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研究生:饒瑞孟
論文名稱:輕石油腦異構化觸媒之製備,特性分析及催化研究
論文名稱(外文):Light Naphtha Isomerization Catalysts: Preparation, Characteration and Catalysis
指導教授:張仁瑞
學位類別:碩士
校院名稱:國立中正大學
系所名稱:化學工程研究所
學門:工程學門
學類:化學工程學類
論文種類:學術論文
論文出版年:1995
畢業學年度:83
語文別:中文
論文頁數:92
中文關鍵詞:觸媒催化
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本研究中,利用正戊烷、正己烷及正庚烷異構化產物之octane barrel之提昇、正庚烷異構化裂解氣相產物之生成,以及觸媒對硫份之容忍性,探討製備方式,前處理條件及鎳鉑雙金屬觸媒對輕石油腦異構化鉑/絲光(mordenite)觸媒反應性質之影響。同時,利用一氧化碳及氨之化學吸附及程溫脫附,快速傅立葉轉換紅外線光譜儀,X─射線繞射分析儀及程溫還原法分析觸媒之性質。實驗在一順流連續式反應系統操作,系統之操作條件與商用製程之操作條件類似。實驗之結果顯示,觸媒經不同之製備方式及前處理條件導致不同之金屬分散度,觸媒之反應性質隨著金屬分散度增加而增加。但是,在金屬分散度約為0.6時,反應性質有偏低之現象。經由快速傳利葉轉換紅外線光譜儀及X一射線繞射儀之分析結果,是因為觸媒孔道有pore mouth plugging現象,導致觸媒孔道內部質傳阻力增加之故。除此之外,觸媒以離子交換法製備,鍛燒與還原溫度維持450℃,並且以0.5℃/min之升溫速率升溫可以得到最好之金屬分散度。然而,在進料中含硫份時,金屬分散度並非影響觸媒反應性質之唯一因素,觸媒金屬之穩定性也是重要因素之一。當進料中含硫份時,觸媒以530℃還原時,可以得到最好之穩定性。原因是,在此操作條件,金屬在分散度和穩定性相互影響下達到最適值之故。
另外,加入適量之鎳在鉑/絲光觸媒上,可以增加異構化產物之octabe barrel抑制觸媒活性之衰減。實驗之結果顯示,鎳鉑雙金屬觸媒在以含500ppm之正己烷為進料進行反應時,可以增加觸媒對硫份之容忍性。同時,在正戊烷,正己烷及正庚烷異構化反應中,一方面可以降低正庚烷之氣相裂解產物,另一方面可以提高產物之octane barrel。經由程溫還原法及NH3程溫脫附分析觸媒,原因是鎳和鉑形成雙金屬合金觸媒導致觸媒金屬叢不容易發生金屬聚集現象之故。

The effects of catalyst preparation and pretreatment and the role of second metal, nickle, on the metal dispersion of mordenite-supported Pt catalysts and the resulting catalyst performance were investigated by examining CO chemisorption, octane barrel upgrading of n-pantane(C5) ,n-hexane (C6) and n-heptane (C7) isomerization, fuel gas formation of n-heptane (C7) hydrocracking, and. catalyst deactivation by sulfur poisoning. The test reactions were carried out with a continuous fixed-bed reaction system and the operation conditions were similar to those of a commercial scale isomerization process. The correlation of octane barrel of Cg isomerization reaction products with metal dispersion indicated that octane barrel upgrading was increased with increased Pt dispersion, except with catalysts of moderate metal dispersion (CO/Pt is about 0.55), which have a unusual low ocatne barrel. This unusual catalytic performance is thought to be a result of pore mouth plugging, inferred from fast Fourier transform infrared (FFT-IR) spectroscopy characterizing CO chemisorbed on the Pt catalysts and X-ray diffraction (XRD) spectroscopy characterizing zeolite structure. The catalyst with highest Pt dispersion was prepared by the ion exchange method. Before reaction it was pretreated by calcination in flowing air at 450℃, followed by reduction in flowing H2 at 450℃. Temperature ramping rate is also important for the preparation of a high Pt-dispersion catalyst; the catalyst, heated at 0.5 ℃/min to specified temperature, had a better dispersion than that heated at 6 ℃/min. Moreover, catalyst pretreatment conditions affect not only Pt dispersion, but also the stability of Pt clusters, thereby affecting the catalyst performance during sulfur poisoning. For n-hexane feed containing 500 ppm sulfur, a catalyst reduced at 530℃ has the best stability maintenance. Since the Pt dispersion of a thus-reduced catalyst is lower than that of a catalyst reduced at 450℃, the better stability maintenance is inferred to be due to the better Pt clusters stability.
The catalyst deactivation can also be inhibited by adding the second metal nickle on the Pt/mordenite. The results indicated that the addition of mordenite amount of Ni to the Pt catalyst not only lessens the fuel gas formation, but upgrandes octane barrel C5,C6 isomerization products as well. Mover, sulfur resistance of the Ni-Pt catalyst is also higer. The superior performance of the catalyst is thought to result from geometric and electronic effects of bimetal catalyst inferred from TPR and chemisorption results.

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