Catalysts For Fischer-Tropsch Synthesis Research Articles

Synergistic Effects of Cerium and Strontium Promoters on Copper‐Modified Iron‐Based Fischer–Tropsch Synthesis Catalysts

Synergistic Effects of Cerium and Strontium Promoters on Copper‐Modified Iron‐Based Fischer–Tropsch Synthesis Catalysts

PROSPECTS FOR USING A COBALT CATALYST FOR FISHER-TROPSCH SYNTHESIS BASED ON SYNTHETIC SILICA ALUMINA

The possibility of the use of commercially available silica-alumina hydrate Siral-40, containing 40 wt.% of SiO2, in the composition of a composite cobalt Fischer–Tropsch synthesis (FTS) catalyst was studied. The use of silica aluminas may become a new promising direction in the development of catalysts for a shortened technological chain based on the use of bifunctional catalysts that make it possible to eliminate the hydroprocessing stage. In addition, such catalysts can be useful for expanding the range of products obtained, including those unconventional for single-reactor Fischer–Tropsch synthesis. The initial silica alumina powder was pretreated in air flow at different temperatures to adjust the concentration of acid cites on its surface. The initial and calcined powders were studied using X-ray diffraction analysis, IR spectroscopy and sorption methods. The catalysts were investigated by diffraction and sorption methods. It has been shown that an increase in the calcination temperature of the initial Siral-40 powder leads to a decrease in the specific surface area and pore volume of catalysts based on it, with temperatures above 900 °C having the greatest effect. The synthesized catalysts were active in FTS, and the composition of the obtained C5+ hydrocarbons depended more on the properties of the Siral-40 powder than the catalytic performance. The composition of C5+ hydrocarbons, obtained in the presence of all investigated catalysts contained at least 60% of diesel fraction and more than 30% of wide base oil fraction. Thus, synthetic amorphous silica aluminas are a promising component for new Fischer–Tropsch synthesis catalysts, which make it possible to obtain a wide range of products without the use of a deep hydroprocessing stage in the technological chain. For citation: Sineva L.V., Asalieva E.Yu., Gryaznov K.O., Mordkovich V.Z. Prospects for using a cobalt catalyst for Fisher-Tropsch synthesis based on synthetic silica alumina. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 88-98. DOI: 10.6060/ivkkt.20246710.7y.

Adsorption Property and Morphology Evolution of C Deposited on HCP Co Nanoparticles.

Despite extensive studies of deposited carbon in Fischer-Tropsch synthesis (FTS), an atomic-level comprehension of the effect of carbon on the morphology of cobalt-based FTS catalysts remains elusive. The adsorption configurations of carbon atoms on different crystal facets of hexagonal close-packed (hcp) Co nanoparticles were studied using density functional theory (DFT) calculations to explore the interaction mechanism between C and Co surfaces. The weaker adsorption strength of C atoms on Co(0001), Co(10-10), and Co(11-20) surfaces accounted for lower diffusion energy, leading to the facile formation of C dimers. Electronic property analysis shows that more electrons are transferred from Co surfaces to C atoms on corrugated facets than on flat facets. The deposition of carbon atoms on Co nanoparticles affects surface energy by forming strong Co-C bonds, which causes the system to reach a more energetically favorable morphology with an increased proportion of exposed Co(10-12) and Co(11-20) areas as the carbon content increases slightly. This transformation in morphology implies that C deposition plays a crucial role in determining the facet proportion and stability of exposed Co surfaces, contributing to the optimization of cobalt-based catalysts with improved performance.

