Synthesis gas conversion to short olefins and aromatics using bifunctional catalysts has gained much attention in recent years. Here, we study the interaction between the components of bifunctional catalysts to design a more stable catalyst system. Mixing α-alumina supported iron (-carbide) promoted with sodium and sulfur with an H-ZSM-5 zeolite to convert synthesis gas to aromatics and short olefins we observed selectivity loss of the iron (-carbide) catalyst as well as the acid function. This was displayed by increasing methane and decreasing aromatics selectivity when the two individual catalysts were mixed in close proximity. We introduced different approaches to understand this selectivity related deactivation. Larger spatial separation of the iron and zeolite allowed a more stable system with constant methane and aromatics selectivity. Alternatively, iron supported on carbon nano tubes mixed with the zeolite in close proximity did not display selectivity related deactivation. We conclude that the selectivity loss was caused by migration of sodium ions that were used next to sulfur as promoters on the iron catalyst over the α-alumina support to the zeolite, which was supported by XPS model experiments. This migration seems hindered on carbon supported iron catalysts.

近年来，使用双官能催化剂将合成气转化为短烯烃和芳族化合物备受关注。在这里，我们研究双功能催化剂的组分之间的相互作用，以设计更稳定的催化剂体系。混合α-H-ZSM-5沸石用钠和硫促进的-氧化铝负载的铁（碳化物）将合成气转化为芳烃和短烯烃，我们观察到铁（碳化物）催化剂的选择性损失以及酸功能。当将两种单独的催化剂紧密混合时，甲烷的增加和芳烃的选择性的降低表明了这一点。我们引入了不同的方法来了解这种与选择性相关的失活。铁和沸石的较大空间分离使得甲烷和芳烃选择性恒定的体系更加稳定。备选地，负载在与沸石紧密混合的碳纳米管上的铁没有显示出与选择性有关的失活。XPS模型实验支持了沸石对α-氧化铝的支持。这种迁移似乎在碳负载的铁催化剂上受到了阻碍。