Fischer-Tropsch Synthesis Reaction Research Articles

A Brief Review of Recent Theoretical Advances in Fe-Based Catalysts for CO2 Hydrogenation.

Catalytic hydrogenation presents a promising approach for converting CO2 into valuable chemicals and fuels, crucial for climate change mitigation. Iron-based catalysts have emerged as key contributors, particularly in driving the reverse water-gas shift and Fischer-Tropsch synthesis reactions. Recent research has focused on enhancing the efficiency and selectivity of these catalysts by incorporating alkali metal promoters or transition metal dopants, enabling precise adjustments to their composition and properties. This review synthesizes recent theoretical advancements in CO2 hydrogenation with iron-based catalysts, employing density functional theory and microkinetic modeling. By elucidating the underlying mechanisms involving metallic iron, iron oxides, and iron carbides, we address current challenges and provide insights for future sustainable CO2 hydrogenation developments.

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.

Effects of Co3C formation on the catalytic performance for Fischer-Tropsch synthesis over Co/SiO2 catalysts

Cobalt carbides demonstrate higher selectivity towards light olefins and alcohols in the Fischer-Tropsch synthesis (FTS). In this study, we present an investigation of a series of supported cobalt catalysts that were carburized with CO for different time. The presence of Co3CCo, Co and Co2CCo phases in these catalysts was confirmed through Transmission Electron Microscopy (TEM). The Co/SiO2-RC-0.5 h catalyst with both Co3C and Co structure exhibits the highest CO conversion for the FTS reaction. By utilizing the chemisorption techniques, we studied the structure-performance relationships between the phase and activity, and confirmed that Co3C has the highest intrinsic activity, which is beneficial for CO activation. This study provides further insight into the positive effects of Co3C on the FTS reaction and guides us in the rational design of high active Co-based FTS catalysts.

Eco-friendly solid-state synthesis of Na-promoted Mn-Fe/ZrO2 catalyst for Fischer-Tropsch synthesis

The advancement of large-scale and environmentally-friendly solid-state synthesis methods is of paramount importance for the production of precipitated catalysts, notably Fe-based catalysts utilized in Fischer-Tropsch synthesis (FTS). In this study, we present an innovative solvent-independent, wastewater-free solid-state approach for the synthesis of highly efficient Fe/ZrO2 catalysts, elucidating the mechanisms of promotion within this specific methodology. The prepared catalysts underwent rigorous evaluation under industrially-relevant FTS conditions (230–270 °C, 20 bar, and WHSV = 5400 mL/(gcat⋅h)). A comprehensive suite of characterization techniques was employed to establish the intricate interplay between catalytic activity and structural attributes. We meticulously examined the impact of Na as an alkali promoter and the role of transition metals (Cu and Mn) in enhancing FTS catalytic performance. The catalytic outcomes obtained clearly demonstrate the pivotal role of the synergistic interaction between Mn and Na within the Na-Mn-Fe/ZrO2 catalyst system in driving the FTS reaction. This synergism significantly enhances FTS performance, yielding an impressive CO conversion rate (89.91 %) while maintaining low selectivity to CH4 (7.75 %). The incorporation of Mn and Na into the catalyst matrix enhances the dispersion of Fe2O3, thereby improving the reducibility of Mn/Fe oxides and elevating the electron density on the catalyst surface. These factors facilitate the formation of active Hägg iron carbide (χ-Fe5C2), stimulating chain propagation and ultimately leading to the generation of valuable C5+ hydrocarbon products, which underscores its potential as an optimal candidate for future industrial applications in Fe-based Fischer-Tropsch synthesis.

Atomic-scale understanding of the impact of CoO phase in cobalt-catalyzed Fischer-Tropsch synthesis: A combined computational and experimental study

