Reactant-promoted reaction mechanism for catalytic water-gas shift reaction on MgO
Reactant-promoted reaction mechanism for catalytic water-gas shift reaction on MgO
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DOI：
10.1016/0021-9517(90)90261-h
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发表时间：
1990-03
影响因子：
7.3
通讯作者：
T. Shido;K. Asakura;Y. Iwasawa
中科院分区：
文献类型：
--
作者：
T. Shido;K. Asakura;Y. Iwasawa
利用傅里叶红外光谱研究了MgO表面催化水气转换反应（WGSR）中反应中间体的行为。配位不饱和Mg原子顶部的羟基与CO反应生成三种表面甲酸酯，分别为：桥型、双齿型和桥型，顺序为桥型、>、>双齿型。在室温下生成了不确定类型的甲酸酯，并在约450 K下分解。桥型和双齿型甲酸盐的形成和分解在较高的温度下进行（分别约为400和550 K）。在吸附水存在的情况下，未识别型甲酸酯转变为桥型甲酸酯，因此在反应条件下大多数甲酸酯为桥型甲酸酯。与之前的报道相反，甲酸中间产物在没有水的情况下从未转化为HZ和co2。所有甲酸类均自行分解为CO和表面OH，而吸附水通过吸附水与甲酸类之间的电子相互作用促进甲酸类分解为WGSR产物HZ和co2。在有水存在的情况下，WGSR稳态反应速率与过渡到HZ和co2的桥式甲酸酯的分解速率一致。
The behavior of reaction intermediates in the catalytic water-gas shift reaction (WGSR) on the MgO surface was studied by means of FT-IR spectroscopy. The hydroxyl groups on top of coordinatively unsaturated Mg atoms reacted with CO to produce three kinds of surface formates of unidentate, bidentate, and bridge types in the order bridge > unidentate > bidentate. Unidentate-type formate was produced at room temperature and decomposed at ca. 450 K. The formation and decomposition of bridge- and bidentate-type formates proceeded at higher temperatures (ca. 400 and 550 K, respectively). In the presence of adsorbed water, unidentate-type formate changed into bridge-type formate and hence most formates are bridge type under reaction conditions. Contrary to previous reports, formate intermediates were never converted to HZ and CO2in the absence of H2O. While all the formates decompose to CO and surface OH by themselves, adsorbed water promoted the decomposition of formates to the WGSR products HZ and CO2through electronic interaction between the adsorbed water and the formate. The reaction rate of WGSR at steady state agreed with the decomposition rate of the bridge-type formate intermediate to HZ and CO2in the presence of water.