Synthesis and using aucuzn base catalysts for changing of hydrogen consumption in methanol reaction by temperatue programmed redution tpr

THAI NGUYEN UNIVERSITY OF AGRICULTURE AND FORESTRY NATIONAL TSING HUA UNIVERSITY  GRADUATE REPORT Title: “SYNTHESIS AND USING AUCUZN-BASE CATALYSTS FOR CHANGING OF HYDROGEN CONSUMPTION IN METHANOL REACTION BY TEMPERATURE PROGRAMMED REDUCTION (TPR)” Full name : Le Anh Tu Class : K42 - AEP Supervisor : 鈺軫博士（Dr Yuh-Jeen, Huang） Dr Duong Van Thao Taiwan - 2014 ACKNOWLEDGMENT First of all, I would like to express my sincere thanks to the school board of Thai Nguyen University of Agriculture and Forestry, International Training and Development Center; Advanced Education Program, Dr Duong Van Thao, thank the teachers who has imparted to me knowledge and valuable experience during the process of learning and researching here In the process of implementing and completing thesis, I have received the enthusiastic help of the teachers of Tsing Hua National University I would like to express my special thanks to 鈺 軫 博士 (Dr Yuh-Jeen, Huang) who has spent a lot of time and created favorable conditions, enthusiastically guided me to complete this thesis I sincerely thank my friends in the laboratory, especially 廖 翊 君 (Ms Kimi) who facilitated, and provided the information and data necessary for my implementation process and helped me finish this thesis In the process of implementing the project, due to limited time, financial and research levels of myself, this project has many inevitably shortcomings So, I hope to receive the attention and feedbacks from teachers and friends for this thesis to make it is more completed Taiwan, 2014 Students perform LE ANH TU Thai Nguyen University of Agriculture and Forestry Degree Program Student name Student ID Thesis Title Bachelor of Environmental Science and Management Supervisor (s) Dr Duong Van Thao LE ANH TU DTN 0953060035 Synthesis and using aucuzn-base catalysts for changing of hydrogen consumption in methanol reaction by temperature programmed reduction (TPR) 鈺 軫 博士 (Dr Yuh-Jeen, Huang) Abstract: Nano gold particle supported on copper zinc catalyst to proceed methanol reforming was investigated in this study A synthesis method was developed which utilized co-precipitation to produce copper zinc catalyst, gold was added at pH by deposition precipitation method after copper zinc catalyst was precipitated and dried This synthesis procedure avoids severe gold loss and preserves significant reactivity after calcination Different gold content, 1%, 2%, 3% and 4%, on the 30% copper Supported on zinc oxide catalyst synthesis by procedure mentioned above, were characterized and tested in a fixed bed reactor through partial oxidation of methanol (POM), steam reforming of methanol (SRM) and oxidative steam reforming of methanol (OSRM) reaction The addition of gold can suppress the carbon monoxide In addition, with the increasing gold content, less CO was formed Furthermore, in the absent of oxygen, addition of gold also decreased the CO formation in SRM reaction Higher oxygen concentration in POM reaction did not decrease the CO formation significantly, but caused severe hydrogen combustion Meanwhile, higher oxygen concentration in OSRM reaction leaded to higher CO formation Besides, the addition of gold can lower the initiation temperature Gold is an ideal additive to improve the initiation temperature and decrease CO formation Lower initiation temperature without pre-activation allows simpler heating module and reduces cost for the reformer Gold, which is a least active element, has been regarded as a poor promoter for catalyst However, recent research found that nano gold particle deposited on metal oxide by deposition precipitation or coprecipitation method showed excellent promoting effect Au supported on ceria oxide, zinc oxide, aluminia oxide and other metal oxide were found as a great improvement on CO preferential oxidation Au doped catalysts are capable of absorbing CO at room temperature and oxidizing to CO2 at mild temperature Keywords: gold, initiation temperature, CO Number of pages: 47 Date of Submission : 09/01/2015 Contents Introduction 1.1.Rationale of the study 1.2.Aims of the study 1.3.Research questions and hypothesis Error! Bookmark not defined 1.4.Limifation of the study 1.5 Definition of Terms…………………………………………………………………………….…………7 Literature review 2.1 Proton exchange membrane fuel cells (PEMFCs) 2.2 Hydrogen storage 10 2.3 Oxygen vacancies on CuZn catalyst 15 2.4 POM reaction over catalysts by different synthesis method 16 Methods 21 3.1.Materials and Equipments (Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University………………………… ………………………….