Abstract:

Complex systems with multi-level and multi-scale structures are widely encountered in the structure optimization of catalysts and catalytic reaction process, from synthesis conditions to structure regulation of catalysts, from catalytic performance to the active sites regulation, it is important to understand mesoscale structure of catalytic system. In this paper, Fe-Mn catalyst precursors (Fe/Mn mole ratio 1/4) with different structures were prepared by four methods (low-temperature co-precipitation, deposition-precipitation, calcination of mixed precursors, and mechanical mixing). The relationship between their structure and activation process, distribution of iron carbides and the catalytic performance for preparation of olefins from syngas were investigated. The results showed that the synthesis method had a significant impact on the structure of the catalysts, which mainly reflected in three aspects: activation process, iron carbides size and catalytic performance. The Fe-Mn catalysts prepared by co-precipitation had shown a higher CO conversion rate (20.07%), olefin/paraffinratio (2.32), and iron space-time yield (4.37×10^-5 mol CO?(g Fe)^-1?s^-1), which were mainly due to the smaller particle size of iron-carbon compounds and more Fe₅C₂ active phases formed after the catalyst was activated.

Key words: catalyst, iron carbides, mesoscale, olefins, syngas

摘要：

催化剂结构调控及反应过程普遍面对多层次多尺度结构的复杂系统，从宏观合成条件到催化剂结构尺度调控，从催化性能到催化剂表面活性位尺度调控，均离不开对催化体系介尺度结构的认识。采用四种方式（低温共沉淀、沉积沉淀、前体混合煅烧及机械混合）制备不同结构Fe-Mn催化剂（Fe与Mn摩尔比为1∶4），探究催化剂结构对其活化历程、铁碳化合物分布以及催化合成气制烯烃性能的影响。结果表明，合成方法对催化剂结构有显著影响，体现在三个方面：活化过程、铁碳化合物尺寸及催化反应性能。发现共沉淀制备的Fe-Mn催化剂显示出较高的CO转化率（20.07%）、烯烷比（2.32）及铁时空收率（4.37×10^-5 mol CO?(g Fe)^-1?s^-1），这主要得益于该催化剂活化后形成的较小的铁碳化合物颗粒尺寸及更多的Fe₅C₂活性相。

关键词: 催化剂, 铁碳化合物, 介尺度, 烯烃, 合成气