Fischer-Tropsch Synthesis Products Research Articles

Oxidative oligomerization of a synthetic fraction of hydrocarbons from the Fischer-Tropsch synthesis

The work investigated the process of oxidative oligomerization of Fischer-Tropsch synthesis products - a fraction of C10-C15 hydrocarbons with a total content of alkenes (mainly β- and γ-alkenes) of 64.7 wt. % using zirconium octoate as a catalyst. The hydrocarbon fraction was obtained on a zeolite-containing catalyst at a pressure of 2.0 MPa, a temperature of 250 °C, H2/CO ratio at the reactor inlet of 1.70, a gas space velocity of 1000 h-1 and circulation mode ratio range 0-16. It was found that at a temperature of 160 °C the catalyst content is 5.0 wt. %, process duration 6 hours and pressure (air) - 2.5 MPa, target fraction yield - 52.7 %. It was found that the oligomerization product has a low pour point of minus 31 °C. It was proposed to improve the viscosity characteristics of the oligomerization product by introducing additives into its composition, for example, polymethacrylates or polyisobutylene.

Fisher-Tropsch synthesis in the presence of bifunctional catalysts based on hierarchical zeolite MFI

The effect of the hierarchical pore structure of ZSM-5 zeolites obtained by alkali modification on the composition of the synthesized products and the catalytic properties of bifunctional cobalt catalysts for the Fischer-Tropsch synthesis was studied. The bifunctional catalysts were prepared by mechanically mixing the Co-Al2O3/SiO2 catalyst, HZSM-5 zeolite and boehmite binder. The HZSM-5 zeolite was preliminarily subjected to alkali modification with different alkali concentrations (0.1, 0.25, 0.5, and 1.0 M) to create a hierarchical porous structure and change the acidic properties of the zeolite. The samples of ZSM-5 zeolites and the bifunctional catalysts prepared on their basis were characterized by SEM, low-temperature nitrogen adsorption-desorption, X-ray diffraction and H2 TPR. Catalytic tests were carried out in a tubular reactor with a fixed catalyst bed at a pressure of 2.0 MPa, a temperature of 250 °C and a gas space velocity of 1000 h–1. The tests were performed for 70–80 h of continuous operation. The fractional composition of the Fischer-Tropsch synthesis products was studied at a temperature of 250 °C. It was shown that preliminary treatment of zeolite ZSM-5 with a 0.5 M alkali solution contributed to an increase in the yield and productivity of branched hydrocarbons to 62% and 70.3 kg/(m3cat∙h) compared to a similar bifunctional catalyst based on the industrial microporous zeolite HZSM-5.

Oligomerization of Fischer-Tropsch Olefins by Radical Initiation Method for Synthesizing Poly Olefin Base Oils

In the present work we have investigated the oligomerization process of Fischer-Tropsch synthesis products – gasoline (C5-C10) and diesel (C11-C18) hydrocarbon fractions with a total olefin content (consisting mainly olefins with a branched isomeric chain) of 79.3 and 31.8 wt.%, respectively. Oligomerization was carried out by radical initiation method using azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide and methyl ethyl ketone peroxide (Butanox M-50) as initiators. It was established that the yield of the oligomerization process depending on the initiator used decreases in the following order: azobisisobutyronitrile > benzoyl peroxide > dicumyl peroxide > Butanox M-50. It was determined that when the oligomerization is carried out in polar solvents such as acetone and dichloromethane the yield of product increases by ~2.1 and ~1.7 times, respectively, while at the same time adding a non-polar solvent such as tetrachloromethane to the reaction mixture decreases the product yield by ~2.0 times. The optimal technological parameters for carrying out oligomerization process of synthetic gasoline and diesel fractions were determined: where azobisisobutyronitrile, content 0.5 wt.%., is used as an initiator, acetone as solvent, with reaction temperature of 200 °C, and duration of 12 hrs. under inert atmosphere. The product yield from the diesel fraction is 39.5 %, and from the synthetic gasoline fraction – 36.0 %. At the same time, in terms of characteristics, the oligomerization product of the diesel fraction showed properties similar to commercially available Base oil 3cSt (Group III), and the gasoline fraction showed properties on par with the commercially produced PAO-2 (Group IV). Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Exploring C1-C3 variations and Fischer–Tropsch chemistry via electrochemical CO2 reduction on electrodeposited Cu/Ag and Ag/Cu electrodes

