- 學位論文
製備疏水性觸媒及其在酯化反應的應用
Preparation of Hydrophobic Catalysts and Application of Esterification Reaction
摘要
本論文主要目標是製備疏水性觸媒，並應用於酯化反應。首先，選用顆粒型的觸媒載體為含浸過鈀的沸石(CBV760-Pd) 。以微濕含浸法將鎳置入觸媒載體，其鎳含量佔全部載體的2.5wt%，接著將真空抽氣乾燥去除溶劑之樣品置入方形高溫爐中鍛燒，在空氣氛圍下，以450 ℃進行30分鐘鍛燒奈米碳管之觸媒，再將鍛燒完的觸媒載體，以化學氣相沉積法生長奈米碳管層，其中還原氣體為氫氣、碳源為乙炔、升降溫區段之環境氣體為氬氣，生長溫度為500 ℃，在不同的生長時間(15~130分鐘)下，可以得到的產物為(Pd/CNT/zeolite)，是一種核殼結構的疏水性觸媒載體(不同的核殼比)。 一開始，我們是以0.5 g 觸媒載體重量來進行CVD生長，在SEM觀察下，可以發現其表面由CNT覆蓋，管徑是隨著生長時間增加而增加。經過疏水性測試，我們可得知，當生長時間超過50分鐘，接觸角都大於150˚，其表面為超級疏水性。之後將觸媒載體重量從0.5 g變成2.5 g，其接觸角還是有大於140˚。藉由親和性測試結果得知，CNT層不會使乙醇、乙酸、乙酸乙酯無法擴散至觸媒載體內部，Pd/zeolite與溶液親和性: 水≈乙酸乙酯>乙酸>乙醇，Pd/CNT/zeolite與溶液親和性: 乙酸乙酯>乙醇>乙酸>>水。酯化反應部分，以批次反應器進行反應，進料為75%乙醇，其平衡轉化率約52~53%，Pd/zeolite之轉化率提升速度比Pd/CNT/zeolite快。在連續式固定床反應器部分， 在壓力為1和10 atm 時，Pd/zeolite之乙醇轉化率都高於Pd/CNT/zeolite，在壓力提升至20 atm的時候，反應差不多達平衡，轉化率差異不大，介於59~62%。乙酸乙酯產率部分，在壓力為10和20 atm時， Pd/zeolite和Pd/CNT/zeolite產率都差異不大。Pd/CNT/zeolite的CNT外層還具有保護觸媒之功用，可以防止金屬基Pd的流失，可以增加觸媒反應的時間。
並列摘要
The objective of this study is to prepare hydrophobic catalyst. The selection of granule type catalyst support is Pd/zeolite(CBV760-Pd). We deposited nickel nitrate solution as a nickel catalyst precursor on the catalyst supports by incipient wetness impregnation, nickel catalyst content of Pd/zeolite was 2.5 wt.%, and calcined the sample that had been removed the solvent by vacuum drying method under atmosphere at 450 ℃for 30 minutes in the box furnace. Then, grow CNT layer by CVD process after the catalyst precursor was calcined, which hydrogen acted as reduction agent, acetylene as carbon source and argon as ambient gas for heating and cooling stage. The reaction temperature was 500 ℃. At different reaction time(15~130 min), we obtained the Pd/CNT/zeolite which is a hydrophobic catalyst support of core-shell structure(different core-shell ratio). At the beginning, we used 0.5 g catalyst supports to do CVD growth. Observed from the SEM, the surface of Pd/CNT/zeolite was covered by CNTs. The CNT diameter increases as the reaction time goes on. After doing the hydrophobic measurement, the contact angle of Pd/CNT/zeolite is bigger than 150˚ when the reaction time is more than 50 minutes. The surface of Pd/CNT/zeolite is super hydrophobicity. After that, the weight of catalyst supports was increased from 0.5 g to 2.5 g. The contact angle of Pd/CNT/zeolite is also bigger than 140˚ when the reaction time is more than 50 minute. CNT layer can let EtOH, HOAc, EtOAc diffused into the catalyst by affinity test. The affinity between Pd/zeolite and solution: H2O ≈ EtOAc > HOAc > EtOH. The affinity between Pd/CNT/zeolite and solution: EtOAc > HOAc > EtOH >> H2O. The batch reactor used to esterification reaction. The feed is 75% EtOH. The equilibrium conversion is 52~53%. For conversion, the increased rate of Pd/zeolite is higher than Pd/CNT/zeolite. The continuous fixed-bed reactor used to esterification reaction. At 1 and 10 atm, the conversion of Pd/zeolite is higher than Pd/CNT/zeolite. At 20 atm, the equilibrium conversion of Pd/zeolite and Pd/CNT/zeolite is 59~62%. At 10 and 20 atm, the yield of Pd/zeolite close to Pd/CNT/zeolite. The outer layer of Pd/CNT/zeolite as a protection catalyst role. It can prevent Pd loss. Increased catalyst reaction time.
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