Study On Preparation And Properties Of ?Pt?/BaCO₃-CeO₂/?-Al₂O₃ NSR Catalyst

Diesel engine has caused widespread concern in the automotive industry because of its fuel economy and good thermal efficiency and other advantages.However,diesel engine exhaust gas contains a lot of NOx gas,which can bring about serious pollution to the environment and pose a significant threat to human health.Therefore,It is of great significance that how to effectively reduce the diesel engine NOx emissions.NOx storage and reduction has been widely concerned by scholars because of its high removal efficiency,no additional reducing agent and small sizes.It is also expected to be one of the important techniques to solve the problem of NOx emissions.However,there are relatively few investigations on the preparation of NSR catalysts.In this thesis,the catalysts were prepared by citric acid sol-gel method at different calcination heating rates and different pH values.The as-prepared NSR catalysts were characterized by X-ray Diffraction?XRD?,Scanning Electron Microscope?SEM?,Transmission Electron Microscope?TEM?,Brunauer,Emmett and Teller?BET?,Fourier Transform Infrared Spectrometer?FTIR?and H2 Temperature Programmed Reduction?H₂-TPR?to analyze the phase composition,microstructure,specific surface area and the pore size distribution,functional bonds contained in the catalyst and the reduction performance.And then the NOx storage capacity of the NSR catalyst was tested and analyzed by constructing a simulated gas test platform.The main conclusions are as follows:?1?For the BaCO₃-CeO₂/?-Al₂O₃ catalysts obtained at different calcination heating rates,the as-prepared NSR catalyst powders can be observed to be typical mesoporous materials,in which Ba and Ce are mainly in the forms of BaCO₃ and CeO₂,and partial CeO₂ is amorphous.BaCO₃ and CeO₂ are evenly distributed on the carrier surface,and there is no obvious agglomeration.When the rate of calcination heating rates is 6 ?/min,the BaCO₃ and CeO₂ particles are finer and more uniform,and the specific surface area and pore size of the catalyst reach the maximum.In particular,the reduction temperature of the catalyst is the lowest,and the catalyst has the best low temperature reduction performance.?2?The Pt/BaCO₃-CeO₂/?-Al₂O₃ catalysts prepared at different pH values show that the catalysts are composed of three kinds of phases: ?-Al₂O₃,BaCO₃ and CeO₂,and that no diffraction peaks of Pt are found.While pH = 5,there are many long rods,which can be derived from the interactions between Pt and Ce in the catalyst,and the catalyst has the largest specific surface area and the optimal pore structure.In the H₂-TPR curves,the reduction peaks of PtO₂ and CeO₂ appear in the catalyst,and the reduction of CeO₂ are involved in the reduction of the surface and internal phases.What is more,in this case the PtO₂ and CeO₂ have the lowest reduction temperature,indicating that the catalyst has better low temperature reduction performance under acidic condition.?3?Through the NOx storage experiments,it can be seen that the reaction time of the catalyst is the longest,the absorption amount of NO is the largest,and the storage performance is the optimal when the calcination heating rate and pH value are 6 °C/min and 5,respectively.At the same time,the NOx curve climbs slowly with the increase of reaction time,indicating that the catalyst reacts with the reaction gas more fully and that the NOx storage performance of the catalyst is the best.