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Conversion of syngas into olefins with high hydrogen atom economy.

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Title: Conversion of syngas into olefins with high hydrogen atom economy.
Authors: Gao, Chang, Song, Wenlong, Wang, Huiqiu, Chen, Xiao, Cui, Chaojie, Hao, Wangshu, Yan, Ning, Yang, Yuan, Yang, Shenglong, Lv, Hao, Ma, Mingyu, Lian, Xinli, Zhang, Ruixia, Qian, Weizhong
Source: Science; 10/30/2025, Vol. 390 Issue 6772, p1-7, 7p
Subject Terms: HYDROGEN economy, CATALYSTS, ALKENES, SYNTHESIS gas, TECHNOLOGICAL innovations, CARBON oxides, WATER gas shift reactions, ENVIRONMENTAL responsibility
Abstract: In synthesizing olefins from syngas, low hydrogen atom economy (HAE), the fraction of reactant hydrogen in the hydrocarbon product, arises from hydrogen loss in water by-product. We report a sodium-modified FeCx@Fe3O4 core-shell catalyst coupling water-gas shift (WGS) with syngas-to-olefins (STO) to convert water into hydrogen in situ. HAE reaches about 66 to 83%, exceeding that of methanol-to-olefins (MTO, 50% upper limit). The approximately 95% carbon monoxide conversion and >75% olefin selectivity were simultaneously obtained. The coupling effect was validated by isotope tracing with deuterium oxide and blocking the WGS pathway, and the contribution of WGS was quantitatively evaluated. These results, using lower hydrogen to carbon monoxide ratios, implied that reducing steam consumption in the WGS reaction and reducing the overall output of carbon dioxide and wastewater enabled a sustainable STO process for potential industrialization. Editor's summary: Two different strategies can produce olefins from synthesis gas (syngas, a mixture of carbon monoxide and hydrogen) with fewer CO2 by-products over iron-based catalysts (see the Perspective by Saeys). Cai et al. fed trace amounts of bromomethane with syngas over iron-based catalysts. Surface-bound bromine interacted with iron active sites to inhibit water dissociation, carbon monoxide and oxygen atom recombination, and olefin hydrogenation, and enabled near-zero CO2 production and high α-olefin selectivity. In another study, Gao et al. found that a sodium-promoted FeCx@Fe3O4 core-shell nanoparticle catalyst could couple water-gas shift and syngas-to-olefins reactions in situ. Starting from syngas with low hydrogen/carbon monoxide ratios, the authors achieved high olefin selectivity and hydrocarbon yield, along with a reduction in CO2 and water by-products that led to high hydrogen atom economy. —Phil Szuromi INTRODUCTION: The synthesis of olefins from syngas through methanol has long been hindered by a low hydrogen atom economy (HAE), primarily due to the formation of water by-products and the requirement for high H2/CO ratios. This limitation not only increases production costs but also raises environmental concerns, prompting the need for innovative catalytic solutions in the emerging technology of direct syngas to olefins. RATIONALE: To address this challenge, we developed a sodium-modified FeCx@Fe3O4 core-shell catalyst that integrates the water-gas shift (WGS) and syngas-to-olefins (STO) reactions. By coupling these two processes, the catalyst enables in situ conversion of water generated during STO into hydrogen through the WGS reaction, thereby reducing the dependence on external hydrogen sources and improving HAE. RESULTS: Under the conditions of 623 K and 2 MPa with a low H2/CO ratio feedstock, the catalyst achieved outstanding performance: a CO conversion rate of ~95%, an olefin selectivity exceeding 75% (based on hydrocarbon products), and a hydrocarbon yield of 33 wt % (based on feedstock). The catalyst performance was stable over 500 hours of testing. Its HAE reached ~66 to 86% within an H2/CO ratio range of 1 to 3, far surpassing the ~43 to 47% of the traditional WGS–methanol synthesis–methanol to olefins (MTO) route (at an H2/CO ratio of ~2 to 2.05). Isotope-tracing and WGS-blocking experiments validated the coupling mechanism, and the contribution of the WGS reaction was quantitatively determined. CONCLUSION: This study represents a substantial breakthrough in enhancing HAE for syngas conversion. The new WGS-STO coupling route of the developed catalyst reduces steam consumption, wastewater generation, and CO2 emissions, with a 46% reduction in complete environmental factor compared with the WGS-MTO route. It also provides a sustainable alternative to existing olefin production technologies, offering great potential for the resource-efficient transformation of the olefin industry and contributing to the achievement of carbon neutrality goals. Improvement of hydrogen atom economy and olefin yield under the WGS-STO coupling effect. [ABSTRACT FROM AUTHOR]
