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Fischer-Tropsch (FT) synthesis is an important module for the production of clean and sustainable fuels and chemicals, making it a topic of considerable interest in energy research. This mini-review covers the current literature on FT catalysis and offers insights into the primary products, the nuances of the FT reaction, and the product distribution, with particular attention to the Anderson-Schulz-Flory distribution (ASFD) and known deviations from this fundamental concept. Conventional FT catalysts, particularly Fe- and Co-based catalysis systems, are reviewed, highlighting their central role and the influence of water and water-gas shift (WGS) activity on their catalytic behavior. Various mechanisms of catalyst deactivation are also investigated, and the high methanation activity of Co-based catalysts is illustrated. To make this complex field accessible to a broader audience, we explain conjectured reaction mechanisms, namely, the carbide mechanism and CO insertion. We discuss the complex formation of a wide range of products, including olefins, kerosenes, branched hydrocarbons, and by-products such as alcohols and oxygenates. The article goes beyond the traditional scope of FT catalysis by addressing topics of current interest, including the direct hydrogenation of CO2 for power-to-X applications and the use of bifunctional catalysts to produce tailored FT products, most notably for the production of sustainable aviation fuel (SAF). This mini-review provides a holistic overview of the evolving landscape of FT catalysts and is aimed at both experienced researchers and those new to the field while covering current and emerging trends in this important area of energy research. [ABSTRACT FROM AUTHOR]

Abstract Carbon monoxide (CO) is a primary air pollutant and a poisonous species for human beings, animals, and some catalytic reactions. Meanwhile, CO is also a versatile feedstock in the chemical industry to produce high‐value chemicals and clean fuels, which has stimulated extensive research interests in exploiting efficient CO conversion processes. Redox potential is a key thermodynamic quantity in these processes whereas only standard reduction potentials at 25°C and 1 atm are currently available. Herein, it is the first time to report the effects of temperature (0–1000°C), pressure (1–100 atm), and adsorption on the redox potentials of 18 CO conversion reactions to form carbon dioxide, methane, straight‐chain alkanes (ethane, propane, and butane), light olefins (ethylene, propylene, and butylene), benzene, alcohols, aldehydes, acids, and dimethyl ether, based on theoretical calculations. It was noticed that gas‐phase, aqueous‐phase, and adsorption‐state redox potentials decrease with increasing temperature at an increased rate while they show different responses to pressure change. Namely, gas‐phase and most aqueous‐phase redox potentials increase with pressure at a gradually declined rate, while adsorption‐state redox potentials are not influenced by pressure. Most importantly, the significant differences up to 2.06 V under varied conditions highlight the necessity of applying operando redox potentials for CO conversion reactions.

Fischer–Tropsch Synthesis (FTS) is an important process in the production of liquid fuels in the energy sector, due to its flexibility for use with other technologies that can produce carbon monoxide (CO) and hydrogen. Catalysts have found substantial use in FTS to improve the process efficiency. However, the use of conventional FTS catalyst reduction techniques using (hydrogen (H2), CO and syngas) to activate the metal precursor has been accompanied by strong metal-support interactions. Such limitations have driven the quest for better technologies to ensure FTS catalysis reaches its full capacity. In this article, we review the activation techniques used, with emphasis on the contemporary auto-reduction technique, which has revealed energy-saving merits. Auto-reduction has the advantage of reducing the number of steps involved in catalyst preparation prior to FTS as well as eliminating costly reducing agents such as H2, CO and syngas. Auto-reduction in this article refers to the reduction of the metal precursor using a carbon support. We firstly provide a comprehensive review of the traditional reducing agents, followed by a review of the contemporary auto-reduction technique. A comparison of the conventional FTS catalyst reduction and auto-reduction techniques is provided to allow for a fundamental understanding of the merits and demerits of both techniques. The different types of nanostructured carbon materials used in aiding auto-reduction for the FTS process are reviewed. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a primary air pollutant and a poisonous species for human beings, animals, and some catalytic reactions. Meanwhile, CO is also a versatile feedstock in the chemical industry to produce high‐value chemicals and clean fuels, which has stimulated extensive research interests in exploiting efficient CO conversion processes. Redox potential is a key thermodynamic quantity in these processes whereas only standard reduction potentials at 25°C and 1 atm are currently available. Herein, it is the first time to report the effects of temperature (0–1000°C), pressure (1–100 atm), and adsorption on the redox potentials of 18 CO conversion reactions to form carbon dioxide, methane, straight‐chain alkanes (ethane, propane, and butane), light olefins (ethylene, propylene, and butylene), benzene, alcohols, aldehydes, acids, and dimethyl ether, based on theoretical calculations. It was noticed that gas‐phase, aqueous‐phase, and adsorption‐state redox potentials decrease with increasing temperature at an increased rate while they show different responses to pressure change. Namely, gas‐phase and most aqueous‐phase redox potentials increase with pressure at a gradually declined rate, while adsorption‐state redox potentials are not influenced by pressure. Most importantly, the significant differences up to 2.06 V under varied conditions highlight the necessity of applying operando redox potentials for CO conversion reactions. [ABSTRACT FROM AUTHOR]

