Nghiên cứu tạo lớp mạ tổ hợp ni ceo2 cuo định hướng ứng dụng làm chất xúc tác cho quá trình oxy hóa khí thải từ động cơ đốt trong tt tiếng anh

MINISTRY OF EDUCATION MINISTRY OF NATIONAL AND TRAINING DEFENCE ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY MAI VAN PHUOC RESEARCH ON CREATING Ni-CeO2-CuO COMPOSITE PLATING ORIENTED TO APPLICATION AS A CATALYST FOR OXIDATION OF EMISSIONS FROM INTERNAL COMBUSTION ENGINES Specialized: Chemical Engineering Code: 52 03 01 SUMMARY OF ENGINEERING DOCTORAL THESIS Hanoi - 2019 THIS DISSERTATION IMPLEMENTED IN ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY Scientific supervisor: Prof.Dr.Sci Nguyen Duc Hung Reviewer 1: Prof.Dr Mai Thanh Tung Reviewer 2: Assoc Prof Dr Vu Thi Thu Ha Reviewer 3: Assoc Prof Dr Nguyen Duy Ket The defense of this dissertation will be held at the Academy of Military Science and Technology Council, at …… in 2019 Contacting with the dissertation by: - Library of Academy of Military Science and Technology - National Library of Vietnam INTRODUCTION The necessity of the thesis: Toxic substances such as carbon monoxide, hydrocarbons, solid particles and NOx are usually emitted when gas and oil fuel being used These are substances that greatly affect human health and the environment, as creating acid rain, photochemical blindness, affecting the ozone layer, leading to climate change and the increase of types of lung and cardiovascular diseases, especially cancers Therefore, it is necessary to remove these toxic substances from the exhaust air stream before discharging into the environment Improvements in the structure and operation mode of the engine cannot meet the requirements and standards of emissions Therefore, catalytic processor is the most effective tool to treat emissions to achieve environmental standards Catalytic activity phases usually are precious metals such as platin (Pt), rhodium (Rh), palladium (Pd) Recently, many studies have shown that the catalytic activity of CeO2-based systems for oxidation is significantly improved by doping not only precious metals but also transition metals Therefore, the discovery of catalysts based on low-cost but highly catalytic transition metals has attracted the attention of scientists Among them, the mixture of CuO and CeO2 is a catalyst with many preeminent properties to minimize the pollution of engine exhaust The catalytic activity of these two oxide mixtures for oxidation reactions is comparable to catalysts based on precious metals CeO2-CuO catalytic system can be made by various methods such as co-precipitation, sol-gel, combustion, thermal decomposition, precipitation decomposition, chelation, impregnation, hydrothermal, chemical plating, mechanical mixing metal oxides together, By using these fabrication methods, to disperse the CeO2-CuO catalyst on the catalyst carrier must first create a carrier layer (commonly known as cordierite 2MgO.2Al2O3.5SiO2, γ-Al2O3), then the catalyst layer disperses and adheres to monolithe substrate (monolithe ceramic or metal monolithe) CeO2-CuO catalyst can be created directly on the surface of steel plate by making Ni-CeO2-CuO electroplating from CeO2 and CuO nano catalytic particles In particular, Ni acts as a binder, disperses and binds CuO and CeO2 particles directly to the carrier without creating intermediate substrate as other methods The above are the bases for PhD student to select and propose the thesis topic "Research on creating Ni-CeO2-CuO composite plating oriented to application as a catalyst for oxidation of emissions from internal combustion engines" Objectives of the thesis: - Creating Ni-CeO2-CuO composite coatings on 430 stainless steel - Finding the optimal conditions to creat Ni-CeO2-CuO composite plating (direct current plating technique, pulse current plating