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Depletion of oil and gas resources is a major concern for researchers and the global community. Researchers are trying to develop a way to overcome these issues using the Fischer-Tropsch synthesis (FTS) process. The FTS reaction converts a mixture of hydrogen and carbon monoxide gases into a liquid fuel. The reactions are performed in the reactor and in the presence of a catalyst. A series of catalysts, such as iron, cobalt, nickel, and ruthenium, have been used for the FTS process. In iron-based catalysts, the Fe5C phase is the active phase that produces C5+ hydrocarbons. At higher conversion rates, the presence of water in the products is a problem for cobalt catalysts because it can trigger catalyst deactivation mechanisms. Ni-based catalysts play key roles as base catalysts, promoters, and photothermal catalysts in FTS reactions to produce different useful hydrocarbons. Ruthenium catalysts offer not only high activity but also selectivity toward long-chain hydrocarbons. Moreover, depending on the Ru particle size and interaction with the oxide support, the catalyst properties can be tuned to enhance the catalytic activity during FTS. The detailed reaction pathways based on catalyst properties are explained in this article. This review article describes the issues and challenges associated with catalysts used for the FTS process. [ABSTRACT FROM AUTHOR]

New bifunctional composite catalysts for the Fischer—Tropsch synthesis were developed on the basis of a mixture of the Co—Al2O3/SiO2 catalyst, meso-HZSM-5 hierarchical mesoporous zeolite, and boehmite binder. The mesoporous zeolite was obtained by alkaline treatment of the industrial HZSM-5 zeolite. The developed catalysts are suitable for one-pot conversion of syngas into linear C5+ hydrocarbons, which then undergo cracking and isomerization reactions. The effect of the concentration of NaOH solution on the porosity and catalytic efficiency of the obtained meso-HZSM-5 zeolite was studied. The performances of the bifunctional catalysts obtained from alkali-treated and pristine HZSM-5 in the conversion of syngas were compared. In the presence of the catalyst based on the alkali-treated zeolite, the total productivity to C5+ hydrocarbons somewhat decreases. However, the increase in the total yield of branched and unsaturated hydrocarbons provides the formation of motor fuels with high anti-knock properties. [ABSTRACT FROM AUTHOR]

Structured Fischer–Tropsch synthesis catalysts were tested in tubular reactors of industry-standard diameters of 0.5 or 0.75 inches. The structured catalyst bed was manufactured by the obturation of a straight bunch of graphite-based extrudates (D = 1.5 mm, L = 30 mm). A conventional loose bed of granulated catalyst (D = 1.5 mm, L = 3 mm) was tested as a reference. In a 1000–3000 h−1 syngas space velocity range, structured and loose catalyst bed testing showed no significant differences in their main catalytic parameters. Nevertheless, their C5+ hydrocarbon group composition was quite different, i.e., the alkene fraction rose from 9 to 23%, while n-alkanes dropped from 81 to 64%. This could be a result of secondary reaction intensification in the conventional loose bed due to its zeolite acid site's higher availability. Further FTS testing of the structured catalysts in 4000–6000 h−1 manifested distinctive limits in C5+ productivity for 0.5 and 0.75 inches of 512 kg C5+/(m3 reactor·h) and 362 kg C5+/(m3 reactor·h), respectively. This may be explained by limitations in structured bed thermal conductivity. It suggests that the arrangement of extrudates in the structured catalyst can significantly affect the reaction heat and mass transfer conditions and affords new opportunities for group composition control by means of catalyst bed organization. [ABSTRACT FROM AUTHOR]

Cobalt carbides have been recognized as an active phase for the production of light olefins and alcohols in Fischer–Tropsch synthesis. In this study, in situ X-ray diffraction experiments were performed to investigate the stability and catalytic performance over a single-phase Co3C catalyst under reaction conditions. The in situ X-ray diffraction results indicated that the Co3C phase remained stable with no significant changes until the temperature reached 300 °C. The high stability can be attributed to the twinning structure of the single-phase Co3C catalyst. The catalytic evaluation results showed that the single-phase Co3C catalyst had higher activity with high selectivity to long-chain products due to the unique surface structure of Co3C. This work provides guidance for the rational design of efficient cobalt carbide catalysts for Fischer–Tropsch synthesis reactions. [ABSTRACT FROM AUTHOR]

Cobalt-based catalysts exhibit excellent reactivity and carbon chain growth capability in the Fischer-Tropsch synthesis reaction, and their catalytic performance is closely related to the reduction degree and size of metal Co particles. Regulating the reduction degree and dispersion degree of metal Co by adding promoters is an important way to enhance their catalytic performance in Fischer-Tropsch synthesis reaction. By using SiC as a support with chemical inertness and good thermal conductivity, and adding a small amount of nanodiamonds (NDs) with rich surface functional groups as structural regulators, the dispersion degree and reduction degree of Co species in the catalyst were effectively improved, and its catalytic performance in Fischer-Tropsch synthesis reaction was enhanced. The results of N2 physical adsorption/desorption show that the addition of NDs has little effect on the parameters such as specific surface areas and pore sizes of the catalysts. The results of CO chemisorption show that the addition of an appropriate amount of NDs promotes the dispersion of active metal Co in the catalysts, increases the surface area of metal Co and provides more active sites for the Fischer-Tropsch synthesis reaction. The results of transmission electron microscopy (TEM) show that after the addition of NDs to Co/SiC (m(NDs):m(SiC) = 1.0%), the particle sizes of metal Co in the catalysts are reduced, and NDs are uniformly dispersed on the catalyst surface. The results of H2-temperature programmed reduction (H2-TPR) and CO-H2-temperature programmed surface reaction (CO-H2-TPSR) show that the addition of NDs reduces the reduction temperature of Co3O4 to metal Co and promotes the reduction of Co3O4 and the activation of CO. Compared with the Co/SiC catalyst, the NDs-modified Co/1.0NDs-SiC (W(Co) = 10%, OT(NDS):M(SiC) = 1.0%) catalyst exhibits an increase of CO conversion rate from 15.6% to 29.0%, and the selectivity of C5+ hydrocarbon products still maintains at above 75%, and shows stable operation and no significant deactivation for 70 h. The above results can provide a new research idea for the development of efficient catalysts modified with nanocarbon materials in Fischer-Tropsch synthesis reaction. [ABSTRACT FROM AUTHOR]