Fischer-Tropsch synthesis (FTS) is a widely recognized process that catalytically converts syngas into higher hydrocarbons and oxygenates, which are ultimately upgraded into transportation fuels and chemicals. Effective temperature control and heat dissipation are crucial considerations due to the exothermic nature of the FT reaction. Underutilization of the catalytic bed is another challenge in fixed-bed reactors. The implementation of a multilayered catalytic bed, with the catalytic activity in an ascending order, has shown positive effects in addressing these issues. It mitigates adiabatic temperature rise, reduces the maximum reactor temperature, and minimizes catalyst deactivation at high temperatures. Moreover, this multilayered bed effectively addresses the underutilization issue by ensuring optimal utilization of the entire bed as the catalytic activity transitions from one layer to another during the reaction. Layers with a higher cobalt loading remain active until the completion of the reaction, resulting in minimal fluctuations in CO conversion. To achieve uniform temperature profiles, catalytic activities, and product distributions in all reactor tubes in a multitubular reactor, it is imperative to maintain consistent reaction conditions, utilize the same catalyst loading in all tubes, employ an appropriate heating system, and implement an efficient cooling system to dissipate the heat generated by the exothermic reaction. Furthermore, investigations into the properties of the used catalysts after the reaction indicate that catalyst deactivation primarily occurs due to the deposition of FT products on the catalyst surface and pores and blockage of active cobalt sites, and sintering of cobalt particles. [Display omitted] • Multilayered catalytic bed of Co/Al 2 O 3 catalysts for Fischer–Tropsch synthesis in multitubular fixed-bed reactor. • Multilayered catalytic bed reduced the maximum adiabatic temperature rise during the reaction. • Utilization of catalytic bed increase by using the multilayered catalytic bed in the reactor. • Accumulation of FT products and sintering of cobalt particles are the main catalyst deactivation mechanisms. [ABSTRACT FROM AUTHOR]

The deposition of nanostructured carbon particles on the surface of a catalyst (carburization) is routinely considered an inalienable and undesirable secondary process in Fischer–Tropsch synthesis. However, very little is known about the actual role of the nanocarbon particles and how they influence catalysis. This paper reports research on the influence of carbon deposition on the performance of a cobalt-based Fischer–Tropsch-synthesized catalyst in an industrial-scale fixed-bed reactor (length—6000 mm, inner diameter—16.5 mm). The comparison of the structure and catalytic performance of a pelletized cobalt catalyst with the same catalyst, which was preliminary carburized, is presented. Pellet pore structure, catalyst surface, cobalt cluster morphology and the main catalytic properties (CO conversion, C5+ hydrocarbon productivity and selectivity to C5+ hydrocarbons and CH4 formation) were investigated. It is shown that the primary pre-carburization effect is a result of the physical blockage of the catalyst pore structure not followed by drastic changes in the cobalt cluster's structure. [ABSTRACT FROM AUTHOR]