In cobalt-catalyzed Fischer-Tropsch synthesis (FTS), the active metallic cobalt phase always suffers from oxidation under FTS reaction conditions, leading to the coexistence of metallic cobalt and cobalt oxide (CoO) phases. However, there still exist contradictory views on the impact of CoO phase in FTS. Some researchers proposed that the oxidation of metallic Co to CoO causes the deactivation of cobalt-based FTS catalysts, while some held the view that CoO phase could act as the potential active phase in FTS. In this study, by combining theoretical calculations and experiments, we systematically investigated the fundamental FTS reactions including CO adsorption and activation, C-C coupling, and CxHy hydrogenation on CoO phase, and compared them with those on metallic cobalt phase, aiming at identifying the exact role of CoO, understanding how CoO influences the activity and selectivity, and unraveling the intrinsic mechanism that determines the catalytic behaviors of CoO phase in FTS. The results reveal that the CoO(200) crystal facet is the dominantly exposed surface structure for CoO phase under FTS reaction conditions. The d-band center of CoO(200) surface shifts downward in comparison with that of active metallic Co surface, which causes difficulties in adsorbing and activating CO and gives rise to high energy barriers for the dissociation of C-O bond. This determines the inactive nature of CoO phase in FTS reaction. As for the product selectivity, the CoO(200) surface restricts the C-C chain growth due to its higher barriers for C-C coupling, facile desorption ability for light olefins, and lower energy barrier for CH4 formation compared with metallic cobalt, and consequently leads to the loss of selectivity to C5+ hydrocarbons and enhancement of selectivity to light olefins and undesired methane. Moreover, a strong linear relationship between the experimental observed selectivity change and the DFT-calculated energy difference of CoO and metallic cobalt phases was found, validating the DFT-calculated results. This study provides a comprehensive understanding of the nature and intrinsic catalytic behaviors of CoO phase in cobalt-catalyzed FTS.

Experimental analysis on products distribution, characterization and mechanism of waste polypropylene (PP) and polyethylene terephthalate (PET) degradation in sub-/supercritical water

Supercritical water (SCW) treatment of plastics is a clean technology in the ‘waste-to-energy’ path. In this work, PP and PET plastics were processed by sub-/supercritical water. The results showed that temperature was the most important factor of the PP and PET degradation. The influence of factors on the degradation of plastics follows the following order: temperature > residence time > plastic/water ratio. These factors influenced the yield of gas products by promoting or inhibiting various reactions (such as reverse water gas shift reaction, methylation reaction, and Fischer-Tropsch synthesis reaction). Besides, the composition of liquid oil was also analyzed. The main composition of the liquid oil produced by PET was benzoic acid and acetaldehyde, which were generated from the decarboxylation of terephthalic acid (TPA) and dehydration reaction of ethylene glycol (EG). The liquid oil from PP was mainly long-chain olefins, long-chain alkanes, cycloalkanes, etc., which were formed by the interaction of various methyl, alkyl, hydroxyl, and other free radicals. This study could build fundamental theories of plastic mixture treatment.

О МЕХАНИЗМАХ ОБРАЗОВАНИЯ НАНОСТРУКТУРНЫХ ЭЛЕКТРОЛИТИЧЕСКИХ ПОКРЫТИЙ Fe-Ni, Co-Mn, Ni-Cr С ФУНКЦИОНАЛЬНЫМИ СВОЙСТВАМИ

The evolution of modern industry is impossible without the development of new materials and technologies. Nanostructured coatings, in particular electrolytic coatings, are among the most demanded in mechanical engineering. The purpose of this work was to study the different mechanisms of obtaining Fe-Ni, CoMn, Ni-Cr galvanic alloys and their relationship with the specified universal physical and mechanical properties. Fe-Ni alloy is characterized by high microhardness and corrosion resistance in sea water, low cold brittleness; Co-Mn – by a specified phase composition (α-Co >> α-Mn, amorphous and metastable phase Co(OH)2); Ni-Cr – by high coating microhardness, specified phase composition. The main methods of production: high-frequency alternating current for Fe-Ni and Co-Mn alloys; introduction of a special additive (carbamide or H-acid) for Ni-Cr alloy. The main mechanisms are: Fe-Ni due to phase transition α-Fe ε-Fe; Co-Mn by means of high-frequency alternating current and carbamide addition, providing a specified phase composition; Ni-Cr by means of stationary method of addition of H-acid (high-chromium alloy of 68 mass percent of Cr) and carbamide (low-chromium alloy of 25 mass percent of Cr). Recommended uses for electroplating: Fe-Ni – for protection of oil and gas production equipment in the Arctic; CoMn – in modulation systems and as a nanocatalyst in the Fischer-Tropsch synthesis reaction; Ni-Cr – for corrosion-resistant protective coatings in petrochemistry and for resistive elements.

Cobalt Stabilization through Mesopore Confinement on TiO2 Support for Fischer-Tropsch Reaction.

Cobalt supported on mesostructured TiO2 catalysts has been prepared by a wet-impregnation method. The Co/TiO2 catalytic system showed better catalytic performance after support calcination at 380 °C. Co nanoparticles appeared well distributed along the mesopore channels of TiO2. After reduction pretreatment and reaction, a drastic structural change leads to mesopore structure collapse and the dispersion of the Co nanoparticles on the external surface. Along this complex process, Co species first form discrete nanoparticles inside the pore and then diffuse out as the pore collapses. Through this confinement, a strong metal-support interaction effect is hindered, and highly stable metal active sites lead to better performance for Fischer-Tropsch synthesis reaction toward C5+ products.

