ACTIVITY AND STRUCTURE-SENSITIVITY OF THE WATER-GAS SHIFT REACTION OVER CU-ZN-AL MIXED-OXIDE CATALYSTS
ACTIVITY AND STRUCTURE-SENSITIVITY OF THE WATER-GAS SHIFT REACTION OVER CU-ZN-AL MIXED-OXIDE CATALYSTS
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DOI：
10.1016/0926-860x(95)00146-8
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发表时间：
1995-10-26
影响因子：
5.5
通讯作者：
APESTEGUIA, CR
中科院分区：
文献类型：
--
作者：
GINES, MJL;AMADEO, N;APESTEGUIA, CR
研究了Cu-Zn-Al复合氧化物催化剂的水煤气变换反应活性和结构敏感性。采用共沉淀法制备了三组不同Cu/Zn和（Cu+Zn）/Al原子比的样品。根据阳离子的比例，三元羟基碳酸酯前体含有水滑石，绿铜矿和/或rosasite相。分解的前驱体含有CuO、ZnO、ZnAl 2 O 4和Al 2 O3。这些相的相对比例取决于样品的化学组成和用于分解前体的煅烧温度。在用氢气活化后，在503 K下测试样品的WGS反应。无论铜金属表面积在3 ~ 35 m2/g Cu之间变化，金属铜分散度在0.5 ~ 5.0%之间变化，所测试的18个样品的转换频率基本相同（0.2-0.3 s（-1））。这表明WGS反应是结构不敏感的反应，因为比反应速率r（0）（mol CO/h/g Cu）总是与铜金属表面积成比例。因此，需要制备具有高铜分散度的混合氧化物以获得更高活性的催化剂。发现金属铜分散度的值与包含在羟基碳酸酯前体中的水滑石的量有关：前体中的水滑石含量越高，所得催化剂中的铜金属分散度越高，因此催化剂活性越高。三元Cu/ZnO/Al 2 O3催化剂表现出明显快于二元Cu/ZnO催化剂的WGS活性。铝的加入，虽然对WGS反应是惰性的，但对于改善催化剂性能是需要的。
The activity and structure-sensitivity of the water-gas shift (WGS) reaction over Cu-Zn-Al mixed oxide catalysts were studied. Three sets of samples with different Cu/Zn and (Cu+Zn)/Al atomic ratios were prepared by coprecipitation. Depending on the cation ratio, the ternary hydroxycarbonate precursors contained hydrotalcite, aurichalcite and/or rosasite phases. The decomposed precursors contained CuO, ZnO, ZnAl2O4, and Al2O3. The relative proportion of these phases depended on both the chemical composition of the sample and the calcination temperature employed for decomposing the precursor. After activation with hydrogen, samples were tested for the WGS reaction at 503 K. The turnover frequency of the eighteen samples tested was essentially the same (0.2-0.3 s(-1)) irrespective of changing the copper metal surface area between 3 and 35 m(2)/g Cu and the metallic copper dispersion between 0.5 and 5.0%. This indicated that the WGS reaction is a structure-insensitive reaction, as the specific reaction rate r(0) (mol CO/h/g Cu) is always proportional to the copper metal surface area. Preparation of mixed oxides with a high copper dispersion is therefore required for obtaining more active catalysts. It was found that the value of the metallic copper dispersion is related to the amount of hydrotalcite contained in the hydroxycarbonate precursor: the higher the hydrotalcite content in the precursor, the higher the copper metal dispersion in the resulting catalyst and, as a consequence, the higher the catalyst activity. Ternary Cu/ZnO/Al2O3 catalysts exhibited a substantially faster WGS activity than binary Cu/ZnO catalysts. The addition of aluminium, although inactive for the WGS reaction, is required for improving the catalyst performance.