Exploring the Reaction Paths in the Consecutive Fe-Based FT Catalyst–Zeolite Process for Syngas Conversion

Abstract

Direct conversion of syngas into aromatics with tandem catalysts containing Fe-based Fischer−Tropsch synthesis (FTS) catalysts and zeolites has been attracting significant attention because of the great costefficiency. However, the interaction role between two active species and reaction paths are still unclear. We report here that a high yield of aromatics was achieved by serial reactions directly from syngas on a Na-Fe-ZrO 2 /ZSM-5 tandem catalyst. Results point out significant impacts of zeolite in the catalytic system on performance including activity and selectivity. The role of the zeolite on reaction pathways about both CO conversion and aromatic formation has been systematically investigated by steady-state isotopic transient kinetic analysis and designed experiments. The presence of zeolite in the catalytic system promotes the CO hydrogenation rate by means of improving the iron carburization degree, possibly because of the enhanced CO adsorption and the formation of surface intermediates. It also enhances selectivity to aromatics by coupling CO to participate in the olefin transformation on ZSM-5. In addition, the formation rate of aromatics is proportional to the number of Lewis acidic sites, suggesting the dehydroaromatization route as the main mechanism of olefin aromatization. These findings provide some insights into the effect of ZSM-5 on reaction paths over the FTS catalyst−zeolite tandem catalyst system.

Light olefin synthesis from a diversity of renewable and fossil feedstocks: state-of the-art and outlook

“…zeolite) for the subsequent creaking of long-chain olefins to LOs are also considered. 293 However, hydrogen transfer occurring within the zeolites often results in significant production of light paraffins and aromatics 294–296 and thus, makes combinations of a FT catalyst and a zeolite not suitable for selective LO synthesis from CO 2 or CO.…”

“…zeolite) for the subsequent creaking of long-chain olefins to LOs are also considered. 293 However, hydrogen transfer occurring within the zeolites often results in significant production of light paraffins and aromatics [294][295][296] and thus, makes combinations of a FT catalyst and a zeolite not suitable for selective LO synthesis from CO 2 or CO. Molybdenum carbide, 297-299 sulfide 300 and nitride 301 catalysts exhibit noticeable activity in the CO/CO 2 hydrogenation. Though these catalysts usually have much lower activity compared to more conventional metallic or iron carbide catalysts, one of their important features is their stability in the presence of different impurities in syngas.…”

Applications of Zeolites to C1 Chemistry: Recent Advances, Challenges, and Opportunities

“…This may be due to the positive effect of Lewis acid sites on transformation of C 6+ alkenes into aromatics via dehydroaromatization. [ 17 ] Ion exchange can also be used to tune zeolite Brønsted acidity to control product selectivity. [ 18 ] For instance, Tsubaki and co‐workers studied the performance of mesoporous zeolite Y‐supported cobalt catalysts (Co/Y meso ) on syngas conversion.…”

Effect of Shell Thickness on Skeletal Fe@HZSM-5 Core-Shell Catalysts for Fischer-Tropsch Synthesis

“…由煤炭或生物质制取的合成气中 H 2 和 CO 的物质 的量比约为 1 [25] , 不适用于钴基催化剂上汽油段产物的 生产. 由于铁具有良好的 WGS 催化活性, 可以催化 CO 化 学 学 报 研究论文 n(H 2 )/n(CO)的比例 [3,26] . 在之前的工作中, 我们对反应 后的 Fe@Z-5-4d 催化剂开展了 57 Fe Mössbauer 谱研究, 拟合结果显示存在 FTS 反应活性相 Hägg 碳化铁, 同时 有氧化态的铁(Fe(II/III)和 Fe 3 O 4 )产生 [19] , 而氧化态的铁 能够催化 WGS 反应 [27] , 因此 Fe@Z- [19] .…”