Erratum to: Deactivation and Regeneration of a Zeolite-Containing Cobalt Catalyst in a Fischer–Tropsch Synthesis Reactor

Erratum to: Deactivation and Regeneration of a Zeolite-Containing Cobalt Catalyst in a Fischer–Tropsch Synthesis Reactor

Recognizing iso-olefins as paramount intermediates for optimum isoparaffins production via CO hydrogenation

Synthesizing ‘high quality gasoline’ from syngas via will be a sustainable and clean option to ensure energy security. Herein, we rationally prove a hypothetical phenomenon that can enhance isoparaffins in the Fischer-Tropsch Synthesis (FTS) by employing iso-olefins as main intermediates. The experimental study comprised mass variation of ‘Na’ promoted ‘Fe’ with the addition of different zeolites as catalysts to convert syngas directly to gasoline ranged isoparaffins. The initial targets of olefins and iso-olefins were optimized over a the mesoporous SiO2 supporting Fe and Na phases. The iso-olefins were subsequently converted to isoparaffins over the zeolites. Among reactions investigated, the Fe-Na/SiO2 with (Fe = 20 wt%, and Na = 2 wt%) and HZSM-5(80) zeolite in the mass ratio of 1:2, stack in a dual bed configuration demonstrated highest selectivity for isoparaffins. A 53.5 % selectivity of isoparaffins was realized in 70.6 % selectivity for liquid hydrocarbons which represented a selectivity of 75.8 % of the total liquid hydrocarbons. The results from this work offer a new path into production and further studies focused on optimizing isoparaffins production from FTS reactions.

H2O Derivatives Mediate CO Activation in Fischer-Tropsch Synthesis: A Review.

The process of Fischer-Tropsch synthesis is commonly described as a series of reactions in which CO and H2 are dissociated and adsorbed on the metals and then rearranged to produce hydrocarbons and H2O. However, CO dissociation adsorption is regarded as the initial stage of Fischer-Tropsch synthesis and an essential factor in the control of catalytic activity. Several pathways have been proposed to activate CO, namely direct CO dissociation, activation hydrogenation, and activation by insertion into growing chains. In addition, H2O is considered an important by-product of Fischer-Tropsch synthesis reactions and has been shown to play a key role in regulating the distribution of Fischer-Tropsch synthesis products. The presence of H2O may influence the reaction rate, the product distribution, and the deactivation rate. Focus on H2O molecules and H2O-derivatives (H*, OH* and O*) can assist CO activation hydrogenation on Fe- and Co-based catalysts. In this work, the intermediates (C*, O*, HCO*, COH*, COH*, CH*, etc.) and reaction pathways were analyzed, and the H2O and H2O derivatives (H*, OH* and O*) on Fe- and Co-based catalysts and their role in the Fischer-Tropsch synthesis reaction process were reviewed.

Mass transfer enhancement and drying mechanism of high adhesion saturated impregnated Co-Al2O3 monolithic catalyst

The drying process significantly influences the dispersion of metals, physical properties, and performance of monolithic catalysts. In this research, a cordierite-based monolithic catalyst with Co/γ-Al2O3 was prepared using the slurry and impregnation method. The impact of ambient humidity on metal dispersion, mass transfer performance, and catalytic performance was investigated. The findings revealed distinct crystallization-deliquescence curves in the saturated impregnated monolithic catalysts, with alternating crystallization and deliquescence phenomena occurring as the ambient humidity changed. When the coating adhesion was high, the simultaneous occurrence of internal crystallization and surface dissolution resulted in concentrated internal stress, which facilitated the micro-stripping of the coating, leading to the formation of a cobweb-like microstructure. This process affected the distribution of pore sizes and enhanced mass transfer performance. The Co-based catalysts prepared in this study demonstrated a high selectivity for C5+ products (73.93%) when employed in the Fischer-Tropsch synthesis reaction. This research offers an optimization strategy for catalyst preparation, aiming to develop monolithic catalysts with low melting points, high crystallinity, and supersaturated supported transition metals.

