MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY NGUYEN THE TIEN SYNTHESIZE AND INVESTIGATE THE CATALYTIC ACTIVITY OF THREE-WAY CATALYSTS BASED ON MIXED METAL OXIDES FOR THE TREATMENT OF EXHAUST GASES FROM INTERNAL COMBUSTION ENGINE CHEMICAL ENGINEERING DISSERTATION HANOI-2014 MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY NGUYEN THE TIEN SYNTHESIZE AND INVESTIGATE THE CATALYTIC ACTIVITY OF THREE-WAY CATALYSTS BASED ON MIXED METAL OXIDES FOR THE TREATMENT OF EXHAUST GASES FROM INTERNAL COMBUSTION ENGINE Speciality: Chemical Engineering Code: 62520301 CHEMICAL ENGINEERING DISSERTATION SUPERVISOR: ASSOCIATE PROFESSOR, DOCTOR LE MINH THANG HANOI-2014 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine ACKNOWLEDGEMENTS This PhD thesis has been carried out at the Laboratory of Environmental Friendly Material and Technologies, Advance Institute of Science and Technology, Department of Organic and Petrochemical Technology, Laboratory of the Petrochemical Refinering and Catalytic Materials, School of Chemical Engineering, Hanoi University of Science and Technology (Vietnam) and Department of Inorganic and Physical Chemistry, Ghent University (Belgium). The work has been completed under supervision of Associate Prof. Le Minh Thang. Firstly, I would like to thank Associate Prof.
Le Minh Thang. She helped me a lot in the scientific work with her thorough guidance, her encouragement and kind help. I want to thank all teachers of Department of Organic and Petrochemical Technology and the technicians of Laboratory of Petrochemistry and Catalysis Material, Institute of Chemical Engineering for their guidance, and their helps in my work. I want to thank Prof.
Isabel and all staff in Department of Inorganic and Physical Chemistry, Ghent University for their kind help and friendly attitude when I lived and studied in Ghent. I gratefully acknowledge the receipt of grants from VLIR (Project ZEIN2009PR367) which enabled the research team to carry out this work. I acknowledge to all members in my research group for their friendly attitude and their assistances. Finally, I want to thank my family for their love and encouragement during the whole period.
Nguyen The Tien September 2013 Nguyen The Tien 1 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine COMMITMENT I assure that this is my own research. All the data and results in the thesis are completely true, was agreed to use in this paper by co-author. This research hasn’t been published by other authors than me. Nguyen The Tien Nguyen The Tien 2 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine CONTENT OF THESIS LIST OF TABLES 6 LIST OF FIGURES 7 INTRODUCTION 10 1 LITERATURE REVIEW 11 1.1 Air pollution and air pollutants 11 1.1 Air pollution from exhaust gases of internal combustion engine in Vietnam 11 1.2 Volatile organic compounds (VOCs) 11 1.4 Some other pollutants 12 1.3 Composition of exhaust gas 13 1.2 Treatments of air pollution 14 1.1 Separated treatment of pollutants 14 1.2 Simultaneous treatments of three pollutants 16 1.1 Two successive converters 17 1.2 Three-way catalytic (TWC) systems 17 1.3 Catalyts for the exhaust gas treatment 19 1.1 Catalytic systems based on noble metals (NMs) 20 1.2 Catalytic systems based on perovskite 21 1.3 Catalytic systems based on metallic oxides 23 1.1 Metallic oxides based on CeO2 23 1.2 Catalytic systems based on MnO2 24 1.3 Catalytic systems based on cobalt oxides 25 1.4 Other metallic oxides 26 1.4 Other catalytic