Surface Chemical Effects on Fischer–Tropsch Iron Oxide Catalysts Caused by Alkali Ion (Li, Na, K, Cs) Doping

Among the alkali metals, potassium is known to significantly shift selectivity toward value-added, heavier alkanes and olefins in iron-based Fischer–Tropsch synthesis catalysts. The aim of the present contribution is to shed light on the mechanism of action of alkaline promoters through a systematic study of the structure–reactivity relationships of a series of Fe oxide FTS catalysts promoted with Group I (Li, Na, K, Cs) alkali elements. Reactivity data are compared to structural data based on in situ, synchrotron-based XRD and XPS, as well as temperature-programmed studies (TPR-H2, TPC-CO, TPD-CO2, and TPD-H). It has been observed that the alkali elements induced higher carburization rates, higher basicities, and lower adsorbed hydrogen coverages. Catalyst stability followed the trend Na-Fe > unpromoted > Li-Fe > K-Fe > Cs-Fe, being consistent with the ability of the alkali (Na) to prevent active site loss by catalyst reoxidation. Potassium was the most active in promoting high α hydrocarbon formation. It is active enough to promote CO dissociative adsorption (and the formation of FeCx active phases) and decrease the surface coverage of H-adsorbed species, but it is not so active as to cause premature catalyst deactivation by the formation of a carbon layer resulting in the blocking active sites.

Numerical Investigation into Gas-Solid Fluidized Bed Reactors for Activating the Iron-based Fischer-Tropsch Synthesis Catalyst

Abstract The present work conducted experimental and computational fluid dynamics simulation studies on the hydrodynamic characteristics of gas-solid fluidized bed reactors for activating the iron-based Fischer-Tropsch synthesis catalyst. In order to provide reliable guidance for the design and scale-up of the reactor, the present study applied experimental data from a pilot fluidized bed device to verify the accuracy of the drag force model used in the two-fluid model and further used the validated drag force model to simulate an industrial-scale fluidized bed activation reactor. It was found that the bubbling-EMMS drag model can accurately simulate the pilot-scale fluidized bed in the flow regimes ranging from bubbling to turbulent fluidization. Simulation studies on the industrial-scale fluidized bed activation reactor showed that the reactor was in a turbulent fluidization regime under the designed operating gas velocity, with high gas-solid dispersion efficiency, reasonable utilization of reactor space, and low gas-solid separation load.

Novel Approach to Organization of Structured Cobalt-Based Fischer–Tropsch Catalyst

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.

Impact of Inverse Manganese Promotion on Silica-Supported Cobalt Catalysts for Long-Chain Hydrocarbons via Fischer–Tropsch Synthesis

One of the challenges in Fischer–Tropsch synthesis (FTS) is the high reduction temperatures, which cause sintering and the formation of silicates. These lead to pore blockages and the coverage of active metals, particularly in conventional catalyst promotion. To address the challenge, this article investigates the effects of the preparation method, specifically the inverse promotion of SiO2-supported Co catalysts with manganese (Mn), and their reduction in H2 for FTS. The catalysts were prepared using stepwise incipient wetness impregnation of a cobalt nitrate precursor into a promoted silica support. The properties of the catalysts were characterized using XRD, XPS, TPR, and BET techniques. The structure–performance relationship of the inversely promoted catalysts in FTS was studied using a fixed-bed reactor to obtain the best performing catalysts for heavy hydrocarbons (C5+). XRD and XPS results indicated that Co3O4 is the dominant cobalt phase in oxidized catalysts. It was found that with increase in Mn loading, the reduction temperature increased in the following sequence 10%Co/SiO2 < 10%Co/0.25%Mn-SiO2 < 10%Co/0.5%Mn-SiO2 < 10%Co/3.0%Mn-SiO2. The catalyst with the lowest Mn loading, 10%Co/0.25%Mn-SiO2, exhibited higher C5+ selectivity, which can be attributed to less MSI and higher reducibility. This catalyst showed the lowest CH4 selectivity possibly due to lower H2 uptake and higher CO chemisorption.

Effects of surface hydrophobization on the phase evolution behavior of iron-based catalyst during Fischer–Tropsch synthesis

Iron-based Fischer–Tropsch synthesis (FTS) catalyst is widely used for syngas conversion, but its iron carbide active phase is easily oxidized into Fe3O4 by the water produced during reaction, leading to the deterioration of catalytic performance. Here, we show an efficient strategy for protecting the iron carbide active phase of FTS catalyst by surface hydrophobization. The hydrophobic surface can reduce the water concentration in the core vicinity of catalyst during syngas conversion, and thus inhibit the oxidation of iron species by water, which enhances the C − C coupling ability of catalyst and promotes the formation of long-chain olefins. More significantly, it is unraveled that appropriate shell thickness plays a crucial role in stabilizing the iron carbide active phase without Fe3O4 formation and achieving good catalytic performance.

