Preparation Of Copper-based Catalysts Based On Ce-BTC And Its Study On CO Oxidation In Hydrogen-rich Atmosphere

In the current situation where environmental pollution and energy scarcity are becoming more and more serious,the development of clean and renewable new energy is the only way for energy development.Hydrogen energy is the most ideal fuel for proton exchange membrane fuel cells because of its high combustion calorific value,clean and pollution-free characteristics,and new energy vehicles driven by proton exchange membrane fuel cells are the key to realize the large-scale application of hydrogen energy.However,the raw hydrogen produced by hydrocarbon reforming and water gas conversion routes will contain 0.5-2%CO,which will easily poison the platinum electrode of the proton exchange membrane fuel cell.Therefore,CO oxidation in hydrogen-rich atmosphere is a more effective and economical means to remove the small amount of CO from the raw hydrogen.CuO/CeO₂ catalysts are widely used in hydrogen-rich atmosphere CO oxidation reactions due to their excellent catalytic performance and good economics,mainly because of the strong oxygen storage and release capacity of CeO₂ in the Ce⁴⁺/Ce³⁺redox process and the strong interaction between copper and cerium.However,the temperature range of CuO/CeO₂ catalysts for high CO conversion is narrow and their low temperature activity for hydrogen-rich atmosphere CO oxidation needs further improvement.In this thesis,copper-based catalysts based on Ce-BTC metal-organic frameworks were prepared for CO oxidation in hydrogen-rich atmosphere,and the low-temperature catalytic activity of the catalysts was improved by improving the catalyst preparation method,modulating the morphology of the carrier,and optimizing the composition of the precursors,the details of the study are as follows:（1）Plasma-assisted preparation of Ce-BTC-loaded copper catalysts for CO oxidation in hydrogen-rich atmosphereDielectric barrier discharge（DBD）plasma can shorten the preparation time of catalysts,enhance the active species dispersion,and reduce the particle size of catalysts,thus improving the catalytic activity of catalysts.In this chapter,the CuO/CeO₂ catalysts were prepared with the aid of dielectric barrier discharge plasma using Ce-BTC synthesized in a microchannel reactor,and the results showed that the copper oxide species in the catalysts prepared by DBD plasma showed a highly dispersed state.The CuO/CeO₂ catalyst with a plasma treatment time of 20 min had smaller grain size,higher Ce³⁺content,higher oxygen vacancy concentration,and surface lattice oxygen concentration with 100%CO conversion at 125℃.（2）Preparation of different shaped Ce-BTC-loaded copper catalysts for CO oxidation in hydrogen-rich atmosphere by impregnationThe carrier morphology can affect the dispersion of the active species and the interaction between the metal active species and the carrier,and it can help to improve the performance of the catalyst by modulating the carrier morphology.In this chapter,CuO/CeO₂ catalysts were obtained by impregnation method based on different sized or shaped Ce-BTC carriers synthesized by different flow rates of microchannel reactors and different preparation methods.CuCeO-IMP-90 mL/min catalysts had the best activity and reached 100%CO conversion at 100℃.The catalysts were prepared by impregnating the carrier at a suitable microchannel reactor flow rate,which was able to increase its specific surface area and pore volume,enhance the content of highly dispersed CuO_x species,enhance the interaction force between Cu-Ce,and generate more oxygen vacancies as well as surface lattice oxygen.（3）One-step preparation of CuCe-BTC for CO oxidation in hydrogen-rich atmosphereThe bimetallic MOF precursors can promote the dispersion of the catalyst metal active sites and obtain better catalytic performance.In this chapter,bimetallic MOF（CuCe-BTC）and its oxides were synthesized in one step by microchannel reactor,and CuCe-BTC precursors with different Cu doping were in bundle shape.The best performance was achieved when the cerium-Copper ratio was 1:0.2,and the CO conversion reached 100%at 90℃.The CuO/CeO₂ catalysts were also prepared based on the solvothermal method using different solvents,and the microchannel reactor one-step synthesis of CuO/CeO₂ catalysts with CO oxidation in hydrogen-rich atmosphere performance is more excellent.A moderate amount of Cu doping can lead to a smaller grain size,larger specific surface area and pore volume.H₂-TPR and XPS characterization showed that a moderate amount of Cu doping can enhance the number of highly dispersed CuO species,increase the Cu⁺species content,oxygen vacancy concentration and surface lattice oxygen concentration,enhance the Cu-Ce interactions.