Dissertation > Excellent graduate degree dissertation topics show

Study of Dynamic Oxygen Storage Capacity and Three-way Catalytic Activities over Pd-CZ-Al2O3 Model Automobile Catalyst

Author: ZhaoMinWei
Tutor: WangYaQuan；ShenMeiQing
School: Tianjin University
Course: Chemical processes
Keywords: Gasoline Three way catalyst Ceria-zirconia Precious metal Alumina Dynamic oxygen storage capacity
CLC: O643.36
Type: PhD thesis
Year: 2008
Downloads: 347
Quote: 1
Read: Download Dissertation

Abstract


As the key part of the StateⅢ/Ⅳthree-way-catalyst （TWCs）, ceria-zirconia mixed oxides minimize the effect of air to fuel （A/F） fluctuation to catalytic activities and extend the A/F window. On the basis of ceria-zirconia and dynamic oxygen storage/release measurement, the relationship between ceria-zirconia, precious metal and alumina as well as its effects on dynamic oxygen storage capacity （DOSC） and catalytic activities were also studied, aiming at developing advanced StateⅢ/ⅣTWCs.Combining the XRD, BET, HRTEM, EPR and dynamic oxygen storage/release measurement, effects of intrinsic textural and structural properties, such as surface area, Ce/Zr ratio and alkine earth metal doping etc, on DOSC and dynamic oxygen storage rate （DOSR） were studied. Moreover, in-situ EPR reactor and a set of methods were successfully developed for measuring oxygen vacancy in material. It was shown that DOSC and DOSR are proportional to the surface area and Ce/Zr ratio. Alkine earth metal doping improves the DOSC of ceria-zirconia mixed oxides. Total oxygen storage capacity （TOSC） is proportional to the number of oxygen vacancies in material. The results of in-situ EPR show that oxygen vacancies are essential to Ce/Zr ratio and proportional to oxygen migration.By supporting the Pd on ceria-zirconia, interaction between Pd and ceria-zirconia and its effects on DOSC and TOSC were investigated. When reducibility is lower than 10%～12% and temperature is lower than 450～500℃, Pd supporting promotes the DOSC and DOSR obviously. After hydrothermal aging, both of ceria-zirconia sintering and Pd sintering deteriorate the Pd-（Ce, Zr） Ox interface, as a result of deterioration of DOSC and TOSC. However, compared with sintering of ceria-zirconia, sintering of precious metal has more influence on the OSC deterioration.By mixing the ceria-zirconia and alumina in different mixing scale, DOSC and thermal stability of ceria-zirconia-alumina mixed oxides were investigated. Combining the XRD, BET, XPS, EPR and TEM measurements, mixing scale between ceria-zirconia and alumina is the key factor of improvement of DOSC and thermal stability. Mixing with alumina at small scale improve the distribution and morphology of ceria-zirconia as well as DOSC performance. Whilst mixing with ceria-zirconia at small scale and Ce3+ distribution modifies the surface of alumina and improve the thermal stability.After introducing the Pd into ceria-zirconia-alumina binary oxides, the process of precious metal distribution on binary supports was optimized. The effects among ceria-zirconia, Pd and alumina on DOSC and catalytic activities were investigated. The results show combination of Pd and support, morphology and valence affects the DOSC and catalytic activities. Pd dispersion has less influence on DOSC and catalytic activities. Meanwhile, thermal stability of supports and Pd distribution between ceria-zirconia and alumina play the important role to improve the DOSC and catalytic activities.By charomatagraph distributing the precious metal on single oxide, effects Pd-（Ce, Zr） Ox and Pd （Al2O3） on DOSC and catalytic activities were investigated. DOSC and DOSR are more promoted by Pd-（Ce, Zr） Ox than Pd （Al2O3）. Pd-（Ce, Zr） Ox interface promotes the DOSC and CO catalytic conversion, CO conversion correlate to the DOSC performance; meanwhile, Pd （Al2O3） interface promotes the NO and HC catalytic conversion, NO and HC conversion show less relationship with DOSC performance.

Related Dissertations

  1. Ceramic Theramal Sterss Cleaving Technology Based on Laser,TQ174.62
  2. Study on the Chimisorption Removal of FCC Gasoline Sulfur Compound,TE624.55
  3. Gel - Foam Preparation of porous alumina insulation materials,TQ174.1
  4. Study on the Synthesis of the Polypyrrole-Cobalt Oxides and Their Catalytic Behavior for the Electroreduction of H2O2,O643.32
  5. Study on Reducing the Mower Vibration by Optimizing the Crank-rod Mechanism of 170F Engine,S817.111
  6. Lithium anode material calcined alumina crucible Development,TQ174.6
  7. Research of the Starting Pull Force on Vertical Small Gasoline Engine - LC1P70FA,TK417
  8. Application of Rotating Packed Bed in Recovering of Vapor Gasoline,TE89
  9. CFD Simulation and Verification Experiment of Fluidized Bed with a Adjustable Slit Height Blast Cap,TQ051
  10. Synthesis, Characterization of Co3O4 /Al2O3 Nanomaterials and Catalytic Degradation on Rhodamine B,TB383.1
  11. Study on the Air Fuel Ratio Control for PFI Gasoline Engine Based on Model,TK417
  12. Based on the porous structure to improve efficiency of LED light,TN312.8
  13. Injector Selection and Matching Technology for Advanced GDI Engines,TK413.84
  14. Instrument-to-Instrument Calibration Transfer and Standardization of Spectra,O657.33
  15. Precipitation from aqueous solution ultrafine spherical alumina Process,TB383.3
  16. Porcelain steel surface preparation in the lining layer of Technology,TG174.45
  17. One -dimensional properties of the material humidity,TB383.1
  18. Control System Design and Control Method Research for the Gasoline Electronic Throttle,U464.171
  19. Study on Mechanism of Adsorption Desulfurization in Microscale Pore,X701.3
  20. Alumina vacuum carbothermal reduction experimental study of the mechanism and process - aluminum chloride process,TF821
  21. Alumina vacuum carbothermal reduction experimental study,TF821

CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
© 2012 www.DissertationTopic.Net  Mobile