Ag and Cu bimetallic electrodes are extensively studied for producing C-C coupled C2+ reduction products through electrochemical CO2 reduction. In this study, we prepared electrodes with Cu electrodeposited on Ag supports (CuED/Ag) and Ag electrodeposited on Cu supports (AgED/Cu) via electrodeposition, demonstrating behaviors for reduction products under various electrochemical conditions. The products were categorized as H2, C1 (CO, CH4, formate, methanol), C2 (C2H4, ethanol, acetate, acetaldehyde, glycolaldehyde, and ethylene glycol), C3 (propanol, isopropanol), and Fischer–Tropsch (F-T) synthesis products (CnH2n and CnH2n+2, n ≥ 2). Notably, ethylene glycol was only observed over AgED/Cu. The reduction products dynamically changed with applied potentials and electrolyte concentrations. The mechanism was understood to involve surface H* adsorption, CO2 adsorption, C-C coupling, hydrogenation, and dehydration. Minor F-T synthesis chemistry was observed, explained by *CO and *CH2 insertion chain growth. The distinct product behaviors over the CuED/Ag and AgED/Cu electrodes provide valuable insights into the development of electrodes for producing value-added carbon products via CO2 utilization.

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.

Tuning selectivity in low-temperature Fischer-Tropsch synthesis by applying gas recycle mode

While hydrocarbons production by Fischer-Tropsch synthesis (FTS) is widely recognized, commercial interest in FTS products is mainly constrained by oil prices. The FTS-derived fuels, although higher quality and greener, cannot currently compete with cheaper fossil fuels, motivating to shift the FTS products distribution to higher value-added chemicals, such as olefins-C5+. The high olefin selectivity in FTS over Co-based catalysts is usually ascribed to Co2C on the catalyst surface with its inherent deficiencies. This study demonstrates a novel approach to alter low-temperature FTS selectivity by applying off-gas recycling. At slow gas recycling rates, C19+ selectivity increases due to re-adsorption and re-incorporation into the growing chain of gaseous olefins from the off-gas. High-intensity gas recycling facilitates C5+ olefin vapors removal from the reactor by enhanced gas flow with their subsequent cut-off in the cold trap, thus reducing residence time of condensed olefins and probability of their secondary reactions.

Study on the intermediate products of Fischer Tropsch synthesis as a collector for coal flotation: Molecular dynamics and experimental studies

As a general coal flotation collector, diesel is often used in the industrial production process, and diesel is not renewable and belongs to the hazardous reagents, so there is an urgent need to find a new type of flotation collector to replace diesel. In this paper, three intermediate products produced by Fischer-Tropsch synthesis technology were used as collector. And five emulsifiers, Span80, Tween80, sodium dodecyl sulfate, betaine, and hexadecyl trimethyl ammonium bromide were used to emulsify 3# synthetic oils to produce emulsion with good stability. The flotation performance of three synthetic oil products as well as emulsified collectors were investigated, and the adsorption capacity of 2# and 3# synthetic oils on the coal surface was studied by molecular dynamics simulation. The results showed that the flotation results of synthetic oil were better than those of diesel, with collector 1# having the best flotation results. The oil in water (O/W) emulsion formulated with Tween80 had the best properties, and remained unstratified in half a month, and there were a large number of 0.1–1 μm oil droplet in the emulsion. Moreover, the emulsified collector of Tween80 with oil-water ratio of 4:6 showed excellent flotation performance, which was nearly 1.5 % higher than that of diesel. The molecular dynamics results are consistent with the synthetic oil flotation results at high concentration dosages, where 3# oil showed better adsorption behavior on the coal surface than 2# oil, but was slightly inferior to diesel adsorption. Therefore, the synthetic oil can be completely used as a substitute for diesel, and the emulsion with oil-water ratio of 4:6 formulated with Tween80 has excellent flotation performance and greatly saves the actual consumption of synthetic oil, which has very high economic and environmental value.