systems 27 1.4 Mechanism of the reactions 28 1.1 Mechanism of hydrocarbon oxidation over transition metal oxides 28 1.2 Mechanism of the oxidation reaction of carbon monoxide 29 1.3 Mechanism of the reduction of NOx 31 1.4 Reaction mechanism of three-way catalysts 33 1.5 Aims of the thesis 35 2 EXPERIMENTAL 37 2.1 Synthesis of the catalysts 37 2.1 Sol-gel synthesis of mixed catalysts 37 2.2 Catalysts supported on γ-Al2O3 37 2.2 Physico-Chemistry Experiment Techniques 38 2.1 X-ray Diffraction 38 Nguyen The Tien 3 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine 2.2 Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) 40 2.3 BET method for the determination of surface area 40 2.4 X-ray Photoelectron Spectroscopy (XPS) 40 2.7 Temperature Programmed Techniques 42 2.1 Micro reactor setup 43 2.2 The analysis of the reactants and products 44 2.4 Three -pollutant treatment 47 3 RESULTS AND DISCUSSIONS 48 3.1 Selection of components for the three-way catalysts 48 3.1 Study the complete oxidation of hydrocarbon 48 3.1 Single and bi-metallic oxide 48 3.2 Triple metallic oxides 51 3.2 Study the complete oxidation of CO 53 3.1 Catalysts based on single and bi-metallic oxide 53 3.2 Triple oxide catalysts MnCoCe 54 3.3 Influence of MnO2, Co3O4, CeO2 content on catalytic activity of MnCoCe catalyst 59 3.3 Study the oxidation of soot 62 3.2 MnO2-Co3O4-CeO2 based catalysts for the simultaneous treatment of pollutants 66 3.1 MnO2-Co3O4-CeO2 catalysts with MnO2/Co3O4=1/3 66 3.2 MnO2-Co3O4-CeO2 with the other MnO2/Co3O4 ratio 68 3.3 Influence of different reaction conditions on the activity of MnCoCe 1-3-0.4 Activity for the treatment of soot and the influence of soot on activity of MnCoCe 1-3-0.5 Influence of aging condition on activity of MnCoCe catalysts 74 3.1 The influence of steam at high temperature 74 3.2 The characterization and catalytic activity of MnCoCe 1-3-0.75 in different aging conditions 77 3.6 Activity of MnCoCe 1-3-0.75 at room temperature 80 3.3 Study on the improvement of NOx treatment of MnO2- Co3O4-CeO2 catalyst by addition of BaO and WO3 81 3.4 Study on the improvement of the activity of MnO2-Co3O4- CeO2 catalyst after aging by addition of ZrO2 84 3.5 Comparison between MnO2-Co3O4-CeO2 catalyst and noble catalyst 87 4 CONCLUSIONS 91 REFERENCES 92 LIST OF PUBLISHMENTS 100 Nguyen The Tien 4 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine ABBREVIATION TWCs: Three-Way Catalysts NOx: Nitrous Oxides VOCs: Volatile Organic Compounds PM10: Particulate Matter less than 10 nm in diameter NMVOCs: Non-Methane Volatile Organic Compounds HC: hydrocarbon A/F ratio: Air/Fuel ratio λ: the theoretical stoichiometric value, defined as ratio of actual A/F to stoichiometric; λ can be calculated λ= (2O2+NO)/ (10C3H8+CO); λ = 1 at stoichiometry (A/F = 14.7) SOF: Soluble Organic Fraction DPM: Diesel Particulate Matter CRT: Continuously Regenerating Trap NM: Noble Metal Cpsi: Cell Per Inch Square In.: inch CZ (Ce-Zr): mixtures of CeO2 and ZrO2 CZALa: mixtures of CeO2, ZrO2, Al2O3, La2O3 NGVs: natural gas vehicles OSC: oxygen storage capacity WGS: water gas shift LNTs: Lean NOx traps NSR: NOx storage-reduction SCR: selective catalytic reduction SG: sol-gel MC: mechanical FTIR: Fourier-Transform Infrared Eq.: equation T100: the temperature that correspond to the pollutant was completely treatment Tmax: The maxium peak temperature was presented as reference temperature of the maximum reaction rate in TG-DTA (DSC) diagram Vol.