Direct conversion of carbon monoxide into fuel through Fischer–Tropsch synthesis (FTS) is economically and environmentally beneficial as an alternative clean energy source. However, the activity and product selectivity need further investigation. In this work, a Co-MOF-71 (Co(1,4-BDC) (DMF)) was prepared solvothermally and pyrolyzed under nitrogen flow at low pyrolysis temperature to obtain a highly mesoporous Co@C-500 catalyst. The obtained catalyst exhibits high cobalt loading (53 wt%), high reducibility, optimum nanoparticle size (10.49 nm), and well-dispersed active sites. The catalytic activity of the catalyst was tested under different reaction conditions using a stainless steel fixed-bed reactor. The optimal performance showed a high CO conversion (82.7%), high C5+ selectivity (82.77%) with C5–C12 gasoline range hydrocarbons (71.9%), low C2–C4 selectivity (13%), and low methane selectivity (3.7%). Furthermore, the catalyst has a high C5+ yield of 68%, with the gasoline fraction (C5–C12) being the main product (59.1% yield). The catalyst shows superior FTS performance compared with other reported Co-containing catalysts, especially after being tested for more than 120 h without deactivation. Therefore, this work could contribute to the design of high-efficiency MOF-derived Co-FTS catalysts that could be used in the production of green and sustainable transportation fuel (gasoline). [ABSTRACT FROM AUTHOR]

New bifunctional cobalt catalysts for combined Fischer–Tropsch synthesis and hydroprocessing of hydrocarbons containing Pt were developed. To prepare catalysts in the form of a composite mixture, the FT synthesis catalyst Co-Al2O3/SiO2 and ZSM-5 zeolite in the H-form were used as metal and acid components, respectively, with boehmite as a binder. The catalysts were characterized by various methods, such as XRD using synchrotron radiation, SEM, EDS, TEM and TPR. The effect of the Pt introduction method on the particle size and conditions for cobalt reduction was studied. The testing of catalysts in Fischer–Tropsch synthesis was carried out at a pressure of 2.0 MPa, a temperature of 240 and 250 °C, an H2/CO ratio of 2 and a synthesis gas volumetric velocity of 1000 h−1. It is shown that the method of introducing a hydrogenating metal by adjusting the nano-sized spatial structure of the catalyst determined the activity in the synthesis and group and fractional composition of the resulting products. It is established that the presence of Pt intensified the processes of synthesis and hydrogenation, including isomeric products, and reduced the content of unsaturated hydrocarbons. The application of Pt by impregnation onto the surface of the metal component of the catalysts provided the highest productivity for C5+ hydrocarbons, and for the acidic component, it enabled maximum cracking and isomerizing abilities. [ABSTRACT FROM AUTHOR]

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]

In this work, cobalt catalysts based on zeolite ZSM˗5 were prepared by the triple impregnation method and chemically analyzed. Zirconium dioxide was used as a promoter (3 wt. %). Chemical analysis of the elemental composition and structure of the obtained catalysts was carried out using scanning electron microscopy. It is shown that the elemental composition of the catalysts with satisfactory accuracy corresponds to their given composition. Experiments for catalytic tests of the prepared catalysts were carried out on a laboratory Fischer-Tropsch synthesis unit and synthetic hydrocarbons were obtained. Comparative characterization of activity of the obtained catalysts with cobalt content of 10 % and 20 % has been carried out, dependence of carbon monoxide conversion and selectivity with respect to formation of gas hydrocarbons and yield of liquid products on temperature has been studied. [ABSTRACT FROM AUTHOR]

Carbon aerogel (CA) as a novel catalyst support in Fischer‐Tropsch synthesis (FTS) was synthesized by polymerization of a resorcinol‐formaldehyde (RF) precursor through an ambient pressure drying route. The cobalt‐doped CA was synthesized by three main strategies: (a) impregnation of the metal precursor on the CA (Co‐CA‐I), (b) carbonization of cobalt‐doped organic RF aerogel (Co‐CA‐II), and (c) addition of the cobalt precursor to the RF mixture (Co‐CA‐III). The pores and cobalt particle size increased in the order of Co‐CA‐I > Co‐CA‐II > Co‐CA‐III and cobalt particles wrapped between the graphite layers when cobalt was added to the RF mixture. The CA as the catalyst support presented high CO conversion and high stability under FTS conditions. The CH4 selectivity increased by reducing the size of the cobalt particles. Hydrogen spillover from the support to metallic particles was observed in the case of Co‐CA‐I and Co‐CA‐III catalysts. This phenomenon improved the reducibility and also resulted in higher hydrogenated products being produced. [ABSTRACT FROM AUTHOR]

Cobalt-iron bimetallic catalysts promoted with Nb, Ru or Rh and supported on multiwalled-carbon nanotubes (MWCNTs) were synthesized using a reverse-microemulsion method. The synthesized catalysts were characterized by TEM, N2-physical adsorption, XPS, XRD, and TPD/R/O methods. XPS analyses showed an increasing trend of the Co2+/Co3+ atomic ratios for the promoted catalysts, compared to that of the un-promoted Co–Fe/CNTs catalyst. The dispersion for the un-promoted Co–Fe /CNTs catalyst was 15.9% and it increased to 23.0, 20.4, and 17.7% in the presence of 0.1 wt.% Nb, Ru, and Rh promoter, respectively. The addition of Nb-promoter also improved the reducibility of the catalyst as exhibited by the H2-TPR study. The presence of Nb, Ru, and Rh promoters improved the catalytic performance in a Fischer–Tropsch synthesis where the TOF over the un-promoted catalyst increased from 5.1 to 6.2, 5.7, 5.2 × 10–1 s−1 upon the addition of Nb, Ru and Rh promoter, respectively. Thus, the Nb promoter was a better promoter than Ru and Rh for the Co–Fe/CNTs catalyst. [ABSTRACT FROM AUTHOR]

