The Study On The Catalytic Degradation Of 1,3-Butadiene By Multicomponent Transition Metal Oxides

In recent years,volatile organic compounds?VOCs?have become the main pollutants in the atmospheric environment,which has attracted more and more attention.VOCs are important precursors of secondary organic aerosols and ozone,and are directly related to air pollution problems such as smog.Therefore,it is very important to control the emissions of VOCs.Catalytic oxidative degradation technology is widely used in the treatment of VOCs,and the choice of catalyst is the key to the treatment effect.Due to its low cost and high activity,transition metal oxides have become a research hotspot.In order to further improve the catalytic activity of the catalyst and reduce the preparation cost of the catalyst,this paper carried out related research on the preparation of multi-component transition metal oxide catalysts with low active component content and high catalytic activity.In order to better select VOCs for experiments and to understand the pollution status of VOCs,this paper studies the concentration levels of VOCs emitted by the three main processing stages?including molding,painting and vulcanization?in rubber footwear industries?RFI?.Based on this VOC emission characteristics,the ozone formation potential and health risks of VOCs were evaluated.At the same time,the VOCs emission list during the RFI production process in China from 2000 to 2016 was compiled.The results show that olefins have a high ozone generation potential.Studies of VOCs in the actual atmosphere of Beijing also show that olefins have higher concentration levels and high ozone generation potential,and 1,3-butadiene in olefins also has a carcinogenic risk to humans.Therefore,using 1,3-butadiene in olefins as model pollutants,a series of multi-component transition metal oxide catalysts such as Ce_0.027W_0.02Mn_0.054TiO_x?TiO₂?Ce_0.027TiO_x?Mn_0.054TiO_x?Ce_0.027W_0.02TiO_x?Ce_0.027Mn_0.054TiO_x?W_0.02Mn_0.054TiO_x were prepared for degradation.The preparation process such as the type of precipitant,the pH value of the reaction,the calcination temperature,and the W doping amount were optimized.Ce_0.027W_0.02Mn_0.054TiO_x prepared under optimal conditions has the best catalytic effect on 1,3-butadiene,and the degradation rate reach more than 90%at150?.Various characterization methods prove that the excellent catalytic performance of Ce_0.027W_0.02Mn_0.054TiO_x is related to its high specific surface area,high proportion of active oxygen species and strong oxidation ability.In the catalyst's anti-poisoning ability test,Ce_0.027W_0.02Mn_0.054TiO_x has good resistance to NO and H₂O,however,in the presence of SO₂,the oxidation activity of the catalyst is significantly reduced.Studying the synthesis mechanism of the catalyst and the degradation mechanism of pollutants can deepen the understanding of the process of catalyst degradation of VOCs.Through energy dispersive X-ray spectroscopy analysis of precursors with different pH values in the preparation process of the catalyst,it is found that the catalyst was a metal salt of W,Ce,Mn that gradually form on titanium dioxide.The degradation mechanism of 1,3-butadiene by Ce_0.027W_0.02Mn_0.054TiO_x is also explored by in-situ infrared testing.The results show that the degradation process of 1,3-butadiene by the catalyst is mainly to first degrade it into low molecular olefins and alkanes,and finally further oxidize it into CO₂ and H₂O.In the presence of SO₂ or NO,corresponding metal inorganic salts will be formed on the catalyst surface.Especially the presence of SO₂will cause the activity of the catalyst to decrease significantly,which may be due to its irreversible reaction with the active components on the surface of the catalyst.In order to improve the sulfur resistance of the catalyst,this study doped the element V with Ce_0.027W_0.02Mn_0.054TiO_x catalyst,and then explored its 1,3-butadiene degradation activity and sulfur resistance.The results show that Ce_0.027W_0.02Mn_0.054TiO_x catalyst not only has high degradation activity,but also has excellent sulfur resistance.