Synthesis, Characterization and Catalytic Combustion Properties of Manganese Oxide Octahedral Molecular Sieve
|Course||Physical and chemical|
|Keywords||Cryptomelane Octahedral molecular sieve Volatile Organic Compounds Catalytic combustion|
Current world of volatile organic compounds (VOCs) removal technology development and research have invested a lot of manpower and material resources, and has made some achievements, but compared with the rapid economic growth, VOCs governance links are still lagged . Prevention and control of air pollutants generated in the production rule requiring industrial combustible gas shall be recycled, requiring more economical, efficient removal of VOCs. This paper describes the VOCs to the environment and serious harm to the human body and the current domestic and international governance methods and characteristics of the process, wherein the catalytic combustion method for its efficient, economical, with a high removal rate, no secondary pollution, low energy consumption, and received wide attention. Thesis focuses on cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) Catalysts for a detailed exposition of this manganese oxide is widely used in ion exchange materials, battery materials, radioactive waste, fixing materials, catalytic materials , because there is lattice Mn 4 sup>, Mn 3 sup> and Mn 2 sup> ions, has a good oxidation reduction. Contents of this thesis is divided into three parts: a study of new catalysts cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) of the synthetic preparation methods, and toluene and formaldehyde as molecular probes to study its VOCs gas catalytic combustion reaction in the application, using XRD, FE-SEM, O 2 -TPD, TPD-MS and H 2 -TPR and other characterization techniques used to study molecular sieve catalyst shape and surface properties and thermal desorption of oxygen reduction performance. Experimental results show that the synthesis of the catalyst prepared in surface properties and catalytic combustion have a significant impact. Catalyst prepared by refluxing toluene for the catalytic combustion has a high activity, and the solid phase synthesis of the catalyst in catalytic combustion of formaldehyde is more catalytically active, catalytic combustion surface of the catalyst depends on the morphology and molecular sieve oxygen species species. Samples prepared by refluxing due to the large specific surface area and surface desorption more reactive oxygen species (α oxygen species), is conducive to the catalytic combustion of toluene, and the solid-phase synthesis of higher levels of the catalyst surface lattice oxygen species (β oxygen species) formaldehyde molecules of small size greater role in promoting the catalytic combustion. Second, by impregnation, ion exchange method OMS-2 catalyst loading to prepare active component Ce Ce-OMS-2 catalyst, and further investigate its performance of catalytic combustion of formaldehyde. By XRD, N 2 absorption - desorption, O 2 -TPD-MS and H 2 -TPR characterization techniques such as Ce investigated after load , molecular sieve catalyst morphology and surface properties and thermal desorption of oxygen reduction performance. It was found that, regardless of impregnation or ion exchange prepared Ce-OMS-2 catalysts, the catalytic activity of formaldehyde has decreased to some extent, especially in a large load, OMS-2 was severely clogged pore structure , the specific surface area is simultaneously decreased, β reduce the releases oxygen species, the catalytic combustion to reduce active sites, resulting in decreased activity of the catalyst. Third, the combination of experimental data and the literature, for VOCs gas in the catalytic reaction mechanism of the combustion process to do a preliminary study, Mars-van Krevelen mechanism also applies to OMS-2 as catalyst catalytic combustion of volatile organic compounds (VOCs) reaction .