Synthesis And Characterization Of Cu-OMS-2 And Its Catalytic Performance In Ozone Decomposition

Prolonged contact with ozone could damage the human body,resulting impaired immune system and neural system.The residue ozone near the earth surface mainly derives from medical service,food preservation,water treatment and other sectors.The green,safe and economical techniques that can effectively and stably decompose ozone,are urgently needed.Catalytic decomposition of ozone at room temperature is heated discussed in the academic society for its safe and economical features.OMS-2?Manganese oxide octahedral molecular sieve?,a new material,has a similar structure of zeolite molecular sieve.There are a number of mixed valence Mn ions,namely Mn²⁺,Mn³⁺,Mn⁴⁺,in the framework structure of this material.Besides,this material features relatively high specific surface area and average wet resistance.Thus,this material has excellent performance on ion exchange and redox reaction.In addition,the channel effect and adsorption effect of this material are conducive to the ozone adsorption and ozone decomposition.The experiment prepared a series of OMS-2 catalysts with hydrothermal method,reflux method and solid phase method.The experiment also prepared M-OMS-2catalysts with anterior doping method by introducing transition metals.The experiment studied the effects of different calcination temperatures and humidity conditions on the catalysts'performances on ozone decomposition.The performances were evaluated with different characterization methods,namely XRD,FESEM,BET,H₂-TPR and XPS.The results were as follows.Under dry condition,RF-OMS-S catalyst prepared with reflux method,performed better on ozone decomposition,compared to HM-MOS-2 catalyst prepared with hydrothermal method and SP-OMS-2 catalyst prepared with solid phase method.The RF-OMS-S catalyst prepared with reflux method,featured a high degree of crystallinity and relatively low reduction temperature,which were conducive to the catalytic ozone decomposition.RF-OMS-2 catalysts prepared at different temperatures showed different catalytic activities.Among others,the RF-OMS-2-500?catalyst prepared at 500 degrees showed better catalytic activity.Different wet conditions had significant influences on the catalytic activities.That could be explained by the block of effective contact between ozone and the catalyst.The block could be caused by the adsorption of water molecules on the surface of catalyst.Among the M-OMS-2 catalysts prepared with anterior doping method by introducing transition metals,the Cu-OMS-2 catalyst performed the best catalytic activity on ozone decomposition.Compared to Ce-OMS-2 catalyst,Co-OMS-2 catalyst,Ni-OMS-2 catalyst and Fe-OMS-2 catalyst,Cu-OMS-2 catalyst featured higher specific surface area and lower reduction temperature,which were conducive to the catalytic ozone decomposition and the redox reaction.The Cu-OMS-2 catalysts prepared with anterior doping method were employed different Cu-Mn ratios and calcined at 400 degrees.At the initial stage of the reaction,the ozone conversion of the Cu-OMS-2 catalyst at the Cu-Mn ratio of 1 to 100,reached100 percent.After 150 minutes,the activity remained largely unchanged.The activity of this catalyst was higher than that of RF-OMS-2 catalysts and other Cu-OMS-2catalysts at different Cu-Mn ratio.The Cu-OMS-2 catalyst at the Cu-Mn ratio of 1 to 100,had rich Mn³⁺and adsorbed oxygen on its surface.That was conducive to the combination of ozone that led to the synthesis of peroxide.Furthermore,that made the desorption of the peroxide happen easier.Besides,the Cu-OMS-2-400?catalyst at the ratio of 1 to 100?RH=80%?was more active,in terms of catalytic ozone decomposition,than RF-OMS-2?RH=0%?.With the above analyses,it could be concluded that the introduction of copper improved the wet resistance of the catalyst.