For Fischer–Tropsch Synthesis Research Articles

Selective hydrogenation of CO2 and CO over potassium promoted Co/ZSM-5

The utilization of CO2 as a C1 feedstock for synthesis of value-added chemicals and fuels could both mitigate the negative effects associated with increasing CO2 emissions and decrease dependence on fossil fuels as part of a future circular carbon economy. Co-based catalysts have been well-developed for Fischer-Tropsch synthesis (FTS), but replacing the CO reactant with CO2 (CO2-FTS) typically results in low selectivity toward desirable light olefins. To better understand the structure-property relationships of Co-based catalysts, and extend promising FTS results to CO2-FTS, we have studied the effect of a potassium promoter and acidic properties of ZSM-5 on catalytic performance. The selectivity of FTS and CO2-FTS is shown to be a strong function of Si/Al ratio in co-impregnated catalysts, with findings supported by in situ XAFS and FTIR, demonstrating light olefin selectivity can be tuned by Si/Al ratio and the method of introducing the K promoter.

Stabilization of \u03b5-iron carbide as high-temperature catalyst under realistic Fischer\u2013Tropsch synthesis conditions

The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. ε-Iron carbide (ε-Fe2C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K). Here, we succeed in stabilizing pure-phase ε-Fe2C nanocrystals by confining them into graphene layers and obtain an iron-time yield of 1258 μmolCO gFe−1s−1 under realistic FT synthesis conditions, one order of magnitude higher than that of the conventional carbon-supported Fe catalyst. The ε-Fe2C@graphene catalyst is stable at least for 400 h under high-temperature conditions. Density functional theory (DFT) calculations reveal the feasible formation of ε-Fe2C by carburization of α-Fe precursor through interfacial interactions of ε-Fe2C@graphene. This work provides a promising strategy to design highly active and stable Fe-based FT catalysts.

Impact of Coordination Features of Co(II)-Glycine Complex on the Surface Sites of Co/SiO2 for Fischer–Tropsch Synthesis

To investigate the effect of coordination features of Co(II)-glycine complex on the performance of Co/SiO2 for Fischer–Tropsch (FT) synthesis, Co(II)-glycine complex precursors were prepared by the conventional method, i.e., simply adding glycine to the solution of Co nitrate and novel route, i.e., reaction of glycine with cobalt hydroxide. The SiO2-supported Co catalysts were prepared by using the different Co(II)-glycine complexes. It is found that glycine is an effective chelating agent for improving the dispersion of Co and the mass-specific activity in FT synthesis when the molar ratio of glycine/Co2+ = 3, which is independent to the preparation method in this study. Significantly, the surface Co properties were significantly influenced by the coordination features of the Co2+ and the molar ratio of glycine to Co2+ in the Co(II)-glycine complex. Specifically, the Co(3gly)/SiO2 catalyst prepared by the novel route exhibits smaller and homogenous Co nanoparticles, which result in improved stability compared to Co-3gly/SiO2 prepared by the conventional method. Thus, the newly developed method is more controllable and promising for the synthesis of Co-based catalysts for FT synthesis.

Nano-ZSM-5 decorated cobalt based catalysts for Fischer-Tropsch synthesis to enhance the gasoline range products selectivity

The amount of acid sites is crucial for modifying the product selectivity for Fischer-Tropsch synthesis (FTS) since the acid sites may affect the hydrocracking performance of heavy hydrocarbons. Fewer acid sites usually present poor hydrocracking ability while the excessive acid sites result in over hydrocracking of heavy hydrocarbons. Here, a kind of hybrid Co/M-Z catalyst with different amount of acid sites was prepared by mixing different amount of nano-H-ZSM-5 zeolite with Co/M catalyst, which combined the great activity and stability of Co/M (Co/MCF) catalyst and the acid function of nano-H-ZSM-5 zeolite. The NH3-TPD result indicates that the amount of acid sites increased to 1.96 × 10−4 mol gcat−1 with the mass content of nano-H-ZSM-5 zeolite increasing to 80 wt%. N2-adsorption desorption result proves the Co/M catalyst presents suitable mass transfer ability. FTS performance indicates that CO conversion, STY value and the C21+ product selectivity decrease with the content of nano-H-ZSM-5 zeolite increase. While, the CH4 selectivity is on the opposite. Among these catalysts, the Co/M-Z catalyst presents the highest C5-11 selectivity (53.5%) due to the suitable amount of acid sites.

