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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/3765


    Title: 以稻殼灰分沈澱固著製備擔體銅觸媒 之反應性研究;Preparation of Rice Husk Ash-Supported Copper Catalyst by Deposition-Precipitation
    Authors: 黃士益;Shih-Yi Hung
    Contributors: 化學工程與材料工程研究所
    Keywords: 擔體銅觸媒;稻殼灰分;沉澱固著;rice husk ash;deposition-percipitation;copper catalyst
    Date: 2002-06-28
    Issue Date: 2009-09-21 12:22:05 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 中文摘要 本研究以稻殼為起始原料,經過水洗、酸洗、熱解及碳燒等前處理方法,製成稻殼灰分,並以其為擔體,利用沈澱固著法製備成稻殼灰分擔體銅觸媒(簡稱為Cu/RHA觸媒),同時利用感應耦合電漿質譜儀(ICP-MS)、元素分析儀(EA)、感應耦合電漿原子放射光譜儀(ICP-AES)、氮吸附法、X射線繞射儀(XRD)、熱重分析儀(TGA)、程式升溫還原(TPR)、N2O分解吸附(dissociative adsorption of nitrous oxide)及掃描式電子顯微鏡(SEM)等各項儀器與分析技術,分別對擔體及觸媒進行鑑定,並利用乙醇脫氫反應作為催化活性的測試,藉以評估稻殼灰分做為觸媒擔體的可行性, 在稻殼灰分的組成分析方面,從分析結果得知:二氧化矽的純度達99%,其晶態屬於非晶型的二氧化矽,氮吸附分析結果指出其BET比表面積約為153m2/g。而在稻殼灰分擔體銅觸媒(Cu/RHA)方面,從分析結果得知:沈澱固著乾燥後所形成的觸媒前趨物為一種類似孔雀(chrysocolla-like)的層狀矽酸銅(copper hydrosilicate)結構,而矽酸銅熱分解溫度至少要673K,且層狀矽酸銅在高溫下鍛燒會分解成高表面積的網狀結構。由氮吸附結果指出,鍛燒後的Cu/RHA觸媒,其BET比表面積隨銅金屬載量增加而增加。從TPR圖譜可看出,Cu/RHA觸媒的還原溫度隨銅金屬載量增加而降低。從N2O分解吸附結果可知,Cu/RHA觸媒的分散度隨銅金屬載量增加而降低,但銅平均粒徑隨銅金屬載量增加而變大。從XRD圖譜也可看出銅粒徑有增加的趨勢。隨著金屬載量的增加,將有助於觸媒表面活性積數目的增加,然而過高的載量,會造成銅晶粒變大,整體對乙醇的吸附能力便弱,將造成活性下降。鍛燒的條件會影響觸媒活性,最佳的鍛燒溫度為673k。最佳的還原溫度為573k,最佳的還原時間1hr。 19.8wt.% Cu/RHA觸媒在548K下進行乙醇脫氫反應,能發揮最佳的活性,但隨著反應的進行因產生積碳現象而使活性衰退,一直到130分鐘才趨於穩定。比較稻殼灰分與氧化矽膠的分析結果,稻殼灰分確實有異於氧化矽膠的擔體性質存在,不僅能負載較多的銅活性金屬,也可使負載於表面的銅金屬有較高的金屬表面積,而且分散性佳,應用於催化反應時也較不易積碳,有較佳的活性表現。 Abstract In this work, rice husk ash (RHA) was used as a catalyst support. RHA-supported copper catalysts (Cu/RHA) were prepared by the deposition-precipitation method. Characterization of the RHA-supported copper catalysts (Cu/RHA) indicates that the formation of the copper hydrosilicate with structural properties similar to the mineral chrysocolla. The thermal decomposition of the copper hydrosilicate starts above 673K. The specific surface area of the calcinated catalysts increases with increasing the copper loading. The dispersion of copper catalysts decreases with increasing copper loading. Furthermore, the mean size of copper crystallites increases with an increase in copper loading. RHA supported copper catalysts was tested by the dehydrogenation of ethanol at 473-548K. The results indicate that the optimal preparations and operating conditions are 19.8wt.% in copper loading, 673K in calcination temperature, 573K in reduction temperature, 1hr in reduction time and 548K in reaction temperature. Moreover, copper catalysts supported on RHA display higher catalytic activity than those supported on silica gel, as revealed by the test of ethanol dehydrogenation. Thus, RHA is found to be preferable over silica gel as a support.
    Appears in Collections:[化學工程與材料工程研究所] 博碩士論文

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