The study investigated a number of cobalt-based hybrid catalysts (prepared as composite mixtures) for integrated Fischer–Tropsch (FT) synthesis and hydroprocessing. The metal component was a Co-based catalyst for FT synthesis prepared by impregnation (Co–Al/SiO2 in one sample and Co–Ru/SiO2 in another); the acid component was a ZSM-5 zeolite in the H-form that additionally contained Ru (incorporated by impregnation in one sample and by ion exchange in another); and the binder was boehmite. The catalysts were characterized by XRD, low-temperature argon adsorption/desorption, EDX, SEM, TEM, H2-TPD, and TPR. The promoter incorporation method was shown to affect the particle size and cobalt reduction conditions. The catalysts were tested in FT synthesis at 2.0 MPa, 240°C, H2/CO = 2, and GHSV 1000 h–1. The method for loading Ru as a hydrogenating agent was found to govern the catalytic activity as well as the group and fractional compositions of the reaction products. It was further shown that co-loading Co and Ru intensifies the hydrogenation and synthesis of hydrocarbons—including C11–C18 (diesel fuel) and in particular iso-alkanes—and minimizes the content of unsaturated hydrocarbons. Incorporating Ru into the acid component favors the isomerization activity of the catalyst. Using impregnation for this purpose maximizes the gasoline productivity (C5–C10 hydrocarbons). [ABSTRACT FROM AUTHOR]

The use of carbide catalysts in Fischer–Tropsch synthesis (FTS) is an active area of research, as carbide phases have been shown to improve the stability and performance of catalysts in this reaction. This study compared the catalytic activity and product selectivity of cobalt and iron catalysts supported on SBA-15, with and without a carbide phase and reduction treatment before the reaction. Results showed that the presence of the carbide phase had a noticeable influence on the catalytic behavior of the catalysts, and the reduction of the catalyst with hydrogen also affected the product selectivity. The presence of the carbide phase in non-reduced cobalt catalysts resulted in increased selectivity to liquid phase products, as evidenced by a CO conversion of 37% with 68% selectivity to the products in the liquid phase. The catalytic activity of the iron carbide catalyst for CO dissociation was found to be 38% after reducing the catalyst with hydrogen, leading to the formation of more active sites. The presence of metal carbides and formation of metallic cobalt and iron during the FT reaction and reduction step was found to have a significant effect on the catalytic performance and product selectivity. The findings of this research provide new insights into the role of carbide in the performance of cobalt and iron catalysts in Fischer–Tropsch synthesis. [ABSTRACT FROM AUTHOR]

BACKGROUND: Syngas conversion to olefins via Fischer‐Tropsch Synthesis (FTs) route and then subsequently into aromatics (syngas−olefins−aromatics (SOA)) was considered a promising industrialization route due to its ability to match reaction temperatures between syngas to olefins (300–400 °C) and olefins to aromatics (300–500 °C). In this reaction route, the syngas to olefin process can be efficiently and easily realized by Fe‐based FTs catalysts. However, the aromatization process occurring over the zeolite catalyst was still considered a big challenge due to zeolites' complex topology, variable morphology, and elusive acidic properties. RESULTS: A series of ZSM‐5 zeolites with different morphologies, including nano ellipsoid, nano cube, nano aggregate, nano bead, and nano pile were successfully synthesized. The effects of the ZSM‐5 zeolite's morphology and reaction temperature on the aromatics synthesis from syngas based on a modified FTs route were systematically studied. CONCLUSION: In all the studied ZSM‐5 zeolites, the nano cube ZSM‐5 zeolite (Z5‐NC) zeolite had the best aromatization ability. The hybrid catalyst combination of FeMnK&Z5‐NC obtained the highest xylene selectivity of 12% (2.8% + 9.2%), and its total aromatics selectivity was also the highest (42.5%). The study on reaction temperature suggested that a higher reaction temperature (320–360 °C) could efficiently impede the formation of CO2. However, the selectivity of aromatics was restrained to around 44% at higher temperatures because a high temperature facilitated the hydrocracking of higher hydrocarbons, leading to the increase of the selectivity of lighter CH4 and paraffin. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Ambient-pressure X-ray photoelectron spectroscopy (XPS) was used to investigate the reactions of CO, H2, and their mixtures on Co foils. We found that CO adsorbs molecularly on the clean Co surface and desorbs intact in vacuum with increasing rate until ∼90°C where all CO desorbs in seconds. In equilibrium with 100 mTorr gas, CO dissociates above 120°C, leaving carbide species on the surface but no oxides, because CO efficiently reduces the oxides at temperatures ∼100°C lower than H2. Water as impurities or produced by reaction of CO and H2 efficiently oxidizes Co even at room temperature. Under 97:3 CO/H2 mixture and with increasing temperatures, the Co surface becomes more oxidized and covered by hydroxyl groups until ∼150°C where surface starts to get reduced, accompanied by carbide accumulation indicative of CO dissociation. A similar trend was observed for 9:1 and 1:1 mixtures, but surface reduction begins at higher temperatures. (Figure Presented).

