A WELL – DISPERSED CATALYTIC COATING PROCESS ONSTAINLESS STEEL MICRO REFORMER

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DUONG DINH TUAN A WELL – DISPERSED CATALYTIC COATING PROCESS ON STAINLESS STEEL MICRO – REFORMER BACHELOR THESIS Study Mode : Full-time Major : Environmental Science and Management Faculty : International Training and Development Center Batch : 2011-2015 Thai Nguyen, September 2015 Thai Nguyen University of Agriculture and Forestry Degree Program : Bachelor of Environmental Science and Management Student name : Duong Dinh Tuan Student ID : DTN 1153070102 Thesis Title : A well – dispersed catalytic coating process on stainless steel micro – reformer Supervisor (s): Ph.D Phan Dinh Binh Assocs Prof Huang Yuh-jeen Abstract: In this thesis, we explored a binder to coat powders of Cu/ZnO catalyst onto stainless steel plates The catalyst was prepared in the laboratory through the sequential precipitation method Coated plates were then used for fabrication of micro-channel reactor (MCR) to produce hydrogen Partial oxidation reforming (PO) of butane would be used as a model reaction for the production A series of coating slurries were prepared by mixing the catalyst powders with the dispersant and binder Prepared well-dispersed slurries were coated on the surface or the micro-channels of stainless steel substrates through the coating method Adhesion stability of coated layers on the substrates was estimated by fraction of weight loss (FL) during a standard ultrasonic impulsion in a D.I water bath Keywords: Cu/ZnO catalyst, stainless steel plates, hydrogen, microchannel, weight loss (FL) Number of Pages: 43 Date of Submission: 30/9/2015 i ACKNOWDLEDGEMENTS I would like firstly to emphasize the sincere appreciation to teachers in International Training and Developments as well as teachers in Thai Nguyen University of Agricultural and Forestry, who have taught me knowledge not only for my subjects but also for my living skills and gave me a chance to my thesis abroad In addition, I would like to thank all supports and help from Biomedical Engineering & Environment Science Department, National Tsing Hua University for the time I did my research in Taiwan It is my pleasure to work with a great teacher - Associate Professor Huang Yuh-Jeen, who always helped me any time She also gave me the best conditions, supported all materials for my research and discussed about any problems I got whenever I did experiments in her Environment Nano Analysis and Energy Laboratory I would like to give special thank to Dr Phan Dinh Binh, who always supported and cheered me up whole the time I worked oversea He also helps me a lot on spending much time for checking my thesis report I consider it is an honor to work with Ms Janet, a master student, who particularly helpful in guiding me toward a qualitative methodology and inspiring me in whole period of internship time She was always helpful, friendly and very kind with me Without her guidance, I cannot complete this thesis ii Finally, I would like to express my gratitude to my family and friends, who always beside me all the time Their helps, supports and encouragement created the pump leading me to success Sincerely, Duong Dinh Tuan iii TABLE OF CONTENT LIST OF FIGURES LIST OF TABLES LIST OF ABBREVIATIONS CHAPTER 1: INTRODUCTION 1.1 Background 1.2 Objective .5 1.3 Limitations 1.4 Definitions CHAPTER 2: LITERATURE REVIEW 2.1 An overview about experiment .7 2.2 Factors influence coating quality 2.2.1 Particle dispersion 2.2.2 Particle size distribution 2.2.3 Coating methodology .10 2.2.4 Drying and calcinations 13 CHAPTER 3: METHODS 15 3.1 Material .15 3.2 Experimental .17 3.2.1 Catalyst preparation 17 3.2.2 Catalyst slurry preparation .19 3.2.4 Adhesion test 21 3.3 