…………………… 21 3.2 Catalyst preparation method 21 3.3 Transmission electron microscopy (TEM) 300 3.4 Temperature programmed reduction (TPR) 31 Results 33 4.1 Results of synthesis catalyst 33 4.2 Results of transmission electron microscopy 36 4.3 Results of temperature programmed reduction 36 Discussion and conclusion 411 5.1 Synthesis catalyst 411 5.2 Transmission Electrons Microscopy 411 5.3 Temperature programmed reduction 42 References 443 List of Figures Fig 2-1 A chart of MEA consist of two electrodes, anode and cathode and the polymer electrolyte Error! Bookmark not defined Fig 2-2 Model for the activity ZnO in the hydrogenation of CO The space-filling model shows the (000ī) surface with one oxygen vacancy The ball-and-stick models show the chemisorption of CO at the oxygen vacancy Error! Bookmark not defined Fig 2-3 Transmission electron microscopy imaging of catalysts by different preperation methods .Error! Bookmark not defined Fig 2-4 The temperature profile of catalysts prepared by different method in the POM reaction Error! Bookmark not defined Fig 3-1 A schematic diagram for the temperature programmed reduction system used in this study, rearranged from S.Y Huang, Ph.D.Dissertation, National Tsing Hua University,Hsinchu, Taiwan, ROC,(2006) Error! Bookmark not defined Fig 4-1 Asporator 34 Fig 4-2 Drying cabinet .Error! Bookmark not defined Fig 4-3 Incubation for hour .Error! Bookmark not defined Fig 4-4 After 1h compounds are filtered and washed with deionized water 4L The precipitate was dried at 1050C overnight Error! Bookmark not defined Fig 4-5 After drying at 1050C, the precipitate was pulverized and calcined in air flow of 30 ml/min at 4000C for two hours .Error! Bookmark not defined Fig 4-6 A Au4CuZn sample Error! Bookmark not defined Fig 4-7 A4CZ TEM Error! Bookmark not defined Fig 4-8 Using the U-shaped grass pipes for catalyst 50.5 (mg) Error! Bookmark not defined Fig 4-9 Regulators same parameters TPR reactor .Error! Bookmark not defined Fig 4-10 The gas flow valve in the process of TPR Error! Bookmark not defined Fig 4-11 Results of Temperature programmed reduction Error! Bookmark not defined List of Tables Table 1-1 Summary of major differences of the fuel cell types Table 2-1 Potential hydrogen storage materials Error! Bookmark not defined Table 3-1 Chemicals and solutions Error! Bookmark not defined Table 4-1 The quantity of materials used Error! Bookmark not defined Table 4-2 Regulators same parameters TPR reactor Error! Bookmark not defined Abbreviations DM Thermal decomposition of methanol OSRM Oxidative stream of reforming of methanol PEMFCs Proton exchange membrane fuel cells POM Partial oxidation of methanol SRM Steam reforming of methanol TEM Transmission electron microscopy TPO Temperature programmed oxidation TPR Temperature programmed reduction Introduction 1.1 Rationale of the Study Energy used for transport, food, pharmaceuticals, chemicals, manufacturing, high technique industry and so forth is very important in our daily life of modern society The sources of energy are almost composed by fossil fuels, which consist of oil, coal and natural gas However, when we burn fossil fuels, NOx, SOx, CO, CO2, CH4, etc Are produced and then caused many kinds of pollution such as acid rain, greenhouse effect, health impairament, and intensifying natural climate, etc Furthermore, specialists in fossil fuels industry estimated that current reserves would only last for about 40 years Fossil fuel has been bring the disadvantages of environmental pollution and emitting green house gases Nowadays, climate change and the exhausting crude oil deposition are becoming ineligible (Charles, 1971) Fuel cell (FC) as one of the most potential and efficient devices in renewable energy, has higher efficiency of electricity generation than internal combustion engine systems since chemical energy is almost directly converted to electric energy in fuel cells Fuel cells convert chemical energy directly into electricity without the combustion process Moreover, a fuel cell is not governed by thermodynamic laws, such as the Carnot efficiency associated with heat engines, currently used for power generation Fuel cells can be just as efficient as large one Page | Table 1-1 Summary of major differences of the fuel cell types (Mark, 2002) Fuel cell type PEMFC AFC PAFC MCFC SOFC Operating temperature 353ºK 338-493ºK 473ºK 923ºK 873 – 1273ºK Alkalinelye Phosphorica cid Molten carbonate solution Ceramic solid electrolyte Electrolyte Ionex change Membranes Charge carrier H+ OH- H+ CO32- O2- Fuel H2,CH3OH H2 H2 CH4,LPG CH4,LPG Oxidationme dia Oxygenfro mair Oxygen Oxygen fromair Oxygen fromair Oxygen fromair Catalyst Platinum