Syngas conversion is a useful technology for converting nonpetroleum carbon resources into chemicals such as olefins. Iron- and cobalt-based catalysts, as two major categories, have been extensively studied in Fischer–Tropsch synthesis to olefins (FTO) reactions. Although both iron and cobalt catalysts have shown distinct merits and shortcomings, they are also complementary in their properties and catalytic performances when combined with each other. Herein, Na-modified CoFe bimetallic catalysts were fabricated using a co-precipitation method. It was found that there was a synergistic effect between Co and Fe that promoted a CO dissociation rate and carburization, and an appropriate Co/Fe ratio was conducive to improvements in their catalytic performances. The desired olefins selectivity reached 66.1 C% at a CO conversion of 37.5% for a Co2Fe1 catalyst, while the methane selectivity was only 4.3 C%. In addition, no obvious deactivation was found after nearly 160 h, indicating their potential industrial application. [ABSTRACT FROM AUTHOR]

Hydrogenation of carbon monoxide (Fischer–Tropsch synthesis) is a promising route to ultraclean motor fuels, base oils and petrochemicals on the basis of non-petroleum feed such as natural gas, coal and biomass. Although cobalt-based industrial catalysts for this process are in operation for many years, they still need to be improved in terms of specific activity and selectivity to target hydrocarbons. This paper describes the effect of catalyst support coating with carbon on the formation of cobalt active phase and catalytic performance in CO hydrogenation. Carbonization of Mg–Al spinel was performed by impregnating with aqueous glucose solution followed by thermal treatment in inert atmosphere. Thus prepared carbonized material was used for cobalt deposition by incipient wetness impregnation method. The catalysts were characterized by N2 adsorption–desorption, scanning electron microscopy, thermoanalytical measurements combined with mass spectrometry of released gases, X-ray diffraction and in situ magnetic measurements during activation in H2 flow. Catalytic performance in Fischer–Tropsch synthesis was assessed at T = 210 °C, P = 20 bar. The size of Co3O4 crystallites in calcined catalysts and metallic cobalt in activated catalysts decreases with carbon content in the support. Cobalt precursor is reduced completely to metal within 2 h in typical activation conditions for FTS cobalt catalysts: H2 flow, 450 °C. Activity in CO hydrogenation decreases while selectivity to higher hydrocarbons increases with carbon content. High proportion of olefins in synthesized light hydrocarbons (> 65%) is a remarkable feature of the elaborated catalysts. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of γ-alumina pore size on the ability of alumina-supported cobalt (Co/Al2O3) catalysts in Fischer–Tropsch synthesis (FTS), ordered mesoporous alumina (OMA) samples with different pore sizes (4.8, 7.2, 9.7 and 12.6 nm) were synthesized by various methods. Co/OMA catalysts with a Co loading of 15 wt% were prepared by the impregnation method. N2 physisorption, X-Ray Diffraction (XRD), H2-Temperature-Programmed Reduction (H2-TPR), and H2 Temperature-Programmed desorption (H2-TPD) experiments were conducted to characterize the structure and properties of these catalysts, and the catalyst structure–FTS performance relationships were also analyzed. The TOF increases with OMA pore size increase from 4.8 to 9.7 nm and decreased when the OMA pore size increased further to 12.6 nm. The C5+ selectivity of catalysts increases with OMA pore size, while the CH4 selectivity decreased with which. The Co3O4 particle size of catalysts were depended highly on the OMA pore size, which was the vital factor affecting the performance of catalyst. [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]

Modified kaolinites possess excellent adsorption properties and, therefore, are regarded widely as potential catalytic components. The use of modified kaolinites as a catalytic component for Fischer–Tropsch synthesis (FTS) has remained unexplored, however. In the current study, delaminated and pit-rich nano-kaolinite was prepared via acid treatment of N-methylformamide (NMF)-intercalated kaolinite (intercalation-etching strategy), and was used as a support to prepare a cobalt-based FTS catalyst (denoted as 15%-Co-HNKln). Compared with other FTS catalysts, the supports for which were raw kaolinite or directly acid-treated kaolinite, the 15%-Co-HNKln showed several advantages such as large specific surface area, dispersed Co particles with small particle size, more new active sites, and significant surface acidity. Given the aforementioned advantages, the 15%-Co-HNKln catalyst demonstrated very good FTS performance. Compared with that of the raw kaolinite-supported FTS catalyst, the CO conversion rate and C5–C12 hydrocarbon selectivity of 15%-Co-HNKln increased by 20% and 15%, respectively. [ABSTRACT FROM AUTHOR]

A number of catalysts were synthesized from a composite mixture consisting of a metal component (specifically, a Co–Al2O3/SiO2 catalyst in an amount of 20–40% for the synthesis of long-chain hydrocarbons), an acid component (Beta zeolite in the H-form, 20–50%), and a binder (boehmite). The catalysts were characterized by XRD, low-temperature argon adsorption/desorption, and TPR, and tested in Fischer–Tropsch synthesis at 2.0 MPa, 240°C, and GHSV 1000 h–1. The activity and selectivity of the catalysts were compared, and the composition of the synthetic products was investigated. The content of the zeolite component was found to be critical to the cracking and isomerization activity of the catalysts. It was further shown that the ratio between the active components correlates with the C5+ productivity and the selectivity towards fuel-range hydrocarbons. The catalysts with Co–Al2O3/SiO2 to HBeta ratios of 0.75 and 1.3 were found to be optimal for high-performance synthesis of gasoline-range (C5–C10) and diesel-range (C11–C18) hydrocarbons, respectively. [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]

