半導體廠PFCs及VOCs廢氣排放處理之研究; The investigation of abatement of PFCs and VOCs exhaust gases from semiconductor industries

NCU Institutional Repository > 工學院 > 化學工程與材料工程研究所 > 博碩士論文 > Item 987654321/3793

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题名:	半導體廠PFCs及VOCs廢氣排放處理之研究;The investigation of abatement of PFCs and VOCs exhaust gases from semiconductor industries
作者:	劉世尹;Shih-Yin Liu
贡献者:	化學工程與材料工程研究所
关键词:	六氟乙烷;四氟甲烷;揮發性有機氣體;全氟化物;半導體業;起燃溫度;電漿;異丙醇;金觸媒;苯;Au catalyst;light off temperature;plasma;VOCs;PFCs;semiconductor industries;CF4;C2F6;2-propanol;benzene
日期:	2008-06-20
上传时间:	2009-09-21 12:22:46 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	半導體產業的快速成長，雖然帶動了台灣的經濟發展，但也造成了環境方面的污染。半導體業在製造過程中，由於製程機台種類相當繁多，無可避免地必須使用不同種類的化學物質，而各種排放物質種類更是不勝枚舉。截至目前為止，環保署已實施「半導體製造業空氣汙染管制及排放標準」，嚴格管制晶圓製造等相關半導體產業所排放之空氣汙染；另外，具國際約束力的「京都議定書」(Kyoto Protocol)也於2005年2月正式實施，以規範溫室效應氣體的排放量。因此，如何針對半導體製程廢氣種類的個別汙染特性，發展出一套有效的處理技術，是未來必須面對的重要課題。全氟化合物(perfluorocompounds, PFCs)是一極穩定且很難裂解去除的強效溫室效應氣體。然而現今半導體廠所採用的處理方式普遍對PFCs之去除效果不彰。本論文的第三章說明以高溫電漿火炬進行對半導體全氟化合物氣體直接裂解破壞與去除的實驗，由實驗結果顯示，對於C2F6廢氣濃度控制於20,000ppm且流量為200L/min及CF4廢氣濃度於10,000ppm且流量為50L/min時，並經由控制適當高溫電漿火炬(12kW)進行裂解後，去除效率均能達到94%以上，產物主要為CO2與HF，而氫氟酸(HF)廢氣則可輕易藉由技術早已成熟的濕式洗滌(wet scrubber)裝置來進一步收集與廢水處理，以避免此強酸之排放。另外，電漿火炬運轉壽命經改善後，壽命已可由原來的215小時提高到800小時以上。揮發性有機化合物(VOCs)為半導體業另一種值得重視的廢氣，本論文中的第四章與第五章分別探討以金觸媒進行異丙醇(IPA)及苯(Benzene)的完全氧化反應。以異丙醇的反應而言，Au負載於CeO2擔體時其活性優於負載於其他擔體(如Fe2O3、γ-Al2O3及TiO2)，而影響Au/CeO2觸媒於異丙醇之完全氧化活性之因素包括有：觸媒煅燒溫度、金粒子大小、金負載量及進料中是否含有水氣。就金負載量而言，過多的金負載(eg.2.1%)將導致金粒子的聚集，不利於活性表現。結果顯示以1.6%Au/CeO2觸媒能表現出較低的起燃溫度，且奈米Au顆粒(≦5nm)能高度分散在CeO2擔體上。另外，Au/CeO2觸媒於300℃下煅燒會表現出較佳的活性，此與金粒子的高氧化價態(Au+n)形成有關。而進料中含有水氣，亦可明顯提升活性。就苯的完全氧化反應而言，主要是以沉積沉澱法將奈米金顆粒沉積在CeO2上製備Au/CeO2觸媒，另以初濕含浸法將V2O5負載在氧化鈰上作為添加劑，製備Au/V2O5/CeO2觸媒。探討不同金含量、與煅燒溫度對苯完全氧化反應之影響。結果顯示，煅燒300℃之Au/CeO2(b)觸媒，在200℃能將苯完全氧化，而當添加2%釩氧化物於Au/CeO2(b)且於相同溫度300℃煅燒之觸媒，對原來的活性僅有些微的影響。而400℃煅燒下添加釩氧化物於Au/CeO2(b)之觸媒則相較原來未添加釩氧化物之活性有顯著的幫助。然而比較煅燒300℃之Au/CeO2(b)觸媒與400℃煅燒之Au/V2O5/CeO2(b)觸媒的活性相當，由兩者的XPS分析都含有Au+n，由此了解觸媒表面Au具有高氧化態能提升苯的完全氧化反應活性，藉由降低煅燒溫度或添加釩氧化物皆能產生Au+n，而釩氧化物中釩氧化價位的變化對苯氧化活性的影響應不大。耐久性測試方面，Au/CeO2觸媒在120小時內能保持100%的轉化率，而Au/V2O5/CeO2觸媒則已有活性衰退現象。就Pt和Au觸媒同時對苯完全氧化的活性比較後發現，Au觸媒仍然較Pt觸媒具有較低的反應溫度。另外，Au觸媒不需事先還原及價格上相對較Pt便宜為其優勢。 The evolution of semiconductor industries promotes the economic development of Taiwan, but it also results in environmental pollution problems. The employment of a variety of chemicals during the semiconductor manufacturing process is very complicate due to the numerous types of process facilities. Till now, the Environmental Protection Administration has carried out the rule of“Regulation Governing the Air Pollution of Semiconductor Manufacturing Industries”, in order to restrain stringently the emission of related semiconductor manufacturers. Moreover, the Kyoto Protocol has been signed on December 11, 1997, and entered into force on 16 February 2005. Countries that ratify this protocol commit to reduce their emissions of carbon dioxide and five other greenhouse gases. Therefore, it is a very important issue that how to develop an effective method to abate the waste gases from semiconductor process in the future. Perfluoro compounds(PFCs) are greenhouse gases which is very chemical stable and difficult to remove by decomposition. Nowadays, the PFCs destruction of semiconductor manufacturer by present treatment methods are not