technique: current density, solid particle concentration, stirring speed, plating time, ) - Determining the catalytic activity for oxidation of CO, hydrocarbons of the emissions from internal combustion engine of CeO2-CuO mixture on Ni-CeO2-CuO composite plating Main tasks of the thesis: - Investigating the effect of CuO and CeO2 particles on the discharge of Ni2+ ions in nickel sulphate solution by cathodic potentiodynamic and electrochemical impedance spectroscopy - Surveying the technological parameters of direct current plating technique affecting the content of CeO2 and CuO particles on the platings - Investigating the technological parameters of pulse current plating technique affecting the content of CeO2 and CuO particles on the platings - Researching mechanical properties of Ni-CeO2-CuO composite platings: corrosion resistance, abrasion resistance, thermal shock stability, micro hardness - Evaluating the catalytic activity for oxidation of CO, hydrocarbons of the emissions from internal combustion engine of CeO2-CuO mixture on the Ni-CeO2-CuO composite plating Research methodogoly of the thesis: - The effects of CuO and CeO2 particles on the discharge of Ni2+ ions in plating process was identified by cathodic potentiodynamic measurements and electrochemical impedance spectroscopies - The content of CuO and CeO2 particles on the surface of NiCeO2-CuO composite platings was determined by energy dispersive analyzer spectrum (EDX) - The distribution of CuO and CeO2 particles on the platings was determined by scanning electron microscopy method (SEM) and element mapping - The catalytic activity of the composite platings was found out by micro current-reaction method The significance of the thesis: - Scientific significance: results of the thesis generate scientific basis for electrochemical technology to make catalytic metal-CuO, CeO2 nanocomposite coating - Practical significance: contribute to the establishment of plating technology process of producing catalytic plating applied in the field of engine exhaust treatment The layout of the thesis : The 149-page thesis include: Introduction (4 pages); Chapter Overview (39 pages); Chapter Experimental and Research Methods (13 pages); Chapter Results and discussion (73 pages); Conclusions (2 pages); 146 references CHAPTER OVERVIEW - The overview of forming process of composite electroplating, properties and applications of functional composite coatings - Engine exhaust components; exhaust treatment methods using catalytic sets; domestic and foreign researches on engine exhaust treatment by catalyts - Catalytic properties of CeO2 and CuO mixture and methods for preparing them CHAPTER EXPERIMENTAL AND RESEARCH METHODS 2.1 Chemicals - CeO2 (Richest Goup Ltd Shanghai, China) and CuO (Nano Global, Shanghai, China) are in nano size - Nickel sulphate, Nickel chloride, Copper sulphate, Boric acid, Sodium lauryl sulphate, Sulfuric Acid, Hydrochloric Acid, Sodium hydroxide: PA, China - Electrodes: Ni, Cu, Ti mesh coated RuO2 Cathode material is 430 stainless steel sheet with thickness of 0.2 mm 2.2 Experiments - Research solution systems: Table 2.1 The study solutions and symbols Symbols Composition of plating solution S0 NiSO4.7H2O 300 g/L, H3BO3 30 g/L, sodium lauryl sulphate 0.1 g/L S0Cux NiSO4.7H2O 300 g/L, H3BO3 30 g/L, sodium lauryl sulphate 0,1 g/L, CuO nồng độ x g/L S0Cey NiSO4.7H2O 300 g/L, H3BO3 30 g/L, sodium lauryl sulphate 0.1 g/L, CeO2 y g/L S0CuxCey NiSO4.7H2O 300 g/L, H3BO3 30 g/L, sodium lauryl sulphate 0.1 g/L, CuO powder x g/L, CeO2 powder y g/L - Rectifier sources: direct current rectifier source and square pulse reversed rectifier source at Institute of Chemical-Materials/Military Science and Technology Institute Manufacture of catalytic core sets carrying Ni-CeO2-CuO coating Two 430 