Platinum Platinum Nickel Perovskites Simplicity: The essentials of a fuel cell are very simple, without moving parts The simplicity can lead to highly reliable, long lasting systems and power output quickly and easily Low emissions: Combustion is not involved, no combustion by - products, such as nitrogen oxide (NOx), sulfur oxide (SOx), or particulates, produced In hydrogen fuel cell, water is the main product from reaction In other word, fuel cell is essentially “zero Page | emission” during vehicles operation Silence: Fuel cells, due to their nature of operation, are extremely quiet in operation, even those with extensive extra fuel processing equipment This allows fuel cells to be used in residential or built - up areas where the noise pollution is undesirable High power density: A high power density allows fuel cells to be relatively compact source of electric power, favorable in application with space constraints The advantages of fuel cell impact particularly strongly on combining heat and power systems and on mobile power systems, especially for vehicles and many kinds 1.2 Aims of the Study Proposed that Au doped catalyst showed better CO suppression and better catalytic ability (Chang, et al 2005, 2009) Gold, which is a least active element, and it has been regarded as a poor promoter for catalyst Recent research found that nano gold particle deposited on metal oxide by deposition precipitation or co-precipitation method showed excellent promoting effect (Haruta, 1997) With the information below I decided to use the precipitation method to synthesize gold This method will examine the effect of catalyst by a schematic diagram and facilities used for the temperature programmed reduction USED system in this study, rearranged by SY Huang, Ph.D National Tsing Hua University Dissertation, Hsinchu, Taiwan, ROC, (2006), to perform this project graduation Au supported on ceria oxide, zinc oxide, aluminia oxide and other metal oxide are found great improvement on CO preferential oxidation (Haruta and Daté, 2011) Au doped catalysts are capable to absorb CO at room temperature and oxidize to CO at Page | Results 4.1 Results of synthesis catalyst Precipitation method created Cu30Zn with the percentage of Cu : Zn = : Use 2g Zn, from then we have the quantity of Cu (g): 2/7 x = 6/7 = 0.86 (g) (1) The volume of Zn (g) in Zinc nitrate hexahydrate (Zn (NO3)2.3H2O) need: 2/65 409 (M of Zn) = X / 297.49 (M of Zn (NO 3)2.3H2O) => X = 9096 (g) (2) The volume of Cu (g) require to create Copper (II) nitrate trihydrate (Cu (NO3)2.3H2O) 0.86 / 63 546 = y / 241.6 => Y = 3.26 (g) The amount of Cu (g) necessary is 3.26 (g) (3) Solutions to create Na2CO3 2M with 500ml dieonized water: X / 106 (M of Na2CO3) = 2x0.5 (l)  X = 106 (g) So put 106 (g) Na2CO3 into 500 ml dieonized water getting 2M Na2CO3 solution After that, calculate the quantity of materials needed to use, put sample into beaker containing deionized water and heat at temperature of 70ºC, then put 2M Na2CO3 solution until the pH = Turn off stirring hot plates Page | 33 Take sample to Asporator for treatment: Fig 4-1 Asporator Fig 4-2 Drying cabinet Then put into drying cabinet at 105ºC overnight After the sample was left overnight we calculate value of Au to use We have the percentage of Au in Au4Cu30Zn66: : 66 = y : => y= 0.1212(g) 0.1212(g) : 196.96(MAu) = YAu (g): 393.83 (MHAuCl4.3H2O) => YAu= 0.242 (g) When having the amount of materials need use 500 ml deionized water boiling at 70ºC, put mixture including Cu, Zn after treating overnight and use buret to mix hydrogen tetrachloroaurate (III) HAuCl4 with 10 ml deionized water, then drip solution into above mixture 2M Na2CO3 used balance PH = Finishing process phase HAuCl4 carry out incubation within hour and use 10% HCl to balance PH = 7~7.5 Page | 34 Fig 4-3 Incubation for hour Fig 4-4 After 1h compounds are filtered and washed with deionized water 4L The precipitate was dried at 1050C overnight Fig 4-5 After drying at 105ºC, the precipitate was pulverized and calcined in air flow of 30 ml / at 400ºC for two hours Page | 35 Fig 4-6 A Au4CuZn sample Table 4-1 The quantity of materials used Au yAu(g) YAu(g) Zn(g) Cu(g) Au1 0.029 0.058 9.096 3.26 Au2 0.059 0.118 9.096 3.26 Au3 0.089 0.179 9.096 3.26 Au4 0.121 0.242 9.096 3.26 4.2 Results of transmission electron microscopy Fig 4-7 A4CZ TEM Page | 36 4.3 Results of temperature programmed reduction Uses PTR to assess the quality and extent of catalyst Fig 4-8 Using the U-shaped grass pipes for catalyst 50.5 (mg) Table 4-2 Regulators same parameters TPR reactor C D 5ºC 7º C C R T – 700 R T – 700 -180~250 -180~350 Pb 3.2 0.8 0.8 Ti 7’0 5’4 18’8 13’4 Td 11.7 31.3 22.3 CD1 37.2 34.8 8.9 5.6 