Synthesis new Co–Mn mixed oxide catalyst for the production of light olefins by tuning the catalyst structure

In order to increase the catalyst activity for Fischer–Tropsch synthesis (FTS), the preparation methods of two new catalysts were studied. The chemically identical bimetallic Co–Mn/Al2O3 catalysts were synthesized by different synthetic methods: (a) via thermal decomposition of the complex [Co1.33Mn0.667(C7H3NO4)2(H2O)5].2H2O (1) and (b) by the impregnation technique. The complex was characterized by the single‐crystal analysis, elemental analysis, and Fourier‐transform infrared (FT‐IR) spectroscopy. Both catalysts were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectrometry (EDS), Brunauer–Emmett–Teller (BET) specific surface area, hydrogen temperature‐programmed reduction (H2‐TPR), and H2‐chemisorption. The catalysts' activity was investigated for the Fischer–Tropsch synthesis in a fixed bed microreactor. Higher activity was obtained for the catalyst prepared by thermal decomposition of the inorganic precursor due to its small particle size, superior dispersion, and higher surface area. The results show that the catalyst prepared thermal decomposition has 21% ethylene, 10% propylene, and 50% C5+ selectivity, while methane selectivity of this catalyst is 11% at 250°C. On the other hand, the catalyst obtained by the impregnation method displays 15% ethylene, 8% propylene, 29% C5+, and 29% methane selectivity at the same temperature.

Sodium modified Fe-Mn microsphere catalyst for Fischer–Tropsch synthesis of light olefins

Both one-pot solvothermal method and impregnation were adopted to synthesize sodium modified Fe-Mn microsphere catalysts for Fischer–Tropsch synthesis (FTS) of light olefins. The effects of Mn and Na promoters on the microsphere morphology, electronic state and catalytic performance of Fe3O4 catalysts were evaluated by Ar adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy mapping (EDS-mapping), H2 temperature-programmed reduction (H2-TPR), CO temperature-programmed desorption (CO-TPD), X-ray photoelectron spectroscopy (XPS) and Mössbauer spectra. SEM, TEM and Ar adsorption-desorption showed that catalysts were in a uniform spherical shape with the size of 300−400 nm, while FeMn microsphere owned a smaller size and a larger surface area. Mn promoter could enhance the chemisorption of CO, and suppressed the hydrogenation of olefins, then lead to higher selectivity of light olefins. Na promoter strengthened the FTS reaction activity due to its basicity and electronic donation. Mn15Na32im showed the highest CO conversion of 97.21 % with the light olefin selectivity of 33.02 %.

Effect of Rare-Earth Promoters on Precipitated Iron-Based Catalysts for Fischer–Tropsch Synthesis

FeMn catalysts that were either unpromoted or promoted by five rare-earth metals (La, Ce, Nd, Sm, and Eu) for Fischer–Tropsch synthesis (FTS) were prepared by the coprecipitation method and charact...

Microwave Assisted Co/SiO2 preparation for Fischer-Tropsch synthesis

Cobalt catalyst has been widely used for Fischer-Tropsch (FT) Synthesis in Industry. The most common method to prepare cobalt catalyst is impregnations. Metal is deposited on porous support by contacting dry support with solution containing dissolved cobalt precursor. This step will follow by drying, calcination and reduction. The heating step used in this conventional method, however, may lead to the formation of metal silicate which is inactive site for catalysis. In this study, author explore the use of microwave to prepare catalyst compared to conventional drying method. Cobalt catalyst with SiO2 support was prepared and characterized. Particle size, surface area, and cobalt content were investigated. Crystallite size of 3-8 nm was formed which was reported to be the optimum size for cobalt catalyst in FT Synthesis. Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM) image revealed that microwave catalyst showed better uniformity and cobalt dispersion on silica support. Thermo-Gravimetric Analysis (TGA) study also indicated that this catalyst has good stability at Low Temperature Fischer-Tropsch Synthesis. The catalysts were then applied plasma assisted FT process over a range of power plasma (20-60W) to investigate the effect on the conversion and selectivity. The results showed that microwave catalyst exhibit lower CO conversion at 42.06% compared to conventional method at 68.32%. However, microwave catalyst is more favourable for long chain hydrocarbon selectivity.