[Display omitted] • Investigation of promoter type and its composition on the light olefin production via Fischer-Tropsch Synthesis (FTS). • Evaluating designated catalyst performances by computational approaches: Response Surface Methodology (RSM) and Artificial Neural Network (ANN). • Both methods create promising models for light olefin production via FTS based on MSE and R2. • Ho, Cu and Zn promoters were found to have a positive effect on light olefin production. • 0.5Ho10Fe2Co/α-Al 2 O 3 catalyst attained the highest light olefin production among a total of 49 designated catalysts. The production of light olefins via Fischer-Tropsch Synthesis (FTS) was investigated by both experimental and modeling studies. Experimental studies were conducted by employing promoted FeCo/α-Al 2 O 3 (FeCo) bimetallic catalysts. The Response Surface Methodology (RSM) and Artificial Neural Network (ANN) methods were used in modeling. Specifically, effects of the types and concentration of promoters on the catalytic performances of α-Al 2 O 3 supported iron-cobalt bimetallic catalysts are investigated by using Ce, Ni, La, Ho, Ga Cu, Mn, and Zn used as promoters. A total of 49 catalysts were prepared by co-impregnation method and tested at 310 °C and 1 bar in a high-speed catalyst performance test system (HT-CPA). The FTS performances of catalysts showed that both the types and amounts of the promoters can affect light olefin production. The light olefin (C 2 =–C 3 =) production of unpromoted FeCo catalyst was about 3.87 × 10−3 (mol C/g active metal. h). The best performances were obtained from FeCo catalysts promoted with Ho, Cu, and Zn. Presence of these promoters increased olefin production up to ∼ 84 %, 76 % and 70 %, respectively. Performance parameters (MSE and R2) of RSM and ANN models revealed that both methods can be used to support experimental studies and provide a procedure for optimizing catalyst formulations yielding the desired product selectivity in FTS processes. The RSM outcomes aligned with experimental findings, suggest that that Ho, Cu, and Zn can serve as suitable promoters for the light olefin production in FTS. ANN model attained higher performance parameters (R2 = 0.95 and MSE = 2E−7) than RSM model (R2 = 0.85 and MSE = 3.4E−7). This indicates that ANN model, which designed as one hidden layer including 7 neurons, can provide better predictions and a fitting capacity. Therefore, it may be used in further optimization and sensitivity analysis approaches. Alignment degree between the experimental and modeling results demonstrates that the proposed methodology can provide a reliable and efficient way to guide experiments to optimize catalyst formulations through identification of potential promoters and their amounts to be used. [ABSTRACT FROM AUTHOR]

Sulfur is a common poison for cobalt-catalyzed Fischer–Tropsch Synthesis (FTS). Although its effects on catalytic activity are well documented, its effects on selectivity are controversial. Here, we investigated the effects of sulfur-covered cobalt surfaces on the selectivity of FTS using density functional theory (DFT) calculations. Our results indicated that sulfur on the surface of Co(111) resulted in a significant decrease in the adsorption energies of CO, HCO and acetylene, while the binding of H and CH species were not significantly affected. These findings indicate that sulfur increased the surface H/CO coverage ratio while inhibiting the adsorption of carbon chains. The elementary reactions of H-assisted CO dissociation, carbon and oxygen hydrogenation and CH coupling were also investigated on both clean and sulfur-covered Co(111). The results indicated that sulfur decreased the activation barriers for carbon and oxygen hydrogenation, while increasing the barriers for CO dissociation and CH coupling. Combining the results on elementary reactions with the modification of adsorption energies, we concluded that the intrinsic effect of sulfur on the selectivity of cobalt-catalyzed FTS is to increase the selectivity to methane and saturated short-chain hydrocarbons, while decreasing the selectivity to olefins and long-chain hydrocarbons. [ABSTRACT FROM AUTHOR]