Influence of the Phase Composition of the Fe/Biochar Catalysts on the Composition of Fischer–Tropsch Synthesis Products: The Lapidus Theory of Bifunctional Catalytic Centers

Influence of the Phase Composition of the Fe/Biochar Catalysts on the Composition of Fischer–Tropsch Synthesis Products: The Lapidus Theory of Bifunctional Catalytic Centers

Effect of metal promoters on catalytic performance of Co/AC for higher alcohols synthesis from syngas

Shifting products of Fischer-Tropsch Synthesis (FTS) from paraffins to value-added higher alcohols receives great attention but remains great challenge. Herein, metal oxides of Mn, Zn, La and Zr are investigated as promoters to tune the activity and product distributions of Co/AC catalyst for syngas conversion. It is found that these promoters show different promotion effect on CO dissociation rate, the formation of Co2C phase and the alcohols selectivity. The formed Co2C/Co0 constitutes the dual active site for higher alcohols synthesis. The strongest CO dissociation rate is observed for Zn-promoted Co/AC catalyst, resulting in the highest activity and space-time yield (STY) of alcohols. The Mn promoter is most conducive to the formation of Co2C, but slightly decreases the activity. The similar CO dissociation rate and CO conversion are obtained over both Zr- and La-promoted Co/AC catalysts, but the Zr-promoted Co/AC catalyst exhibits the highest alcohols selectivity due to the function balance between CO non-dissociative insertion and CO dissociation.

Influence of the Phase Composition of the Fe/Biochar Catalysts on the Composition of Fischer–Tropsch Synthesis Products: The Lapidus Theory of Bifunctional Catalytic Centers

Supported iron catalysts based on a carbon-containing material, biochar obtained by the hydrothermal carbonization of biopolymers (cellulose and lignin), were studied. The catalytic systems showed high activity in the Fischer–Tropsch synthesis. A composition of C5+ liquid products, uncharacteristic for ironcontaining catalysts, characterized by high isoalkane content (up to 55%) was recorded. This fact was discussed in the context of the theory of bifunctional centers proposed by A.L. Lapidus with coworkers. It was suggested that the active centers of the test catalysts can be considered bifunctional (a carbide phase and an oxide phase). A correlation between the Fischer–Tropsch synthesis data on the test catalysts and the data obtained by Lapidus and coworkers on cobalt-containing catalysts was shown.

Operando characterisation of the products of Fischer-Tropsch synthesis in a fixed-bed reactor studied by magnetic resonance

Operando measurement of catalyst performance presents many difficulties as it is necessary to obtain measurements at reaction temperature and pressure and also at relevant length scales of multiple pellets to replicate the pellet-scale mass transport. Non-invasive measurement under such conditions is challenging. In this study we have developed an NMR/MRI compatible reactor that is of industrially-relevant scale and can operate at typical conditions for Fischer-Tropsch synthesis (FTS). The pilot-scale fixed-bed reactor (20 mm i.d.) used for FTS is operated at 220 °C and 37 bar and is packed with 1 wt % Ru/TiO2 catalyst pellets. Multiple magnetic resonance techniques have been developed and applied to achieve quantitative characterisation of product species including hydrocarbons, water, oxygenates and branched alkanes in pores. In addition to spatially-resolved measurements of molecular diffusion coefficients of the product species from which the carbon chain length of the saturated hydrocarbons can be determined, preliminary estimates of the relative amount of oxygenate and water species and branched saturated hydrocarbons present within the pore space of the catalyst are also determined using non spatially-resolved two-dimensional 1H T1-chemical shift and two-dimensional 1H double quantum filtered correlated spectroscopy (DQF-COSY), respectively. The concentrations of water and oxygenates detected inside the pores of catalyst pellets decrease when the feed H2/CO ratio decreases. The amount and extent of branching of saturated hydrocarbon species is observed to be higher than for the effluent wax product, most likely due to the effect of mass transfer limitation within the reactor. This work demonstrates that a toolbox of operando magnetic resonance techniques is available to characterise different product species of FTS from within catalyst pellets. The information provided by these techniques can give insight into how both catalyst and reactor can be optimised.