Fischer–Tropsch Synthesis: ZIF-8@ZIF-67-Derived Cobalt Nanoparticle-Embedded Nanocage Catalysts

The preparation of highly active and stable catalysts for syngas conversion is a major challenge for Fischer–Tropsch synthesis (FTS). Herein, we report a strategy to prepare a highly dispersed Co-embedded porous carbon nanocage (CoPCN) structure derived from a core–shell metal–organic framework (MOF) ZIF-8@ZIF-67 precursor. High Co loading (over wt 30%) is achieved while maintaining an optimal dispersion and particle size of the active Co phase when a ZIF-8@ZIF-67 is pyrolyzed at 920 °C. Besides, the porous channels and hollow structures of the CoPCN strengthen the diffusion of reactants and the hydrocarbon product, enhancing the C5+ selectivity and CO conversion. The CoPCN shows high stability in FTS with a CO conversion of 18.3%, 80.2% selectivity for long-chain hydrocarbons (C5+), and 8.9% selectivity for short-chain hydrocarbons (C2–C4) after 100 h time on stream. Compared with other MOF-derived FTS catalysts, CoPCN-920 can achieve higher C5+ selectivity at a lower reaction temperature. The present work uncovers the relationship between the porous structure and catalytic performance, providing an efficient method to prepare promising materials for enhanced FTS stability, activity, and selectivity.

Identify Zr Promotion Effects in Atomic Scale for Co-Based Catalysts in Fischer–Tropsch Synthesis

Introducing promoters on cobalt-based catalysts for Fischer-Tropsch synthesis (FTS) have been found efficient for adjusting their performance in converting syngas into long-chain hydrocarbons. Deta...

THE USE OF COBALT/RUTHENIUM CATALYST SUPPORTED IN SBA-15 IN THE PROMOTION OF FISCHER-TROPSCH SYNTHESIS

The aim of this work is to produce a cobalt/ruthenium catalyst supported in SBA-15, for Fischer-Tropsch synthesis (FTS). The synthesis was carried out in a slurry reactor operating at 513 K, 20 atm, and CO:H2 molar ratio of 1:1. The addition of cobalt in SBA-15 decreased the specific superficial area of the molecular sieve. The ranges of temperature reduction typical of iron oxides phases were found using RTP results. Fischer-Tropsch synthesis activity and C5+ hydrocarbon selectivity increased with the addition of Ru. The increase in activity and selectivity were attributed to the increased number of active sites as a result of the higher reducibility.

Hollow Zeolite Nanoparticles Combined with Fe3O4@MnO2 Tandem Catalyst for Converting Syngas to Aromatics-Rich Gasoline

Adjusting the hydrocarbons selectivity remains a big challenge for Fischer-Tropsch synthesis (FTS). Hollow ZSM-5 zeolite nanoparticles with adjustable acidity are synthesized, which combine with Fe...

Removal of sodium compounds from Co/SBA-15 catalysts for Fischer-Tropsch Synthesis

In the present work, the synthesis of Co/SBA-15 catalysts intended for Fischer-Tropsch (FT) synthesis was performed. During the synthesis of catalysts there was contamination of samples with sodium nitrate due to the nature of the reducing agent used for the synthesis of metallic phase. This kind of impurity is not advantageous for the FT reaction. Attempts at removal of sodium compounds were carried out by means of simple leaching treatments, using ethanol and acid ethylenediaminetetraacetic (EDTA) as solvent and complexing agent, respectively, followed by heat treatment at temperatures of 150 or 300°C. It was possible to conclude that the treatment using EDTA was more effective in removing almost all the alkaline phase of samples, despite the occurrence of oxidation, agglomeration, and removal of the metal nanoparticles in this process. In addition, there were no significant differences in the product selectivity of FT synthesis of the catalysts after sodium removal, although the nanoparticles were larger than 10 nm.

Preparation of low carbon olefins on a core-shell K-Fe5C2@ZSM-5 catalyst by Fischer-Tropsch synthesis.