Coating methods 21 CHAPTER 4: RESULTS AND DISCUSSION 22 4.1 Comparison between different wafer treatments 22 4.2 Comparison with different coating methods .26 4.3 Effect of binder content on adhesive ability of slurry .27 4.4 Proper catalyst/binder ratio 31 4.5 Effect of ethanol on adhesive ability of slurry 32 CHAPTER 5: CONCLUSION AND DISCUSSION 36 5.1 CONCLUSION 36 5.2 DISCUSSION 38 REFERENCES .39 iv LIST OF FIGURES Figures Page Fig 3.1 Stainless steel plate and its composition 16 Fig 4.1 Wafer without treatment (only clean by acetone) 23 Fig 4.2 Wafer was scraped by abrasive paper and treated with acetone, acid 24 (5M nitrate acid and hydrogen peroxide) and NaOH Fig 4.3 Wafer treated with a 1:1:1:5mixture of hydrogen peroxide (H2O2), 25 phosphoric acid (H3PO4), acetic acid (CH3COOH) and NaOH Fig 4.4 Effect of binder content on adhesive ability of slurry (Binder: 28 8% CeO2 colloid at pH=7, Catalyst: Cu/ZnO 100mg) Fig 4.5 Effect of binder content on adhesive ability of slurry (Binder: PVA, 28 Catalyst: Cu/ZnO 100mg) Fig 4.6 Bad loading after ultrasonic treatment of 1% PVA and 10% catalyst 30 with water Fig 4.7 Effect of catalyst content with 5% PVA on adhesive ability (Binder 32 PVA, catalyst: Cu/ZnO) Fig 4.8 SEM surface images of coating from solution of ethanol/water = 1/1 34 (PVA 5wt%, catalyst 2%) Fig 4.9 SEM surface images of coating from using only water as solution 35 (PVA 5wt%, catalyst 2%) Fig 4.10 The best result after ultrasonic vibration test of 5wt% PVA, 2% catalyst with the ratio of ethanol to water is 1:1 37 LIST OF TABLES Tables Page Table 4.1 Different treatments showed different results of weight loss (2% 22 PVA, 10% catalyst Cu/ZnO) Table 4.2 Different percentage of weight loss between open-channel injection 26 directly method and brushing method (boehmite 20%, 0.0224g bentonite, 0.5g catalyst Cu/ZnO and 50 mL D.I water) Table 4.3 Different ratios of binder PVA showed different results of weight loss 29 Table 4.4 The best result of weight loss is 5wt% PVA and 20mg catalyst in 1g 31 slurry (the solution is D.I water) Table 4.5 Percentage of weight loss by using solution of ethanol/water = 1/1 33 (PVA 5wt%, catalyst 2%) Table 4.6 Percentage of weight loss by using water as solution (PVA 5wt%, 33 catalyst 2%) LIST OF ABBREVIATIONS FC Fuel Cell FEMFC Proton exchange membrane fuel cells FL Fraction of weight loss during ultrasonic treatment W Load amount of catalyst before the treatment WL Load after the treatment W0 Weight of wafer before coating W1 Weight of wafer after coating W2 Weight of wafer after calcine and ultrasonic vibration test CHAPTER 1: INTRODUCTION 1.1 Background In recent years, climate change is a “hot” issue on the world It becomes more and more seriously day by day This is due to the fact that most of energy sources people use every day comes from fossil fuel like oil, natural gas and coal When we burn them, some polluted gas will release such as CO, NO2, CO2…They are the major sources that cause greenhouse effect to climate change Therefore, an environmental friendly and renewable energy is important and necessary Today, there are many kinds of clean energy such as wind power, solar power, geothermal power and biomass could be a positive way to replace fossil fuel and safety for environment Fuel cell (FC) is one of the most efficient and potential devices in renewable energy It is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with low emission of pollutants Proton exchange membrane fuel cells (PEMFC) are a type of fuel cell being developed for transport application as well as for stationary fuel cell applications and portable fuel cell application One main part in PEMFC is catalytic process Catalyst plays an important role in PEMFC because catalysts increase the