The promotional effects of ZrO2 modification on the activity and selectivity of Co/SiC catalysts for Fischer-Tropsch synthesis

Co/SiC catalysts have exhibited excellent performance in Fischer-Tropsch synthesis reaction. However, few research focuses on investigating the effect of SiC supports surface properties of on catalyst performance. In this study, ZrO2 was utilized to modify the SiC surface, leading to the preparation of a series of Co-ZrO2/SiC catalysts. The physicochemical properties of the catalyst were comprehensively analyzed by using N2 adsorption, XRD, H2-TPR, XPS analyses. Catalytic performance was evaluated using a fixed bed reactor, shedding light on the effect of ZrO2 modified SiC support on cobalt-based Fischer-Tropsch synthesis catalysts. The results indicated that ZrO2 surface modification on SiC resulted in an enhanced reduction degree of Co/SiC catalysts. Additionally, ZrO2 exhibited strong interaction with the amorphous phase on the SiC surface, thereby weakening the interaction between Co and the amorphous phase. This led to an increase in the electron density of cobalt species, consequently improving the selectivity of Co/SiC catalysts towards long-chain hydrocarbons.

The catalytic activity of bimetallic FeCoBEA zeolite catalysts in Fischer-Tropsch synthesis – The role of cobalt in framework position of dealuminated SiBEA zeolite

The catalytic activity of bimetallic FeCoBEA zeolite catalysts in Fischer-Tropsch synthesis – The role of cobalt in framework position of dealuminated SiBEA zeolite

Sonochemical and mechanochemical synthesis of iron-based nano-hydrotalcites promoted with Cu and K as catalysts for CO and CO2 Fischer-Tropsch synthesis

A novel class of Fe-based nano hydrotalcites as catalysts for Fischer-Tropsch (FT) synthesis, with a focus on CO2 hydrogenation have been prepared, characterized and tested. These catalysts were synthesized using two green, energy- and time-saving synthesis methods: ultrasound-assisted co-precipitation and solvent-free mechanochemical syntesis. The catalysts demonstrate very satisfactory CO and CO2 conversion capacities, in particular with good selectivities towards heavy hydrocarbons. The ultrasound-processed variant is particularly noteworthy, displaying about 10 % higher activity under specific conditions. The unique physicochemical properties of these catalysts, which were extensively characterized by XRD, TGA, (ATR) FT-IR, ICP-OES, SEM, TEM, BET, and TPR, are responsible for their remarkable potential for CO and CO2 conversion with varied product distribution. These findings highlight as these iron-based hydrotalcites can be considered as a new promising class of catalyst for CO and CO2 conversion by Fischer-Tropsch reaction.

Strategic assembly of active phases on Co-Fe bimetallic catalysts for efficient Fischer-Tropsch synthesis

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 + Fe2C 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 + Fe2C 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/H2 ratio to inhibit the hydrogenation of CHx* 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 C5+ products (3011.2 gC5+ kgCo−1h−1), which surpasses the Co/NC (monometallic Co) and Co + Fe/NC (Co + Fe2C 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.