In this study, a core–shell catalyst based on Fe5C2@ZSM-5 (ZSM-5 capped Fe5C2 as active phase) is prepared by the coating-carbonization method for Fischer–Tropsch synthesis (FTS). Further, the designed ZSM-5 zeolites are utilized to screen the low carbon hydrocarbons from the products generated on the iron carbide active centre, and for catalytic disassembly of the long-chain hydrocarbons into low carbon olefins. Prior to utilization, the physical–chemical properties of the prepared catalysts are systematically characterized by various techniques of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) observations, in addition to the effects of coating-carbonization, molecular sieve coating amount, and K-doping on core–shell iron-based catalysts. Next, the performance of Fischer–Tropsch synthesis is investigated in a micro-fixed bed reactor. The results manifest that, comparing with Fe5C2 and a supported Fe/ZSM-5 catalyst prepared by the traditional impregnation method, the core–shell Fe5C2@ZSM-5 catalysts show higher CO conversion rate, reaction activity and selectivity to low-carbon olefins. Comparatively, the Fe5C2@ZSM-5C catalyst prepared by carbonization after the coating method exhibited more surface area, smaller average pore size, and more reactive active sites, resulting in the improvement of screening of high carbon hydrocarbons and the enhancement of selectivity to low carbon olefins, in comparison to those prepared by the carbonization-coating method. In conclusion, the K-doping catalyst had significantly improved the reactive activity of the core–shell Fe5C2@ZSM-5 catalyst and the selectivity to low carbon olefins, while the CO conversion on K–Fe5C2@ZSM-20C still remained good.

The Preparation and Characterization of Co–Ni Nanoparticles and the Testing of a Heterogenized Co–Ni/Alumina Catalyst for CO Hydrogenation

Samples of well-controlled nanoparticles consisting of alloys of cobalt and nickel of different atomic ratios were synthesized using wet chemical methods with oleylamine as the solvent and the reducing agent. These materials were characterized by a variety of techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Small amounts of heterogenized catalysts were prepared using alumina as the support. However, the potential for use of Co–Ni catalysts in CO hydrogenation was explored using a larger amount of Co–Ni/alumina catalyst prepared from standard aqueous impregnation methods and tested in a continuously stirred tank reactor (CSTR) for Fischer–Tropsch synthesis (FTS). Results are compared to a reference catalyst containing only cobalt. The heterogenized catalysts were characterized using synchrotron methods, including temperature programmed reduction with extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge spectroscopy (TPR-EXAFS/XANES). The characterization results support intimate contact between Co and Ni, strongly suggesting alloy formation. In FTS testing, drawbacks of Ni addition included decreased CO conversion on a per gram catalyst basis, although Ni did not significantly impact the turnover number of cobalt, and produced slightly higher light gas selectivity. Benefits of Ni addition included an inverted induction period relative to undoped Co/Al2O3, where CO conversion increased with time on-stream in the initial period, and the stabilization of cobalt nanoparticles at a lower weight % of Co.

Bio-syngas converting to liquid fuels over co modified Fe3O4-MnO2 catalysts

A bifunctional Co modified Fe3O4-Mn catalyst was prepared for Fischer-Tropsch synthesis (FTS). The influence of Co loading on the synergistic effect of Fe-Co as well as FTS performance over Fe1CoxMn1 catalysts was studied. Incorporation of Co species into the Fe3O4-Mn catalyst promoted the reduction of iron oxides, increasing iron active sites during FTS. Moreover, the adding of Co species enhanced the electron transfer from Fe to Co metal, which strengthened the synergistic effect of Fe-Co, improving the catalytic performance. The Fe1CoxMn1 catalyst with higher Co loading promoted further the hydrogenation ability, favoring the shifting of the product distribution towards shorter hydrocarbons. Under optimized conditions of 280 °C, 2.0 MPa and 3000 h−1, the highest yield of liquid fuels was obtained for the Fe1Co1Mn1 catalyst.

Nano-ZSM-5-supported cobalt for the production of liquid fuel in Fischer-Tropsch synthesis: Effect of preparation method and reaction temperature

