THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY PHIMNAPHA SYHABOUTH PERFORMANCE TEST: MN AND MN-CE MIXED OXIDE AS LOW TEMPERATURE CATALYSTS IN NH3-SCR PROCESS FOR NOX REMOVAL FROM STATIONARY SOURCES BACHELOR THESIS Study mode : Full-time Major : Environmental Science and Management Faculty : International Programs Office Batch : K45 AEP (2013-2017) Thai Nguyen, 17/11/2017 c DOCUMENTATION PAGE WITH ABSTRACT Thai Nguyen University of Agriculture and Forestry Degree program Bachelor of Environmental Science and Management Student’s name Phimnapha Syhabouth Student ID DTN1353110557 Thesis Title Performance Test: Mn And Mn-Ce Mixed Oxide As Low Temperature Catalysts in NH3-SCR Process For NOx Removal From Stationary Sources Supervisors Hsun Ling Bai, Ph. Nguyen Thi Thu Huong, MSc. Abstract: This thesis describes a laboratory-scale experiment to evaluate the performance of catalysts in conversing NOx from stationary sources. Mn oxide/TiO2 and Mn- Ce/TiO2 mixed oxide catalysts, denoted as Mn20/TiO2, Mn20Ce10/TiO2, and Mn20Ce20/TiO2 were used as samples.
The process of the synthesis, preparation, and performance test of those sample catalysts were recorded and described in detail. Moreover, the experimental result shows that at operating temperature at 150°C, concentration of NH3 and NO at 200ppm, and hourly volumetric feed gas flow rate/reaction volume (GHSV) at 20,000 h-1, the NO concentration of the outflow gas from all three experiments with three kinds of catalysts were above 80%. However, Mn-Ce catalysts performed better than only Mn-catalyst. Page 1 c Keyword SCR, low temperature catalyst, Mn/TiO2, Mn– Ce/TiO2, NOx Number of page 40 Date of submission 10/10/2017 Page 2 c ACKNOWLEDGEMENT I would like to express my heartfelt gratitude to my supervisors.
Firstly, to Prof. Hsun Ling Bai, thank you for accepting me as an intern student to conduct experiments in the laboratory and for all suggestions and advice of my experimental work. Secondly, thank you MSc. Nguyen Thi Thu Huong for taking time from your busy schedule to correct my writing and also for your continuously kind support and guidance not only for my thesis but throughout my final year of college.
A special thank goes to AEP program for offering us advanced education. With the diversity of teaching methods, professional teachers, cultural environments provided by AEP, it allows me to graduate as a quality citizen. Moreover, thank you both Thai Nguyen University of Agriculture and Forestry and National Chiao Tung University for encouraging us to conduct a graduation project in Taiwan. It was a last but one of the most meaningful time of my college duration.
Furthermore, this thesis would not successfully been conducted without my advisor, Lin Yun-Ting, a good friend who was with me in every laboratory sessions and offer me helps since the arrival until the departure from Taiwan. Lastly, to my parents, sister and my big family, thank you for believing in me, the encouragement and also financial support throughout my Page 3 c life. I own this success to all of you. This thesis is a product of supports from all of you that I have mentioned above.
Even though, the time in doing this thesis is limited, so that I only obtained small amount of data, however, with my writing, I wish this thesis could be used as a reference for the beginner in NH3-SCR field. Phimnapha Syhabouth Page 4 c TABLE OF CONTENT ACKNOWLEDGEMENT. 3 TABLE OF CONTENT. 5 LIST OF ABBRIVIATION.
7 LIST OF TABLE. 12 PART 2: LITERATURE REVIEW .2 Sources of NOx .3 Adverse Impacts of NOx .2 Selective Catalytic Reduction (SCR) .2 MnO2-CeO2 Catalysts .1 Overview of Research Design .2 Materials and Equipment .1 For Catalyst Synthesis .2 For Catalyst Preparation .3 For Catalyst Performance Test. 25 PART 4: RESULTS AND DISCUSSION.1 The Synthesis of the Catalyst .2 The preparation of catalyst .3 Performance test of the catalysts. 36 Page 6 c LIST OF ABBRIVIATION SCR - Selective Catalytic Reduction GHSV - Hourly volumetric feed gas flow rate/reaction volume ppm - parts per million ccm - Cubic Centimeter DI - Deionized Water Page 7 c LIST OF TABLE Table 1 Methodology to Answer Research Questions.