[Display omitted] • Oxidation of metallic cobalt occurs under relevant Fischer-Tropsch (FTS) conditions. • The extent of oxidation up to around 1.2w% is independent of cobalt weight loading. • Interaction between cobalt and surface titanols are key to the oxidation behavior. • Metal-support compounds only form at very high oxidizing potential in absence of CO. • Oxidation and sintering are linked and steam induces particle growth. The study of titania-supported cobalt nanoparticles is relevant for industrial Fischer-Tropsch synthesis (FTS). Herein, we report about various deactivation pathways of cobalt supported on P25 titania (cobalt loading 2–8 wt%) under simulated high conversion conditions using in situ Mössbauer spectroscopy. A fraction of metallic cobalt was oxidized under humid FTS conditions. The absolute amount of oxidized cobalt was ∼ 1.2 wt% independent of the cobalt loading, indicating that specific cobalt-titanol interactions are involved in the oxidation process. The formation of cobalt-titanate-like compounds was only observed under very high water-to-hydrogen ratios in the absence of carbon monoxide. Steam considerably enhances cobalt sintering under FTS conditions. As such, deactivation under humid FTS conditions is not only caused by cobalt oxidation but also by enhancing sintering of the active phase. [ABSTRACT FROM AUTHOR]

Introducing promoters to cobalt-based catalysts for Fischer–Tropsch synthesis (FTS) has been found to be efficient in adjusting their performance in converting syngas into long-chain hydrocarbons. High spatial proximity of the promoter and reactive metal is desired to maximize the effectiveness of the promoters. In this work, CoMn@C composites were synthesized by the one-step carbonization of bimetal–organic frameworks (BMOFs: CoMn-BTC). BMOF-derived catalysts naturally exhibited that cobalt nanoparticles (NPs) are confined in the carbon matrix, with a concentrated particle size distribution around 13.0 nm and configurated with MnO highly dispersed throughout the catalyst particles. Mn species preferentially bind to the surfaces of Co NPs rather than embedded into the Co lattice. The number of Mn–Co interfaces on the catalyst surface results in the weakened adsorption of H but enhanced adsorption strength of CO and C. Hence, the incorporation of Mn significantly inhibits the production of CH4 and C2–C4 paraffin boosts light olefin (C2–4=) and C5+ production. Furthermore, the FTS activity observed for the Mn-promoted catalysts increases with increased Mn loading and peaks at 2Co1Mn@C due to the abundance of Co–Mn interfaces. These prominent FTS catalytic properties highlight the concept of synthesizing BMOF-derived mixed metal oxides with close contact between promoters and reactive metals. [ABSTRACT FROM AUTHOR]

A review of modern approaches to the development of cobalt catalyst technology used in most known ways of synthesizing hydrocarbons from CO and H2 using the Fischer–Tropsch is presented. The development of efficient catalysts solves the problem of replacing fossil fuels with ultra-clean alternative fuels and reduces their negative impact on the environment. An analysis of results from scientific and technological research, including ones obtained recently by the authors, shows current lines in developing the technology of high-performance catalysts for the Fischer–Tropsch synthesis of hydrocarbons using classical and integrated GTL technology, including the creation of new types of polyfunctional systems. The review mainly describes the catalytic characteristics of supported cobalt catalysts synthesized via impregnation and polyfunctional hybrid catalysts obtained on their basis for the selective synthesis of fuel fraction hydrocarbons. Problems of controlling selectivity, productivity, and changes in the activity and physicochemical properties of catalysts during long-term operation are considered. [ABSTRACT FROM AUTHOR]

Some kinetic parameters of Fischer–Tropsch synthesis (FTS) were determined in the presence of a granular cobalt/zeolite catalyst. Usually, kinetic studies of granular catalysts are considered to be complicated by external and internal diffusion. We managed to obtain a catalyst with a special structure of the active surface, where sites active in FTS are isolated from each other due to the environment of inactive spinel CoAl2O4 and inter-site transport is provided by an extensive intragranular graphitic network serving simultaneously as a heat-conductive medium. As a result, FTS proceeded in the kinetic region. It was found that the reaction kinetics obey the Arrhenius law; whereas, the activation energy is different in different temperature ranges, i.e., 118.2 kJ/mol in the range of 180–210 °C, and 173.6 kJ/mol in the range of 232–243 °C. This behavior is determined by the presence of zeolite, which becomes active in the secondary transformations of FTS products at temperatures beyond 210 °C. [ABSTRACT FROM AUTHOR]

Provision of sustainable transportation fuels is required for the energetic transition. A new process is presented for the production of synthetic sulfur free maritime fuel. This fuel is produced by Co-catalyzed Fischer-Tropsch synthesis (FTS) using syngas based on a plasma technology that contains traces of O2. Gravimetric experiments and steady state measurements with a Co/Pt/Al2O3 catalyst at low temperature FTS conditions (10–30 bar, 180–230 °C) show that, with H2 present in the system, the catalyst remains active for FTS, and shows no influence on the distribution of C2+-hydrocarbons. O2 is only converted to H2O and CO2 in varying proportions (H2O: 70–80%, CO2: 20–30%), whereby a higher CO concentration increases the CO2 selectivity. This work may wield a new CO2 source for carbon-neutral fuels. [ABSTRACT FROM AUTHOR]

This paper demonstrates the basic feasibility of bifunctional Co/zeolite catalysts for Fischer–Tropsch synthesis (FTS) to produce C18–C40 hydrocarbons. These hydrocarbons are intermediate between high-molecular-weight hydrocarbons (up to C100) produced by conventional FTS in the presence of Co/oxide catalysts and engine fuel components (up to C18) synthesized by FTS over Co/zeolite catalysts. The synthesis conditions that favor olefin-involving chain-growth reactions on zeolite acid sites are sensitive to zeolite type. The study findings can serve as a foundation for the development of a novel technology for the synthesis of C18–C40 hydrocarbons as valuable feedstocks for various oil applications. [ABSTRACT FROM AUTHOR]

The effect of the gas recirculation mode on the selectivity and deactivation rate of the Co-Al2O3/SiO2 catalyst of the Fischer‒Tropsch synthesis at high pressure (6 MPa) has been studied. The use of recirculation with a gas recycle ratio of up to 2.2 promotes the formation of C19+ hydrocarbons due to the readsorption of gaseous olefins and their involvement in chain propagation. The increased selectivity for C19+ paraffin leads to accelerated deactivation of the catalyst. An increase in the gas recycle ratio to 8 leads to increased selectivity for C5+ olefins and a lower yield of C19+ waxes due to the removal of C5+ olefin vapors from the reaction zone. The latter is associated with a decreased contribution of the readsorption of higher C5+ olefins to the elongation of the carbon chain. At high gas recycle ratios, CoO was reduced to the metal, which partially compensates for catalyst deactivation as a result of the blocking of the active sites of chain propagation by C19+ waxes. [ABSTRACT FROM AUTHOR]

