本研究主要針對Pt觸媒(包含擔體及金屬觸媒),以自建流動式吸脫附系統進行苯的吸脫附實驗,此實驗係於323K以質譜儀(m/z=78)偵測下探討,藉由吸附等溫線、吸脫附過程脫氫現象及吸附後程溫脫附圖譜,探討苯的吸附特性,並比較不同吸附特性對Pt觸媒苯氫化反應的影響。 實驗結果發現於苯分壓30torr以下,苯在TiO2、Pt Powder、Pt/ TiO2表面的吸附以不可逆吸附為主,在吸附過程中有顯著的脫氫行為發生。而由30torr分壓下的吸附量,苯在表面上的分子吸附形式可能不是如真空吸附文獻中所述的苯環平行於吸附表面,而是以傾斜形式吸附的可能性較大,表面紅外光譜分析也顯是有表面C-O鍵結生成,顯示吸附可能是在表面-OH位置上產生脫氫。 前處理步驟也會影響不同的TiO2、 Pt/ TiO2苯的吸附行為,實驗發現其吸附量大小順序:LTR≧C/LTR(C)>HTR。經不同前處理Pt/ TiO2對苯氫化反應之TOF與觸媒對苯吸附量呈正比,顯示觸媒中的苯吸附量會影響氫化反應活性。
In this study, benzene adsorption and reaction were examined over oxide support and supported Pt catalysts surface under atmopsperic pressure and 323K. The built-in-lab system is a flow-type adsorption system. Mass spectrometer was used for uptake detection, based on m/z=78. Only irreversible adsorption was observed over Pt powder , TiO2 , Pt/ TiO2 where benzene adsorption partial pressure was below 30torr . Concurrent dehydrogenation were observed in all sample , but seemed more severe over Pt powder and Pt/ TiO2 . Based on the estimated monolayer coverages, the calculated cross sectional area were much smaller than van der Walls cross sectional area of benzene; therefore, this indicates that benzene adsorption over these sample is not lying flat. The pretreatment was found to affect the benzene uptake over TiO2 and Pt/ TiO2,which follows LTR>C/LTR>HTR. The TOF of benzene hydrogenation over Pt/ TiO2 followed the same sequence as benzene uptake .This suggest benzene uptake over Pt/ TiO2 affects the hydrogenation activity over Pt/ TiO2.