Study Of Catalytic Oxidation Of Toluene With Ozone By Platinum-cerium Bicomponent Catalyst

Volatile organic compounds?VOCs?are an important precursor for the formation of PM_2.5and O₃ and one of the major air pollution problems.The catalytic ozonation purification technology can effectively deal with low-concentration VOCs under mild conditions and is suitable for VOCs treatment with high air volume and low concentration.In catalytic ozonation system,the catalyst is the key to the efficient removal and deep oxidation of VOCs,so the selection of catalyst plays a very important role.It is of great importance to study the reaction mechanism of catalytic ozonation technology to improve the performance of catalysts and guide their practical application.In general,the bi-component catalyst shows superior performance than the one-component catalyst due to the interaction effect between the two components and the oxygen vacancy in catalysts is the important active site for catalytic decomposition of ozone into active oxygen species.Rare earth metal?CeO₂?is easy to form oxygen vacancy,which has better ability to store and release oxygen.In a lot of oxidation reaction systems,the Pt and CeO₂can produce strong interaction,which can improve the performance of the catalyst.Thus,in this paper,the four kinds of catalysts?BEA,Pt/BEA,Ce/BEA and Pt-Ce/BEA?were prepared,the bi-component interaction between Pt and CeO₂,catalytic decomposition of ozone and catalytic oxidation of toluene by ozone were further discussed.The main contents and conclusions are as follows:?1?By the X-ray diffraction?XRD?,transmission electron microscope?TEM?,hydrogen temperature programmed reduction?H₂-TPR?,oxygen-temperature programmed desorption?O₂-TPD?,X-ray photoelectron spectroscopy?XPS?and ultraviolet Raman spectra?UV Raman?characterization methods,the physical and chemical properties of the catalyst were tested.Pt and CeO₂ were closely contacted instead of separately presenting on the surface,and electron transfer could occur between them.CeO₂ could cause lattice distortion of Pt,while Pt could improve the reduction performance of CeO₂,and reduce the formation energy of oxygen vacancy of CeO₂ and promote the formation of oxygen vacancy.?2?By the investigation of the catalytic decomposition of ozone,it was found that the BEA has no activity sites for ozone decomposition,which were the Pt nanoparticles?NPs?and the oxygen vacancy on the CeO₂ respectively for Pt/BEA and Ce/BEA.Pt-Ce/BEA had both the two active sites of Pt NPs and oxygen vacancy on CeO₂,but oxygen vacancy on CeO₂ plays a leading role,so it has the best ozone decomposition performance.?3?By the investigation of the adsorption and desorption for toluene of catalysts and the catalytic oxidation of toluene by ozone,it was found that the catalytic oxidation of toluene by ozone conformed to the theory of Langmuir Hinshelwood dual-site,the adsorption and activation of toluene and ozone were not on the same active site.The adsorption and activation of toluene was on the carrier BEA,while the adsorption and activation of ozone was on the Pt NPs or oxygen vacancy of CeO₂,and then the activated oxygen species oxidized and degraded the adsorbed toluene.The Pt-Ce/BEA catalytic oxidation of toluene by ozone showed the best performance due to the strong interaction between Pt NPs and CeO₂,and the toluene could be completely degraded to CO₂ without residual ozone in a long period of time at 90^?.