結合臭氧與氧化錳觸媒去除氯苯之研究; Chlorobezene oxidation with ozone over supported manganese oxide catalyst

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题名:	結合臭氧與氧化錳觸媒去除氯苯之研究;Chlorobezene oxidation with ozone over supported manganese oxide catalyst
作者:	梁旭昇;Hsu-sheng Liang
贡献者:	環境工程研究所
关键词:	PCDD/PCDF;觸媒;臭氧;10%MnOX/SiO2;PCDD/PCDF;10%MnOX/SiO2;catalytic ozonaion
日期:	2010-07-28
上传时间:	2010-12-08 13:50:18 (UTC+8)
出版者:	國立中央大學
摘要:	戴奧辛(PCDD/PCDF)近年來引起很大的關注，但在研究上由於無法即時分析且具有高毒性，本研究遂以氯苯做為替代污染物，以瞭解觸媒與臭氧結合對其破壞消減之效應。此外含氯揮發性有機物(Chlorinated Volatile Compounds, Cl-VOCs)本身也廣泛使用在工業上，常用於製造業乾洗及脫油的溶劑，根據學者研究，每年約有一百五十萬噸含氯有機物排放至大氣中，因此尋求破壞含氯有機物的技術也將是必要的。本研究以含浸法製備10 wt % MnOx/SiO2觸媒，經氮氣吸附儀測定比表面積為286 m2/g，XRD鑑定為無晶相結構，實驗以固定床反應器進行臭氧催化氧化氯苯反應，分別改變溫度、臭氧含量及空間流速並探討其效應。在未添加臭氧情況，120℃時氯苯轉化率僅2.7%，加入900 ppm臭氧使氯苯轉化率大幅提升至90.4%，但將空間流速由300,000降至60,000 h-1，氯苯轉化率僅由90.4提升至92.7%，顯示增加氯苯停留時間對其轉化率增加並不明顯。在觸媒穩定性實驗方面，經過96小時測試，氯苯轉化率由90.8%降至79.6%，氣相含碳產物僅有CO及CO2，CO2與CO產物選擇性分別為58.5與41.5%，碳平衡介於76.2與74.1%之間。 PCDD (Polychlorinated dibenzodioxin) and PCDF (Polychlorinated dibenzofuran) are commonly known as dioxins which have received great concerns due to their persistency and toxicity. In this study, chlorobenzene (CB) was employed as dioxin model molecule to evaluate the destruction behavior due to the high toxicity of dioxin. In this study, 10 wt % MnOx/SiO2 was prepared by impregnation method. The surface area of MnOx/SiO2 measured by the BET method was 286 m2/g. No distinct peaks were observed in the XRD pattern, indicating that manganese oxide was of an amorphous structure. Catalytic oxidation of gaseous chlorobenzene with ozone over 10% MnOx/SiO2 was experimentally carried out with a packed bed reactor to investigate the feasibility of the low-temperature decomposition process. The effects of reaction parameters (i.e reaction temperature, ozone concentration and space velocity (SV)) on the chlorobenzene oxidation were discussed. The conversion of chlorobenzene achieved with MnOx/SiO2 in the absence of ozone was only 2.7% at 120℃. On the other hand, the conversion increased to 90.4% over MnOx/SiO2 with 900 ppm ozone at 120℃. CB conversion slightly increases from 90.4% to 92.7% with the decrease of space velocity from 300,000 to 60,000 h-1 due to the fact that longer reaction time results in higher CB conversion. The results of the long-term operation indicate that the conversion of chlorbenzene shows a little drop from 90.8% to 79.6% after 96 h operation. At the steady state, CO and CO2 were the only carbon-containing products detected in gas streams at the outlet of the reactor. The selectivities of CO2 and CO were 58.5 and 41.5%, respectively. The average carbon and chlorine balance were 76.2 and 74.1%, respectively.
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