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標題: | 以過氧化氫為氧化劑進行苯乙烯環氧化反應研究 Study on Epoxidation of Styrene with Hydrogen Peroxide as an Oxidizer |
作者: | Chieh-Lin Chen 陳玠霖 |
指導教授: | 萬本儒 |
關鍵字: | 苯乙烯環氧化反應,氧化苯乙烯,TS-1,錳,對苯二酚, styrene expoxidation,styrene oxide,TS-1,Mn,hydroquinone, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 氧化苯乙烯為一具有高附加價值之化學品,本研究室過去以Mn-beta為觸媒,在-5oC下催化苯乙烯環氧化反應,氧化苯乙烯產率最高達64.6%。然而低溫反應較耗能,故在本研究第一部分以尋找室溫以上觸媒系統作為研究方向。在經過文獻搜尋後,選擇以TS-1觸媒系統於60 oC進行苯乙烯環氧化反應。然而本研究無法再現文獻結果,經檢驗各項可能原因後,將研究心得用於低溫錳觸媒系統,希望能提升氧化苯乙烯產率。
本研究第一部分以TS-1為觸媒於60 oC進行相關反應,結果顯示生成之大部分產物無法以GC分析,而且苯乙烯轉化率過低,致使氧化苯乙烯產率僅為6.6%,無法再現文獻44.9%產率。本研究歸納出該未知產物應是苯乙烯聚合產物,並發現降低苯乙烯濃度能有效減少未知產物,但是會減少氧化苯乙烯之產率。針對苯乙烯轉化率過低問題,發現增加觸媒用量能增加苯乙烯轉化率,氧化苯乙烯產率可提升至23.2%,但是也會增加未知產物;在反應中增加雙氧水用量能提升苯乙烯轉化率,不過會生成更多未知產物,因此氧化苯乙烯產率無法有效增加。聚合之產生可能受TS-1或H2O2之酸性影響,本研究曾嘗試添加鹼性物質尿素於反應系統中,結果顯示無法減少未知產物,但是能降低副產物苯甲醛生成,而使氧化苯乙烯產率稍微增加至26.9%。本研究中也曾嘗試添加聚合反應抑制劑對苯二酚,發現無法減少未知產物,僅能降低副產物苯甲醛之生成,無法提升氧化苯乙烯產率。 第二部分則應用前述經驗嘗試提升低溫錳觸媒系統中氧化苯乙烯產率。過去在-5 oC使用非均相觸媒Mn-beta可獲得64.6%氧化苯乙烯產率,並有16.0%苯甲醛及苯甲酸副產物產率。本研究檢驗在反應溶液中添加尿素或對苯二酚對相關反應之影響,發現添加尿素對反應並無明顯影響,而添加對苯二酚則能提升氧化苯乙烯產率,能使未知產物明顯減少,苯甲醛副產物略為減少。檢驗反應溫度影響可發現,隨溫度降低可使未知產物減少,氧化苯乙烯產率上升,在-15 oC時達最高氧化苯乙烯產率81.8% ( 氧化苯乙烯濃度0.52 mol/L )。本研究曾嘗試降低H2O2/styrene反應比例以利節約生產成本,但是發現比例降低會導致苯乙烯無法完全轉化甚至反應不進行。基於前述氧化苯乙烯產率最高之反應條件,比較非均相觸媒Mn-beta與均相觸媒MnSO4之催化活性,結果發現MnSO4能在較高濃度苯乙烯系統下維持高產率,生產較高濃度之氧化苯乙烯(0.66 mol/L)。 Styrene oxide is a high value-added chemical. In this study, H2O2 was used to oxidize styrene into styrene oxide. The first part of this work focused on styrene epoxidation with temperature higher than the room temperature. TS-1 was used as the catalyst, and H2O2 was used as the oxidizer in the system. Activity test showed that there were large amount of unknown products which could not be analyzed by GC. And styrene conversion was too low, which led to only 6.6% styrene oxide yield, so that 44.9% yield shown in the literature could not be reproduced. The unknown products might be from styrene polymerization. It was found that by decreasing the concentration of styrene, the yield of the unknown products could be reduced. By adding more TS-1, styrene conversion could be increased, accompanied with the rise of the yield of styrene oxide to 23.2%, but the yield of unknown products was also increased. By using more H2O2 in the reaction system, styrene conversion increased, but the yield of styrene oxide did not increase at all, and accompanied with an increase of the yield of unknown products. Adding urea in the reacton system reduced the yield of benzaldehyde, and increased the yield of styrene oxide to 26.9% (0.095 mol/L). Adding hydroquinone reduced the yield of benzaldehyde, but could not increase the yield of styrene oxide. The second part of this research work focused on reactions under temperature lower than the room temperature. Mn catalysts were used, and H2O2 was the oxidizer. 64.6% yield of styrene oxide was achieved in Hung’s research in the past, accompanied with 16.0% yield of benzaldehyde and benzoic acid of by-products. In order to reduce the by-products in this research, urea or hydroquinone was added in the reaction system. It was found that adding urea make little difference from the results in the past. However, adding hydroquinone could increase the yield of styrene oxide by decreasing the amount of the unknown products. In addition, by lowering the reaction temperatures, the yield of styrene oxide could be increased and that of the unknown products were decreased. At -15oC, the maximum yield of styrene oxide of 81.8% (0.52 mol/L) was obtained. On the other hand, the study of lowering the ratio of H2O2/styrene in reaction system was made, in order to save the production cost, which is important in industry. Nevertheless, it was not successful, because the reaction became much slower. The catalytic activities of heterogeneous catalyst Mn-beta and homogeneous catalyst MnSO4 were compared in this research. It was found that only MnSO4 could produce high yield of styrene oxide in the solution with higher concentrations of styrene; therefore, styrene oxide with higher concentration (0.66 mol/L) was obtained. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/59563 |
DOI: | 10.6342/NTU201700772 |
全文授權: | 有償授權 |
顯示於系所單位: | 化學工程學系 |
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