when the loading of active species was 15%;T_50%?the ignition temperature?and T_90%?the complete conversion temperature?were 240? and 300? respectively.The catalysts La_0.8Ce_0.2MnO₃/PG appeared obvious reunion phenomenon if increased the supported loadings,as result its catalytic activity no longer increased.The catalysts made by the coprecipitation were superior to the one made by impregnation method when the calcination temperature was 700?,the loading amount of La_0.8Ce_0.2MnO₃was 15%,the inlet concentration of toluene was 1000 mg/m³ and the airspeed was 12000 H^-1in catalysts preparation methods study,and the results showed and T_50%and T_90%of catalysts made by the coprecipitation reduced 20°and 30? or so respectively compared to the catalysts made by the impregnation method in toluene catalytic combustion.T_50%of La_0.8Ce_0.2MnO₃/PG roasted at 600? was lower about 70? than La_0.8Ce_0.2MnO₃/PG roasted at 700? and T_90%was approximate 60?.At this time La_0.8Ce_0.2MnO₃ was non-crystallized and the lattice oxygen activity was stronger,in addition to the more acidic sites on the surface of PG,the fewer internal channel fold and the bigger specific surface area,therefore the best calcination temperature of La_0.8Ce_0.2MnO₃/PG was 600?.The modified conditions of K was explored by the high temperature roasting and hydrochloric acid pickling,and the best conditions were:600? calcination for 2h,3mol/L hydrochloric acid pickling for 8 h at 70? constant temperature,among them hydrochloric-kaolin ratio is 1:25.The catalytic combustion of toluene was excellent once La_0.8Ce_0.2MnO₃was supported on the kaolin.In addition,the optimal active component loading amount was10%,and T_50%was 275?,T_90%was 330? at the moment.