ferrit steel roll billets were cut along the length of the roll to have a large length with a width of 25 mm, a thickness of 0.20 mm, in which one was used for forming laminating in length profile of 6.5 m, another was used as buffer between two shaping layers with the length of m) as shown in Figure 3.49, 3.51 Characteristics of catalyst: - Catalytic core diameter: 120 mm - Length: 100 mm (including rolls) - Gas contact surface area of catalytic core: S = (Sflat plate + Sdeformation) x = (5 x 0.025 + 6.5 x 0.025) x x = 2.3 m2 Figure 3.49 Specification of Figure 3.51 Mold for rolled shape workpiece preparation to machine Creating steel foil profile was made by forming laminating method Figure 3.52 Rolling the steel foil on the jig to create a coating (a) and shaping together after coated the Ni-CeO2-CuO composite plating (b) 2.3 The research methods 2.3.1 Research methods used to study the plating process Cathodic potentiodynamic and electrochemical impedance spectroscopy 2.3.2 Methods and techniques used for evaluating the platings - Scanning electron microscopy SEM, energy dispersive analyzer EDX, element mapping; - Hardness measurement of plating; abrasion resistance measurement; characteristics of electrochemical corrosion of plating; platings thermal shock stability measurement; acceleration test assesses environmental durability - Catalytic activity of the platings determined on the microcurrent reaction system: Figure 2.3 Principle diagram for determining the catalytic ability of platings on the micro-current reaction system CHAPTER RESULTS AND DISCUSSION 3.1.Properties of nano CuO and CeO2 3.1.1 Morphology 3.1.1.1 SEM and TEM images SEM and TEM images of CuO and CeO2 particles showed that shape and size of these oxides were quite even Figure 3.1 SEM images of nano paricles: CeO2 (1a), CuO (1b); TEM images of CuO (2a, 2b) and CeO2 (2c, 2d) CuO and CeO2 particles had nano size They were not in spherical form but often angular, that gave advantages in the process of burying particles into the plating layer 3.1.1.2 EDX XRD results of CeO2 and CuO particles were shown in figure 3.5 and 3.6, respectively Figure 3.5 EDX results of CeO2 particles Hình 3.6 EDX results of CuO particles 3.1.2 Catalytic activity of CuO and CeO2 material particles for conversion of CO and CxHy gas from engine exhaust Độ chuyển hóa CO (%) 100 Bột CuO Bột CeO2 80 Hỗn hợp bột CuO/CeO2 = 1/7 60 40 20 0 50 100 150 200 250 300 350 400 450 500 550 600 Nhiệt độ (oC) Figure 3.7 The conversion degree of CO and C3H6 gas of the CeO2 and CuO materials The catalytic activity of mixture of CeO2 and CuO was higher than the individual particle with the ability to convert CO gas got 100% at low temperature (300 oC) The catalytic ability for C3H6 gas conversion of CuO and CeO2 mixture reached 96.18% at 450 oC The conversion degree increased and kept stable at a high level in the temperature range of 200 oC to 500 oC This result showed that it is possible to use nano-sized CuO and CeO2 particles in the treatment of CO, hydrocarbons in gasoline engine exhaust with high effective 3.2 Properties of sulphate solution containing CuO and CeO2 particles used to create Ni-CeO2-CuO composite coating 3.2.1 Cathodic polarization curves Polarization curves showed that the polarization decreased as concentration of NiSO4 in solution increased Therefore, it was necessary to use a solution with a concentration of NiSO4 of about 250 ÷ 350 g/L The thesis chosed the electrolyte solution of NiSO4 300 g/L for further studies i (A/cm2) - NiSO4 100g/L - NiSO4 200g/L - NiSO4 300g/L -0.08 -0.16 - NiSO4 50g/L -0.12 - NiSO4 350g/L -0.04 1- S0 - S0Cu4Ce4 - S0Cu8 - S0Ce8 -0.12 i (A/cm2) -0.16 -0.08 -0.04 0.00 0.00 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -0.4 -0.6 EAg/AgCl (V) -0.8 -1.0 -1.2 -1.4 