Proximity Effect of Fe–Zn Bimetallic Catalysts on CO2 Hydrogenation Performance

The interaction between a promoter and an active metal crucially impacts catalytic performance. Nowadays, the influence of promoter contents and species has been intensively considered. In this study, we investigate the effect of the iron (Fe)–zinc (Zn) proximity of Fe–Zn bimetallic catalysts on CO2 hydrogenation performance. To eliminate the size effect, Fe2O3 and ZnO nanoparticles with uniform size are first prepared by the thermal decomposition method. By changing the loading sequence or mixing method, a series of Fe–Zn bimetallic catalysts with different Fe–Zn distances are obtained. Combined with a series of characterization techniques and catalytic performances, Fe–Zn bimetallic proximity for compositions of Fe species is discussed. Furthermore, we observe that a smaller Fe–Zn distance inhibits the reduction and carburization of the Fe species and facilitates the oxidation of carbides. Appropriate proximity of Fe and Zn (i.e., Fe1Zn1-imp and Fe1Zn1-mix samples) results in a suitable ratio of the Fe5C2 and Fe3O4 phases, simultaneously promoting the reverse water–gas shift and Fischer–Tropsch synthesis reactions. This study provides insight into the proximity effect of bimetallic catalysts on CO2 hydrogenation performance.Graphical

Tailoring Carbon Deposits on a Single-Crystal Cobalt Catalyst for Fischer–Tropsch Synthesis without Further Reduction: The Role of Surface Carbon and Penetrating Carbon

The preparation of Fischer–Tropsch synthesis (FTS) catalysts that exhibit excellent catalytic performance and are suitable for direct use in a fixed-bed reactor without further reduction is crucial in industrial applications. However, only marginal progress has been made with respect to the preparation of cobalt-based FTS catalysts owing to tendency of metallic cobalt to oxidize easily; this tendency necessitates the activation of these catalysts via reduction despite having undergone reduction treatment during their preparation. Herein, this problem has been addressed by tuning the carbon deposits (surface C and penetrating C) on the surface of a single-crystal cobalt catalyst. Screen-like surface C on a catalyst pretreated with 5% CO (p-Co–CO) exhibits diffusion suppression and chemical inertness to oxidizing gas, thus preventing the oxidation of metallic cobalt and resulting simultaneously in high activity and low CH4 selectivity (7.2%) without requiring further reduction. Moreover, the exact role of surface C and penetrating C deposited on cobalt catalysts in the FTS performance is explored. Both surface C and penetrating C enhance the activity of the cobalt catalyst but with opposite effects on the FTS selectivity. Surface C improves the adsorption ability of bridged-type CO and the formation of long-chain hydrocarbons, whereas penetrating C is conducive to adsorbing linear CO and increases undesired CH4 selectivity. This study clarifies the effect of deposited carbon on the FTS reaction and provides insights into the design of high-performance nonconventional FTS catalysts that do not require further reduction.

Adsorption and activation of CO on perfect and defective h-Fe7C3 surfaces for Fischer-Tropsch synthesis

As a structure-sensitive reaction, one important issue in Fischer–Tropsch synthesis (FTS) reaction is to clarify the relationship between the iron catalyst composition and its effects on activity and selectivity. In this work, the adsorption and activation of CO on both perfect and defective h-Fe7C3 surfaces were investigated theoretically. The results indicate that the direct CO dissociation pathway is preferred with the effective energy barriers less than 1.50 eV on both perfect (101) and (11¯1) surfaces, which play a dominant role in FTS reaction. Instead, the effective energy barriers of the preferred HCO pathway on the perfect (11¯1¯) and (11¯0) surfaces are higher than 2.40 eV. When defects occur on the surfaces, CO is inclined to adsorb on resemble B5 site and direct CO bond dissociation with barriers around 0.8 eV is more favorable than hydrogenation routes for all the four defective surfaces. Thus it can be concluded that the presence of B5-like site can facilitate to form a multiple coordinated state and lead to a stretched CO bond. Specifically, we have theoretically revealed that on B5-like site, the stronger interaction between CO and h-Fe7C3 surface with more electrons transformation, the higher activation of CO bond facilitated to CO direct dissociation.

Theoretically Predicted CO Adsorption and Activation on the Co-Doped hcp-Fe7C3 Catalyst

The Hcp-Fe7C3 phase has attracted more attention due to the high catalytic activity in Fischer–Tropsch synthesis (FTS) reactions. In this work, the adsorption and activation of CO on a Co-doped hcp-Fe7C3 catalyst were investigated by density functional theory (DFT) in order to understand the effect of Co doping on the initial step of FTS reactions on iron-based catalysts. Different Co-doped hcp-Fe7C3 001 and 11¯0 surfaces were constructed, and the CO adsorption configurations were studied. The calculated results show that the structure of the 001 surface remains basically unchanged after doping with Co atoms, while the replacement of Fe or C atoms on 11¯0 surfaces with Co atoms has a significant impact on the surface structure. The top sites on the doped Co atoms of hcp-Fe7C3 are disadvantages for the CO adsorption, whereas the T, 2F, or 3F sites around the doped Co atoms are beneficial for promoting the adsorption of CO. The CO direct dissociation pathways on the four types of Co-doped hcp-Fe7C3 001 surfaces are exothermic, while the H-assisted dissociation pathways of CO are endothermic. The H-assisted activation via HCO on the 3F1 site of the 2Co2-doped hcp-Fe7C3 001 surface shows the lowest energy barrier of 1.96 eV. For the Co-doped hcp-Fe7C3 11¯0 surfaces, the H-assisted activation via HCO is the preferred activation pathway for CO on the Co-doped surfaces with the energy barrier of approximately 1.30 eV.

