Study On Preparation And Catalytic Performance For Toluene Oxidation Of Supported Catalyst Based On Ultra-thin Two-Dimensional TiO₂

Volatile organic compounds（VOCs）are one of the main atmospheric pollutants emitted from a wide range of sources,which cause serious harm to the natural environment and human health.Therefore,there is an urgent need to formulate effective emission reduction measures to reduce their emissions.The waste plastic recycling and recycling industry is one of the industrial sources of VOCs emissions.Therefore,it is necessary to investigate and study the VOCs emissions and effects during plastic recycling and regeneration processing in order to formulate VOCs control measures.At present,catalytic oxidation technology is the most promising VOCs treatment technology.It has the advantages of high treatment efficiency,low energy consumption,and no secondary pollution.The core of catalytic oxidation technology is catalyst.Compared with precious metals,the transition metals manganese,copper and cobalt are cheaper and more readily available,and have good redox properties,so they are often used in catalyst research.TiO₂ has the advantages of low price,simple preparation,stable properties,which often used as a catalyst carrier for the design and preparation of catalysts.In this regard,this paper studies the VOCs emissions and effects in the process of plastic recycling and regeneration,and designed and prepared Mn-Co/TiO₂ and Mn-Cu/TiO₂catalysts using two-dimensional structured TiO₂ nanosheets as the carrier,and used them for the study of the catalytic oxidation performance of toluene.The main work of this paper is as follows:First,in order to systematically understand the VOCs emissions and impact of the plastic recycling and regeneration,which selected three companies as the research objects,it was collected samples on the spot,and brought them back to the laboratory for analysis.The results show that the VOCs emitted during the recycling and reproduction process of waste plastics are roughly the same.In the plastic recycling process,halogenated hydrocarbons（HHs）are the main component,accounting for more than 95%,while in the plastic regeneration process,halogenated hydrocarbons（HHs）,aliphatic hydrocarbons（AIHs）and oxygenated VOCs（OVOCs）are the main components.The VOCs emitted during the recycling and regeneration of waste plastics promote the generation of ozone in the surrounding atmosphere,which can reach a maximum of 1.4×10⁴ ug·m^-3,and poses a major threat to the health of workers.Two-dimensional structured TiO₂ nanosheets were prepared by hydrothermal method as catalyst support,and Mn-Co/TiO₂ series catalysts were prepared by citric acid-impregnation method for the study of toluene catalytic oxidation.The effect of preparation and reaction conditions on the catalytic activity was studied.The results show that the preparation conditions are Mn/Co molar ratio 8:1,loading amount 16wt%,calcination temperature 300℃,Mn8-Co1/TiO₂ catalyst has the highest toluene catalytic activity,and its toluene conversion rate at reaction temperature 240℃Up to100%.TiO₂nanosheets are more conducive to the dispersion of active components than P25,and form a strong interaction between active components and carriers,which improves the catalytic activity of toluene.The Mn-Cu/TiO₂ catalyst was prepared by the same preparation method and used to catalyze toluene.The physical and chemical properties of the catalyst were studied by systematic characterization methods.The results show that Mn-Cu/TiO₂ exhibits a better toluene conversion rate（100%）than Mn/TiO₂ and Cu/TiO₂at a reaction temperature of 240℃,and has good stability and water resistance.The high dispersion of active components of the Mn-Cu/TiO₂ catalyst and the synergy between Mn and Cu are the main reasons for the excellent catalytic performance of the catalyst.The active oxygen cycle is mainly formed by the interaction between9)³⁺+²⁺→9)⁴⁺+⁺,which can catalytically degrade toluene.In addition,in-situ infrared experiments proved that toluene degrades between Mn and Cu to form intermediate products of benzyl alcohol and benzoic acid,which are finally oxidized to CO₂ and H₂O.This article provides a certain reference for the formulation of VOCs control measures in the waste plastic recycling and regeneration.In addition,the new type of VOCs catalyst with excellent catalytic activity was prepared by using two-dimensional structured TiO₂ nanosheets as the carrier.This work broadens the application of two-dimensional TiO₂ nanosheets and provides a certain reference for the improvement and development of new VOCs catalysts.