奈米級含氮二氧化鈦應用於微量汞蒸氣去除之研究

Photocatalytic study of nanoscale N-doped TiO2 on low-concentration mercury vapor remova

粘聖宏(Sheng-Hung Nian)

指導教授 ： 陳孝行 ； 席行正

國立臺北科技大學/工程學院/環境工程與管理研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00309

摘要

本研究分為觸媒製備及光催化應用部分，製備含氮觸媒TiOxNy 進行 SEM、TEM、FTIR 之觸媒特性分析，再與觸媒 P-25 分別去除標的汙染物氣相汞，期望在不同實驗條件下氧氣、水分、光線種類及反應溫度，透過光觸媒作用對於氣相汞進行吸附達到去除效果，並比較改質後之差異性，評估其改質之實際效益。
經基本性質分析結果顯示改質後觸媒粒徑增大，晶相有轉變金紅石晶相趨勢，且測得觸媒含有氮元素且以官能團型式存在於表面；在光催化系統結果，其改質與未改質觸媒對在 0% 氧氣時皆發生因水分子競爭吸附造成汞脫附，TiOxNy 和 P-25 之脫附比例分別為 50% 及 12%，摻入氮後觸媒表面形成官能基，以化學鍵結減緩水分子對其競爭能力，即提高對水之抵抗性。
而在以照紫外光及可見光下，改質前後之觸媒皆有良好汞吸附效率，增加氧氣濃度效率隨之增加，在21% 氧氣及照紫外光下，其吸附效率可分別達 68% 及72%，而在有氧情況下，促進環境中氧化汞形成，使得沒有汞脫附產生，吸附觸媒表面上大多以氧化汞為主要形式，當形成後馬上吸附於觸媒表面；而提高環境溫度，隨著溫度上升而兩種觸媒之吸附效率皆是降低，但改質 TiOxNy 在環境 50℃ 時較穩定，在 21% 氧氣濃度下吸附效率可達 48 %。
煙道氣體一氧化氮、二氧化硫及鹽酸氣體對於光觸媒吸附效率皆為負面影響，在 6% 氧氣及照紫外光之實驗條件下，二氧化硫及鹽酸氣體使原本 70% 效率降至 40-50%，而一氧化氮存在則降至 30%。

關鍵字

元素汞蒸氣 ； 含氮二氧化鈦 ； 吸附效率 ； 氧化效率

並列摘要

Mercury was identified as one of hazardous air pollutants sourced from coal-fired because of its toxicity and bioaccumulation. The goal of this study was to remove gaseous elemental mercury by prepared N-doped TiO2. The subject was divided into two parts. The first is to prepare nitrogen doped titanium dioxide (TiOxNy) and analyze characteristic of photocatalyst. The second is to test removal efficiency for gaseous elemental mercury by adsorption of TiO2 and TiOxNy under various conditions. (oxygen concentrations, irradiations etc.). Finally the different results of removal efficiency for removal mercury between different catalysts were discussed.
In first part, the molecular state nitrogen was successfully incorporated into TiO2 by calcination. The particle size of TiOxNy became lager because of high temperature and calcination with ammonia chloride. The FTIR measurement showed there are functional groups on the surface of TiOxNy.
In the second part, the removal efficiency increase with increasing oxygen concentration and imply an enhancement in the presence of light irradiation. The optimum removal efficiency of TiO2 and TiOxNy in 21%O2 condition were 68% and 72% individually and parts in this study. The affection of H2O molecules, was supposed to compete adsorption site with Hg and made a greatly desorption without oxygen under ultraviolet irradiation that decreased Hg0 removal. However doping nitrogen in TiO2 reduced proportions of desorption, and was attributed the chemical bonding to functional groups on catalyst surface. The adsorptive reaction of Hg at 50℃ was worse than at 25℃,and no efficiency at 100℃. This result indicated the Hg0 removal decreased with increasing temperature of reaction.
The flue gases (NO, SO2 and HCl) were found an inhibitory effect on Hg0 removal over catalyst due to the competition of flue gases with Hg0 for the adsorption sites and radicals.

並列關鍵字

N-doped TiO2 ； photocatalysis ； elemental mercury ； continuous system

參考文獻

12. 李淑莉, 台灣地區燃煤發電廠含汞物質流布與管理之研究, 2008, 國立台北科技大學環境工程與管理研究所.

1. Innanen, S., The ratio of anthropogenic to natural mercury release in Ontario: Three emission scenarios. Science of the Total Environment, 1998. 213(1-3): p. 25-32.

2. Hsu, B.C., Chen, S. S.,Su, C.,Liu, Y. T., Preparation and characterization of nitrogen-doped titanium dioxide. Journal of Nanoscience and Nanotechnology, 2007. 7(9): p. 3104-3110.

3. Pacyna, E.G., J.M. Pacyna, and N. Pirrone, European emissions of atmospheric mercury from anthropogenic sources in 1995. Atmospheric Environment, 2001. 35(17): p. 2987-2996.

5. Global mercury assessment, 2002, UNEP Chemicals.