Investigation of Mn and Ca promoter effects in iron-based catalysts: CO hydrogenation reaction

Cu–Fe catalysts incorporated with different amounts of Ca and Mn promoters were prepared using a wet-impregnation method and applied in the Fischer–Tropsch synthesis reaction.

Study of the process of obtaining hydrocarbons on the basis of synthesis gas and the fischer-tropsch synthesis reaction

The Fischer–Tropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperatures of 150–300°C (302–572°F) and pressures of one to several tens of atmospheres. The Fischer–Tropsch process is an important reaction in both coal liquefaction and gas to liquids technology for producing liquid hydrocarbons. In the usual implementation, carbon monoxide and hydrogen, the feedstocks for FT, are produced from coal, natural gas, or biomass in a process known as gasification. The process then converts these gases into synthetic lubrication oil and synthetic fuel. This process has received intermittent attention as a source of low-sulfur diesel fuel and to address the supply or cost of petroleum-derived hydrocarbons. Fischer-Tropsch process is discussed as a step of producing carbon-neutral liquid hydrocarbon fuels from CO2 and hydrogen. The article is devoted to the use of synthesis gas as an alternative petroleum raw material for obtaining artificial liquid fuels, hydrocarbons (Fisher-Tropsch synthesis) and aldehydes (hydroformylation or oxo-synthesis). The mechanisms of the considered reactions are discussed.

Hydrogenation of CO2 to Olefins over Iron-Based Catalysts: A Review

The widespread use of fossil fuels has caused high CO2 concentrations in the atmosphere, which have had a great impact on climate and the environment. Methods for efficiently utilizing CO2 to produce high value-added chemicals have received increasing attention. Among the products of CO2 hydrogenation, olefins, an important petrochemical feedstock, are one of the essential target products. Therefore, CO2 hydrogenation to olefins has been extensively studied, especially for the development of high-performance catalysts. Iron-based catalysts, which are widely used in Fischer–Tropsch synthesis reactions, have also been considered attractive for use in the CO2 hydrogenation to olefins due to their excellent performance in catalytic activity and reaction stability. Most studies have focused on the modulation of morphology; reduction and adsorption properties by tuning the methods of catalyst syntheses; pretreatment conditions and the composition of catalysts, in order to improve hydrogenation activity and olefin yield. In this review, we briefly discuss a thermodynamic overview of the CO2 hydrogenation to olefins reaction, the optimization of catalyst modifications, and current insights into the reaction mechanism; moreover, we summarize current challenges and future trends in the CO2 hydrogenation to olefins.

A hybrid modeling framework for efficient development of Fischer-Tropsch kinetic models

Fischer-Tropsch synthesis (FTS) receives an extensive attention as it can be used to produce various chemicals and fuels, such as linear alpha olefin, gasoline and jet fuel, in a sustainable way. While a kinetic model can help optimize the operating conditions of FTS reactors for a specific product portfolio, such a model is very challenging to develop due to the large number of species and reactions involved in FTS. To this end, in this work, we propose a hybrid modeling framework to efficiently build a kinetic model for FTS. Specifically, experiments are conducted using a Fe-Cu-K-SiO2 catalyst with the following operating variables: pressure, temperature, H2/CO ratio in syngas, and gas hourly space velocity. Then, using the experimental data, the effectiveness of the proposed framework is illustrated, which consists of three key components. The overall LHHW model is first used to predict the overall consumption rates of CO and H2 as well as the production rates of CO2 and overall hydrocarbons. Then, a convex piecewise linear fitting problem is formulated for the ASF distribution model, which can identify the break points (where the value of chain growth probability α changes) with global optimality. Finally, surrogate modeling is performed to obtain the models describing the changes in the optimal α values with respect to the operating conditions. The final model showed the overall relative error of 9.98% for CO, CO2 and H2, and 15.8% for hydrocarbons, which are comparable to the values reported in the literature.