Oxidative Steam Reforming of Methanol over CuZnAl(Zr)-Oxide Catalysts for the Selective Production of Hydrogen for Fuel Cells: Catalyst Characterization and Performance Evaluation
Oxidative Steam Reforming of Methanol over CuZnAl(Zr)-Oxide Catalysts for the Selective Production of Hydrogen for Fuel Cells: Catalyst Characterization and Performance Evaluation
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DOI：
10.1006/jcat.2000.2940
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发表时间：
2000-09
影响因子：
7.3
通讯作者：
S. Velu;Kenzi Suzuki;M. Okazaki;M. Kapoor;T. Osaki;F. Ohashi
中科院分区：
文献类型：
--
作者：
S. Velu;Kenzi Suzuki;M. Okazaki;M. Kapoor;T. Osaki;F. Ohashi
以CuZnAl（Zr）-羟基碳酸盐为前驱体，在450 ° C左右分解含类水滑石（HT）/金铜铝石相的层状双氢氧化物（LDH），制备了一系列新型CuZnAl（Zr）-氧化物催化剂。通过X射线衍射（XRD）、紫外-可见漫反射光谱（DRS）、程序升温还原（TPR）、电子顺磁共振（EPR）和比表面积测量等手段对催化剂的物化性质进行了表征。XRD的催化剂表明，存在结晶不良的CuO和ZnO相的混合物，其结晶度随着Al含量的降低而增加。TPR结果表明，Zr替代Al提高了Cu的还原性和分散性。UV-vis DRS和EPR结果表明，富Al样品中与Al相互作用的Cu2+离子主要是孤立的，而富Zr样品中的Cu2+离子主要是块状或团簇状。在这些催化剂上在180 ° C至290 ° C的温度范围内在大气压下使用H2O/CH3OH（摩尔比= 3）进行甲醇的氧化蒸汽重整反应。最初，Cu：锌：优化了Al的金属组成，发现随着Al含量的降低，催化剂的甲醇转化率和H2产率增加。在CuZnAl氧化物催化剂中，Cu：Zn：Al = 37.6：50.7：11.7（wt %）的催化剂活性最高。用Zr部分或完全取代Al进一步改善了催化性能。含Zr催化剂的高催化性能归因于提高的Cu还原性、更高的Cu金属表面积和分散性。甲醇接触时间对含锆催化剂催化性能的影响的研究表明，CO和CO2作为主要产物产生，并且CO随后通过水煤气变换反应和CO氧化转化为CO2 + H2。
A new series of CuZnAl(Zr)-oxide catalysts were prepared by the decomposition of CuZnAl(Zr)-hydroxycarbonate precursors containing hydrotalcite (HT)-like layered double hydroxide (LDH)/aurichalcite phases around 450°C. The physicochemical properties of the catalysts were investigated by X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), electron paramagnetic resonance (EPR) spectroscopy, and surface area measurements. XRD of the catalysts indicated the presence of a mixture of poorly crystallized CuO and ZnO phases whose crystallinity increased with decreasing Al content. TPR results demonstrated that substitution of Zr for Al improved the copper reducibility and dispersion. UV–vis DRS and EPR results revealed that isolated Cu2+ ions interacting with Al were formed in the Al-rich samples, while mostly bulk-like or cluster-like Cu2+ species were present in the Zr-rich samples. The oxidative steam reforming of methanol reaction was performed over these catalysts in the temperature range 180° to 290°C at atmospheric pressure using H2O/CH3OH, molar ratio=3. Initially, the Cu : Zn : Al metallic composition was optimized and it was found that catalytic performance in terms of methanol conversion and H2 production rate increased with decreasing Al content. Among CuZnAl-oxide catalysts the one with Cu : Zn : Al=37.6 : 50.7 : 11.7 (wt%) was found to be the most active. Replacement of Al either partially or completely by Zr further improved the catalytic performance. The higher catalytic performance of Zr-containing catalysts was attributed to the improved Cu reducibility, higher Cu metal surface area, and dispersion. Studies of the effect of MeOH contact time on the catalytic performance over a Zr-containing catalyst revealed that both CO and CO2 were produced as primary products, and CO was subsequently transformed into CO2+H2 by the water–gas shift reaction/and CO oxidation.