EAg/AgCl (V) Figure 3.11 Cathodic Figure 3.9 Cathodic polarization curves polarization curves of nickel of nickel electrode in the electrolyte electrode in the electrolyte solution of NiSO4 (50 ÷ 350 g/L) + H3BO3 (30 g/L) + sodium lauryl sulphate solutions: S , S0Cu8, S0Ce8 S0Cu4Ce4 (0.1 g/L) 2+ The discharge potential of Ni in the sulphate solution and in the composite plating solution were E* = -0.70 V (Ag/AgCl) and E* = 0.66 V (Ag/AgCl), respectively When CeO2 and CuO particles were added simultaneously to the sulphate solution, the cathode polarization increased reducing the cathode discharge current at a specific value of voltage, allowing plating with a smaller current dgure 3.33 Effect of stirring speed on the total amount of CuO and CeO2 on the composite coating Figure 3.34 SEM images of composite coatings made at different stirring speed 3.2.3.5 Influence of the ratio of CuO/CeO2 in electrolyte Table 3.10 The content of CeO2 and CuO on the composite coatings varied with the concentration of particles in electrolyte Samples Concent Concentr Content Content Ratio Total ration ation of of CeO2 of CuO of content of CuO CeO2 in on the on the CuO/ of CeO2 in the the coating coating CeO2 and CuO electrol electroly (% wt) (% wt) on the on the yte te coating coating x (g/L) y (g/L) M.S0Cu7Ce1 7.0 1.0 2.25 37.22 16.54 39.47 M.S0Cu6Ce2 6.0 2.0 4.12 34.64 8.41 38.76 5.0 3.0 5.04 31.08 1.23 36.12 M.S0Cu4Ce4 M.S Cu Ce 4.0 4.0 17.24 21.22 1.23 38.46 3.0 5.0 20.13 17.36 0.86 37.49 2.0 6.0 31.46 6.28 0.20 37.74 M.S Cu Ce M.S Cu Ce M.S0Cu1.6Ce6.4 M.S Cu Ce 0.8 1.6 6.4 31.90 4.46 0.14 38.18 1.0 7.0 33.78 3.46 0.10 37.24 0.8 0.8 7.2 34.68 2.15 0.06 36.83 M.S Cu Ce 20 3.2.4.4 Influence of ratio of anode time/cathode time () Total amount of CeO2 and CuO particles on the composite coatings reached the highest value of 37.69% at  = 0.2 and decreased clearly when  increased to 0.4 3.3 Mechanical, physical and chemical properties of Ni-CeO2CuO composite plating - Corrosion resistance of the coating: Ni-CeO2-CuO composite plating had a very small corrosion current of 1.601.10-5 (A/cm2) that was smaller than the corrosion current as well as the corrosion rate of pure nickel plating – 1.688.10-5 (A/cm2) - Abrasion resistance of the plating: the abrasion resistance of NiCeO2-CuO composite coating was 4.2 times greater than that of pure Ni coating - Microhardness of the coating: the microhardness of Ni-CeO2CuO composite plating was 240.40 HV, which was 1.5 times greater than that of pure nickel plating made from sulphate solution of 163.16 HV - Adhesion of the coating: the composite coating still adhered to the background without peeling after thermal shock test - Test the resistance to salt frost and moist heat of the coating: The coating did not blister There were no stains and other irregularities on the surface of the platings 3.4 Catalytic activity of Ni-CeO2-CuO composite coatings for conversion of engine exhaust gas Catalytic activity of Ni-CeO2-CuO composite coatings for CO conversion Ni plating CuO-CeO2 1:7 100 100 CuO/CeO2 = 1/7 80 CuO/CeO2 = 1/10 CuO/CeO2 = 1/15 60 40 CO conversion (%) Độ chuyển hóa CO (%) CuO/CeO2 = 1/5 CuO-CeO2 1:7 mix powder 80 60 40 20 20 0 0 50 100 150 200 250 300 350 400 450 500 550 600 50 100 150 200 250 300 350 400 450 500 550 600 Temperature (oC) Nhiệt độ (oC) Figure 3.45 Catalytic efficiency of CO-conversion of Ni-CeO2-CuO composite coatings containing different ratios of particles Figure 3.46 Catalytic efficiency of CO-conversion of pure Ni plating, Ni-CeO2-CuO plating and CuO + CeO2 mixture 21 Catalytic activity of Ni-CeO2-CuO composite coatings for CxHy conversion CuO/CeO2 = 1/10 60 40 Ni planting CuO/CeO2 = 1/7 100 CuO/CeO2 = 1/5 CuO/CeO2 = 1/7 80 CuO/CeO2 = 1/7 C3H6 conversion (%) Độ chuyển hóa C3H6 (%) 100 80 mix powder 60 40 