Selective synthesis of tungsten carbide phases W2C and WC as hydrogenation catalysts
Selective synthesis of tungsten carbide phases W2C and WC as hydrogenation catalysts
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DOI：
10.1016/j.jcat.2021.11.025
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发表时间：
2021-12-09
影响因子：
7.3
通讯作者：
Jentoft, Friederike C.
中科院分区：
文献类型：
--
作者：
Bretzler, Patrick;Huber, Michael;Jentoft, Friederike C.
碳化钨是贵金属催化剂的可能的低成本替代品，但不同碳化物化学计量（W2 C，WC）及其多晶型物对催化行为的作用知之甚少。我们开发了一个“动态，等温”碳化钨在甲烷和H-2的混合物，以控制相组成和催化性能。实验设计方法表明，关键参数是合成温度（670至775摄氏度）和添加二氧化硅作为稳定剂（0或70摩尔%）。X射线衍射表明，该组合物可以从14至99重量%的W2 C，由WC和一小部分的W金属补充调整。W2 C的晶畴尺寸小于WC的晶畴尺寸（>= 10 nm），从而提供了W2 C的热力学稳定性，与计算预测一致（Shrestha等人，化学材料2021，33，4606-4620）。CO吸附量与W2 C含量成比例，在丁醛或甲苯加氢中的性能也是如此。(C)2021爱思唯尔公司All rights reserved.
Tungsten carbides are possible low-cost replacements for noble metal catalysts, but the role of different carbide stoichiometries (W2C, WC) and their polymorphs for catalytic behavior is poorly understood. We develop a "dynamic, isothermal" carburization of WO3 in a mixture of CH4 and H-2 to control phase composition and catalytic properties. A design-of-experiments approach reveals that the key parameters are synthesis temperature (670 to 775 degrees C) and addition of silica as stabilizer (0 or 70 mol%). X-ray diffraction shows that the composition can be adjusted from 14 to 99 wt% W2C, complemented by WC and a small fraction of W metal. Crystalline domain sizes for W2C are smaller than those of WC (>= 10 nm), affording thermodynamic stabilization of W2C in agreement with computational predictions (Shrestha et al., Chem. Mater. 2021, 33, 4606-4620). The amount of CO adsorbed scales with W2C content, and so does the performance in butyraldehyde or toluene hydrogenation. (C) 2021 Elsevier Inc. All rights reserved.