臺灣博碩士論文加值系統

本研究以各種異相光觸媒(TiO2, La2Ti2O7及Fe-La2Ti2O7)與不同光源(UV-254, UV-365及LED395nm)光催化還原一氧化氮，探討光強度、氨氣與一氧化氮初始濃度、氧氣濃度與相對濕度對還原效率之影響及其光還原反應機制。實驗結果顯示，在設定的操作條件下，若表面反應為總反應之速率決定步驟時，一氧化氮之光還原速率為Eley-Rideal模式。
ㄧ氧化氮與氨氣的光還原實驗結果顯示:一氧化氮之光還原效率與光強度呈正比，但過高的光強度下，電子、電洞的再結合現象會明顯影響還原效率；當吸附於觸媒表面的氨氣濃度、與吸附於觸媒表面氨氣行光還原反應之ㄧ氧化氮濃度及還原活性點Ti3+為Ti4+的氧氣濃度彽於特定值時，一氧化氮之光還原為質傳控制反應，反之，則為表面化學反應控制反應；水與氨氣分子間的競爭吸附導致較低的一氧化氮光還原效率，此現象於Fe-La2Ti2O7光催化程序中更為明顯，可歸因於其表面性質易受水氣影響；於不同氨氣初始濃度下，一氧化氮光還原速率之理論值與實驗值不謀而合；透過表觀光量子產率與耗能結果可發現UV-365/TiO2為最適化之光催化程序。

The mechanism of photo-SCR on the selective reduction of nitrogen oxide is investigated in this study. The performances of nitrogen oxide reduction reaction under various light intensities, initial ammonia and nitric oxide concentrations, oxygen concentrations and relative humidity are discussed by using diverse photocatalysts, such as TiO2, La2Ti2O7 and Fe-La2Ti2O7, and light sources, eg. UV (254nm), UV (365nm) and UVLED (395nm). The reaction rate is expressed based on an Eley-Rideal kinetic model with assumption that the surface reaction is the rate-determining step in overall reaction, while the reaction rate at a given operating condition can be simulated.
The experimental results indicate that NO removal efficiency increased with light intensity, but the electron-hole pair recombination of the photocatalysts under various light sources and light intensities is strongly affecting the NO removal efficiency. Reaction control can be observed once the concentration of ammonia adsorbed on the surface of photocatalyst, nitric oxide reacted with ammonia which adsorbed on photocatalyst’s surface and oxygen used for the reduction of Ti3+ to Ti4+ under specific values; otherwise, the reaction will be processed under mass transfer control. The compaction of water molecular and ammonia molecular result in the decrease the NO removal efficiency; furthermore, the effect of relative humidity for Fe-La2Ti2O7 is more significant than the other photocataltsts because of its surface properity. In addition, the simulated results of reaction rate under various initial concentration of ammonia agree fairly well with the available experimental data. According to the results of the apparent quantum yield and the electrical energy per order (EEO), to operate under UV-365/TiO2 photoreduction process is the optimal on the viewpoint of photon utilization and energy saving.

English Abstract……………………………………………………………………………i
Chinese Abstract………………………………………………………………………… iii
Acknowledment…………………………………………………………………………..iv
Table of Content………………………………………………………………………......v
List of Figures…………………………………………………………………………....vii
List of Tables………………………………………………………………………..........xi
List of Symbols…………………………………………………………………………..xii
Chapter 1 Introduction…………………………………………………………………….1
1.1 Background……………………………………………………………………..1
1.2 Objective and Scope……………………………………………………………2
Chapter 2 Literature Review………………………………………………………………3
2.1 Control Technologies for NOx in Gaseous Effluents…………………………..3
2.1.1 Decomposition of NOx by Reduction…………………………………….3
2.1.2 Decomposition of NOx by Oxidation…………………………………….8
2.1.3 Comparison of Controlling Technologies for NOx……………………..11
2.2 Parameters Effect of SCR……………………………………………………..14
2.2.1 Effect of Reaction Temperature…………………………………………14
2.2.2 Effect of Ammonia Concentration………………………………………15
2.2.3 Effect of Nitric Oxide Concentration……………………………………17
2.2.4 Effect of Oxygen Concentration………………………………………...18
2.2.5 Effect of Retention Time……………………………………………......20
2.2.6 Effect of Water Vapor Concentration…………………………………...20
2.2.7 Effect of NO/NH3 Dosage…………………………………………….....22
2.3 Photolysis and Photocatalytic Process……………………….………………..23
2.3.1 Fundamental of Photolysis and Photocatalytic Processe………………..24
2.3.2 Basic Properties of Photocatalysts………………………………………25
2.3.3 Reaction Mechanisms and Kinetics……………………………………..33
2.3.4 Applications of Photocatalysis…………………………………………..36
2.4 Fundamentals and Applications of LEDs in Photocatalytic Processes………..36
2.4.1 Fundamentals of LEDs…………………………………………………..37
2.4.2 Characteristics and Development of LEDs……………………………...39
2.4.3 Application of LEDs on UV/TiO2 process……………………………...42
Chapter 3 Experimental …………………………………………………………………44
3.1 Instruments…………………………………………………………………….44
3.2 Chemicals……………………………………………………………………...46
3.3 Experiment System and Photoreactor…………………………………………47
3.4 Experiment Framework……………………………………………………….49
3.5 Experimental Procedures……………………………………………………...50
3.5.1 Photocatalyst Preparation………………………………………………..50
3.5.2 Coating the photocatalyst……………………………………………….52
3.5.3 Photocatalyst Process……………………………………………………52
3.6 Analysis………………………………………………………………………..56
3.6.1 NO/NOx analyzer……………………………………………………….56
3.6.2 GC/TCD…................................................................................................57
3.7 Background Experiments……………………………………………………...58
Chapter 4 Results and Discussion………………………………………………………..64
4.1 Characterization of photocatalysts ……………………………………………64
4.2 Photo-SCR with NH3 by UV/TiO2 process…………………………………...67
4.2.1 Effect of light intensity………………………………………………….67
4.2.2 Effect of initial ammonia concentration………………………………...77
4.2.3 Effect of initial nitric oxide concentration………………………………82
4.2.4 Effect of Oxygen Concentration………………………………………...87
4.2.5 Effect of Relative Humidity……………………………………………..92
4.2.6 Reaction kinetics of photo-SCR with NH3 using Fe-La2Ti2O7 as
Photocatalyst……………………………………………………………97
4.3 Electrical energy determination……………………………………………...104
Chapter 5 Conclusions and Recommendations…………………………………………108
Reference……………………………………………………………………………….110
Vita……………………………………………………………………………………...116

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