20 20 0 0 50 100 150 200 250 300 350 400 450 500 550 600 50 100 150 200 250 300 350 400 450 500 550 600 Temperature (oC) Nhiệt độ (oC) 3.48 Catalytic Figure 3.47 Catalytic efficiency Figure efficiency of C H -conversion of of C3H6-conversion of Ni-CeO2430 steel substrate coated Ni, CuO composite coatings 1.6 6.4 containing different ratios of S Cu Ce composite coating and CuO + CeO2 mixture CuO and CeO2 particles The catalytic activity of Ni-CeO2-CuO nanocomposite coatings was highly dependent on the mass ratio of CuO and CeO2 particles on the surface The composite coating had the best catalytic activity at the ratio of CuO/CeO2 = 1/7, in which the conversion of CO got 100% from 300 oC; the conversion of C3H6 reached the highest value of 85.76% at 500 oC 3.5 Test results of catalytic activity for conversion of engine exhaust gas of Ni-CeO2-CuO composite coating The catalytic effect of exhaust treatment with an oxygen sensor motor Figure 3.53 HC emission at temperature of 270 oC, 147 oC Results from Figure 3.53 showed that the reduction in average HC emission was 45.8 ppm Figure 3.54 CO emission in case with and without BXT 22 The results in Figure 3.54 showed that reduction of average CO emission was 0.02 vol% In this case the catalyst had little effect to reduce CO concentration The catalytic effect of exhaust treatment with internal combustion engine that did not have oxygen sensors: The results in Figure 3.55 and Figure 3.56 showed that the reduction of HC and CO average emission were 100 ppm and 3.2% vol The conversion efficiency was relatively high, indicating that this catalyst was suitable for an internal combustion engine that did not have oxygen sensors Figure 3.55 HC emission in case with and without BXT Figure 3.56 CO emission in case with and without BXT CONCLUSIONS * Research results of the thesis: The changes of concentration of CuO and CeO2 nanoparticles in the composite plating solution virtually unchanged the shape of cathodic polarization curve but affected on cathode polarization leading to the change of the discharge potential of Ni2+ in the sulphate solution There were two processes including charge transfer and adsorption taking place simultaneously, but the adsorption process controlled the speed of the reaction in S0CuxCey solution Ni-CeO2-CuO composite plating made by direct current galvanizing technique from sulphate solution containing NiSO4 300 g/L, H3BO3 30 g/L, sodium lauryl sulphate 0.1 g/L, total content of 23 CeO2 and CuO g/L at current density A/dm2, stirring speed 600 rpm, temperature 50 oC, plating time 20 minutes had the highest amount of particles of 38.46% Ni-CeO2-CuO composite plating made by pulse current galvanizing technique under plating condition: itb = A/dm2, β = 0.2; f = 100 Hz; CeO2 g/L; CuO g/L; stirring speed 600 rpm, temperature 50 oC, plating time 20 minutes had 37.69 % CeO2 and CuO Ni-CeO2-CuO composite platings made from the electrolyte containing 10 ÷ 16 g/L particles under revered square pulse had higher content of particles compared to platings made under direct current The presence of CeO2 and CuO particles on Ni layer improved some mechanical properties of the plating: increased microhardness of the coating (reached the value of 240.40 HV); increased the abrasion resistance of Ni-CeO2-CuO composite coating (4.2 times greater than that of pure Ni coating); corrosion rate of Ni-CeO2-CuO composite plating on steel substrate was very small, and the plating was resistant to level of wet heat resistance test, harsh frost resistance test and thermal shock resistance test Ni-CeO2-CuO composite coating fabricated on 430 steel substrate from the solution containing NiSO4 300 g/L, H3BO3 30 g/L, sodium lauryl sulphate 0.1 g/L, CeO2 6.4 g/L and CuO 1.6 g/L at current density A/dm2, stirring speed 