Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts
Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts
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DOI：
10.1021/j100211a039
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发表时间：
1982-07
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影响因子：
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通讯作者：
Toshiaki Mori;H. Masuda;H. Imai;A. Miyamoto;S. Baba;Y. Murakami
中科院分区：
文献类型：
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作者：
Toshiaki Mori;H. Masuda;H. Imai;A. Miyamoto;S. Baba;Y. Murakami
用脉冲表面反应速率分析（PSRA）技术精确测定了Ni/SiO/sub 2/催化剂上吸附CO分子甲烷化反应动力学和氢氘同位素效应。当CO脉冲注入流动的氢气中时，它立即被吸附在催化剂上，并逐渐加氢为CH/sub 4/和H/sub 2/O。测定了吸附CO在不同时间加氢生成CH/sub 4/和H/sub 2/O的量，发现CH/sub 4/和H/sub 2/O的生成速率相同。当注入O/sub 2/代替CO时，立即产生H/sub 2/O。从这些结果中，反应的速率控制步骤被发现是吸附的CO分子或部分氢化的CO物种的C-O键解离。利用PSRA测定了不同温度下每个吸附CO分子的C-O键解离过程的速率常数（k/sub H/），并获得了速率常数的Arrhenius参数。还测定了流动氘中的速率常数（k/sub D/）。发现k/sub D/比k/sub H/大得多，表明了逆同位素效应。k/sub H//k/sub D/的平均值为0.75。从这些结果可以得出结论，在PSRA实验的条件下，吸附的CO不直接解离为表面碳和氧原子，而是在C-O键解离之前部分氢化。八位数。«少
Kinetics and hydrogen-deuterium isotope effects in the methanation of adsorbed CO molecules on a Ni/SiO/sub 2/ catalyst were precisely measured by using pulse surface reaction rate analysis (PSRA). When a CO pulse was injected into flowing hydrogen, it was immediately adsorbed on the catalyst and gradually hydrogenated to CH/sub 4/ and H/sub 2/O. The amounts of CH/sub 4/ and H/sub 2/O produced by the hydrogenation of the adsorbed CO were determined up to various times, and it was found that CH/sub 4/ and H/sub 2/O were produced at the same rate. When O/sub 2/ instead of CO was injected, H/sub 2/O was immediately produced. From these results, the rate-determining step of the reaction was found to be C-O bond dissociation of an adsorbed CO molecule or a partially hydrogenated CO species. By PSRA, the rate constant for the C-O bond dissocition process per adsorbed CO molecule (k/sub H/) was determined at various temperatures, and the Arrhenius parameters of the rate constant were obtained. The rate constant in flowing deuterium (k/sub D/) was also determined. it was found that k/sub D/ is considerably larger than k/sub H/, indicating an inverse isotope effect. The average value of k/sub H//k/sub D/ was 0.75.more » From these results, it was concluded that adsorbed CO is not directly dissociated to surface carbon and oxygen atoms but it is partially hydrogenated before C-O bond dissociation under the conditions of the PSRA experiment. 8 figures.« less