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    Please use this identifier to cite or link to this item: http://ir.cnu.edu.tw/handle/310902800/9113


    標題: 不同製備方法對於CeO2觸媒催化含酚廢水濕式氧化反應之影響
    Effect of catalyst preparing method on the CWAO of phenolic wastewater using CeO2
    作者: 張世燊
    Shih-Hsiung Chang
    貢獻者: 林秀雄
    嘉南藥理科技大學:環境工程與科學系碩士班
    關鍵字: 反應條件
    再生
    誘導期
    氧化鈰觸媒
    觸媒濕式氧化反應
    不同製備方法
    induction period
    CeO2 catalyst
    CWAO
    preparing method
    regeneration and reaction conditions
    日期: 2006
    上傳時間: 2008-11-24 17:02:02 (UTC+8)
    摘要: 本研究是利用不同製備方法,包括過氧化氫還原法 (CeO2-A,redox reaction in hydrogen peroxide)、沉澱法(CeO2-B,precipitation method)、草酸溶膠法(CeO2-C,sol-gel method with citric acid )、聚丙烯酸溶膠法(CeO2-D,sol-gel method with poly acrylic acid )及直接將CeCl3‧7H2O煅燒(CeO2-E)等五種方法,來製備奈米級CeO2觸媒,利用這些觸媒進行含酚廢水CWAO 反應,並藉由分析酚轉化率與COD去除率,評估前述五種不同觸媒對於含酚廢水CWAO反應之催化效能,並進行反應條件對去除效率影響之探討。
    由實驗結果顯示,反應效能最佳者為CeO2-A觸媒(過氧化氫還原法),在反應溫度160℃、酚濃度1000ppm、氧氣壓力1.5MPa及觸媒添加量1.0g/L之條件下,反應2個小時可達100%酚轉化率及95%COD去除率,效能其次的是CeO2-E觸媒,相同條件下反應2小時,酚轉化率及COD去除率分別可達90%及70%。
    此外,我們發現到誘導期存在於不同的反應條件下,並且隨著觸媒本身活性高低及反應溫度之增減而改變,當觸媒活性較高時,誘導期就比較短,例如:反應溫度160℃,添加A觸媒及E觸媒之誘導期約為1小時,而添加C觸媒及D觸媒之誘導期分別為3小時及22小時。而反應溫度從160℃提升至180℃時,其A、E、C觸媒之誘導期分別降為30分鐘、30分鐘及1小時。
    在觸媒鑑定方面,我們利用XRD、BET、O2-TPD、H2-TPR驗證觸媒活性高低之原因。在XRD圖譜之中,我們可以發現到A觸媒之強度最低及雜訊值最多,表示其晶相缺陷最多,結構最不穩定。由比表面積結果顯示,不同製備方法之CeO2觸媒有著不同之比表面積,一般認為當比表面積越大即活性位址就會越多,由結果得知,效能最好之觸媒為A觸媒其次是E觸媒,其比表面積分別為59.5(m2/g)及54.4 (m2/g),顯示出效能之優劣與比表面積並無直接之關係,此外活性高低主要受到觸媒之結構穩定與否之影響,比表面積的影響相對可能比較小。在O2-TPD圖譜中顯示出A觸媒有較多之可交換之結構氧,在H2-TPR圖譜中發現A觸媒的氫的消耗量最高,表示其被還原之鈰含量最多,相對的鈰在觸媒表面上的分布也最多。
    This study aimed at assessing performance of CeO2 catalyst, prepared via various methods, for the CWAO of phenol. There are five CeO2 catalysts tested, including CeO2-A (redox reaction in hydrogen peroxide), CeO2-B (precipitation method), CeO2-C (sol-gel method with citric acid), CeO2-D (sol-gel method with poly acrylic acid) and CeO2-E (direct calcination of CeCl3‧7H2O). Results of CWAO of phenol show that CeO2-A perform best. With reaction conditions of 160°C, 1.5MPa O2 and 1.0g/L catalyst loading, 1000ppm phenolic solution, after 2 hrs reaction, could attained about 100% phenol conversion and 95% COD removal. Under the same conditions, effectiveness of CeO2-E was only about 90% phenol conversion and 70% COD removal, performing the second best. Induction period was found in CWAO of phenol, which varied with catalyst activity and reaction temperature. The higer the catalyst activity or reaction temperature, the shorter the induction period.
    In addition to CWAO of phenol, effectiveness of various catalysts was further characterized via BET, XRD, O2-TPD and H2-TPR. XRD analysis reveals that CeO2-A has the most crystal defects, conferring it the higest activity. Whilst O2-TPD and H2-TPR measurements indicate that CeO2-A has the most exchangeable structure oxgen and the most active sites (dispersed surface cerium), respectively. Contrastedly, surface area seems have no direct relation ship with the catalyst activity.
    Durability of CeO2-A was also assessed. Used CeO2-A could be effectively regenerated via acetone rinsing. Even after quadric-use, the regenerated CeO2-A exhibited fair performance, (90% phenol conversion and 85% COD removal at 180°C,1.5MPa O2 and 1.0g/L catalyst loading for 4 hrs reaction.
    Finally, according to the results at various reaction conditions, the optimum operating condition is proposed as follows: reaction temperature 180°C, 1.5MPa O2 and 1.0g/L catalyst loading.
    Appears in Collections:[環境工程與科學系(所)] 博碩士論文

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