reaction rates of the chemical reactions They lower the energy required for the initiation of the reactions and thus make the reactions easier to occur Catalysts not have influence on the position of the equilibrium and not enable the reactions that are forbidden by the thermodynamics Typical more than one chemical reaction occurs in chemical reactors Catalysts may influence only the desired reaction and thus increase the selectivity of the process This improves the utilization of the feedstock materials In previous research, they have been used many kinds of catalyst like Cu – Mn Hopcalite monolithic catalyst, Cu/Mn/ZnO catalyst, nicken or aluminum catalyst…that shows good results on coating process with low weight loss (lower than 10 wt% loss) In this research, Cu/ZnO catalysts to coat on stainless steel plates 1.2 Objective The main purpose of this research is to find the best ratio of Cu/ZnO catalyst which was adapted with polyvinyl alcohol (PVA) as a dispersant and organic binder to coating on the stainless plates with low percentage of weight loss The lower rate of weight loss, the higher efficient in PEMFC is 1.3 Limitations The Cu/ZnO catalyst in the coating binder with stainless steel substrates did not perform as well as with other substrates 1.4 Definitions - A Cu/ZnO catalyst belongs to heterogeneous catalysts Heterogeneous catalyst act in a different phase than the reactants Most heterogeneous catalysts are solids that act on substrates in a liquid or gaseous reaction mixture Diverse mechanisms for reactions on surfaces are known, depending on how the adsorption takes place The total surface area of solid has an important effect on 20 weight loss loading 100 15 90 10 85 80 Loading (mg) Weight loss (wt.%) 95 75 70 10 Binder content (wt.%) Figure 4.4 Effect of binder content on adhesive ability of slurry (Binder: 8% CeO2 colloid at pH=7, Catalyst: Cu/ZnO 100mg) 100 weight loss loading 90 70 60 50 40 Loading (mg) Weight loss (wt.%) 80 30 20 10 0 10 Binder content (wt.%) Figure 4.5 Effect of binder content on adhesive ability of slurry (Binder: PVA, Catalyst: Cu/ZnO 100mg) 28 W0 W1 W2 Loading catalyst FL 1wt% 0.2096 0.2208 0.2101 0.0112 0.0005 95.5% PVA 0.2793 0.2812 0.2799 0.0019 0.0006 68.4% 2wt% 0.2207 0.2312 0.2236 0.0105 0.0029 72.4% PVA 0.2084 0.2106 0.2095 0.0022 0.0011 50.0% 5wt% 0.5990 0.6030 0.6019 0.0040 0.0029 27.5% PVA 0.2579 0.2620 0.2592 0.0041 0.0013 68.3% 8wt% 0.3158 0.3187 0.3171 0.0029 0.0013 55.2% PVA 0.2637 0.2685 0.2647 0.0021 0.0010 52.4% 10wt% 0.2564 0.2581 0.2571 0.0017 0.0007 58.8% PVA 0.3245 0.3272 0.3251 0.0027 0.0006 77.8% 0.2593 0.2605 0.2597 0.0012 0.0004 66.7% 82% 61.2% 47.9% 53.8% 67.8% Table 4.3: Different ratios of binder PVA showed different results of weight loss The result of weight loss by 1wt% PVA and 10%wt catalyst with water was shown in Fig 4.6 29 Fig 4.6: Bad loading after ultrasonic treatment of 1% PVA and 10% catalyst with water 30 4.4 Proper catalyst/binder ratio After found out 5wt% PVA was the best binder for coating process, one of the most important steps is that choose the proper ratio between catalyst and binder By changing different weights of catalyst at 10, 20, 50 and 100 mg, we found that the best ratio for coating catalyst on the stainless steel was 20 mg catalyst Cu/ZnO in g slurry (the solution is D.I water) The best result ratio catalyst/binder is 0.4 (Table 4.4) The weight loss was seen by Fig 4.7 W catalyst W0 W1 W2 Loading catalyst WL C/B (mg) 10 0.2525 0.2533 0.2531 0.0008 0.0006 25% 0.2 20 0.333 0.3337 0.3336 0.0007 0.0006 14% 0.4 50 0.3215 0.3237 0.3227 0.0022 0.0012 45% 100 0.2579 0.262 0.0041 0.0013 68% 0.2592 Table 4.4: the best result of weight loss is 5wt% PVA and 20mg catalyst in 1g slurry (the solution is D.I water) 31 100 weight loss loading 90 70 60 50 40 Loading (mg) Weight loss (wt.