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  • 學位論文

雙金屬觸媒Pt-Sn/BN在巴豆醛選擇性氫化之研究

Selective Hydrogenation of Crotonaldehyde Using Bimetallic Pt-Sn/BN Catalyst

指導教授 : 吳紀聖

摘要


本研究主要為以BN支撐的雙金屬觸媒在巴豆醛的選擇性氫化反應,將鉑與錫雙金屬利用共臨界沾濕法負載於BN上,鉑含量皆為1.1 wt%而錫含量則從0.25至0.75 wt%。除外,我們也製備單金屬觸媒1.1wt%Pt/BN及1.0wt%Sn/BN且另選用商業觸媒載體γ-Al2O3及活性碳做為比較。反應結果顯示Pt-Sn/BN中錫的添加量越多,巴豆醇的選擇率與產率越高,Pt-Sn(0.75)/BN在轉化率為60% 下,選擇率可達0.63,推測應為Pt-Sn/BN中的Snn+扮演路易士酸基而能吸附與活化C=O鍵所致。觸媒所使用的檢測有N2吸附BET比表面積測定、氫氣與一氧化碳化學吸附測定、Temperature programmed reduction(TPR)、X-ray diffraction(XRD)、X-ray photoelectron spectroscopy(XPS)及Transmission electron microscope(TEM)。從XPS分析,發現大部分的錫的價態在氫氣300℃還原後仍維持為2+,而Pt-Sn/BN則有部分Sn2+被還原為金屬態而形成PtxSn合金。Pt-Sn/γ-Al2O3在XRD上沒有出現任何PtxSn合金,但有可能因其晶粒太小以致無法由XRD所偵測。從TPR與TEM可知,BN相較γ-Al2O3對於金屬前軀物的固定力較差,以致於在氫氣還原後,金屬聚集較為嚴重。Pt-Sn/γ-Al2O3在相同反應溫度,巴豆醇選擇率亦隨著錫的含量增多而提高,但丁醛的產率大幅降低,且巴豆醇產率也無法顯著提升,其因與Snn+的周圍環境有關,而丁醛的產率大幅下降則可能由Pt的分散度降低及可能出現的PtxSn雙金屬小粒子所引起。Pt-Sn/AC的反應結果與Pt-Sn/γ-Al2O3相似。

並列摘要


In the present study we focused on the selective hydrogenation of crotonaldehyde over bimetallic BN-supported catalysts which were prepared by co-incipient wetness impregnation. The compositions of the catalysts were platinum 1.1 wt% and tin from 0.25 to 0.75 wt%. Besides we also prepared monometallic catalysts 1.1wt%Pt/BN and 1.0wt%Sn/BN. We chose some commercial catalyst supports γ-Al2O3 and activated carbon to compare with BN. The reaction results revealed that the more tin in Pt-Sn/BN, the higher the selectivity to crotyl alcohol. The Pt-Sn(0.75)/BN has the selectivity to crotyl alcohol 0.63 under the conversion 60%. The improvement of the selectivity to crotyl alcohol was contributed to Snn+ as Lewis acid sites that adsorb and activate C=O bond. The catalysts were characterized by N2 adsorption BET method, hydrogen and carbon monoxide selective chemisorption, temperature programmed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) technique. By the XPS analysis, we found mostly the tin remained Sn2+ after reduction in flowing hydrogen at 300oC and PtxSn alloys were formed in Pt-Sn/BN. However we could not find any PtxSn alloys in Pt-Sn/γ-Al2O3 by XRD as the PtxSn particles might be possibly too small to be detected by XRD. BN is more inert than γ-Al2O3 and interacts weakly with metal precursors, and therefore the metal aggregation is more severe. The selectivity to crotyl alcohol in Pt-Sn/γ-Al2O3 was also increased as the tin content increased at the same reaction temperature. However the yield of the butyraldehyde was decreased appreciably and it may be caused by the decrease of the Pt dispersion and the possibly small bimetallic clusters PtxSn. The yield of the crotyl alcohol was not improved apparently due to the different surroundings of the Sn2+. The reaction results of the Pt-Sn/AC were similar to those of Pt-Sn/γ-Al2O3.

參考文獻


2. P. Gallezot and D. Richard, Selective Hydrogenation of
1. 陳昭宇,Pt/BN觸媒在氫化反應上活性與選擇性探討,國立台灣大學碩士論文,2003,p. 60, p. 95。

被引用紀錄


林上傑(2006)。雙金屬觸媒Pt-Sn/BN在丙烷脫氫之研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2006.00102
藍泰蔚(2005)。以光纖反應器直接光催化分解氮氧化物〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2005.01993
鄭台新(2005)。雙金屬Pt-Fe支撐式觸媒檢測及巴豆醛選擇性氫化之研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2005.01503

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