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/H₂ 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 MoC_1−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 H₂ addition providing ~ 150-fold proton NMR signal enhancement.

在此，我们已经表明，碳化钼催化剂的相组成对在用对氢进行的气相丙炔加氢中的成对氢加成选择性具有显着影响。使用Pechini方法或使用CH ₄ / H ₂渗碳气体混合物进行程序升温还原制备碳化钼催化剂。碳化物催化剂的结构通过高分辨率透射电子显微镜，X射线衍射和X射线光电子能谱进行了表征。发现通过Pechini方法制备的碳化钼主要包含面心立方MoC _1-x相，而TPR方法生成六方密堆积Mo ₂C相。通过改变渗碳气体混合物的气体时空速度，可以产生缺陷相。XRD图案的计算机建模用于识别Mo ₂ C催化剂的相组成。发现所有催化剂在成对氢加成中均具有活性。然而，hcp-Mo ₂ C相在成对的H ₂加成中表现出更高的贡献，从而提供了约150倍的质子NMR信号增强。