Colloidal synthesis of metal nanocrystals (NC) offers control over size, crystal structure and shape of nanoparticles, making it a promising method to synthesize model catalysts to investigate structure-performance relationships. Here, we investigated the synthesis of disk-shaped Co-NC, their deposition on a support and performance in the Fischer–Tropsch (FT) synthesis under industrially relevant conditions. From the NC synthesis, either spheres only or a mixture of disk-shaped and spherical Co-NC was obtained. The disks had an average diameter of 15 nm, a thickness of 4 nm and consisted of hcp Co exposing (0001) on the base planes. The spheres were 11 nm on average and consisted of ε-Co. After mild oxidation, the CoO-NC were deposited on SiO2 with numerically 66% of the NC being disk-shaped. After reduction, the catalyst with spherical plus disk-shaped Co-NC had 50% lower intrinsic activity for FT synthesis (20 bar, 220 °C, H2/CO = 2 v/v) than the catalyst with spherical NC only, while C5+-selectivity was similar. Surprisingly, the Co-NC morphology was unchanged after catalysis. Using XPS it was established that nitrogen-containing ligands were largely removed and in situ XRD revealed that both catalysts consisted of 65% hcp Co and 21 or 32% fcc Co during FT. Furthermore, 3–5 nm polycrystalline domains were observed. Through exclusion of several phenomena, we tentatively conclude that the high fraction of (0001) facets in disk-shaped Co-NC decrease FT activity and, although very challenging to pursue, that metal nanoparticle shape effects can be studied at industrially relevant conditions. [ABSTRACT FROM AUTHOR]

• Few-layer graphene nanoflakes with domain size less than 50 nm were used as supports. • Supports with different types of dominating nitrogen species were synthesized. • Stability of nitrogen functional groups was investigated. • Catalysts supported on oxidized both pristine and doped supports were the most active. Nitrogen-doped carbon nanomaterials show unique properties in catalysis both as an active component and as a support. The oxidized and N-doped graphene nanoflakes (GNFs) of low domain size (10–30 nm) have been studied in present work as supports for cobalt-based Fischer-Tropsch catalysts. Three supports with different types of dominating nitrogen species were synthesized and the effect of both the nature and localization of nitrogen species in the support on the structure and performance of 10 wt.% Co catalysts was investigated. Varying the synthesis technique and post-synthesis treatment, the cobalt particle size and hence the activity of catalyst can be tuned. The catalysts supported on oxidized pristine and N-doped GNFs were found to be the most active. Transformations of N-groups during catalyst preparation and reduction were observed. In the case of edge localization of N-groups the cross-linking of support particles was detected that led to the diffusion hindering and low CO conversion over corresponding catalyst. [ABSTRACT FROM AUTHOR]

Society is facing serious challenges to reduce CO2 emissions. Effective change requires the use of advanced chemical catalyst and reactor systems to utilize renewable feedstocks. One pathway to long-term energy storage is its transformation into high quality, low-emission and CO2-neutral fuels. Performance of technologies such as the Fischer-Tropsch reaction can be maximized using the inherent advantages of microstructured packed bed reactors. Advantages arise not only from high conversion and productivity, but from its capability to resolve the natural fluctuation of renewable sources. This work highlights and evaluates a system for dynamic feed gas and temperature changes in a pilot scale Fischer-Tropsch synthesis unit for up to 7 L of product per day. Dead times were determined for non-reactive and reactive mode at individual positions in the setup. Oscillating conditions were applied to investigate responses with regard to gaseous and liquid products. The system was stable at short cycle times of 8 min. Neither of the periodic changes showed negative effects on the process performance. Findings even suggest this technology's capability for effective, small-to-medium-scale applications with periodically changing process parameters. The second part of this work focuses on the application of a real-time photovoltaics profile to the given system. [ABSTRACT FROM AUTHOR]

Climate change calls for a paradigm shift in the primary energy generation that comes with new challenges to store and transport energy. A decentralization of energy conversion can only be implemented with novel methods in process engineering. In the second part of our work, we took a deeper look into the load flexibility of microstructured Fischer-Tropsch synthesis reactors to elucidate possible limits of dynamic operation. Real data from a 10 kW photovoltaic system is used to calculate a dynamic H2 feed flow, assuming that electrolysis is capable to react on power changes accordingly. The required CO flow for synthesis could either originate from a constantly operated biomass gasification or from a direct air capture that produces CO2; the latter is assumed to be dynamically converted into synthesis gas with additional hydrogen. Thus two cases exist, the input is constantly changing in syngas ratio or flow rate. These input data were used to perform challenging experiments with the pilot scale setup. Both cases were compared. While it appeared that a fluctuating flow rate is tolerable for constant product composition, a coupled temperature-conversion relationship model was developed. It allows keeping the conversion and product distribution constant despite highly dynamic feed flow conditions. [ABSTRACT FROM AUTHOR]