Three Fe catalysts with different Na contents were prepared, characterized, and investigated for the CO2‐based Fischer‐Tropsch synthesis (FTS). The FTS results clearly indicated that the selectivity towards long‐chain hydrocarbons was driven by the surface Na content, which promotes the CO dissociation and chain propagation. Additionally, it was shown that Fe3O4, Fe5C2 and Fe7C3 coexist during FTS, revealing specific catalytic activity. As a result, a tandem mechanism was suggested for the CO2 conversion, consisting in a reverse water‐gas shift on Fe3O4 followed by CO hydrogenation on the Fe carbides. [ABSTRACT FROM AUTHOR]

The activity of catalysts with various sizes was compared in a fixed-bed Fischer–Tropsch reactor under similar operating conditions by determining the deactivation model. Catalyst size had no impact on the type of deactivation model. The smaller catalyst showed a smaller deactivation constant of catalyst (k d) and a lower deactivation rate in the initial stage. The decline in the activities of the catalyst with a mesh size of 40 was lower than the other catalysts, suggesting its higher long-term stability (a ss). Larger catalyst sizes led to the fouling of carbon and heavy hydrocarbons, decreasing the specific surface of the catalyst, thus increasing the pore diffusion resistance and further decrementing the catalyst activities. • Deactivation of the cobalt catalyst with various mesh sizes followed the first-order GPLE model. • Changes in the catalyst size had no impact on the type of deactivation model. • Changes in the catalyst size can alter the GPLE model parameters. • Larger catalyst sizes led to declining the catalyst activities in the first stage due to the pore diffusion resistance. • The time of the first step of catalyst deactivation increased by decreasing the size of the catalyst. [ABSTRACT FROM AUTHOR]

The production of fuel components in the integrated Fischer–Tropsch synthesis on bifunctional cobalt catalysts in the form of a mixture of the cobalt catalyst Co–Al2O3/SiO2 and hierarchical zeolite HBeta samples with a binder was studied. The conditions for the preparation of HBeta samples with a developed mesoporous structure by alkaline modification using a solution of NaOH were determined. The effect of the structure and acidic properties of HBeta on the activity of the catalysts in the Fischer–Tropsch synthesis and the hydrocarbon and fractional composition of the resulting products were studied. The studies were carried out in a flow reactor with a fixed catalyst bed at a pressure of 2 MPa, a gas space velocity of 1000 h–1, and a temperature of 240°C. The process parameters for the bifunctional catalysts and the composition of fuel components correlated with the structure and surface condition of the HBeta zeolite samples. [ABSTRACT FROM AUTHOR]

Different carbon nanomaterials are considered as promising supports for Fischer-Tropsch synthesis (FTS) catalysts of syngas transformation into hydrocarbons. At the same time, consolidation of carbon nanoparticles into a dense bulk material is one of the most important challenges faced by the catalytic industry. In this work consolidated Co and Fe catalysts supported on graphene nanoflakes (GNFs) were for the first time synthesized by spark plasma sintering (SPS). The synthesized catalysts contained reduced carbon-encapsulated metal nanoparticles embedded into the GNF framework, which ensured their activity in FTS without pre-activation. SPS significantly increased both the activity (from 77 to 91 µmol CO ×g Co −1 ×s−1) and TOF (from 0.024 to 0.073 s−1) of the Co/GNF catalyst compared to the unsintered sample. In contrast, the activity of the Fe catalysts decreased after SPS, but their C 5+ selectivity and olefins to paraffins ratio increased. These enhancements were attributed to the unique core-shell structure of the nanoparticles, highly active surface cobalt atoms, and close contact between carbon support and iron particles. SPS was proved to be a powerful approach to activate carbon-supported FTS catalysts, increase their density and modify their catalytic performance. [Display omitted] • FTS catalysts supported on graphene nanoflakes by spark plasma sintering. • Carbon-encapsulated Co and Fe particles embedded in nanocarbon framework. • Activity of catalysts in FTS without pre-reduction. • Increased activity of cobalt and enhanced olefin and C5+ selectivities over iron-one. • Structural transformations in iron catalyst and stability of cobalt one. [ABSTRACT FROM AUTHOR]

A number of bifunctional composite cobalt-based catalysts were prepared with various types of molecular sieves in the H-form (zeolites ZSM-5, Y, Beta, and Mordernite, and silicoaluminophosphate SAPO-11) as an acid component. The catalytic performance of these catalysts was comparatively assessed in integrated Fischer-Tropsch synthesis of fuels. The catalysts were found to exhibit high activity and high C5+ selectivity at 2.0 MPa, 240–250°C, and a gas hourly space velocity (WHSV) of 1000 h–1. With the CO conversion reaching 80.9–93.7%, the productivity was in the range of 146.4 kg/(m3cat h). The study further revealed the effects of the crystalline and porous structures of the molecular sieves on the hydrocarbon and fractional compositions of the fuel products and on the selectivity towards branched hydrocarbons. It was shown that catalysts based on HZSM-5 and HBeta zeolites are preferable for high-performance and selective synthesis of fuels. In the presence of the HZSM-5-based catalyst, an effect atypical of Fischer–Tropsch synthesis was observed for the first time: an elevation of the process temperature leads to an enhancement of C5+ selectivity. [ABSTRACT FROM AUTHOR]