19 Table 2 Materials for Catalyst Synthesis. 20 Table 3 The Amount of Precursor in Each Catalyst. 23 Page 8 c LIST OF FIGURE Figure 1 The magnetic stirrer: it is for stirring catalysts precursers in a synthesis process. 21 Figure 2 The pressure plumber to press catalyst powder into a hard piece.
22 Figure 3 The Catalyst Synthesis Process. 24 Figure 4 The Catalyst Preparation Process. 25 Figure 5 SCR system for catalyst’s performance test. 26 Figure 6 The Catalytic Reactor.
27 Figure 7 The synthesized catalyst (after calcination), from left to right (Mn20Ce20/TiO2, Mn20Ce10/TiO2, Mn20/TiO2). 28 Figure 8 The Transformation of Catalyst from Powder into Pellet Type. 29 Figure 9 The stability of Mn20/TiO2 catalyst in NOx conversion. 30 Figure 10 The stability of Mn20 Ce10/TiO2 catalyst in NOx conversion.
30 Figure 11 The stability of Mn20 Ce20/TiO2 catalyst in NOx conversion. 31 Figure 12 The Average NO conversion (%) of each catalyst. 31 Page 9 c PART 1: INTRODUCTION The development of the industrialization all across the globe brings humanization with benefits yet undeniable consequences. For example, the combustion of fossil fuel, such as coal, oil, natural gas, etc.
results in the emission of number of air pollutants, such as CO2, NOx… The great amount of NOx emission, one of the air pollutant substances from both automobile and stationary sources, is now drawing the concerns from scientists in the world. Nitrogen oxide (NOx) is a general term for the oxides of nitrogen. However, the main NOx produced by the combustion process are nitric oxide and nitrogen dioxide. To be specific, Nitric oxide formed by combustion process was accounted for 90- 95%, and 5-10% is nitrogen dioxide (Jarvis DJ et al.
It is an important polluting substance in the atmosphere causing acid rain and form tropospheric ozone (tropospheric ozone is different from stratospheric ozone which aids to protect our world from dangerous ray, and it is needed to be minimized because it is in the ambient of air that we breathe). Nevertheless, there have been attempts to reduce NOx in the atmosphere in every phases of the use of fossil fuel (fuel control, combustion, and post-combustion). Selective catalyst reduction (SCR) is the proven efficient way to reduce NOx emission in the phase of post-combustion from stationary sources. The mechanism to reduce NOx is to use catalyst to accelerate the reaction of ammonia and nitric oxide in the presence of oxygen to form N2 and H2O.
The general reaction of SCR process is: Page 10 c 4NO + 4NH3 + O2 -> 4N2 + 4H2O Conventionally, scientists used V2O5–WO3/TiO2-based catalysts, which can be active only at high temperature (>300ºC). However, in real life situation the temperature in the manufacture ranges from 100-200; so the use of V2O5–WO3/TiO2- based catalysts is not appropriate and requires great amount of energy. Moreover, at the temperature higher than 400, the NH3 will be oxidized to form N2O and NO. Therefore, scientists have been working hard to research for the more proper catalysts which are active even in a low temperature condition.
Recently, scientists discovered that Cr/TiO2, Cu/TiO2 and Mn/TiO2 have high activity at 120ºC. Since then the scientists are interested in using low temperature catalyst to reduce NOx from stationary sources (Kapteijn et al., 1994) (Smirniotis et al. In this proposed study, one type of the low temperature catalyst will be tested in the laboratory for their efficiency. Moreover, there will be a research to obtain the optimum condition for the best use of this catalyst to reduce NOx from stationary sources.
Research’s objectives To describe the synthesis, preparation and performance test of low temperature catalysts (Mn20/TiO2, Mn20Ce10/TiO2, Mn20Ce20/TiO2) To compare the efficiency of three catalysts for NOx reduction from stationary sources Page 11 c Research’s questions 1. How the low-temperature catalysts are synthesized and prepared for SCR process? 2. What is the mechanism of using Mn20/TiO2, Mn20Ce10/TiO2, Mn20Ce20/TiO2 as selective catalytic reduction of NOx with NH3? 3. Compare the efficiency NOx reduction among three catalysts (Mn20/TiO2, Mn20Ce10/TiO2, Mn20Ce20/TiO2) Page 12 c PART 2: LITERATURE REVIEW 2.1 Definition Nitrogen in the form of diatomic molecule (N2) makes up about 80% of the atmosphere.