Redox properties of catalytic environment, namely He as neutral, H 2 as reducing and H 2 –H 2 O as reducing–oxidative one, determine the conversion of hydrocarbons on Co–zeolite catalysts at 170–260 °C as well as product distribution. The highest yield of isomerized products was achieved in reducing medium, while the methane formation was suppressed most efficiently in neutral and reducing–oxidative environments. Two distinct ranges can be identified for temperature dependencies of reaction parameters, namely 170–210 and 220–260 °C. [ABSTRACT FROM AUTHOR]

• Multi-functional catalysis offers intriguing possibilities for CO 2 valorization. • Ca incorporation onto ZSM-5 creates multiple Lewis acidic species. • Brønsted-Lewis acid synergy in Ca-ZSM-5 increases light olefin yield from CO 2. Utilization of multi-functional catalysis is fast becoming the method of choice to boost the production of valuable chemicals from CO 2. Here, we present a possible route to increase selectivity to light olefins by modifying the acidity of the zeolitic component of a multi-functional catalyst. This is carried out via incorporation of Ca on the zeolite ZSM-5 by incipient wetness impregnation. This incorporation, while straightforward, leads to reduced Brønsted acidity and the formation of multiple Lewis acidic species inside the zeolite. NMR investigations point towards incorporation of CO/ketene into the zeolite leading to the creation of surface acetate species, which augments the production of light olefins. Additionally, the suppression of oligomerization due to the reduction of Brønsted acid sites also produces more light olefins at the expense of longer chain hydrocarbons. [ABSTRACT FROM AUTHOR]

• A cobalt/alumina catalyst was modified with tin. • The Sn-modified samples were less active for methanol production. • The methanol rate of formation correlated with H 2 adsorption capacity. • Surface formates on Sn-modified samples showed a markedly lower reactivity. Hydrocarbons are the main reaction products of syngas conversion over cobalt-based catalysts. Methanol is also produced as a minor by-product and has been proposed to be produced via a specific reaction pathway involving formates species located at the interface with the support. The poisoning of a Co/alumina catalyst with Sn was studied here and showed to induce a strong decline in methanol production, similar to that of hydrocarbons. The addition of Sn did not prevent the formation of formates as observed by operando diffuse reflectance FT-IR spectroscopy. However, the reactivity of formates was markedly lowered in the presence of Sn. We propose that these observations have two possible origins. Firstly, Sn addition reduced significantly the H 2 adsorption capacity of the Sn-modified samples. Hydrogen, which is required for the hydrogenation of formates to methanol, is probably activated on the cobalt metal particles, some sites of which were strongly poisoned by Sn. Secondly, Sn addition could also have specifically poisoned interfacial sites, where the most reactive formates are present. [ABSTRACT FROM AUTHOR]

As a century‐old classical reaction, Fischer‐Tropsch (F‐T) synthesis is undergoing new developments especially in its applications of producing jet fuel, olefins, aromatics and oxygenated chemicals, which are completely different from the conventional F‐T product, gasoline, diesel and wax. Producing above new products is not obeying famous ASF distribution law, requiring revolutionary design of new F‐T catalysts and reaction pathways. A mass of new research directions on F‐T synthesis for these liquid fuels and high‐value chemicals are successfully proposed. This review spotlights recent new advances based on F‐T synthesis for non‐automotive applications, and discusses its new possible directions in future. Going beyond cars: This Minireview spotlights recent new advances based on Fischer‐Tropsch synthesis for non‐automotive applications, such as jet fuel, olefins, aromatics and oxygenated chemicals, which are completely different from the conventional Fischer‐Tropsch product, and discusses its new possible directions in future. [ABSTRACT FROM AUTHOR]

