以NCLA9K4活性碳作為VOC濃縮介質與熱脫附方法之改良; Activated charcoal NCLA9K4 as VOC condensed medium and improvment of thermal desorption method

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题名:	以NCLA9K4活性碳作為VOC濃縮介質與熱脫附方法之改良;Activated charcoal NCLA9K4 as VOC condensed medium and improvment of thermal desorption method
作者:	陳彥呈;Yan-cheng Chen
贡献者:	化學研究所
关键词:	致冷晶片;活性碳;有機揮發性氣體;VOC;peltier cooler;activated charcoal
日期:	2011-07-26
上传时间:	2012-01-05 14:28:57 (UTC+8)
摘要:	揮發性有機化合物(volatile organic compound, VOC)，本身為空氣中之汙染物，也是臭氧以及二級有機氣溶膠之前驅物。臭氧、VOC以及有機氣溶膠濃度的上升會造成人們健康的危害。因此對於大氣中VOC的組成有事先的瞭解，將有助於掌握臭氧的形成機構。然而在全範圍的VOC分析中，對於高揮發性的物種量測在現今的技術中仍具相當挑戰。本次研究中運用一多孔洞新材料活性碳NCLA9K4搭配自製不須冷劑補給之熱脫附裝置，將對大氣中之VOC具好的吸附能力且定量良好。值得注意的是VOC中含豐富的乙烷、乙烯、丙烷、丙烯等皆是容易破出之物質。NCLA9K4具微孔的特質(孔徑範圍在0.5 nm ~ 30 nm，平均孔徑1.85 nm)且高比表面積(~3500m2g-1)具良好的VOC吸附特性，並與孔徑材料MCM-48與商品化多重床碳吸附劑進行吸附比較。透過皮爾特晶片的降溫，先將捕捉管之吸附溫度降至-10以及-30℃進行測試，最後針對皮爾特晶片之散熱部分，改用更高效能散熱模組，而能將溫度降至-40℃，利用降溫的輔助提高材料在高揮發性物種的捕捉。利用A9K4搭配Carbosieve SIII所組合之二重床，發現在-40℃下能將C2以及C3物種捕捉效果良好，線性達0.999以上，C2~C11的RSD皆小於3%，偵測極限都在數百個pptv以下。 Ambient volatile organic compounds (VOCs) are air pollutants, and also act as precursors of ozone and secondary organic aerosol (SOA). Elevated VOCs, ozone, and fine aerosol levels cause adverse effects on human health. Knowing the composition of ambient VOCs is the prerequisite of understanding ozone formation and thus its containment strategy. However, the full-range analysis of ambient VOCs in the field is technically challenging, particularly for the more volatile compounds. In this study, a new porous material - activated charcoal NCLA9K4 - will be studied to quantitative enrich ambient level VOCs by a self-built cryogen-free thermal desorption device. Special attention is given to the enrichment efficiency of the most volatile compounds, namely ethane, ethylene, propane, and propylene, since they are more easily to breakthrough. NCLA9K4, which has micropores (pore range = 0.5 nm ~ 30 nm, average pore size = 1.8 nm) and high specific surface area (3500 m2s-1), was compared with MCM-48 and commercial multi-carbon sorbents for their VOC enrichment capability. Test of trapping was first performed by cooling the sorbent trap at -10 and -30℃. Further improvement in the Peltier cooling using a better heat-sink allowed a lower temperature of -40℃and; thus, better trapping efficiency for high boiling compounds. The combination of using A9K4 and Carbosieve III to form a dual-sorbent bed and cooling at -40℃ was able to quantitatively analyze ambient C2-C3 compounds with R2 close to 0.999, RSD better than 3%, and detection limit at sub-ppbv level.
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