環己烯之光催化環氧化反應於V-Ti/MCM41光觸媒之研究

環氧化物是具有高反應活性的化合物，它可以作為中間反應物參與許多化學反應。環氧化物也用於許多精細化學品、藥品和聚合物等的重要前驅物。1,2-環氧環己烷的生成反應已被視為基本的環氧化物反應並加以廣泛研究。 1,2-環氧環己烷的選擇率是一個本反應最關鍵的挑戰。相對於以熱能作為驅動力，本研究利用紫外光作為驅動力以提高環己烯轉化率和1,2-環氧環己烷反應之選擇性。已有不少文獻研究以MCM41等各種不同之中孔洞材料催化生成1,2-環氧環己烷，甚至有文獻研究以原位偵測的方式希望能了解其光催化反應之反應機制。本研究同時以氣相層析分析 (Gas Chromatograph，GC) 及原位-即時拉曼光譜分析 (in-situ, real-time Raman Spectroscopy) 對於反應物及產物之濃度進行分析比較。搭配原位-即時拉曼光譜分析在以非侵入性的方式進行分析，隨著反應的進行同時監測拉曼特徵峰的強度變化，以推導光催化反應之反應機制。如此一來，希望能同時觀測得到環己烯之轉化率、1,2-環氧環己烷之選擇率和產率以及光催化反應之反應機制。除了兩種分析儀器之比較外，我們改變釩、鈦兩種金屬氧化物於觸媒上之負載比例，從中得到釩、鈦兩種金屬氧化物負載比例之最適值。並透過改變反應操作溫度，觀察並比較環己烯之環氧化反應之熱催化反應及光催化反應。在溫和的條件下，增加1,2-環氧環己烷之選擇率及產率。我們發現，藉用光催化的環己烯之環氧化反應，以V-Ti/MCM41 (1-1-100) 做為觸媒時，在溫和的反應條件下能提供較高的1,2-環氧環己烷選擇率及產率。

關鍵字

環氧化反應；環己烯；光催化觸媒反應；中孔洞觸媒； V-Ti/MCM41 ；原位-即時拉曼光譜分析

並列摘要

The epoxides are highly reactive compounds, which can conduct numerous chemical reactions as intermediate. The epoxides are also important precursors for many fine chemicals and pharmaceuticals. Cyclohexene epoxidation is one of basic epoxidation of cyclic olefins, which has been widely investigated. The selectivity of 1,2-epoxycyclohexane is a crucial challenge. Instead of thermal driving force, photon is applied to improve the conversion and selectivity in cyclohexene epoxidation. The photo-catalytic epoxidation of cyclohexene by porous material such as MCM41 is a promise method to produce 1,2-epoxycyclohexane. The mechanism of epoxidation could be explored by in-situ spectroscopy. Silica-supported catalyst, V-Ti/MCM-41, was used to evaluate its performance in the photo epoxidation and achieve extra high selectivity. Different analysis methods were applied in this research, one is Gas Chromatograph (GC), the other one is in-situ real-time Raman Spectroscopy. Quantitative information were delivered by both methods. The progress of the reaction was monitored the changes in intensity of the characteristic Raman bands. In order to find the optimized ratio of metal loading amount on MCM41 with photo-catalytic cyclohexene epoxidation, GC analysis was applied to compare the reaction results. V-Ti/MCM41 (1-1-100) was the best catalyst for photo-catalytic cyclohexene epoxidation, which had highest selectivity while operating reaction at 60o C, 0.5 mW/cm2 of UVA for 6 hours. With different operating temperatures and driving forces, we found that the photo-driven cyclohexene epoxidation has higher selectivity under mild reaction condition.

並列關鍵字

cyclohexene epoxidation ； photo-catalyst ； V-Ti/MCM41 ； in-situ Raman spectroscopy ； TBHP

參考文獻

1. V.-H. Nguyen, Photocatalytic Epoxidation of Propylene with Molecular Oxygen. Van-Huy Nguyen, Taipei; 2010, p. 1-154.

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7. M. Yoon and S. Y. Ryu, Characteristics of excited-state intermediates of TiO2–Y-Zeolite and MCM41 encapsulating photosensitive molecules: design of new photocatalysts. Research on Chemical Intermediates, 30 (2004) 207-233.

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環己烯之光催化環氧化反應於V-Ti/MCM41光觸媒之研究

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