In recent years, rising environmental concerns have led to the focus on some of the innovative alternative technologies to produce clean burning fuels. Fischer–Tropsch (FT) synthesis is one of the alternative chemical processes to produce synthetic fuels, which has a current research focus on reactor and catalyst improvements. In this work, a cobalt nanofilm (~4.5 nm), deposited by the atomic layer deposition (ALD) technique in a silicon microchannel microreactor (2.4 cm long × 50 µm wide × 100 µm deep), was used as a catalyst for atmospheric Fischer–Tropsch (FT) synthesis. The catalyst film was characterized by XPS, TEM-EDX, and AFM studies. The data from AFM and TEM clearly showed the presence of polygranular cobalt species on the silicon wafer. The XPS studies of as-deposited and reduced cobalt nanofilm in silicon microchannels showed a shift on the binding energies of Co 2p spin splits and confirmed the presence of cobalt in the Co0 chemical state for FT synthesis. The FT studies using the microchannel microreactor were carried out at two different temperatures, 240 °C and 220 °C, with a syngas (H2:CO) molar ratio of 2:1. The highest CO conversion of 74% was observed at 220 °C with the distribution of C1–C4 hydrocarbons. The results showed no significant selectivity towards butane at the higher temperature, 240 °C. The deactivation studies were performed at 220 °C for 60 h. The catalyst exhibited long-term stability, with only ~13% drop in the CO conversion at the end of 60 h. The deactivated cobalt film in the microchannels was investigated by XPS, showing a weak carbon peak in the XPS spectra. [ABSTRACT FROM AUTHOR]

The authors reported that the Co(fcc) phase in Co/SiO SB 2 sb easily transformed to carbides under CO treatment, and rapidly reduced to Co(hcp) in H SB 2 sb , due to weaker cobalt-silica interactions and surface deformity. The latter produced both Co(fcc) and Co(hcp) phases, whereas the major phases in the CO activated catalyst were found to be CoO, Co SB 3 sb C, Co SB 2 sb C and minimal amounts of Co°. Keywords: activation; cobalt-based catalyst; Fischer-Tropsch synthesis; pretreatment; reduction EN activation cobalt-based catalyst Fischer-Tropsch synthesis pretreatment reduction 503 538 36 07/05/22 20220701 NES 220701 1 Introduction Growing concern about the limited supply of fossil fuel and serious environmental problems has sparked global interest in producing green fuels ([73]; [115]). Recent developments in catalyst pretreatment technologies for cobalt based Fisher-Tropsch synthesis However, Co(fcc) remained after the full reduction (H-C-H) cycle of Co/Al SB 2 sb O SB 3 sb , which suggests that the CO treatment did not cause the Co(fcc) to fully transform to cobalt carbide. [Extracted from the article]

Olefin/paraffin (C2-C6) = 1.2 (after 2 h) C1 = 25.0%. Olefin/paraffin (C2-C6) = 0.9 (after 4 h) C1 = 17.0%, C2-C4 = 28.0%, C5-C12 = 13.0%, C13-C18 = 23.0%, C19+ = 19.0%. Olefin/paraffin (C2-C6) = 0.9 (after 4 h) C1 = 22.0%, C2-C4 = 42.0%, C5-C12 = 19.0%, C13-C18 = 13.0%, C19+ = 4.0%. Olefin/paraffin (C2-C6) = - (after 2 h) C1 = 26.0%. [Extracted from the article]

This work aimed to synthesize SiC via magnesiothermic reduction reaction (MRR) and also to evaluate its use as support in a cobalt-based catalyst for Fischer–Tropsch Synthesis (FTS). The Co/SiC catalyst obtained using synthesized SiC, showing greater stability and selectivity to C–C coupling than the reference catalyst prepared with commercial SiC. [ABSTRACT FROM AUTHOR]

Here reports the modulation of selectivity in Fischer-Tropsch synthesis through the control of cobalt reducibility within a hexagonal mesoporous silica (HMS) framework. Cobalt loading, varied from 3 % to 12.5 wt%, generated different surface and bulk cobalt species that interact variably with the support, significantly influencing their reducibility and the resultant catalytic behavior. This variation significantly affected the reducibility of the cobalt species, influencing on the catalytic behavior. The control of reducibility and stability of Co species is contingent on the cobalt loading. Higher cobalt content enhances the reducibility of Co species, shifting product selectivity from long-chain hydrocarbons to lighter olefins and oxygenates. At a TOS of 4 h, the active phase predominantly involves metallic Co species, while CO 2 and oxygenates formation is closely linked to the pair Co0-Co2+ active phase. After a TOS of 120 h, samples with higher cobalt content (6.1–15.8 % wt.) exhibited notable deactivation and changes in selectivity and hydrocarbon distribution. These changes were associated with the formation of a Co 2 C phase, which inhibits methane formation and chain growth while enhancing the production of lower olefins and oxygenates through a synergistic interaction at the Co0 and Co 2 C interface, also improves the WGS reaction, thereby increasing CO 2 selectivity. [Display omitted] • Varying Co content significantly influences the reducibility of Co species within HMS rameworks. • Changes in Co reducibility are directly linked to CO conversion, selectivity, and hydrocarbon distribution. • Higher Co reducibility boosts long-chain hydrocarbon growth; lower reducibility favors oxygenates and olefinic compound. • Reducibility degree correlates with Co species stability; lower reducibility leads to the Co 2 C phase formation. • The Co2C phase reduces CO conversion, inhibits methane formation, and suppresses growth of heavy hydrocarbons. [ABSTRACT FROM AUTHOR]

Cobalt oxide (CoO) nanoparticles (NPs) were modified with different silanes (tetraethoxysilane – TEOS, triphenyl ethoxysilane – TPES, or trimethyl chlorosilane - TMCS) by dispersing the as-synthesized CoO NPs in n-hexane solutions containing the silanes. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of these silanes on the cobalt surfaces even after reduction in hydrogen (H 2) at 573 K. Modifying CoO-NPs with TEOS resulted in face-centred cubic (fcc)-cobalt phase upon reduction whereas TPES or TMCS modification induced a mixture of hexagonal close-packed (hcp)- and fcc-cobalt phases. The modification of cobalt surfaces with the silanes alters the adsorption properties of carbon monoxide (CO) on the catalytically active sites. Furthermore, temperature programmed desorption of CO (CO-TPD) showed that the amount of dissociatively adsorbed CO relative to amount of associatively adsorbed CO increases on silane-modified cobalt surfaces, which correlates with an improved rate of CO conversion in the Fischer-Tropsch CO hydrogenation. [Display omitted] • Successful modification of CoO NPs using tetraethoxysilane (TEOS), triphenyl ethoxysilane (TPES), and trimethyl chlorosilane (TMCS). • Alteration of cobalt crystalline phases upon silane modification, with TEOS inducing a face-centred cubic (fcc)-cobalt phase and TPES/TMCS leading to mixtures of hexagonal close-packed (hcp)- and fcc-cobalt phases. • Enhanced adsorption properties of carbon monoxide (CO) on silane-modified cobalt surfaces. • Improved rate of CO conversion in Fischer-Tropsch CO hydrogenation on silane-modified cobalt oxide nanoparticles. [ABSTRACT FROM AUTHOR]

