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 n 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. 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.
Keywords: Cu/ZnO catalyst, stainless steel plates, hydrogen, micro- channel, weight loss (FL). Number of Pages: 43 Date of Submission: 30/9/2015 i n 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 do 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 n 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 n TABLE OF CONTENT LIST OF FIGURES .1 LIST OF TABLES .2 LIST OF ABBREVIATIONS .5 CHAPTER 2: LITERATURE REVIEW.1 An overview about experiment .2 Factors influence coating quality .2 Particle size distribution.4 Drying and calcinations .2 Catalyst slurry preparation .21 CHAPTER 4: RESULTS AND DISCUSSION .1 Comparison between different wafer treatments .2 Comparison with different coating methods.3 Effect of binder content on adhesive ability of slurry.4 Proper catalyst/binder ratio .5 Effect of ethanol on adhesive ability of slurry.32 CHAPTER 5: CONCLUSION AND DISCUSSION.39 iv n 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.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% 37 catalyst with the ratio of ethanol to water is 1:1 1 n 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%, 0.5g catalyst Cu/ZnO and 50 mL D.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.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%). 2 n 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 3 n 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 do not have influence on the position of the equilibrium and do not enable the reactions that are forbidden by the thermodynamics.
Typical more than one 4 n 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.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.3 Limitations The Cu/ZnO catalyst in the coating binder with stainless steel substrates did not perform as well as with other substrates.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 5 n the reaction rate. The smaller the catalyst particle size, the larger the surface area for a given mass of particles. 6 n CHAPTER 2: LITERATURE REVIEW The quality of a slurry coating is determined by all its performance- determining 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 by various techniques.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.
Most 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 micro- channel. Nevertheless, using inorganic binder has some disadvantages.
Chen et al reported that catalytic activity was significantly affected by the acidic sol because the catalysts were partially dissolved in the acidic slurry. Karim et al also mentioned that the low pH of the catalyst slurry caused catalyst dissolving. Lin et al also reported that catalyst activity decreases as the ratio of CeO2 sol increases in the catalyst slurry. Thus, inorganic binder is not recommended because the catalyst’s active regions may be covered by the inorganic sol.
7 n In the present work, 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 with 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 on the stainless steel micro-channel.2 Factors influence coating quality To obtain a good quality in term of coating process, there are several factors which control the quality of coating process: particle dispersion, particle size distribution, slurry characteristics, drying and calcinations etc.1 Particle dispersion The Cu/ZnO catalyst particles should be properly dispersed in the slurry before milling, and this is enabled by its unique chemistry (i. structure and properties).
To model the Cu/ZnO catalyst, a Cu cluster composed of eight Cu atoms was deposited on a oxygen–terminated ZnO (0001) surface. The electronic structure 8 n was calculated using the DFT/PBE method within the periodic slab approach. A fundamental problem when one wants to study heterogeneous catalytic processes from a theoretical frame- work is to include the effect of the high temperatures and pressures typical of industrial heterogeneous catalysis. The inclusion of thermodynamic effects into the description of the catalyst model was accomplished via the initio thermodynamics method, which allowed to approximately calculation surface Gibbs free energy differences from the DFT total energies of a set of Cu/ZnO structures.