以中孔徑矽分子篩作為氣相PAHs吸附劑之探討

Using mesoporous silicate MCM-41 as a sorbent for enrichment of PAHs

劉謹瑜(Jin-yu Liu)

指導教授 ： 王家麟

國立中央大學/理學院/化學系/碩士(2008年)

摘要

本研究以合成之中孔徑矽分子篩MCM-41做為採集空氣中多環芳香族化合物(polycyclic aromatic hydrocarbons, PAHs)的吸附劑，測試其吸附捕捉的能力，嘗試開發這類材料在化學分析中作為濃縮汙染物的可能用途。
中孔徑矽分子篩具有極高的表面積和熱穩定性、孔徑大小一致且可調整孔徑大小(2-50nm)等優點，近年來亦應用於分離、大分子催化反應、光電材料等用途。本實驗室先前的研究顯示，中孔徑矽分子篩MCM-41對大於C6以上的有機物質具有定量的吸附特性，但無法在氣相條件下測試MCM-41對大於C12分子的吸附效率。MCM-41的大孔徑特性預期應能延伸至大於C12的物質吸附，但由於空氣中之大分子濃度非常低，加上線上濃縮法無法有效將低揮發性物質熱脫附進入層析儀，因此本研究改以汽、機車廢氣排氣中之PAHs作為大分子的產生來源，測試MCM-41的吸特性；採樣後經索式萃取、樣品淨化及濃縮後，再以GC/MS測定吸附PAHs的能力，並與商業化吸附材料XAD-2做比較。實驗結果顯示二行程機車廢氣因易受到機油基質干擾，造成定性定量上的困難；而針對四行程機車廢氣，MCM-41與XAD-2均捕捉到naphthalene、acenaphthylene、acenaphthene、fluorene、phenanthrene、fluoranthene與pyrene等氣態PAHs物種，濃度介於15 ~ 2.8 x 105 ng/m3 ；於柴油車動力計採樣則分別針對引擎怠轉、20km/hr、與40km/hr三狀態之採樣，成功檢測出naphthalene、acenaphthylene、acenaphthene、fluorene、phenanthrene之氣態PAHs，濃度介於10~2.5 x 104 ng/m3；而除了揮發度較高之naphthalene其回收率約20~30%之外，其餘回收率均介於50%~150%，展現MCM-41材料作為濃縮半揮發性汙染物的應用潛力。

關鍵字

中孔徑矽分子篩 ； 氣相層析質譜儀 ； 多環芳香族化合物

並列摘要

The feasibility of employing mesoporous silicate MCM-41 as a sorbent for enriching ambient polycyclic aromatic hydrocarbons (PAHs) was investigated. The properties of mesoporous silicates involving high thermal stability, uniform porosity, and adjustable pore size capability (2-50 nm), etc., have created their various applications in abatement of volatile pollutants, separation, large molecule catalytic reactions, photoelectric studies, etc. Based on our preliminary results, MCM-41 can quantitatively absorb volatile organic compounds (VOCs) larger than C6. Nevertheless, the technical difficulties in preparing low boiling gas mixtures and thermal desorption for gas chromatography analysis hindered the sorption test of MCM-41 extending to larger than C12 molecules. As a result, in this study motor vehicle exhaust was employed as the source of low boiling molecules, in which PAHs were the target compounds for the assessment of sorption ability of MCM-41, via comparing with the commercially available XAD-2 serving as a reference.
It was demonstrated that in the test of a 2-stroke motorcycle, lubricating oil in the exhaust contributed a serious matrix effect interfering with the PAH analysis. In testing the 4-stroke motorcycle, both MCM-41 and XAD-2 exhibited similar sorption ability and various target PAHs were found, e.g., naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene, and pyrene with concentration in the range of 15 ~ 2.8 x 105 ng/m3. In the test of diesel buses, 3 conditions of idle, 20 km/hr, and 40 km/hr, respectively, were tested on a dynamometer, and naphthalene, acenaphthylene, acenaphthene, fluorene, and phenanthrene were found with concentration in the range of 10 ~ 2.5 x 104 ng/m3. Other than naphthalene, whose recovery is 20~30% due to its volatility, the recovery for other PAHs are between 50 and 150%, demonstrating high applicability of MCM-41 as a potential sorbent for the enrichment of semi-VOCs.

並列關鍵字

XAD-2 ； MCM-41 ； GC/MS ； PAHs

參考文獻

3.蘇源昌, 內部標準在氣相層析質譜儀分析揮發性有機物的效能探討, 2006, 碩士論文, 中央大學化學研究所.

7.李育誠, 矽與碳結構多孔物質作為VOC線上濃縮之吸脫附特性比較, 2007, 碩士論文, 中央大學化學研究所.

9.Srogi, K., Monitoring of environmental exposure to polycyclic aromatic hydrocarbons: a review, 2007, Environ. Chem. Lett., 5, 169-195.

10.Nollet, L. M. L., Chromatographic Analysis of the Environment, 2006, Taylor & Francis Group.

13.Chiang, T. A., Wu, P. F., Ko, Y. C., Identification of carcinogens in cooking oil fumes, 1999, Environ Res Sec, 81(1), 18–22.