氮掺杂介孔炭负载FeCu双金属催化剂及其CO加氢性能研究

Nitrogen-doped mesoporous carbon supported FeCu bimetallic catalyst and its CO hydrogenation performance

  • 摘要: 利用氮掺杂介孔炭负载FeCu双金属,改变Fe/Cu组成,考察催化剂结构性质特征及其CO加氢反应性能。结果表明,Fe、Cu与N相互作用存在差异,Cu-N相互作用较强,并直接促进了Cu的分散。在较高的金属负载量(45.0%-50.0%,质量分数)下,Cu仍保持了与N一致的均匀分布特征,催化剂表面Fe/Cu组成也因为Fe、Cu分布特征差异而小于体相,这与常见Fe-Cu体系明显不同。在所用预处理条件(300℃的H2气氛)下,Fe未被完全还原,H主要与Fe-O作用,以Fe-O-H形式存在,而Cu-N作用较强,金属Cu与H作用较弱,使得催化剂表面活性氢碳比降低,导致C5+选择性随Fe/Cu比值的减小逐渐增加。与此同时,载体向负载金属的电子偏移能力也随着Fe/Cu比值的减小逐渐增强,促使催化剂表面碱性随Cu含量的增加逐渐增强,最终导致C5+选择性、醇选择性进一步增加。

     

    Abstract: In this work, nitrogen-doped mesoporous carbon (NDMC) was prepared by a hard template method, and the NDMC supported FeCu bimetallic catalysts were prepared by an impregnation method. The physical and chemical properties and CO hydrogenation performance of the catalysts with varying Fe/Cu ratios were studied. The results indicated that Cu-N had strong interaction which directly promoted Cu dispersion on the support. At a relatively high metal loading (45.0%-50.0%), Cu maintained uniform distribution similar to that of N, and the ratios of Fe/Cu on the catalyst surface were smaller than those in the bulk phase, which were different from precipitated Fe-Cu bimetallic catalysts. The XPS results showed that Cu was an electron donor, and the electrons in the Cu-N shifted to Fe. Compared with Fe/NDMC, the reduction of FexCuy/NDMC was facilitated, and their CO hydrogenation activity was significantly increased. Under the pretreatment conditions (H2, 300℃), Fe was not completely reduced, and H might mainly interact with Fe-O in the form of Fe-O-H, while Cu-N interaction was stronger than Cu-H, resulting in a decrease in the ratio of surface active carbon/hydrogen, leading to a gradual increase in C5+ selectivity with the decrease of Fe/Cu ratio. Meanwhile, the introduction of Cu inhibited CO dissociation to some extent, and the electron migration ability of the support to the metal gradually increased with decreasing Fe/Cu ratio, and as a result the surface alkalinity of the catalysts increased with increasing Cu content, leading to further enhancement of C5+ selectivity and alcohol selectivity.

     

/

返回文章
返回