600 rpm, temperature 50 oC, plating time 20 minutes had total amount of particles of 38.18% (in which mass ratio of CuO/CeO2 was 1/7) had CO conversion of 100% at 300 oC which was as high as that of the mixture of two oxide powder The highest C3H6 conversion efficency of this coating was 85.76% at 500 oC Ni-CeO2-CuO composite coating was fabricated on a catalytic core made from 430 steel foil that reduced CO and hydrocarbons average emission of 100 ppm and 3.2% vol This showed that the catalyst was suitable for internal combustion engines that did not use oxygen sensors * News findings of the thesis: - The thesis coordinated research on electroplating techniques and catalysts on plating - Clarified the nature of the composite plating process by polarization curve and electrochemical impedance spectroscopy 24 measurements Created Ni-CeO2-CuO composite coating on 430 steel substrate by direct current and reversed pulse square technique that can be catalyst for the engine exhaust treatment * Further researches: - Further research on the influence of pulse-plating techniques on the distribution of CuO and CeO2 particles on the composite coating surface - Study to overcome the passive surface electrodes - Practical test to determine durability, catalytic life of the plating on engine PUBLISHED SCIENTIFIC WORKS CONCERNING THE THESIS Nguyen Đuc Hung, Trinh Thi Hoàng Anh, Mai Van Phuoc, Đao Khanh Du, Characteristics of the steel sheet plated Ni-CeO2-CuO composite, Journal of Research Military Science and Technology, No 43, 2016, 149-155 Nguyen Duc Hung, Tran Thi Van Nga, Mai Van Phuoc, Thickness determination and control of function Ni-Composite electrodeposited coatings, Journal of Science and Technology, 55 (B1), 2017, 1-6 Mai Van Phuoc, Nguyen Duc Hung, The study on catalytic activity of composite plating Ni-CeO2-CuO for CO oxydation, Viet Nam Journal of catalysis and adsorption, T.6, N0.2, 2017, 142-147 Mai Van Phuoc, Nguyen Duc Hung, Corrosion protection and chacracteristics of Ni-CeO2-CuO electroplating layer on steel substrate, Journal of Science and Technology, 55 (5B), 2017, 181186 Mai Van Phuoc, Nguyen Duc Hung, Some factors affecting on the composition of CeO2 and CuO in Ni-CeO2-CuO composite plating coating, Journal of Research Military Science and Technology, Số đặc san, 2018, 130-135 Mai Van Phuoc, Nguyen Duc Hung, Electrochemical characteristic of the sulfate solution in the formation of the Ni-CeO2CuO composite plating, Vietnam Journal of Chemistry, Volume 56, Number 4e1, September 2018 Mai Van Phuoc, Nguyen Đuc Hung, Study of influencing factors one composition of CeO2 and CuO in Ni-CeO2-CuO composite plating on the 430 steel by using pulse plating., Journal of Research Military Science and Technology, N0 57, 10- 2018, 129-135 Nguyen Duc Hung, Tran Thi Van Nga, Le Thi Phuong Thao, Mai Van Phuoc, “Plating technology of nano, micro composite Ni-CeO2CuO; Ni-TiO2 and Ni-CBN for manufacturing of functional coatings”, Vietnam-UK Researcher links Workshop Green electrochemical and materials processing for environment and energy challenges, Hanoi 30 Octo - 02 Novem 2018, Hanoi University of Science and Technology, VietNam ... activity of Ni- CeO2- CuO composite coatings for CxHy conversion CuO /CeO2 = 1/10 60 40 Ni planting CuO /CeO2 = 1/7 100 CuO /CeO2 = 1/5 CuO /CeO2 = 1/7 80 CuO /CeO2 = 1/7 C3H6 conversion (%) Độ chuyển hóa C3H6... of Ni- CeO2- CuO composite coatings for conversion of engine exhaust gas Catalytic activity of Ni- CeO2- CuO composite coatings for CO conversion Ni plating CuO -CeO2 1:7 100 100 CuO /CeO2 = 1/7 80 CuO /CeO2. .. CO-conversion of Ni- CeO2- CuO composite coatings containing different ratios of particles Figure 3.46 Catalytic efficiency of CO-conversion of pure Ni plating, Ni- CeO2- CuO plating and CuO + CeO2 mixture