利用NaY、Pt-NaY及V2O5-NaY吸附劑去除空氣中之乙醇：探討Pt及V2O5對吸附行為之影響

Removing Ethanol From Air Stream Using NaY, Pt-NaY, And V2O5-NaY: Impact Of Pt And V2O5 On The Nature Of Adsorption

陳宜婷(Chen, Yiting)

指導教授 ： 張仁瑞

國立中正大學/工學院/化學工程學系/碩士(2012年)

摘要

藉由PXRD配合Rietveld Refine、FTIR、SEM及孔徑分佈分析NaY成型前後之結構變化，結果顯示，在成型過程中鋁從zeolite結構被酸析出，因此熱穩定性佳且具疏水性。實驗中將鉑金屬及釩金屬加入NaY成型吸附劑以促進吸附及再生性能。利用NaY、V2O5-NaY 及Pt-NaY吸附劑於固定床 (fixed-bed) 反應器中進行去除空氣中之乙醇。由乙醇吸附貫流曲線( Breakthrough curve) 得知，NaY及V2O5-NaY之吸附速率較Pt-NaY之吸附速率快，其吸附容量 (adsorption capacity) 顯示Pt-NaY＞NaY＞V2O5-NaY。造成此現象之結果可利用XAS及FTIR進行特性分析。由EXAFS結果顯示氧化釩在沸石中呈現孤立結構，因佔據沸石之吸附活性位，導致吸附能力降低。另一方面，Pt-NaY不僅僅吸附乙醇，也將吸附之乙醇催化氧化成乙氧基 (Ethoxide) 及醛 (Aldehyde)，這些生成物提供乙醇吸附額外的活性基，並藉由表面擴散經Pt到NaY上，因此造成吸附速率下降。

關鍵字

觸媒吸附劑 ； 貫流曲線 ； 乙醇吸附 ； 傅立葉轉換紅外線光譜儀 ； 延伸X光吸收精細結構

並列摘要

The structure of NaY before and after forming a pellet was characterized by synchrotron PXRD with the Reitveld refinement, FTIR, SEM, and pore size distribution. The results indicated that aluminum atoms were removed from zeolite framework by acid leaching during forming process, resulting in an increasing thermal stability and hydrophobic properties. Platinum and vanadium were added in pellet NaY adsorbent to improve the adsorption and regeneration properties. The performances of NaY, Pt-NaY, and V2O5-NaY in removing ethanol from air stream were examined using a fixed-bed adsorber. The resulte showed that the adsorption rates on NaY and V2O5-NaY were higher than that on Pt-NaY, while the adsorption capacities decrease in the order: Pt-NaY>NaY>V2O5-NaY. To elucidate the differences in the performances, surface species on the adsorbent were characterized by XAS and FT-IR. The results indicated that isolated vanadia formed on NaY have no adsorption capability. The adsorption sites covered by the vanadia species may thus decrease adsorption capacity. In contrast, Pt clusters on NaY not only adsorbed ethanol but catalytically converts the adsorbed ethanol to ethoxides and aldehyde. The formation of these species induces more active sites for adsorption, whereas, as opposed to ethanol adsorbed directly on NaY, surface diffusion of the reaction species from Pt clusters to NaY retards the adsorption rate.

並列關鍵字

Catalytic adsorbent ； Breakthrough curve ； Ethanol adsorption ； Fourier Transform Infrared ； Extended X-ray Absorption Fine Structure

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