Catalytic Oxidation Of Toluene Over Pt@Ce-BTC And Its Heat Treatment Derivatives

Volatile organic compounds?VOCs?are the important precursors of ozone and fine particulate matter,which are harmful for human health and ecological environment.Catalytic oxidation is regarded as one of the most effective technologies for VOCs treatment due to its high efficiency and low generation of by-products.One crucial issue of catalytic oxidation technology is the preparation of high-performance catalysts.Supported noble metal catalysts show excellent catalytic performance toward VOCs,but they often suffer from aggregation of avtive components.Therefore,supported noble metal catalysts require high surface area and high porosity of the support.Metal organic frameworks?MOFs?and their heat treatment derivatives,because of their large surface area and porosity,are considered as promising porous carrier materials and can disperse and anchor active components.This paper focuses on the catalytic oxidation of toluene over ceria-supported Pt catalysts.Pt nanoparticles were confined within the MOFs by in situ growth process,and porous Pt@CeO₂ materials were prepared by pyrolysis of Pt@Ce-BTC precursor.Surface chemistry of the porous derivatives was regulated by changing the pyrolysis atmosphere.The effects of heat treatment strategy on the structure and catalytic performance of porous Pt@CeO₂ catalysts were studied.Moreover,the gaseous oxygen activation ability of porous Pt@CeO₂ catalysts had been recognized and investigated.In this paper,Ce-BTC was chosen as MOFs matrix,and Pt nanoparticles were embedded in Ce-BTC according to a“bottle-around-ship”strategy.Good crystallinity and purity of Ce-BTC were confirmed by XRD and FTIR.BET results showed that Ce-BTC possessed high surface area and abundant pores.SEM and HRTEM revealed that the as-prepared Pt@Ce-BTC was featured as microrods with uniform size as well as highly dispered Pt nanoparticles.During the toluene oxidation tests,Pt@Ce-BTC exhibited good catalytic activity and stability.Ce-BTC and Pt@Ce-BTC were decomposed by one-step or two-step heat treatment strategies to prepared porous derivatives.Results showed that the Pt@CeO₂?N₂-Air?sample exhibited the best catalytic performance,which could completely decompose 100 ppm toluene under 140?.Morphology and structure characterizations confirmed that the organic framework was completely removed after thermal treatment,and the obtained porous derivatives had a large surface area and hierarchical pore structure.The concentrated accumulation of CeO₂ nanocrystallites showed good immobilized effect,so that the migration and aggregation of Pt nanoparticles would be prohibited.Raman and XPS revealed that samples by two-step heat treatment possessed a relatively higher concentration of surface oxygen vacancies and more surface active species than those after one-step heat treatment.With the help of in situ UV Raman,the gaseous oxygen activation ability of porous derivatives had been evaluated.Compared with Pt@CeO₂?Air?,Pt@CeO₂?N₂-Air?exhibited stronger ability to adsorb and activate gaseous oxygen.Benefitting from the strong oxygen activation ability,Pt@CeO₂?N₂-Air?could supply more active oxygen species for toluene oxidation,thus exhibited excellent catalytic activities.Furthermore,the stability of oxygen activation ability was investigated.Results showed that it had outstanding stability during the recycle tests,indicating Pt@CeO₂?N₂-Air?could steadily supply active oxygen species.