The Research Of Preparation And VOCs Catalytic Purification Properties Of OMS-₂/SnO₂ Nanocomposite

With the rapid development of society,various factories have been running day after day,resulting in the random discharge of industrial wastes,especially the volatile organic compounds（VOCs）,which have caused great trouble to people’s health and living environment.Nowadays,industrial methods for controlling volatile organic compounds are adsorption and catalytic methods.Among them,catalytic combustion methods often use supported precious metal catalysts,but their resources are scarce and expensive,and they are always accompanied by high energy consumption.Therefore,in order to reduce cost and energy consumption and improve catalytic efficiency,this paper prepared MnO2（OMS-2）and SnO2nanocomposite catalyst and MnCO₃ nanocatalyst,and discussed their catalytic degradation of carcinogenic typical volatile organic pollutants benzene activity.The main results and innovations are as follows:1.OMS-2/SnO₂ nanocomposite catalysts with different Mn/Sn molar ratios and different temperatures were prepared by hydrothermal method using KMnO₄ and SnSO₄ as raw materials.First,these composite catalysts were characterized by XRD,TEM.The results show that the MnO₂ in these composite catalysts is OMS-2 and the SnO₂ nanoparticles surround the OMS-2 nanorods.Then,the catalytic activity of OMS-2/SnO₂ catalyst was tested.It was found that these OMS-2/SnO₂nanocomposite catalysts have high catalytic activity and excellent stability for catalytic oxidation of benzene under full solar spectrum irradiation.The OMS-2/SnO₂ nanocomposite catalyst with the reaction in 90℃and Mn/Sn molar ratio of 1:1 has the best catalytic activity,and the initial formation rate of CO₂ is nearly 38 times higher than that of pure SnO₂.Then,the catalytic activity of the nanocomposite catalyst under visible-infrared light irradiation was tested and it was found that it still has high catalytic activity.This also enables us to discover a mechanism:the light-driven thermal catalytic mechanism,explaining why the nanocomposite catalyst has high catalytic activity under simulated sunlight.The study also find that there is a synergistic effect between photocatalytic oxidation of OMS-2 and photocatalysis of SnO₂ in the nanocomposite catalyst,which synergistically further enhances its photothermal catalytic activity.Finally,the nature of photothermal synergy was explained through CO-TPR in UV-Vis-IR irradiation and darkness.2.MnCO3 and Mn3O4 catalysts were prepared with urea and manganese acetate as raw materials at different temperatures and calcination conditions.First,through XRD and SEM,it was found that MnCO₃ is a nanoparticle,and Mn₃O₄ is a crystal with a prismatic structure.Then,it was found that the catalytic activity of sole Mn₃O₄alone is very low,while the catalytic activity of MnCO₃ is not bad,especially the MnCO₃ catalyst,which reacts at 120°C for 48 h and calcines for 2 h.This MnCO₃catalyst has very high activity for the thermal catalytic degradation of benzene.Compared with the catalyst obtained by other temperatures（90°C,150°C,180°C）,the reaction temperature were reduced by 81°C,42°C and 80°C respectively when the conversion of benzene reaches 90%.It was then found that the 120°C sample catalyst has high catalytic activity for catalytic oxidation of benzene under full solar spectrum irradiation,and the concentration of CO₂ generated at 5 minutes of irradiation reached 30223.041 mg m^-3.Finally,the CO temperature programmed reduction test showed that the lattice oxygen activity of the sole MnCO₃ catalyst（120°C,150°C,180°C）was higher than that of the MnCO₃ and Mn₃O₄ catalysts（90°C）.Based on the above studies,it is concluded that the catalytic activity of MnCO₃ catalyst is mainly photo-driven thermal catalytic activity.