Formulation of KMoFe/CNTs catalyst for production of light olefins and liquid hydrocarbons via Fischer-Tropsch synthesis: Fixed-bed reactor simulation

Light olefins and C5+ are strategically important products of Fischer-Tropsch synthesis (FTS) over Fe catalysts. In the present work, FTS performance of 0.5K5Mo10Fe/CNTs (DOE 2) and 2 K0.5Mo30Fe/CNTs (DOE 5) catalysts was assessed in terms of CO conversion, C5+ selectivity, and C2-C4 selectivity under industrially relevant FTS conditions (H2/CO = 1.0; GHSV = 2000 h−1; T = 280 ℃; P = 4.13 MPa). The C2-C4 selectivity increased in DOE 2 catalyst to 51.2% with respect to DOE 5 catalyst (2.9%). Meanwhile, the selectivity toward C5+ hydrocarbons decreased from 93.1% in DOE 5 to 8.3% for DOE 2 catalyst. DOE 5 catalyst was more hydrophobic than DOE 2 as confirmed by the water contact angle measurement, lowering CO2 selectivity and water gas shift rate. H2-TPR and CO2-TPD indicated an increase in reducibility and basicity of DOE 5 compared with DOE 2 catalyst, which enhanced iron carbide formation and chain growth probability. The highest amount of metallic Fe in DOE 5 calcined and spent catalysts obtained by XPS and XAS spectra also suggested higher degree of carburization in DOE 5. Additionally, COMSOL Multiphysics software package was employed to provide a 2-dimensional simulation of the FTS fixed-bed reactor. Simulation results were validated using the experimental data for FTS over DOE 2 and DOE 5 catalysts. Effects of temperature on CO conversion as well as distribution of H2, CO, and ethylene were discussed. The simulation illustrated the effects of the fixed-bed reactor wall on both velocity and temperature profiles.

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.

Tuning Fischer-Tropsch synthesis product distribution toward light olefins over nitrided Fe-Mn bimetallic catalysts

A series of Fe-Mn bimetallic catalysts with various pretreatment atmosphere including H2, CO and alternatively NH3, were employed for the Fischer–Tropsch synthesis (FTS). The structure of Fe-Mn bimetallic catalysts was revealed by using multiple characterization techniques, where Mössbauer spectra was used to define the iron species. With direct pretreatment, the reduction efficiency is in the sequence of H2 > CO > NH3. Fe-Mn bimetallic catalysts pre-reduced by H2 that permit an easy nitrogenation. To correlate the phase compositions of spent catalysts with FTS performance, the individual contribution of Fe, iron carbides (χ-Fe5C2, ε-Fe2(.2)C and θ-Fe3C) and iron nitride (Fe2N) to hydrocarbon selectivity was deconvolved by linear regression. It was discovered that C2=-C4= selectivity was proportional to the content of epsilon-iron carbide, which was promoted by the doping with Mn and further nitriding treatment. Successfully nitrided Fe-Mn bimetallic catalysts exhibit a better stability of C2-C4 O/P along time on stream, while either direct CO treatment or NH3 treatment followed by CO treatment result in a rapid decent of C2-C4 O/P ratio against time. Furthermore, Mn enhances long-chain hydrocarbon selectivity and suppresses CH4 formation, whereas the nitrogenation inhibits the chain growth ability, concentrating the hydrocarbon selectivity into C2-C4 fraction. Hence, the nitrided Fe-Mn catalyst is able to maintain a high light olefin selectivity. This study highlights that nitrogenation could provide an opportunity to tune the C2-C4 olefins by optimizing the phase structure of Fe-Mn catalysts.

Carbon species on the surface of carbon-coated catalysts and their effects on Fischer-Tropsch synthesis products

Carbon coated cobalt core–shell catalysts with different coating thickness were prepared by acetylene dissociation at different temperatures, the carbon coating had significant cutting effects on the Fischer-Tropsch synthesis (FTS) products. Further, different carbon species remained on the surface of carbon coated catalysts with adjusting the hydrogenolysis temperature (250, 400, 600 and 700 °C, respectively). Accordingly, the catalyst structure was optimized, the selectivity of C1 ∼ C4 was reduced, while the CO conversion increased, the products in the range of C5 ∼ C12, C13 ∼ C20 and C5 ∼ C20 were obtained with high selectivity. The carbon species were discerned by elemental analysis, temperature programmed hydrogenation, Raman spectra, X-ray photoelectron spectroscopy, H2 temperature programmed reduction and H2 thermogravimetry. The roles of different carbon species in FTS were elucidated, and the relationships between carbon species and FTS products selectivity were studied in detail. The deposited carbon blocks the active center, while graphitic carbon does not block the active center, nor limit the conversion rate of CO, but only limits the diffusion of long chain products.