[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]

• Achieving CoFe alloy & Co + Fe 2 C in Co-Fe bimetallic catalysts by a strategic precursor addition. • Ensuring consistent metal size and support properties for each catalyst. • Investigating the performance mechanism of three active phases in FTS. • Leveraging Co-Fe interaction in CoFe alloy to optimize CO/H 2 adsorption behaviors. • Enhancing FTS performance through increased strongly adsorbed CO and improved CO/H 2 ratio. In the realm of Fischer-Tropsch synthesis (FTS), the escalating cost of cobalt has spurred interest in Co-Fe bimetallic catalysts as substitutes for monometallic Co catalysts. Unfortunately, it is difficult to clarify specific functions and interactions of the two phases, as investigating catalysts in a unified dimension of both metal and support is still a challenge. Herein, we realize precise control over synthesizing nitrogen-doped carbon materials supported bimetallic catalysts containing CoFe alloy and Co + Fe 2 C dual active phases. The catalysts are comprehensively characterized to address the above problem by excluding the influence of metal sizes and support properties. Our findings reveal that compared to metallic Co alone and Co + Fe 2 C dual active phases, the Co-Fe interaction in CoFe alloy with electron transfer from Fe to Co optimizes reactant adsorption behaviors through achieving a larger number of strongly adsorbed CO per active site to increase the density of C* adsorbates and a higher surface CO/H 2 ratio to inhibit the hydrogenation of CH x * intermediates for chain termination, as well as an appropriate ability for CO adsorption/ dissociation. These advantages collectively enhance both CO activation and C-C coupling, and consequently, the CoFe/NC (CoFe alloy) catalyst exhibits the superior catalytic performance in the cobalt space–time yield in C 5+ products (3011.2 g C5+ kg Co −1h−1), which surpasses the Co/NC (monometallic Co) and Co + Fe/NC (Co + Fe 2 C dual active phases) by 2.2 times and 2.4 times, respectively. This study serves as a promising route for the development of efficient and low-cost bimetallic catalysts through the strategic arrangement of multiple active phases for various reactions. [ABSTRACT FROM AUTHOR]

• Carbon deposition in the Co-catalyzed FTS is sensitive to the crystal phase of Co catalyst. • HCP Co is revealed to present much higher anti-carbon deposition stability than FCC Co. • The higher stability of HCP Co is attributed to its much denser active sites with B 5 -type active unit. • HCP Co exhibits better surface C deactivation resistance ability via surface C hydrogenation. • HCP Co with (10–10), (10–12) and especially (10–11) facets can achieve high stability and activity. A very challenging issue with Co-catalyzed FTS, surface carbon deposition and thus FTS catalyst deactivation, remains unresolved for many years. This research is designed to overcome the challenge by using theoretical calculations together with the FTS experiments. Our theoretical calculations for the first time reveal that HCP Co not only have much higher anti-carbon deposition stability but also exhibits a better anti-carbonization capability than FCC Co; the higher stability of HCP Co is attributed to its much denser active sites with the step B 5 -type active unit to eliminate surface carbon species. Our FTS experiments confirm the theoretical calculation results. The great dependence of anti-carbon deposition stability on the crystallographic structure and morphology of the catalysts revealed here may open a new avenue for better, stable catalysts with maximum mass-specific reactivity. [ABSTRACT FROM AUTHOR]

The role of a zeolite in the H-form in heat and mass transfer in pellets of a composite Co catalyst for Fischer–Tropsch synthesis (FTS) has been studied. It has been shown that the introduction of a heat-conducting additive—metallic aluminum—into the catalyst composition leads to an increase in the thermal stability of the pellets; however, it does not provide high productivity. The introduction of a zeolite into the catalyst contributes to the intensification of mass transfer owing to a decrease in the density and average boiling point of the resulting liquid hydrocarbons. In this case, heat transfer is further improved due to heat removal owing to the heat capacity of the removed products. According to the studies on the conversion of liquid hydrocarbons under FTS conditions, a mechanism of the simultaneous occurrence of these processes in the presence of a cobalt–zeolite catalyst has been proposed. [ABSTRACT FROM AUTHOR]

The influence of carbon on the genesis of the active phase of cobalt in aluminum–magnesium spinel supported catalysts on their catalytic properties in the synthesis of hydrocarbons from CO and H2 has been studied. Promotion with carbon was carried out by two independent methods: in the first one, carbon was deposited on a spinel support by thermolysis of glucose followed by the deposition of cobalt; in the second one, the catalyst was prepared by coimpregnation of the support with a solution of cobalt nitrate and glucose followed by thermolysis. The catalysts were characterized by simultaneous thermal analysis in combination with mass spectroscopy of evolved gases, in situ magnetic measurements, low-temperature nitrogen adsorption, and transmission electron microscopy. The modified catalysts showed a significantly higher CO conversion rate (turnover frequency) and selectivity for target liquid hydrocarbons compared to the unpromoted catalyst. [ABSTRACT FROM AUTHOR]

A cobalt catalyst was manufactured using polyacrylonitrile (PAN)-based carbon fiber as a support. The surface of the fiber was covered with thin layer of alumina before cobalt impregnation. The catalyst was studied by a number of physicochemical methods including low-temperature nitrogen adsorption, TPR, DTG, chromatography, electron microscopy (TEM and SEM) and thermal conductivity measurements. The properties measured were discussed along with data on the activity in Fischer–Tropsch synthesis. It was found that the catalyst after the synthesis becomes significantly different from the starting catalyst, mostly because of the deposition and accumulation of high-molecular products of the Fischer–Tropsch synthesis. At the same time, in the steady-state mode, its catalytic parameters correspond to a high-performance granular catalyst based on graphite, which allows us to use the results obtained as a model for identifying the surface states of a porous catalyst of the new generation gas-to-liquid (GTL) process. [ABSTRACT FROM AUTHOR]

