The passivation and reactivation of Mo₂C and W₂C were investigated by thermogravimetry with effluent gas analysis, and by comparison of the toluene hydrogenation activity of fresh carbides with those of passivated and reactivated carbides (21bar, H₂:toluene=33, 150 or 200°C, WHSV=10 or 20gg_cat ⁻¹ h⁻¹). Contrary to the literature, CO₂ and H₂O were unsuitable passivation agents for Mo₂C. Mo₂C and W₂C reacted readily with O₂ at 40°C. The mass gained during oxidation could be quantitatively removed through reduction in 1bar H₂ at 300°C (Mo₂C) or 400°C (W₂C). The rate of toluene conversion was fully recovered only for Mo₂C that had been passivated with an initial O₂ concentration of 0.1vol.% and not for other passivation conditions or for W₂C. Intervening operation of toluene hydrogenation at 300 or 400°C enhanced the activity of samples that were previously oxidized and reduced or harshly reduced. This enhancement suggests that carbide formation is possible at milder temperatures than typically employed.

中文翻译：

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Mo2C和W2C的钝化剂和条件：对甲苯加氢催化活性的影响

通过热重分析和废气分析研究了Mo ₂ C和W ₂ C的钝化和再活化，并比较了新鲜碳化物与钝化和再活化碳化物的甲苯氢化活性（21bar，H ₂：甲苯= 33，150）。或200°C，WHSV = 10或20gg _cat ^-1 h ^-1）。相反文献，CO ₂和H ₂ ö分别为沫不适合钝化剂₂ C.沫₂ C和w ^ ₂下用ö容易反应₂在40℃下。氧化过程中获得的质量可以通过减少1bar H ₂进行定量去除温度为300°C（Mo ₂ C）或400°C（W ₂ C）。甲苯转化率仅对于以初始O ₂浓度为0.1vol。％钝化的Mo ₂ C才完全恢复，而对于其他钝化条件或W ₂ C则无法完全恢复。甲苯在300或400°C下氢化的中间操作C增强了先前被氧化，还原或严重还原的样品的活性。这种增强表明在比通常使用的温度低的温度下可能形成碳化物。