Determination of Kinetic Parameters of Fischer–Tropsch Synthesis in the Presence of a Granular Cobalt Catalyst

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.

Comprehensive understanding of iron-catalyzed Fischer–Tropsch synthesis product distribution with extensive reliable data

By integrating state-of-the-art characterization techniques, the work provided a more comprehensive perspective on FTS product distribution.

Boron-doped CN supported metallic Co catalysts with interfacial electron transfer for enhanced photothermal CO hydrogenation

Solar-driven Fischer-Tropsch synthesis (FTS) is a promising route to produce solar fuels of value-added hydrocarbons. Herein, an approach of boron doping in CN support to modulate the interfacial electronic structure of Co–BCN catalysts is developed to promote the yield of hydrocarbon products in photothermal FTS. Under light irradiation, the optimized Co–BCN catalyst delivers a hydrocarbon selectivity of 96.9 % at a CO conversion over 40 %, which is 4.3 and 10.2 times that of Co–CN and Co–C catalysts, respectively. Detailed characterizations demonstrate that the electron transfer between Co nano-metal and BCN support, where electronic structure at interface is modulated. The formation of electron-rich interface in Co–BCN could promote CO activation with assistance of H* and thus enhance the conversion of CO. This work not only paves the way for the modulation of interface electrons to enhance photothermocatalytic activity but also offers a promising strategy toward the rational design and preparation of highly efficient catalysts.

Carbon-encapsulated metallic Co nanoparticles for Fischer-Tropsch to olefins with low CO2 selectivity

Tuning Fischer-Tropsch synthesis products of metallic Co-based catalysts from paraffins to value-added olefins chemicals attracts great attention but remains challenging. Herein, we succeed in designing the carbon layers confined cobalt metal core-shell nanocatalyst (Co@C) via a reduction-carburization-pyrolysis (RCP) pretreatment of Co/SiO2, which exhibits highly efficient for Fischer-Tropsch to olefins (FTO) with negligible Water-Gas-Shift activity. At 250 °C and 5 bar, 56.4 % of olefins selectivity and limited CO2 selectivity (5.8 %) are achieved for Mn-promoted Co@C nanocatalyst with at least 200 h of stability running. The electronic effect of carbon layers and Mn promoter as well as the confinement structure tailor the local chemical environment and weaken the hydrogenation ability of Co metal sites, thus improving the selectivity toward olefins while largely reducing the formation of CH4 and CO2. This work develops an effective strategy for the rational design of highly active and stable metallic Co-based FTO catalysts with high carbon efficiency.

Barrier Dispersion-Based Coatings Containing Natural and Paraffin Waxes.

Petroleum, synthetic, and natural waxes have been used as hydrophobic bases for dispersions intended for use as barrier coatings for packaging paper. Oil-in-water dispersions with alkaline pH were prepared by a two-step homogenization procedure containing paraffin wax, with various characteristics, the Fischer–Tropsch synthesis product or beeswax. The size of the dispersed particles determined by dynamic light scattering depended on the type of hydrophobic base used and was in the range of 350–440 nm. The ability of dispersion particles in aggregation driven by electrostatic attraction, evaluated by Zeta potential analysis by electrophoretic light scattering, was from −26 to −50 mV. Static multiply light scattering was used for 30 days of stability assessment and helped to select the dispersion with a Sarawax SX70 wax base as the most stable. Dispersions were further used for coating the backing of kraft paper by the Meyer rod method. Coated paper with an applied coating of 6 g/m2 had very good hydrophobic properties (Cobb60 < 4 g/m2), sufficient strength properties, and air permeation, which enabled its application as a packaging material. The dispersions based on Sarawax SX70 wax were evaluated as the best coating for Mondi ProVantage Kraftliner 125 g/m2 backing paper. Good hydrophobic properties and strength properties indicate the possibility of using the SX70-based wax dispersion coating as a replacement for PFAS coatings in some applications.