Preparation Of La-based Perovskite Based On Biological Template And Catalytic Performance

In recent years,the rapid development of modern industry has promoted the widespread use of motor vehicles.However,pollution caused by vehicle exhaust has caused great harm to the ecological environment and public health.Nitrogen oxides（NO_x）,which are the main pollutants of automobile exhaust,are mainly composed of nitric oxide（NO）,nitrogen dioxide（NO₂）,and nitrous oxide（N₂O）,and NO accounts for about 90%of total NO_xemissions.Currently,noble metal catalysts are one of the good choices for NO oxidation,but their widespread use is limited due to resource shortages and high prices.However,perovskite-type oxides（general formula ABO₃）have been reported as effective catalysts for NO oxidation due to their low cost and high activity.Through simple,low-cost and environmentally friendly methods to achieve the goal of controllable material morphology has become the focus of scientific research.In this paper,La-based perovskite catalysts were prepared using sunflower seed shell and egg protein as biological templates.By X-ray diffraction（XRD）,scanning electron microscope（SEM）,Fourier transform infrared spectroscopy（FT-IR）,N₂adsorption-desorption analysis,X-ray photoelectron spectroscopy（XPS）,oxygen temperature programmed desorption（O₂-TPD）and H₂-TPR were used to selectively characterize the prepared La-based perovskite.In addition,the catalytic performance of some samples for NO was tested by an activity evaluation device.In the second chapter of this paper,La Fe O₃perovskite was prepared using sunflower seed husk as a template and template-free samples were synthesized under the same process.The results showed that La Fe O₃perovskite prepared by sunflower seed shell template successfully reproduced the porous fiber structure of sunflower seed and showed larger specific surface area,better reducibility,more oxygen adsorption and higher O_ads/O_lattratio compared with the sample without template.In addition,La Mn O₃was prepared using sunflower seed husk as a template and it has better NO catalytic activity than La Fe O₃prepared using sunflower husk as a template.In the third chapter of this paper,La Mn O₃perovskite is selected as the research object based on the research in Chapter 2.La Mn O₃perovskite catalyst with porous square and porous nanoparticle structure was prepared using egg protein as a biological template and analyzes the crystal structure,chemical bonds,micromorphology,specific surface area,surface element composition,oxygen adsorption behavior,and redox properties of the prepared samples.The catalytic activity of porous square and porous nano-particles La Mn O₃for NO was tested by an activity evaluation device,and their catalytic activity for NO oxidation was compared with that of samples prepared by the conventional citric acid method.The results show that the porous square and porous nanoparticles La Mn O₃prepared by the egg protein template strategy have better catalytic performance for NO.In addition,the porous square La Mn O₃also shows higher catalytic performance than the porous nano-particles La Mn O₃.In the fourth chapter,based on the research in the third chapter,taking the porous square La Mn O₃as the research basis,the effects of citric acid amount,egg protein amount,citric acid amount and egg protein amount,drying temperature and ammonia water amount on the crystal structure and micro morphology of La Mn O₃were studied.The differences in crystal structure and micromorphology of La Mn O₃prepared under different synthesis conditions are analyzed,and the influence of these factors on the crystal structure and micromorphology of La Mn O₃is summarized,which lays the foundation for the further work.