Pairwise Parahydrogen Addition Over Molybdenum Carbide Catalysts
Pairwise Parahydrogen Addition Over Molybdenum Carbide Catalysts
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DOI：
10.1007/s11244-019-01211-z
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发表时间：
2020-03-01
影响因子：
3.6
通讯作者：
Koptyug, Igor V.
中科院分区：
文献类型：
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作者：
Burueva, Dudari B.;Smirnov, Andrey A.;Koptyug, Igor V.
在此，我们已经证明了碳化钼催化剂的相组成对气相丙炔加氢中对氢加氢的选择性有显著的影响。采用Pechini法和CH4/H-2渗碳气体混合物程序升温还原法制备碳化钼催化剂。采用高分辨率透射电镜、x射线衍射和x射线光电子能谱对催化剂的结构进行了表征。结果表明，Pechini法制备的碳化钼主要含有面心立方MoC1-x相，而TPR法制备的碳化钼主要含有六边形密排Mo2C相。通过改变渗碳气体混合物的每小时空速，可以产生缺陷相。利用计算机模拟XRD图谱，确定了Mo2C催化剂的物相组成。结果表明，所有催化剂均具有双加氢活性；然而，hcp-Mo2C相表现出更高的配对H-2添加贡献，提供约150倍的质子核磁共振信号增强。
Herein, we have shown that the phase composition of molybdenum carbide catalysts has a pronounced effect on the pairwise hydrogen addition selectivity in the gas-phase propyne hydrogenation with parahydrogen. Molybdenum carbide catalysts were prepared using either the Pechini method or temperature-programmed reduction with CH4/H-2 carburizing gas mixture. The structures of carbide catalysts were characterized by high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that molybdenum carbide prepared by the Pechini method predominantly contains a face-centered-cubic MoC1-x phase, while the TPR method yields a hexagonal-close-packed Mo2C phase. By varying the gas hourly space velocity of carburizing gas mixture, the defected phase can be produced. Computer modeling for XRD patterns was used to identify the phase composition of Mo2C catalysts. All the catalysts were found to be active in pairwise hydrogen addition; however the hcp-Mo2C phase exhibits a higher contribution of pairwise H-2 addition providing ~ 150-fold proton NMR signal enhancement.