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首页> 外文期刊>Catalysis science & technology >Supported Fe/MnOx catalyst with Ag doping for remarkably enhanced catalytic activity in Fischer-Tropsch synthesis
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Supported Fe/MnOx catalyst with Ag doping for remarkably enhanced catalytic activity in Fischer-Tropsch synthesis

机译：支持Fe / MnOx催化剂Ag兴奋剂催化活性显著提高费托合成

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Although the Mn promoter has been widely demonstrated to be beneficial to promoting the adsorption and dissociation of CO and therefore increasing the selectivity to light olefins in Fe-based FTS, it also brings about a negative effect on the catalytic activity due to its strong interaction with Fe oxides. In this study, Fe oxide was directly dispersed on a synthesized mesoporous spherical-like MnOx support and further doped with Ag nanoparticles to investigate its impact on the FTS reaction. XRD and H-2-TPR characterization confirmed that Mn and Fe tend to form an FeMn solid solution over a 10 wt% Fe/MnOx catalyst. As expected, a small amount of Ag doping on it could remarkably increase the catalytic activity by 1-5 times and even the selectivity to light olefins; this could be attributed to easier reduction of the Fe oxide, Mn oxide and FeMn solid solution due to the hydrogen (H) spillover generated by Ag as the reduced metallic Fe favors the formation of active Fe carbide and more O vacancies in MnOx facilitate CO adsorption and the rapid removal of dissociated O atoms on Fe carbide. Furthermore, the FTS activity related to the H spillover was intensively investigated over the MnOx-supported catalysts with different impregnation sequences of Ag and Fe, and over the hybrid 10Fe/MnOx and 1Ag/MnOx catalysts with particle and powder mixing in order to regulate the distance between Fe and Ag. It was found that the primary and secondary ways of H spillover are involved in the promoted reduction process, which was illustrated by XRD, H-2-TPR, H-2-TPD and CO-TPD characterization combined with catalytic results. The secondary spillover exhibited a much milder effect on the reduction promotion with a farther distance of Fe and Ag. Compared with the co-impregnated 1Ag10Fe/MnOx catalyst, the sequential impregnation of Ag and Fe onto the MnOx support, named the 10Fe/1Ag/MnOx catalyst, showed higher catalytic activity, which might be due to less formation of FeMn solid solution resulting from firstly introduced Ag on MnOx. Interestingly, both Ag-doped and Ag-free 10Fe/MnOx catalysts showed a rapid increase in CO conversion after several tens of hours of stable reaction and the CO conversion can reach 80-90% after a 100 hour test, and the possible reason for this was discussed based on HAADF-STEM observations of spent catalyst samples.
机译：尽管Mn启动子被广泛证明是有益的促进吸附和分离的公司,因此轻烯烃的选择性增加Fe-based FTS,它还带来了一个负面的由于其对催化活性的影响强相互作用与铁氧化物。铁氧化直接合成分散介孔spherical-like MnOx和支持进一步与Ag纳米颗粒掺杂究其对FTS反应的影响。和Mn H-2-TPR表征确认和铁往往形成一个高炉在坚实的解决方案10 wt % Fe / MnOx催化剂。Ag的掺杂可以显著1 - 5次,提高催化活性甚至轻烯烃的选择性;归因于更铁的还原氧化物、锰氧化物和锰铁固溶体生成的氢(H)溢出Ag)的减少金属铁主张的形成活性铁碳化物和MnOx O空缺促进CO吸附和快速删除分离O原子在铁碳化物。FTS活性相关的H溢出MnOx-supported深入调查与不同的浸渍催化剂序列Ag)和铁,在混合10 Fe / MnOx和1 ag / MnOx催化剂颗粒和粉末混合为了调节之间的距离铁和Ag)。二次H溢出参与的方法促进了还原过程,说明通过XRD、H-2-TPR H-2-TPD CO-TPD表征催化相结合的结果。二级溢出表现出温和得多影响减少进一步推广铁和Ag)的距离。co-impregnated 1 ag10fe / MnOx催化剂,连续浸渍Ag)和铁上MnOx支持,命名为10 fe / 1 ag / MnOx催化剂,表现出更高的催化活性,这可能是由于更少的高炉固溶体的形成造成首先介绍MnOx Ag)。有趣的是,Ag-doped和Ag-free10 fe / MnOx催化剂显示,公司迅速增加转换后几十小时的稳定反应和CO转化率可以达到80 - 90%100小时后测试,和可能的原因这是基于HAADF-STEM讨论用过的催化剂样品的观察。

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