º Page | 37 Fig 4-9 Regulators same parameters TPR reactor Fig 4-10 The gas flow valve in the process of PTR Page | 38 In the process of evaluating the catalyst by PTR we have gas cycle (1) Use N2 gas in the first 10 minutes (temperature outside) (2) Use of H2 gas during the temperature increased up to 3000C (3) Use N2 for 10 minutes (at temperature outside) (4) Use N2O for 30 minutes (at temperature outside) (5) Use N2 for 10 minutes (at temperature outside) (6) Use the H2 gas during the temperature increased up to 300ºC In which: (1) and (3) process purge dirty air (2) and (6) reduce Cu2+ => Cu0 (4) and (5) oxidation Cu0 => Cu2+ Page | 39 200 A2CZ A1CZ A4CZ A3CZ 180 160 H2 consumption 140 120 100 80 60 40 20 100 200 300 o Temperature C A1CZ A2CZ A3CZ A4CZ 50 100 150 200 250 300 Temperature( C) Fig 4-11 Results of Temperature programmed reduction Page | 40 Discussion and conclusion 5.1 Synthesis catalyst Through the study of precursors, synthesis procedure and pH deposition, a strategy for the synthesis of Au/Cu 3OZnO catalyst is setting up Method C with copper nitrate and zinc nitrate precursor is employed for the synthesis of copper zinc, gold is deposited onto copper zinc precipitate after washing, drying and pulverization The pH for gold deposition is pH to obtain highest gold content Higher gold content seemed to affect the catalytic performance Although samples was prepared under different process, significant drawback was observed which has to be confirmed in further chapter Besides, high deposition pH is normally adopted to obtain smaller particle size, however, serious loss of gold which will consequently mislead the aim of the study In brief, to study the relationship between gold content and copper zinc catalyst, ensuring the gold loading is more important than reactivity 5.2 Transmission Electrons Microscopy Although the X-ray powder diffraction showed no gold diffraction peak in the diffractograms, but to ensure the particle size of gold particles, TEM was employed for the imaging of the catalysts Meanwhile, TEM also reveal the morphology of the catalysts, providing a piece of the puzzle of the catalysts The gold particles showed on Figure 4-7 are mostly found at the size of 20 nm Haruta indicated that the sintering of nano gold particle would be accelerated at temperature > 400ºC (Manzoli, et al 2008) To avoid serious sintering of gold particle, 400ºC was chose for the calcinations Definitely, if gold particles suffered from sintering, the size of particles might grow bigger to more than nm In this study, only few particles were observed The gold particles in the Page | 41 samples should be hemispheric shape which is mostly reported in literatures (Saltsburg 2010) There were no significant differences in morphology between these catalysts Although the synthesis procedure and precursor were not identical, but actually all the copper zinc oxide-base was synthesized by co-precipitation method, as a result the morphology was similar 5.3 Temperature programmed reduction The copper dispersion was measured by nitrous oxide chemisorption Copper areas were measured by the method of reaction with N2O, followed by TPR using a homemade TPR system described in Fig 3.1 Firstly, 55 mg freshly calcined samples were reduced with 10% H2 in N2 at 240ºC Second, pure N2O was passed through at R.T for 0.5 hour TPR was carried out in a 10% H2/N2 mixture at rate of 7ºC.min−1 The amount of chemisorbed O atoms was determined from the area of the TPR peak The Cu dispersion was calculated by dividing the area of N 2O experiment TPR with normal H2-TPR The result was multiply by as two copper atom bind with one oxygen atom Using TPR gave us the consumption of H2 Au4CZ highest in the catalyst it reaches 200 which is the lowest temperature of 180 degrees Page | 42 References Agrell, J., Birgersson, H., Boutonnet, M., Cabrera, I., Navarro, R.M., and Fierro, J.L.G (2003) Production of hydrogen from methanol over Cu/ZnO catalysts promoted by ZrO2 and Al2O3, Journal of Catalysis, 219, 389-403 Bossel, 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ANH TU DTN 0953060035 Synthesis and using aucuzn- base catalysts for changing of hydrogen consumption in methanol reaction by temperature programmed reduction (TPR) 鈺 軫 博士 (Dr Yuh-Jeen, Huang)... knowledge and valuable experience during the process of learning and researching here In the process of implementing and completing thesis, I have received the enthusiastic help of the teachers of Tsing... (POM), steam reforming of methanol (SRM) and oxidative steam reforming of methanol (OSRM) reaction The addition of gold can suppress the carbon monoxide In addition, with the increasing gold content,