effective. Chapter 3 of the thesis shows the test results for the direct destruction and removal of PFCs by thermal plasma method. According to the test results, the destruction efficiency of PFCs under 12kW of plasma torch power could achieve 94% when the concentrations of C2F6 and CF4 are 20,000ppm and 10,000ppm and the flow rates are 200L/min and 50L/min, respectively. The main products are CO2 and HF, and the HF acidic waste gas could be absorbed completely by wet scrubber and then treats as waste water to avoid the effluence of HF(g). The lifespan of plasma torch has been promoted from 215 hr. to above 800 hr. after improvement. Volatile organic compounds(VOCs) are other important harmful gases which also emitted from semiconductor industry. Chapter 4 and 5 of the thesis report the complete oxidation of 2-propanol and benzene over gold based catalyst respectively. Concerning the complete 2-propanol oxidation, the catalyst of gold deposited on CeO2 support shows more active than on other supports(eg.Fe2O3、γ-Al2O3 and TiO2). The factors which affect the activities of complete oxidation of 2-propanol over Au/CeO2 including the calcination temperature、the gold particle size、the amount of gold loading and the moisture content in feed. Concerning the gold loading on catalyst, too much amount of gold (eg.2.1%Au) will result in aggregation of gold particles which would cause lower activity. According to the activity test, the 1.6Au/CeO2 catalyst shows lower light off temperature, and the nano gold particles(≦5nm) were highly dispersed on the CeO2 support. Moreover, the Au/CeO2 catalyst which calcined at 300℃ is more active than catalysts calcined at other temperations, and this result could be related to the presence of high oxidation state of gold(Au+n). On the other hand, the more moisture content in feed, the more active on complete 2-propanol oxidation over 1.6%Au/CeO2 catalyst. Concerning the complete benzene oxidation, Au/CeO2 and Au/V2O5/CeO2 are studied. The factors affect the activities of complete benzene oxidation are calcination temperature and gold loading. The results indicate that the Au/CeO2(b) catalyst(c300) could oxidize benzene completely at 200℃. After the addition of 2%V2O5 to Au/CeO2(b)(c300), the activity just shows slight enhancement. Moreover, the Au/2%V2O5/CeO2 catalyst(c400) are obviously more active than Au/CeO2(c400). However, the activities are almost the same for Au/CeO2(b)(c300) and Au/2%V2O5/CeO2(b)(c400). The XPS results shows these two catalysts all contained Au+n which indicated that the presence of high oxidation state of Au(Au+n) could enhance the activity of complete benzene oxidation. The high oxidation state of Au(Au+n) could be obtained by lowering the calcination temperature of Au/CeO2 or the addition of V2O5 to Au/CeO2. On the other hand, the durability test shows that the Au/CeO2 could maintain 100% conversion, and the Au/V2O5/CeO2 shows slight activity decrease after 120hr. Comparing the activity of supported Au and Pt catalysts, the Au catalyst is more active than Pt catalyst for complete benzene oxidation. Moreover, The price of Au is cheaper than Pt and Au catalysts do not need to be reduced by hydrogen before use. These could be the advantages for practical application.
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