The results of a study of the synthesis of products from CO and H2 on a supported industrial Co–Al2O3/SiO2 catalyst under medium and high pressures in the gas circulation mode are presented. It was found that an increase in pressure from 2.0 to 8.0 MPa led to an increase in the amount of formed alcohols and synthesis olefins by factors of 10.5 and 2.0, respectively. It was determined that alcohols obtained in the synthesis were not the products of olefin hydration. The effect of an increase in selectivity for C5+ products with temperature at a high pressure in the gas recirculation mode, which is atypical for the Fischer–Tropsch synthesis, was confirmed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CO coverage of the disputed '2 √ 3' structure is θ CO =0.58 ML as determined by TPD. • Two unknown high coverage phases of CO on Co(0001) were identified. • The c(nx2) structures contain (2x2)-3CO domains diluted by antiphase boundaries. • These high density structures do not form at FTS pressures and temperatures. • They should be taken into account in catalyst characterization using CO at RT. The adsorbate overlayer structures formed by CO on highly covered Co(0001) were investigated using temperature programmed desorption, low energy electron diffraction, reflection absorption infrared spectroscopy and synchrotron-based x-ray photoemission spectroscopy, with the purpose to clarify some recent confusion on CO adsorption at high coverages. TPD shows that the coverage of the (2√3 × 2√3)R30o structure (abbreviated as 2√3 structure) is 7/12 (0.583) ML. Its unit cell contains one CO top and six CO bridge species that form three 'bridge dicarbonyls' in which two CO bridge adsorbates share the same cobalt surface atom. Between 0.58 and 0.63 ML the 2√3 structure breaks up into small 2D domains separated by antiphase domain boundaries that consist of 'double bridge dicarbonyls' in which three CO bridge adsorbates share two cobalt surface atoms. A phase transition that occurs around 0.63 ML creates previously unknown c(8 × 2) and c(12 × 2) domain boundary structures which consist of high density strips with a (2 × 2)–3CO structure and top/hollow site occupation which are separated by antiphase domain boundaries with a lower local coverage. Up to 0.63 ML the structures found at low temperature in UHV are very similar to those observed by others using in-situ STM at 300 K under CO pressure. This changes above 0.63 ML, where STM shows that moiré structures form instead of the c(n × 2) domain boundary structures. We propose that the moiré and c(n × 2) structures have a very similar enthalpy of formation so that small variations of temperature and CO chemical potential can lead to different structures for the same CO coverage. We show that these high-density phases that exist above 0.5 ML do not form at the typical pressures and temperatures used in applied FTS, but they do need to be considered when CO adsorption at room temperature is used as a diagnostic tool to characterize the catalyst surface. [ABSTRACT FROM AUTHOR]

Synthesis of mixed alcohols together with clean fuels from syngas via Fischer-Tropsch synthesis is an attractive route for the utilization of coal, natural gas and biomass. In this work, a monometallic cobalt catalyst (Co/SiO 2 -EOAM) was synthesized by impregnation using ethanolamine modified silica pellet as support and employed for the conversion of syngas. The combustion of carbon and nitrogen species during the calcination of catalyst facilitated the interaction between cobalt and support, which promoted the cobalt dispersion while inhibited the reduction of cobalt oxide. The Co/SiO 2 -EOAM catalyst exhibited much higher activity and selectivity to alcohols compared to un-modified silica supported cobalt catalyst (Co/SiO 2). The higher activity was resulted from the improved cobalt dispersion. The co-existence of abundant metallic cobalt and Co2+ species were responsible for the increasing of alcohols selectivity. • Efficient Co/SiO 2 was developed for mixed alcohols synthesis from syngas. • Higher Co dispersion is obtained by using ethanolamine modified silica as support. • Higher amount of Co0 active sites leads to increased activity. • Co-existence of Co0 and Co2+ is responsible for the alcohols formation. [ABSTRACT FROM AUTHOR]

This study investigates the production of diesel fuels by integrated Fischer–Tropsch synthesis over a bifunctional cobalt catalyst consisting of a cobalt component (Co–Al2O3/SiO2) and a zeolite-containing component (ZSM-5). The catalytic properties were tested in a continuous-flow reactor with a stationary catalyst bed at 240–250°C, 2 MPa, and gas WHSV 1000 h–1. The effects of the SiO2/Al2O3 ratio in a HZSM-5 zeolite on the catalytic performance, catalyst deactivation rate, and hydrocarbon and fractional compositions of the synthetic product were identified. The low-temperature properties of the synthesized diesel fuel satisfy the current requirements for winter fuels. [ABSTRACT FROM AUTHOR]

The production of liquid hydrocarbons from syngas (CO and H2) via the combined Fischer‐Tropsch (FT) synthesis and hydroprocessing (HP) is a promising strategy to provide valuable chemicals and fuels based on renewable feedstocks. High yields of liquid products are essential for industrial implementation since short‐chain side products like methane and CO2 reduce the overall carbon efficiency, which holds true especially for bi‐functional Co/zeolite catalysts. In order to investigate the influence of the support material properties on the methane and CO2 selectivities in the combined FT and HP reaction, we synthesized four well‐defined catalyst materials with similar cobalt particle sizes. The active material is supported on either meso‐ or microporous silicates or aluminosilicates. The catalytic properties are investigated in FT experiments at industrially relevant conditions (20 bar, 200–260 °C) and correlated with in situ x‐ray absorption spectroscopy results to determine the chemical environment responsible for the selectivity observed. The origin of the high methane selectivity detected for crystalline and amorphous aluminosilicate was mainly traced back to the strong cobalt‐support interactions. The high CO2 selectivity, observed only for crystalline zeolite materials, is driven by the presence of oxidized cobalt species, while the acidic support in combination with micropores and possible overcracking leads to the observed drop in the C5+ selectivity. [ABSTRACT FROM AUTHOR]