Impact of the support material on the phosphorus poisoning on Co-based catalysts for Fischer-Tropsch synthesis

The role of the support on the poisoning by phosphorus of cobalt-based catalysts for the Fischer-Tropsch synthesis was investigated. Four different supports were used in this study, γ-alumina, titania and two silica gels with different pore sizes and surface areas. The deactivation varies in intensity depending on the type of support. The trend follows the strength of the metal-support interactions, γ-alumina being the least affected, while SiO2 (2 samples with different pore structures) was most affected. These results suggest that in the first case, P interacts mainly with the support while with less interacting supports, P will interact more with the cobalt particles. The addition of different loadings of P was done after the preparation of the catalysts simulating the possible behaviour of a Biomass to Liquids process. The P loading resulted in a decrease in site-time yield and a higher hydrogenation activity leading to a reduced production of value products. Conventional characterization of the catalysts showed two different deactivation mechanisms, including site blocking and electronic effects. The addition of phosphorus decreased the metallic dispersion and reducibility of the catalysts, inhibited the hydrogen desorption and reduced the CO adsorption. Phosphorus species might be altering the catalyst surface, yielding a higher H2/CO ratio adsorbed on the catalyst through the modification of the bonding strength between the cobalt and CO, and preventing the desorption of H2.

Determination of the conditions of technologically optimized reduction of high-performance Fischer–Tropsch synthesis catalysts

Determination of the conditions of technologically optimized reduction of high-performance Fischer–Tropsch synthesis catalysts

Tuning the strong metal support interaction of the Fischer-Tropsch synthesis silica-coated cobalt-based nano-catalyst

The catalyst is crucial in enhancing productivity within the Fischer-Tropsch synthesis (FTS). The metal support interaction (MSI) plays a pivotal role in the FTS catalyst performance, impacting activity, stability, and selectivity. he configuration and composition of the catalyst dramatically impact MSI, with a strong MSI (SMSI) specified for the core-shell structure. In this study, two methods consisting of chemical treatment of etching and adding a promoter (Ru) for tuning the SMSI of the FTS catalyst are presented, and their footprints on the catalysts’ performance are screened by utilizing various characterization tests, molecular dynamic simulation, and catalytic tests. It is recognized that the silica interfacial perimeter acts as a barrier that restricts the charge transfer and boosts the SMSI in the silica-coated catalyst. Conversely, the etched catalyst exhibits a moderate MSI, contributing to increased reducibility, stability, and activity. Furthermore, the Ru-doped etched catalyst represents the optimum MSI, resulting in the highest overall performance.

Life cycle assessment of iron-biomass supported catalyst for Fischer Tropsch synthesis.

The iron-based biomass-supported catalyst has been used for Fischer-Tropsch synthesis (FTS). However, there is no study regarding the life cycle assessment (LCA) of biomass-supported iron catalysts published in the literature. This study discusses a biomass-supported iron catalyst's LCA for the conversion of syngas into a liquid fuel product. The waste biomass is one of the source of activated carbon (AC), and it has been used as a support for the catalyst. The FTS reactions are carried out in the fixed-bed reactor at low or high temperatures. The use of promoters in the preparation of catalysts usually enhances C5+ production. In this study, the collection of precise data from on-site laboratory conditions is of utmost importance to ensure the credibility and validity of the study's outcomes. The environmental impact assessment modeling was carried out using the OpenLCA 1.10.3 software. The LCA results reveals that the synthesis process of iron-based biomass supported catalyst yields a total impact score in terms of global warming potential (GWP) of 1.235E + 01kg CO2 equivalent. Within this process, the AC stage contributes 52% to the overall GWP, while the preparation stage for the catalyst precursor contributes 48%. The comprehensive evaluation of the iron-based biomass supported catalyst's impact score in terms of human toxicity reveals a total score of 1.98E-02kg 1,4-dichlorobenzene (1,4-DB) equivalent.

Physical Grinding of Prefabricated Co3O4 and MCM-22 Zeolite for Fischer-Tropsch Synthesis: Impact of Pretreatment Procedure on the Dispersion and Catalytic Performance.

