CuO/Ce1-xMnxO2-Al2O3觸媒於富氫中CO的選擇性氧化反應研究

CuO/Ce1-xMnxO2-Al2O3 catalysts for the preferential oxidation of CO in H2-rich gases

彭均婷(Chun Ting)

指導教授 ： 陳吟足

國立中央大學/工學院/化學工程與材料工程學系/碩士(2008年)

摘要

摘 要
本研究嘗試於CeO2引入不同比例的Mn，製備Ce1-xMnxO2擔體及CuO/Ce1-xMnxO2觸媒。為了增進觸媒之機械強度與穩定度，另外於Ce1-xMnxO2¬擔體中引入不等量Al2O3與製備CuO/Ce1-xMnxO2-Al2O3觸媒。本研究分別探討CuO/Ce1-xMnxO2觸媒與CuO/Ce1-xMnxO2-Al2O3觸媒之CO選擇性氧化反應特性，並採用BET、TPR、XPS、Raman、CO脈衝吸附與Auger等分析方法探討觸媒之物理特性與表面性質。CO/O/H2/He = 1/1/50/48進料及F/W = 10,000 ml hr-1 g-1下，進行CuO/Ce1-xMnxO2-Al2O3觸媒的活性測試。
CeO2擔體中引入少量的錳(x = 0.1~0.3)，錳是以正四價的形式固溶於CeO2擔體晶格中，形成良好固溶的氧化物Ce1-xMnxO2，Ce1-xMnxO2氧化物較易釋出晶格氧，有較佳redox特性。當錳的引入量大於0.3，會有分離相的產生，錳是以三價的形式存在。
7%CuO/Ce1-xMnxO2觸媒，引入少量Mn (x = 0.1)，觸媒活性增加，達CO完全轉化的T100下降5°C (90~95°C)，此時選擇S100約為100%；Mn引入量0.20.5時，則不利於觸媒活性。反應溫度小於100°C，選擇率均維持100%，反應溫度大於100°C，選擇率始明顯下降。
7%CuO/Ce1-xMnxO2-20%Al2O3觸媒與未引入Al2O3之觸媒相較，其T100大約上升5~10°C。Mn的引入量x = 0.1~0.2，T100為95~100°C與未引入Mn之觸媒相較，下降5°C；x = 0.3，T100為100~105°C，與未引入之Mn之觸媒T100相當。Mn引入量對7%CuO/Ce1-xMnxO2與7%CuO/ Ce1-xMnxO2-20%Al2O3之影響相似。
7%CuO/Ce0.9Mn0.1O2-x%Al2O3觸媒，Al2O3引入量x = 10~30%，觸媒活性差異不大，T100溫度95~100°C，Al2O3引入量大於30%，才稍不利於CO選擇性氧化反應。Al2O3引入量x = 40%時，T100溫度略升 5°C，溫度為100~105°C，選擇率由100%下降至95%。
CO2及H2O對 7%CuO/Ce0.9Mn0.1O2-20%Al2O3觸媒明顯影響，於進料氣中引入15% CO2，T100明顯增至130~135°C，S100下降至71%；於進料中引入10% H2O，會造成觸媒床堵塞，以致無法順利進行。若以無CO2及H2O的進料在100°C下進行7%CuO/Ce0.9Mn0.1O2-20%Al2O3觸媒的穩定性測試，經200小時反應，轉化率由100%僅降至93%。7%CuO/ Ce0.9Mn0.1O2-20%Al2O3觸媒有強吸水性，不適用於燃料電池的CO去除反應，但仍適用於一般的CO氧化反應上。

關鍵字

含浸法 ； 富氫中CO氧化

並列摘要

Abstract
In our previous studies, doping MnOx into CeO2 increase the mobility of lattice oxygen and enhanced the activity of the activity of the 7%CuO/Ce1-xMnxO2 catalyst in the selective oxidation of CO in the H2-rich feed. In order to promote of mechanical strength and the stability of support, moreover to Alumina was incorporated with the solid solution of Ce1-xMnxO2 to form Ce1-xMnxO2-Al2O3 mixed oxides, by the suspension /co-precipitation method, to be used as supports ofCuO/Ce1-xMnxO2-Al2O3 catalyst. They were characterized and effects of Al2O3 on the selective oxidation of CO in excess hydrogen were examined. Characterization of catalysts were performed by XRD, TPR, XPS, Auger. All catalysts were reduced to room temperature in helium and then the feed H2/CO/O2/He(50/1/1/48) mixed was diverted to the reactor at a flow rate of 30ml/ min (F/W = 10,000ml/g h).
For Ce1-xMnxO2 with x = 0.1~0.3, incorporating an appropriate amount of Mn4+ into the CeO2 lattice to form a solid solution facilitated the release of the bulk lattice oxygen. Some MnOx might aggregate and be split out from the solid solution of Ce1-xMnxO2 as the fraction of Mn incorporated excess 0.3, and then Mn3+ into the CeO2.
7%CuO/Ce0.9Mn0.1O2 catalyst was the most active one, it was more active than the 7%CuO/CeO2 catalyst, with a T100 temperature (90-95°C) for complete conversion that was above 5°C less than that of 7%CuO/CeO2 (95-100°C) and the selective oxidation of CO was still 100%. The promotion of CO oxidation became weaker as the fraction of Mn incorporated increase above 0.5.
For doping appropriate small friction as the amount of Mn about o.1 into the Ce1-xMnxO2 for 7%CuO/Ce0.9Mn0.1O2-x%Al2O3 catalysts. This interfacial perimeter also decreased as the amount of Al2O3 incorporated into Ce0.9Mn0.1O2-x%Al2O3 increased above 30%, so that CO oxidation became weaker.
Because a gas stream from reformer always contains CO2 and H2O, so that a catalyst of selective oxidation of CO must be resistant to both CO2 and H2O. The 7%CuO/Ce1-xMnxO2-20%Al2O3 catalyst rose by about 35°C from 95-100°C to 130-135°C when an H2-rich feed in presence of 15%CO2. The 7%CuO/Ce1-xMnxO2-20%Al2O3 created the catalyst bed to stop up and reaction can not finish, so that the catalyst had the hygroscopicity. A long (200 h) run over the 7%CuO/Ce0.9Mn0.1O2-20%Al2O3 catalyst was conducted at 100°C, with about 93% conversion; the performance was stable when the feed no CO2 and H2O.

並列關鍵字

MnOx ； CeO2 ； TPR

參考文獻

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