: weight Cat: catalyst at: atomic min.: minutes h: hour Nguyen The Tien 5 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine LIST OF TABLES Table 1.1 Example of exhaust conditions for two- and four-stroke, diesel and lean-four-stroke engines [67].2 Adsorption/desorption reactions on Pt catalyst [101].3 Surface reactions of propylene oxidation [101].4 Surface reactions of CO oxidation [101].5 Surface reactions of hydroxyl spices, NO and NO2 [101] .1 Aging conditions of MnCoCe catalysts.2 Strong line of some metallic oxides .3 Binding energy of some atoms [102].4 Specific wave number of some function group or compounds .5 Composition of mixture gases at different reaction conditions for C3H6 oxidation .6 Composition of mixture gases at different reaction conditions for CO oxidation.7 Composition of mixture gases at different reaction conditions for treatment of CO, C 3H6, NO.8 Temperature Program of analysis method for the detection of reactants and products.9 Retention time of some chemicals.1 Quantity of hydrogen consumed volume (ml/g) at different reduction peaks in TPR-H2 profiles of pure CeO2, Co3O4, MnO2 and CeO2-Co3O4, MnO2-Co3O4 chemical mixtures .2 Consumed hydrogen volume (ml/g) of the mixture MnO2-Co3O4-CeO2 1-3-0.3 Adsorbed oxygen volume (ml/g) of some pure single oxides (MnO2, Co3O4, CeO2) and chemical mixed oxides MnCoCe 1-3-0.4 Surface atomic composition of the sol-gel and mechanical sample .5 Tmax of mixture of single oxides and soot in TG-DTA (DSC) diagrams.6 Catalytic activity of single oxides for soot treatment .7 Tmax of mixture of multiple oxides and soot determined from TG-DTA diagrams.8 Catalytic activity of multiple oxides for soot treatment at 500oC.9 Soot conversion of some mixture of MnCoCe 1-3-0.75 and soot in the flow containing CO: 4.77% at 500oC for 425 min.10 Specific surface area of MnCoCe catalysts before and after aging in the flow containing 57% vol.H2O at 800oC for 24h .11 Consumed hydrogen volume (ml/g) of the MnCoCe 1-3-0.75 fresh and aging at 800oC in flow containing 57% steam for 24h .12 Specific surface area of MnCoCe 1-3-0.75 fresh and after aging in different conditions .13 Specific surface area of catalysts containing MnO2, Co3O4, CeO2, BaO and WO3.14 Specific surface area of some catalyst containing MnO2, Co3O4, CeO2, ZrO2 before and after aging at 800oC in flow containing 57% steam for 24h .15 Specific surface area of noble catalyst and metallic oxide catalysts supported on γ- Al2O3 .87 Nguyen The Tien 6 Synthesize and investigate the catalytic activity of three-way catalysts based on mixed metal oxides for the treatment of exhaust gases from internal combustion engine LIST OF FIGURES Figure 1.1 Micrograph of diesel soot, showing particles consisting of clumps of spherules [110] .2 A typical arrangement for abatement of NOx from a heavy-duty diesel engine using urea as reducing agent [67] .3 Principle of filter operation (1) and filter re-generation (2) for a soot removal system, using fuel powered burners [67] .4 The working principle of the continuously regenerating particulate trap [67].5 Scheme of successive two-converter model [1] .6 Three- way catalyst performance determined by engine air to fuel ratio [43] .7 Diagram of a modern TWC/engine/oxygen sensor control loop for engine.8 Wash-coats on automotive catalyst can have different surface structures as shown with SEM micrographs [43] .9 Improvement trend of catalytic converter [43] .10 Scheme of catalytic hydrocarbon oxidation; H-hydrocarbon, C-catalyst, R1 to R5-labile intermediate, probably of the peroxide type [97] .11 Reaction cycle and potential energy diagram for the catalytic oxidation of CO by O2 [98] .12 Reaction pathways of CO oxidation over the metallic oxides [34] .13 Chemical reaction pathways of selective catalytic reduction of NOx by propane [99] 32 Figure 1.14 Principle of operation of an NSR catalyst: NOx are stored under oxidising conditions (1) and then reduced on a TWC when the A/F is temporarily switched to rich conditions (2) [67].15 Schematic representation of the seven main steps involved in the conversion of the exhaust gas pollutants in a channel of a TWC [100].1 Aging process of the catalyst (1: air pump; 2,6: tube furnace, 3: water tank, 4: heater, 5,7: screen controller, V1,V2: gas valve).2 Micro reactor set up for measurement of catalytic activity.3 The relationship between concentration of C3H6 and peak area.4 The relationship between concentration of CO2 and peak area .5 The relationship between concentration of CO and peak area .1 Catalytic activity of some mixed oxide MnCo, CoCe and single metallic oxide in deficient oxygen condition.2 Catalytic activity of MnCo 1-3 and CeCo 1-4 catalysts in excess oxygen condition.3 C3H6 conversion of CeCo1-4 in different reaction conditions (condition a: excess oxygen condition with the presence of CO: 0.3%CO, 5%O2, N2 balance, condition b: excess oxygen condition with the presence of CO and H2O: 0.4 XRD patterns of CeCo=1-4, MnCo=1-3 chemical mixtures and some pure single oxides .5 Conversion of C3H6, C3H8 and C6H6 on MnCoCe 1-3-0.75 catalyst under sufficient oxygen condition.6 SEM images of MnCo 1-3 fresh (a),MnCoCe 1-3-0.7 XRD pattern of MnCoCe 1-3-0.75 and original oxides .