%) 80 30 20 10 0.0 0.5 1.0 1.5 2.0 Catalyst/Binder Fig 4.7 Effect of catalyst content with 5% PVA on adhesive ability (Binder PVA, catalyst: Cu/ZnO) 4.5 Effect of ethanol on adhesive ability of slurry Adding Ethanol into slurry could enhance the wetting effect Wetting is the ability of liquids to form interfaces with solid surface For maximum adhesion the adhesive must completely cover the substrate The another advantage is the good dispersion ability of ethanol help the catalysts well-distribution After calcined, there is less cracker on the surface of catalyst layer We can see how differences between when we used only water and the mixture of ethanol and water (Ethanol/water = 1/1) (Table 4.5 and Table 4.6) 32 W catalyst W0 W1 W2 Loading FL 10 0.6937 0.6959 0.6953 0.0022 0.0016 27% 20 0.2057 0.2062 0.2061 0.0005 0.0004 20% 0.6533 0.6539 0.6538 0.0006 0.0005 17% Table 4.5: Percentage of weight loss by using solution of ethanol/water = 1/1 (PVA 5wt%, catalyst 2%) W catalyst W0 W1 W2 Loading 20 0.3614 0.3623 0.3619 0.0009 FL 0.0005 44% Table 4.6 Percentage of weight loss by using water as solution (PVA 5wt%, catalyst 2%) SEM images also proved the different quality between two types of solution (Fig 4.8 and 4.9) 33 Fig 4.8 SEM surface images of coating from solution of ethanol/water = 1/1 (PVA 5wt%, catalyst 2%) 34 Crack Fig 4.9 SEM surface images of coating from using only water as solution (PVA 5wt%, catalyst 2%) 35 CHAPTER 5: CONCLUSION AND DISCUSSION 5.1 CONCLUSION In this research, we found out the ability of using PVA to adapt the surface of Cu/ZnO catalyst The catalyst slurry with ratio of 5:2 (PVA: catalyst) shows better dispersion and good adhesion to the stainless steel substrate In addition, the catalyst preserves its intrinsic activity after calcinations Moreover, the combination of suitable treatment (Wafer treated with a 1:1:1:5 mixture of hydrogen peroxide (H2O2), phosphoric acid (H3PO4), acetic acid (CH3COOH) and NaOH) and brushing method distribute to reduce weight loss Furthermore, by using ethanol/water with ratio 1/1 as solution to dissolve PVA, it helps to increase good dispersion ability of ethanol The best result of 5wt% PVA and 2% catalyst Cu/ZnO shows good adhesion on stainless steel with 14wt% loss after ultrasonic vibration test (180 W, 20 min) (Fig 4.10) 36 Fig 4.10 The best result after ultrasonic vibration test of 5wt% PVA, 2% catalyst with the ratio of ethanol to water is 1:1 37 5.2 DISCUSSION Although time has been a limit to test how compatible between Cu/ZnO and stainless steel substrates, depending on all the 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Schouten J.c., 2011, Roating foam stirrer reactor: effect of catalyst coating characteristics on reactor performance Ind Eng Chem Res; 50(6): 3184-3193 42 [...]... zirconia grinding media for 48 h Hwang et al used polyvinyl alcohol (PVA) as a drying, control chemical additive for pre-coated alumina adhesive layer Peela et al used PVA and colloidal alumina for washcoating γ-alumina on stainless steel microchannels In this study, the catalyst surface was modified by adding PVA as dispersant to avoid the aggregation of particles and as binder for coating catalysts... water was chosen as solvent because it is eco-friendly and cost less compared to organic-based slurry However, the catalyst powder can easily agglomerate in water, which makes it impossible to form a crack-free catalyst coating Some researchers used hydroxyethyl cellulose to improve catalyst dispersion Tadd et al used PVA and a ceria–zirconia binder to prepare the catalyst washcoat which then was ball-milled... various techniques 2.1An overview about experiment The most common way to deposit catalysts within