• Amorphous cobalt silicate was prepared by adding TMOS during ZIF-67 synthesis. • The cobalt silicate material could be reduced at relatively low temperature. • Co reducibility and FTS activity increased with reduction temperature and time. • The Re500-8h exhibited higher FTS activity with good stability. It is always hard to reduce Co 2 SiO 4 to active Co0 on supported Co-based catalyst for Fischer-Tropsch synthesis (FTS). Here, amorphous Co 2 SiO 4 material was prepared by in-situ doping TMOS during synthesis of ZIF-67, which was then reduced at different temperature and time to obtain ReX-2h (X = 400, 450, 500, 550, 600) and Re500-Yh (Y = 2, 4, 8) catalysts. The effects of reduction temperature and time on Co reduction degree and FTS performance were investigated. Results indicated that the ReX-2h and Re500-Yh catalysts exhibited low CH 4 selectivity due to no obvious Co microcrystal found. The reduction degree of ReX-2h increased with reduction temperature, which led to enhanced FTS activity. However, both Re550-2h and Re600-2h exhibited poorer stability than Re500-2h, so the effects of reduction time on Re500-Yh were done. The reduction degree and FTS activity of Re500-Yh were also promoted with extending reduction time. The Re500-8h exhibited higher FTS activity with good stability. [Display omitted] [ABSTRACT FROM AUTHOR]

A bifunctional Fe/HZSM-5 catalyst was prepared for direct synthesis of aromatics from syngas. The influence of iron loading on acidity and syngas to aromatics (STA) performances over the Fe/HZSM-5 catalysts was studied. An increasing iron loading increased the amounts of active iron species, enhancing synergistic effect of active iron sites and HZSM-5 for the STA reaction. Higher iron loading in the Fe/HZSM-5 catalyst resulted in the decrease of Brönsted acid sites and increase of Lewis acid sites, promoting the formation of C 5 + hydrocarbons and aromatics selectivity via weakening the cracking ability and enhancing the dehydrogenation property of HZSM-5. Excessive adding of iron loading induced the formation of graphitic carbon deposition, leading to a decrease of catalytic activity and stability. [ABSTRACT FROM AUTHOR]

Abstract: The Fischer–Tropsch synthesis (FTS) is a structure‐sensitive exothermic reaction that enables catalytic transformation of syngas to high quality liquid fuels. Now, monolithic cobalt‐based heterogeneous catalysts were elaborated through a wet chemistry approach that allows control over nanocrystal shape and crystallographic phase, while at the same time enables heat management. Copper and nickel foams have been employed as supports for the epitaxial growth of hcp‐Co nanowires directly from a solution containing a coordination compound of cobalt and stabilizing ligands. The Co/Cufoam catalyst was tested for Fischer–Tropsch synthesis in a fixed‐bed reactor, showing stability and significantly superior activity and selectivity towards C5+ compared to a Co/SiO2‐Al2O3 reference catalyst under the same conditions. [ABSTRACT FROM AUTHOR]

A series of silica doped alumina (SDA) [Si-Al 2 O 3 ] having high surface area and narrow pore size distribution are synthesized with varying amount of silica and used as a support material to facilitate incorporation of Co, Mg and Zr into it. These supported Co-Mg-Zr/SDA materials are used as catalysts for selective synthesis of middle distillate through Fischer-Tropsch synthesis (FTS) reaction. Trace quantity (∼0.05 wt %) of ruthenium (Ru) has also been used as a promoter for Co -Mg-Zr/SDA catalyst to improve the reducibility, selectivity towards middle distillate and increasing the catalyst life. The detail characterizations of catalysts indicate that Ru promotion and narrow pore size distribution facilitate CO conversion and middle distillate selectivity. Synthetic syngas of composition (H 2  = 28.63%, CO = 14.27%, CO 2  = 9.25%, CH 4  = 1.0%, and N 2  = 46.85%), which may be obtained after coal gasification and H 2 enrichment process by water gas shift (WGS) reaction has been used as a reactant for middle distillate synthesis. The role of Ru and silica proportion on Co-Mg-Zr/SDA is investigated through Low Temperature Fischer-Tropsch (LTFT) synthesis at 220 °C temperature and 30 bar pressure. The surface acidity of the Ru/Co-Mg-Zr/SDA catalyst plays an important role for middle distillate selectivity and CO conversion. To determine the durability of catalysts, 300 h continuous experimental run has been conducted at Gas Hourly Space Velocity (GHSV) of 500 h −1 . Among the catalysts in the present study, Ru/Co-Mg-Zr/SDA(7.5) catalyst shows highest CO conversion (94.2%) with 85% selectivity of C 6 -C 19 hydrocarbon. [ABSTRACT FROM AUTHOR]