To improve the mess-specific activity of Co supported on zeolite catalysts in Fischer-Tropsch (FT) synthesis, the Co-MCM-22 catalyst was prepared by simply grinding the MCM-22 with nanosized Co3O4 prefabricated by the thermal decomposition of the Co(II)-glycine complex. It is found that this novel strategy is effective for improving the mess-specific activity of Co catalysts in FT synthesis compared to the impregnation method. Moreover, the ion exchange and calcination sequence of MCM-22 has a significant influence on the dispersion, particle size distribution, and reduction degree of Co. The Co-MCM-22 prepared by the physical grinding of prefabricated Co3O4 and H+-type MCM-22 without a further calcination process exhibits a moderate interaction between Co3O4 and MCM-22, which results in the higher reduction degree, higher dispersion, and higher mess-specific activity of Co. Thus, the newly developed method is more controllable and promising for the synthesis of metal-supported catalysts.

Synergism of surface Co-rich activated carbon-supported bimetallic Co:Fe catalysts for Fischer-Tropsch synthesis

ABSTRACT The present study explores the remarkable potential of activated carbon-supported cobalt-rich bimetallic catalysts (Co:Fe) in Fischer-Tropsch (FT) synthesis. The H2/CO ratio of the syngas was maintained at 1 to simulate biomass gasification. The temperature, pressure, and GHSV were maintained at 240°C, 20 bar, and 20 mL g.cat−1 min−1, respectively. Totally five combinations of mono- and bimetallic catalysts were synthesized by sequential impregnation of Fe followed by Co, offering a novel and facile approach. The characterization studies revealed the Co-rich surface of the bimetallic catalysts with Co3O4 as an active metal species. The FT activity tests revealed the superior performance of the bimetallic catalysts than their monometallic counterparts. The selectivity to C5+ compounds increased with increase in Co content while the CO conversion increased up to 5% Fe content and then decreased further. The maximum CO conversion (67.4%) and C5+ yield (47.6%) were observed for 15Co5Fe/AC. The study provides a unique perspective on the advancement of C5+ fuel production in Fischer-Tropsch synthesis, achieved through the synergy of FTS-active cobalt and WGS-active iron.

ZSM‐5‐Promoted Co‐Based Light‐Assisted Thermocatalytic Fischer–Tropsch Synthesis Catalyst for Production of Liquid Fuel

Light‐assisted thermocatalytic Fischer–Tropsch synthesis (FTS) provides a more efficient and sustainable approach to synthesizing high‐value chemicals compared to the thermal‐driven FTS. However, producing liquid fuel via cobalt‐based light‐assisted thermocatalytic FTS catalyst poses a challenge since photogenerated electrons increase CO conversion simultaneously with a significant reduction in the selectivity of C5+ product. Herein, a cobalt‐based light‐assisted thermocatalytic FTS catalyst containing ZSM‐5 molecular sieve promoter is prepared by a unique wet chemical reduction method, and the constructed 15%Co/Ta3N5‐ZSM‐5 catalyst exhibits nearly 90% C5+ product selectivity and 63% CO conversion under photothermal condition. Further characterization indicates that the simultaneous increase in the number of active sites and the density of acidic sites in the catalyst is crucial to achieve a simultaneous increase in CO conversion and C5+ product selectivity, which enables the catalyst to produce liquid fuel via light‐assisted thermocatalytic FTS reaction. This work provides an approach to introduce solar energy into the process of liquid fuel production, which can improve the sustainability of the liquid fuel production process.

Importance of zeolite in multifunctional catalysts for syngas conversion

Conversion of syngas into valuable fuels and chemicals has been studied for about 100 years since the discovery of Fischer–Tropsch synthesis (FTS) for conversion of syngas to fuels. Generally, the products in conventional FTS adhere to the Anderson–Schultz–Flory model, which has restricted selectivity to the target products. Other highly demanded compounds such as valuable aromatics and oxygenates, could not be directly obtained from the conventional FTS. According to recent findings, the cascade reactions including isomerization, cracking, and aromatization can optimize the product selectivity, when the zeolite is added to FTS catalysts. Additionally, by offering a confined environment for the C–O bond formation, zeolite makes a substantial contribution to the conversion of syngas into oxygenates. In this review, we primarily focus on the role of zeolites in FTS processes and how it regulates the reaction pathways. The structure–performance interplay of zeolites was particularly discussed, which might be helpful to guide the rational design of zeolites in the development of more effective catalysts.