the micro- channel is the wash -coating (slurry) technique The advantage of wash -coating method is that it is a well- optimized catalyst that can be used directly However, catalyst immobilization into micro- channel has been a challenge, influenced by a low interaction between substrate surfaces and catalyst...the reaction rate The smaller the catalyst particle size, the larger the surface area for a given mass of particles 6 CHAPTER 2: LITERATURE REVIEW The quality of a slurry coating is determined by all its performancedetermining properties, such as loading, adherence, thickness and homogeneity Many factors at each process unit which can influence the coating quality These factors can be measured and controlled... research studies use inorganic binder to improve adherence For commercial CuO/ZnO/Al2O3 catalyst, alumina sol was often used as a binder Some researchers also used ZrO2 sol as binder to immobilize the catalyst onto a stainless steel microchannel Nevertheless, using inorganic binder has some disadvantages Chen et al reported that catalytic activity was significantly affected by the acidic sol because... coatings at room temperature for 1 h, then in an oven at 100oC for 2 h before finally calcining in a furnace at 500oC for 3 h They found that thicker coatings were achieved by dip -coating several times, and that drying and calcining each layer separately could avoid cracks caused by large stresses It was discovered that to achieve an integrated coating without cracks, the critical coating thickness should... how heat energy is supplied, e.g by blowing a stream of hot air or through an encapsulated filament (Ismagilov et al., 2005) The slow drying of coatings has been encouraged as this was viewed to be influential in preventing coating cracks The fast drying of coatings can lead to high evaporation which quickly thins the coating film, thus causing a detrimental breakage (Giani et al., 2006; Fei et al.,... water bath for 10 min before soaking in 0.5M NaOH for 24 hours at room temperature 20 3.2.4 Adhesion test After finishing the stainless steel wafer surface pretreatment, 0.2 ml of catalyst slurry was dropped onto the wafer surface and dried at ambient temperature Then the catalyst-coated wafer was calcined ay 400oC for 2hr The adhesive strength of catalyst slurry on stainless steel wafer was estimated... this research It was quite convenient because the catalyst slurry dropped by a pipette was dried faster in the open-channel However, when contamination formed on the top surface of open micro- channel during catalyst layer, the anodic bonding process may fail and gas leakage may occur The catalyst layer on the surface was thick; if the catalyst slurry is not sticky on the wafer surface that means the... which has been used not only in coating industries, but also in paint, ink and paper industries (Braaten et al., 1998) 2.2.4 Drying and calcinations The drying and calcination conditions used in the coating method can influence the coating properties, such as in the formation of cracks et al (2003) Fei dip-coated Fecralloy® rods in γ–alumina using sol gel preparation, and dried the coatings at room ... polyvinyl alcohol (PVA) as a drying, control chemical additive for pre-coated alumina adhesive layer Peela et al used PVA and colloidal alumina for washcoating γ-alumina on stainless steel microchannels... washcoats for methanol steam reforming in microchannels based on nanoparticles Appl Catal a- Gen, 286(2): p 175-185 Kawamura Y, Ogura N, Yamamoto T, Igarashi A, 2006, A miniaturized methanol reformer. .. catalyst surface was modified by adding PVA as dispersant to avoid the aggregation of particles and as binder for coating catalysts on the stainless steel micro- channel 2.2 Factors influence coating