ZSM-5 zeolite is usually used to modify the product selectivity for Fischer–Tropsch synthesis (FTS). Here, we prepared a nano-ZSM-5 zeolite with a particle size of 80 nm. This zeolite was used as a support to prepare bifunctional Co-based FTS catalysts by incipient wetness impregnation [using water as a solvent (W-Co/H-ZSM-5) or alcohol as a solvent (A-Co/H-ZSM-5)] and an ultrasound-assisted impregnation method (U-Co/H-ZSM-5). These catalysts were characterized by X-ray diffraction (XRD), N2-physical absorption, H2 temperature-programmed reduction (H2-TPR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The FTS catalytic performances of all catalysts were compared in a fixed-bed reactor. Characterization data revealed that the U-Co/H-ZSM-5 catalyst had the best cobalt dispersion, resulting in the most stable CO conversion. Moreover, the nanoscale relationship between the activity and acid sites enhances the hydrocracking ability, increasing the liquid fuel selectivity from 49.7% to 67.8% (no C20+ product was detected for U-Co/H-ZSM-5) for a reaction at 503 K. In addition, the CH4 selectivity increases as the reaction temperature increases from 483 K to 513 K, which is beneficial for producing liquid fuel products (67.8%) at a reaction temperature of 503 K.

A simple coupled ANNs‐RSM approach in modeling product distribution of Fischer‐Tropsch synthesis using a microchannel reactor with Ru‐promoted Co/Al 2 O 3 catalyst

A simple approach using hybrid artificial neural networks (ANNs)-response surface methodology (RSM) was developed to model the detailed product distribution using Ru-promoted cobalt-based catalyst with Al2O3 as the support in a microchannel reactor for Fischer-Tropsch (FT) synthesis. Using the independent process parameters for training, the established model is capable of predicting hydrocarbon production distributions, ie, paraffin formation rate (C2-C15) and olefin to paraffin ratio (OPR C2-C15) within acceptable uncertainties. The ANNs-RSM model and comprehensive mechanistic model using the Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach were compared to identify a few inherent advantages of the proposed model in modeling complex FT synthesis. The proposed ANNs-RSM model shows its appealing merits, ie, faster converge and higher accuracy (less than ±10% uncertainties was achieved from ANNs-RSM model, while LHHW model achieved less than ±15% uncertainties except a few exceptional high errors uncertainties at certain experimental conditions). The statistical significances to the product distributions and hydrocarbon formation rate during FT synthesis could be easily identified and quantitatively analyzed by the established ANNs-RSM model. The future effective alternative of kinetic study of the complex system such as FT synthesis in the microstructured reactor might follow the methods of using empirical reliable approach for process optimization together with mechanistic kinetic study for detailed reaction pathway discrimination.

Effect of Manganese on Co–Mn/CNT Bimetallic Catalyst Performance in Fischer–Tropsch Reaction

Cobalt (Co) catalyst is supported by carbon nanotubes (CNT) using a strong electrostatic adsorption (SEA) method. To promote activity and selectivity as well as find the optimum loading percentage and its effect on catalyst performance, manganese (Mn) has been added to the Co/CNT catalyst. Samples were characterized by a scanning electron microscope (SEM-EDX), transmission electron microscope (TEM), hydrogen temperature programmed reduction (H2-TPR), Zeta potential, Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), and X-ray spectroscopy (XPS). TEM images illustrated an intake of metal particles which were highly dispersed, having a narrow particle size distribution of 6–8 nm to the external and internal CNT support. H2-TPR showed a lower temperature reduction with Mn at 420 °C for Fischer–Tropsch synthesis (FTS) reaction. The Co–Mn/CNT catalyst performance test for FTS was performed at a temperature of 240 °C in a fixed-bed micro-reactor at a pressure of 2.0 MPa. The addition of manganese resulted in a lower methane selectivity and a higher C5+ product with an optimum percentage of 5% of manganese. CO conversion was 86.6% and had a C5+ selectivity of 81.5%, which was higher than the catalysts obtained using only Co on pretreated CNT.

Effects of cobalt carbide on Fischer–Tropsch synthesis with MnO supported Co-based catalysts

Abstract Cobalt carbide (Co2C) was considered as potential catalysts available for large-scale industrialization of transforming syngas (H2 and CO) to clean fuels. Herein, we successfully synthesized Co-based catalysts with MnO supported, to comprehend the effects of Co2C for Fischer–Tropsch synthesis (FTS) under ambient conditions. The huge variety of product selectivity which was contained by different active sites (Co and Co2C) has been found. Furthermore, density functional theory (DFT) shows that Co2C is efficacious of CO adsorption, whereas is weaker for H adsorption than Co. Combining the advantages of Co and Co2C, the catalyst herein can not only obtain more C5+ products but also suppress methane selectivity. It can be a commendable guide for the design of industrial application products in FTS.