The Preparation Of Manganese-based Catalysts And Their Catalytic Performance For Ozone Decomposition At Room Temperature

Ozone pollution in the atmosphere has become more and more serious,and it cause detrimental effect on human health as well as the living environment.The near-surface surface ozone mainly derives from water treatment,medical hygiene,printers and other equipment.Human beings are facing the threat of low-concentration ozone environment for a long time,and urgently need to develop cost-effective,green and stable ozone decomposition technologyCatalytic decomposition of gaseous ozone at room temperature has attracted much attention because of its high efficiency,safety and stability,which is also the most potential and the most promising technology at present.Manganese oxide,as an environmentally friendly and inexpensive catalyst with various crystal structures and morphologies that can be easily regulated,has a significant effect on the catalytic decomposition of ozoneIn this thesis,a series of metal-doped manganese dioxide(M-MnO2)catalysts were synthesized via the one-step hydrothermal approach and found that the catalytic activity of La-MnO2 was better than that of MnO2.Characterization and structure of MnO2 and M-MnO2 were characterized by XRD,FESEM,BET,H2-TPR,Raman,XPS and TEM.It was found that the addition La resulted in M-MnO2 catalyst with poor crystallinity and the formation of mixed crystals,generating more defects,which could be conducive to the adsorption and ozone decomposition.Compared with MnO2,La-MnO2 catalysts featured relatively low reduction temperature and richer surface oxygen vacancies,which are beneficial to the adsorption and decomposition of ozoneThe spherical MnCO3 materials were synthesized by reaction between ammonium hydrogen carbonate(NH4HCO3)and Manganese sulfate monohydrate(MnSO4·H2O)via coprecipitation at room temperature,and the experiment studied the effects of different ratios of NH4HCO3 and MnSO4·H2O,material concentrations,reaction time and reaction temperature on the MnCO3 catalysts' performances of ozone decomposition,which the optimum reaction condition was carried out through the control variable method.Among them,the optimum catalyst preparation process were determined as followed:ratio was 1:1.5,the aging time was 50 minutes,and the reaction temperature was 30?.The catalyst prepared by the optimum conditions was pyrolyzed to prepare MnOx catalysts and investigated the effect of pyrolysis conditions on the catalytic activity of ozone decomposition of MnOx catalysts,which the optimum pyrolysis conditions were as follows:calcination at 320? for 4 h.To further improve the activity of the MnOx catalyst,based on the the optimum synthesis process in the previous study,a series of MxOy-MnOx catalyst was prepared by introducing metals M(M=Ce,Co,Cu,La,Ni)via coprecipitation at room temperature,which found that the CeO2-MnOx's demonstrated superior catalytic activity for ozone decomposition,whose activity is better than that of other MxOy-MnOx catalystsThe performances were characterized with different characterization methods,including XRD,FESEM,BET,H2-TPR,Raman,XPS and TEM,and the characterization results were consistent with expectations.The experimental characterization indicated that CeO2-MnOx catalysts was a mixed crystal catalyst,and its original MnOx structure collapsed further which resulted in poor crystallinity,and generating more defects.Furthermore,the Structural analysis indicated that CeO2-MnOx demonstrates more surface oxygen vacancies and surface defects than the other catalysts,thereby shows excellent catalytic decomposition of ozone activity.