A single atom of nitrogen (N) is reactive and has valence state from plus one to plus five, thus it can form several oxide. In general, nitrogen oxides refer to the binary compounds of nitrogen and oxygen, such as nitrous oxide (N2O), nitric oxide (NO), dinitrogen trioxide (N2O3), nitrogen dioxide NO2, dinitrogen tetroxide N2O4, dinitrogen pentoxide N2O5. In atmospheric chemistry, nitrogen oxide is denoted as NOx, which specially refers to the total concentration of nitric oxide (NO) and nitrogen dioxide (NO2). Theses NO and NO2 are byproducts of fossil fuel combustion, and are the important air pollutants.
NOx to be mentioned in this research involves only NO and NO2.2 Sources of NOx Sources of NOx are both natural and anthropogenic. NOx (NO + NO2) is released by natural sources such as intrusion of stratospheric nitrogen oxides, bacterial and volcanic activities, and lightning. While the major sources of NOx by anthropogenic activities are divided into two categories: stationary sources (fossil fuel combustion, heating, power generation plants), and mobile sources (internal combustion engine) (WHO Regional Office for Europe, 2010).3 Adverse Impacts of NOx Environmental aspect: NOx gases are responsible for the formation of smog and producing brown smog in urban area, especially during summer time. NOx is not only dangerous because of itself but also with the reaction with other atmospheric substance to form ozone (O3) and acid rain.
Ozone in lower atmospheric level is different from what in the stratospheric level because it is in the ambience of air we breathe, affecting our respiratory system. Increase in nitrogen loading in water body affects the chemical balance in water, leading to eutrophication phenomenon (EPA, 1998). Human’s health aspect: Health risks from nitrogen oxides may potentially result from NO2 itself or its reaction products including O3 and secondary particles. Human health concerns include breathing in products on NOx, causing danger to lung and respiratory system (World Health Organization, 2003), lowering the body’s resistance to bacterial infections, visibility irritation, , and allergic diseases (Rusznak et al.2 Selective Catalytic Reduction (SCR) Selective catalytic reduction (SCR) is a method of converting nitrogen oxides (NOx) with the help of catalyst into diatomic nitrogen (N2).
NH3-SCR, is the selective catalytic reduction of NOx by using ammonia. Because of its efficiency, selectivity, and economics, NH3-SCR is well-developed, and widespread, comparing to other flue gas treatment technology.1 Process Description The NOx reduction reaction takes place as the gases pass through the catalyst chamber. Before entering the catalyst chamber the ammonia is injected and mixed with the gases. The chemical equation for a stoichiometric reaction using either anhydrous or aqueous ammonia for a selective catalytic reduction process is (Lee, Bai, 2016): 4NO + 4NH3 + O2 → 4N2 + 6H2O 2NO2 + 4NH3 + O2 → 3N2 + 6H2O NO + NO2 + 2NH3 → 2N2 + 3H2O However, there are several secondary chemical reactions that are likely to occur, which are: 2SO2 + O2 → 2SO3 2NH3 + SO3 + H2O → (NH4)2SO4 NH3 + SO3 + H2O → NH4HSO4 The result of SCR process affected by several factors, such as reaction temperature, space velocity, and presence of H2O and SO2 (Lee, Bai, 2016).3 Catalyst Catalyst is a material that accelerates chemical reactions.
Conventionally, the commercial catalysts used in SCR process are V2O5 /TiO2 (anatase). However, The vanadia-based catalysts are active in a narrow and high operating temperature Page 15 c window of 300-400 °C and also is subjected to deactivation by SO2 (Kompio PGWA, et al, 2012). Moreover, vanadium byproducts formed during catalyst preparation and usage is hazardous to the environment and human health (Chen et al. Therefore, there have been attempts to develop new catalyst which can operate in low temperature (Nakahjima et al.