錳觸媒於低溫催化苯乙烯環氧化反應

Styrene epoxidation with Mn catalysts at low temperature

洪睿文(Jui-Wen Hung)

指導教授 ： 萬本儒

國立臺灣大學/工學院/化學工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.00832

摘要

本研究為苯乙烯環氧化的催化，在液相環境下以H2O2作為氧化劑。由安全性評估得知，在常溫(25℃)下進行反應將可低於各反應物閃火點及爆炸極限，因此應用具低溫催化效應之錳離子交換之沸石為觸媒，嘗試研究苯乙烯反應生成氧化苯乙烯。研究結果顯示：(1) 文獻發表之錳沸石催化反應系統有分相問題，造成反應前後實驗量測莫耳不平衡以及數據嚴重錯誤問題。本研究已藉由Aspen Plus的Decanter模擬精準判斷"相狀態"，並已設計出不分相之溶液組成。 (2) 已製備出三種不同含錳離子之沸石觸媒，反應測試顯示其催化活性高低依序為Mn-Beta > Mn-Y > Mn-A。(3) 碳酸氫鈉是反應關鍵之一，反應系統內如果完全不添加碳酸氫鈉將無任何轉化率，溶液中含0.15 wt % ~ 1.24 wt %的碳酸氫鈉則可使產率提升至56~63%，其中含0.32 wt %具有最佳產率。(4) 檢驗反應溫度影響可知，較低溫能反其道的促使轉化率及選擇率皆顯著提升，原因可能是低溫可降低反應系統中Na+ 與沸石上Mn2+ 活性基之離子交換，以及減少Mn2+與碳酸氫鈉形成碳酸錳沉澱物。(5) 苯乙烯與H2O2的莫爾比例會影響反應結果，在反應溫度為-5℃，0.25:1的比例轉化率達90%以上。(6) 比較Mn-Beta與MnO非均相觸媒及MnSO4均相觸媒行苯乙烯環氧化的催化，本研究Mn-Beta之活性遠高於MnO，略高於MnSO4， 並且Mn-Beta具備重複使用性，目前氧化苯乙烯產率可達71.3%。

關鍵字

環氧化反應 ； 苯乙烯 ； 氧化苯乙烯 ； 低溫 ； 錳-沸石

並列摘要

The research is epoxidation of styrene to styrene oxide with H2O2 oxidant in liquid phase. Because of safety and environment consideration, styrene epoxidation must be carried out at low temperature (i.e., below 25℃). Therefore active catalysts, such as Mn-zeolite, have been used in this research. The following experimental results were obtained: (1) Phase separation problem was found in reaction system with Mn-zeolite catalysts for epoxidation of styrene published in literature, which caused mole in-balance and data-error problems. By using Aspen Plus decanter model simulation, the right composition in reaction system with a homogeneous phase was determined and applied in this research. (2) Mn+2 has been ion-exchanged into three types zeolites (A, Y and Beta). Mn-Beta possesses the best catalytic activity for styrene epoxidation. (3) NaHCO3 plays important role in the reaction. No reaction occurred if no NaHCO3 was added into the reaction system. When 0.32 wt% of NaHCO3 was in reaction solution, styrene oxide yield of about 64% was obtained. (4) The reaction activity decreased with the increase of reaction temperature, which againsts the common sense of reaction kinetics. The reason was from that at higherer reaction temperature, more Mn+2 of active catalytic sites were exchanged out of zeolite support by Na+ in the solution, to form inactive MnCO3 precipates. (5) The concentration of H2O2 affected the reaction results. At -5 ℃ reaction temperature and mole ratio of Styrene and H2O2. at 0.25:1, the highest conversion of styrene of 90% was obtained. (6) Mn-Beta had much higher activity than MnO of heterogeneous catalysts and slightly higher than MnSO4 of homogeneous catalysts. Moreover, Mn-Beta can be recycled and reused. Finally, yield of styrene oxide can reach to 71.3%.

並列關鍵字

expoxidation ； styrene ； styrene oxide ； low temperature ； Mn-zeolite

參考文獻

[3] J. P. Renaud, P. Battioni, J. F. Bartoli, and D. Mansuy, "a very efficient system for alkene epoxidation by hydrogen-peroxide - catalysis by manganese-porphyrins in the presence of imidazole," Journal of the Chemical Society-Chemical Communications, pp. 888-889, 1985.

[4] R. I. Kureshy, N. H. Khan, S. H. R. Abdi, and A. K. Bhatt, "Asymmetric catalytic epoxidation of styrene by dissymmetric Mn(III) and Ru(III) chiral Schiff base complexes synthesis and physicochemical studies," Journal of Molecular Catalysis a-Chemical, vol. 110, pp. 33-40, Jul 1996.

[5] B. S. Lane and K. Burgess, "A cheap, catalytic, scalable, and environmentally benign method for alkene epoxidations," Journal of the American Chemical Society, vol. 123, pp. 2933-2934, Mar 2001.

[6] N. S. Patil, R. Jha, B. S. Uphade, S. K. Bhargava, and V. R. Choudhary, "Epoxidation of styrene by anhydrous t-butyl hydroperoxide over gold supported on Al2O3, Ga2O3, In2O3 and Tl2O3," Applied Catalysis a-General, vol. 275, pp. 87-93, Nov 2004.

[7] V. R. Choudhary and D. K. Dumbre, "Supported Nano-Gold Catalysts for Epoxidation of Styrene and Oxidation of Benzyl Alcohol to Benzaldehyde," Topics in Catalysis, vol. 52, pp. 1677-1687, Nov 2009.