In this study, Fe 3 O 4 nanocubes (NCs) decorated on RGO nanosheets (NSs) structures were successfully synthesized through an innovative and environmentally-friendly rapid sonochemical method. More importantly, iron(II) sulfate heptahydrate and GO were employed as precursors and water as reaction medium, meanwhile, NaOH within the generated free radicals from the high intensity ultrasound were sufficient as reducing and base agent in our clean synthesis. Moreover, the hydrothermal method as a conventional approach was employed to synthesize the same catalysts for the comparison with the ultrasonocation technique. The as-synthesized Fe 3 O 4 and RGO/Fe 3 O 4 NSs catalysts were exposed to industrially relevant Fischer-tropsch synthesis (FTS) conditions at various reaction temperatures (250–290 °C), and they subjected to fully characterization before and after FTS reaction using XRD, TEM, HRTEM, EDS mapping, XPS, FTIR, BET, H 2 -TPR, H 2 -TPD and CO-TPD to understand the structure–performance relationships. Notably, the catalysts produced using the sonochemical method had a better CO conversion rate [Fe 3 O 4 (80%), RGO/Fe 3 O 4 (82%)] than the hydrothermally synthesized catalysts. However, compared to the naked-Fe 3 O 4 catalysts, the sonochemically and hydrothermally synthesized RGO-supported Fe 3 O 4 catalysts had higher long chain hydrocarbon (C5+) selectivity values (72% and 67%) and C 2 -C 4 olefin/paraffin selectivity ratio (3.2 and 2) and low CH4 selectivity values (6% and 8.5%), respectively. This can be attributed to their high surface area, the degree of reducibility, and content of Hägg iron carbide (χ-Fe 5 C 2 ) as the most active phase of the FTS reaction. Proposed reaction mechanisms for the sonochemical and hydrothermal reaction synthesis of Fe 3 O 4 and RGO/Fe 3 O 4 nanoparticles are discussed. In conclusion, our developed surfactantless-sonochemical method holds promise for the eco-friendly synthesis of highly efficient catalysts materials for FTS reaction. [ABSTRACT FROM AUTHOR]

• The influence of surface modification of Fe 5 C 2 by silica-based ligand on C 2 oxygenate selectivity was investigated. • Both the Carbide route and CO bond cleavage become not easy on Fe 5 C 2 after modification. • The CO-insertion mechanism by C + CO coupling becomes easy on Fe 5 C 2 after modification. • The formation of C 2 oxygenate is promoted on Fe 5 C 2 after modification. Elucidating the role(s) of support-like ligands remains a challenge in catalytic reaction like the Fischer-Tropsch Synthesis (FTS) catalyzed by the iron catalyst supported on silica. We herein theoretically investigated surface modification of Fe 5 C 2 by silica-based ligand and its influence on C 2 oxygenate selectivity in FTS, by carrying out DFT calculations on dissociation of CO and formations of CH 4 and C 2 on ha -SiO 2 /Fe 5 C 2 (510). To mimic the structure of surface modification, the ha -SiO 2 /Fe 5 C 2 (510) model was built up by binding the silica cluster (the ha -SiO 2 ligand) to Fe 5 C 2 (510). DFT calculations elucidated that the C + CH coupling with the lowest activation barrier among all the possible routes of C 2 formation on Fe 5 C 2 (510) is suppressed after modification with the ha -SiO 2 ligand because the binding ha -SiO 2 ligand limits the geometry relaxation caused by the C+CH coupling. However, CO molecule is anchored by the ha -SiO 2 ligand via hydrogen bond, suppressing the C O cleavage because the d -valence band center of Fe 5 C 2 (510) lowers in energy by surface modification with the ha -SiO 2 ligand, but facilitating the C + CO coupling with the lowest activation barrier among all the possible routes of C 2 formation. Also, CH 4 formation in the ha -SiO 2 /Fe 5 C 2 (510) case is not so easy as that on Fe 5 C 2 (510). Therefore, C 2 oxygenate is formed more easily in the ha -SiO 2 /Fe 5 C 2 (510) case than in the Fe 5 C 2 (510) case. The result agrees with the experimental observation that C 2 oxygenate selectivity became high for iron-based FTS catalyst after surface modification of by silica-based ligand. [Display omitted] This DFT work disclosed the reason(s) why the selectivity of C 2 oxygenates is enhanced on Fe 5 C 2 after silica modification, that both the carbide route and the C O bond cleavage are suppressed but the CO + C coupling to form C 2 oxygenate is facilitated. [ABSTRACT FROM AUTHOR]