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Abstract:In synthesizing olefins from syngas, low hydrogen atom economy (HAE), the fraction of reactant hydrogen in the hydrocarbon product, arises from hydrogen loss in water by-product. We report a sodium-modified FeC<subscript>x</subscript>@Fe<subscript>3</subscript>O<subscript>4</subscript> core-shell catalyst coupling water-gas shift (WGS) with syngas-to-olefins (STO) to convert water into hydrogen in situ. HAE reaches about 66 to 83%, exceeding that of methanol-to-olefins (MTO, 50% upper limit). The approximately 95% carbon monoxide conversion and >75% olefin selectivity were simultaneously obtained. The coupling effect was validated by isotope tracing with deuterium oxide and blocking the WGS pathway, and the contribution of WGS was quantitatively evaluated. These results, using lower hydrogen to carbon monoxide ratios, implied that reducing steam consumption in the WGS reaction and reducing the overall output of carbon dioxide and wastewater enabled a sustainable STO process for potential industrialization. Editor's summary: Two different strategies can produce olefins from synthesis gas (syngas, a mixture of carbon monoxide and hydrogen) with fewer CO<subscript>2</subscript> by-products over iron-based catalysts (see the Perspective by Saeys). Cai et al. fed trace amounts of bromomethane with syngas over iron-based catalysts. Surface-bound bromine interacted with iron active sites to inhibit water dissociation, carbon monoxide and oxygen atom recombination, and olefin hydrogenation, and enabled near-zero CO<subscript>2</subscript> production and high α-olefin selectivity. In another study, Gao et al. found that a sodium-promoted FeC<subscript>x</subscript>@Fe<subscript>3</subscript>O<subscript>4</subscript> core-shell nanoparticle catalyst could couple water-gas shift and syngas-to-olefins reactions in situ. Starting from syngas with low hydrogen/carbon monoxide ratios, the authors achieved high olefin selectivity and hydrocarbon yield, along with a reduction in CO<subscript>2</subscript> and water by-products that led to high hydrogen atom economy. —Phil Szuromi INTRODUCTION: The synthesis of olefins from syngas through methanol has long been hindered by a low hydrogen atom economy (HAE), primarily due to the formation of water by-products and the requirement for high H<subscript>2</subscript>/CO ratios. This limitation not only increases production costs but also raises environmental concerns, prompting the need for innovative catalytic solutions in the emerging technology of direct syngas to olefins. RATIONALE: To address this challenge, we developed a sodium-modified FeCx@Fe<subscript>3</subscript>O<subscript>4</subscript> core-shell catalyst that integrates the water-gas shift (WGS) and syngas-to-olefins (STO) reactions. By coupling these two processes, the catalyst enables in situ conversion of water generated during STO into hydrogen through the WGS reaction, thereby reducing the dependence on external hydrogen sources and improving HAE. RESULTS: Under the conditions of 623 K and 2 MPa with a low H<subscript>2</subscript>/CO ratio feedstock, the catalyst achieved outstanding performance: a CO conversion rate of ~95%, an olefin selectivity exceeding 75% (based on hydrocarbon products), and a hydrocarbon yield of 33 wt % (based on feedstock). The catalyst performance was stable over 500 hours of testing. Its HAE reached ~66 to 86% within an H<subscript>2</subscript>/CO ratio range of 1 to 3, far surpassing the ~43 to 47% of the traditional WGS–methanol synthesis–methanol to olefins (MTO) route (at an H<subscript>2</subscript>/CO ratio of ~2 to 2.05). Isotope-tracing and WGS-blocking experiments validated the coupling mechanism, and the contribution of the WGS reaction was quantitatively determined. CONCLUSION: This study represents a substantial breakthrough in enhancing HAE for syngas conversion. The new WGS-STO coupling route of the developed catalyst reduces steam consumption, wastewater generation, and CO<subscript>2</subscript> emissions, with a 46% reduction in complete environmental factor compared with the WGS-MTO route. It also provides a sustainable alternative to existing olefin production technologies, offering great potential for the resource-efficient transformation of the olefin industry and contributing to the achievement of carbon neutrality goals. Improvement of hydrogen atom economy and olefin yield under the WGS-STO coupling effect. [ABSTRACT FROM AUTHOR]
ISSN:00368075
DOI:10.1126/science.aea0774