High-temperature Fischer Tropsch Synthesis Research Articles

Coupling the high-temperature Fischer–Tropsch synthesis and the skeletal isomerization reaction at optimal operation conditions in the Power-to-Fuels process route for the production of sustainable aviation gasoline

Power-to-Fuels route for the production of aviation gasoline: stable operation of the coupled high-temperature Fischer–Tropsch synthesis and the skeletal isomerization reaction, at optimal operating conditions respectively.

Effect of alkaline-earth metals (Mg, Ca, Sr, and Ba) on precipitated iron-based catalysts for high-temperature Fischer-Tropsch synthesis of light olefins

For the high-temperature Fischer-Tropsch synthesis (HTFT) of light olefins (C2=-C4=), alkaline-earth metals (Mg, Ca, Sr, and Ba) modified FeMn catalysts were prepared using precipitation and impregnation methods. It was demonstrated that the electron-giving interaction of Ca, Sr, and Ba decreased the adsorption of H species while improving the dissociative adsorption of CO. This interaction resulted in the production of χ-Fe5C2, which increased CO conversion and C2=-C4= selectivity. Compared with Ca and Ba, the FeMnSr catalyst had the strongest CO dissociative adsorption capacity and the highest χ-Fe5C2 content with the best FTS performance. When Sr and Na were introduced simultaneously, the synergistic effect of Sr and Na inhibited the formation of θ-Fe3C and the aggregation of catalyst particles, and also increased the χ-Fe5C2 content. This synergistic effect resulted in the highest surface basicity of FeMnSrNa catalyst, the highest electron cloud density on the surface of Fe atoms, the weakest H species adsorption, the strongest CO dissociative adsorption, and the highest total amount of active iron carbide, which improved the FTS performance. The light olefins yield of FeMnSrNa catalyst (427.0 g/(h·kgCat)) was significantly higher than that of FeMnSr catalyst (341.4 g/(h·kgCat)) and FeMnNa catalyst (80.6 g/(h·kgCat)).

Optimization of coal-to-liquid processes; A way forward towards carbon neutrality, high economic returns and effective resource utilization. Evidences from China

As the world's largest consumer of coal, China is committed to developing a carbon–neutral coal industry. For this purpose, upgrading the carbon emission-intensive coal-chemical industries, such as coal-to-liquids (CTL) is imperative. This study develops a technical–economic framework to model and test four promising CTL upgrading processes. First and second processes involve low-temperature Fischer-Tropsch (FT) synthesis practices with larger gasifiers and air-separating units than the current level. Third, the process combines olefin and fuel co-production practices that utilize low- and high-temperature FT synthesis processes. Finally, the process produces both electricity and fuel by sending the tail gas of the synthesis process to an integrated cycle. Aspen Plus® is used to simulate the chemical processes, and the financial cost accounting model of the American Association of Cost Engineers is utilized to estimate the financial costs accurately. The results show that the upgraded processes can achieve an energy efficiency of more than 48 %, which is 6 % higher than the existing coal-to-oil process. Additionally, the break-even point is 2 %–14.45 % lower than the actual process, reducing carbon emissions by 2.78 %–10.34 %. According to these findings, the upgrade can help China reach its carbon neutrality targets and significantly contribute to global climate change and sustainable development goals.

Effect of alkalis (Li, Na, and K) on precipitated iron-based catalysts for high-temperature Fischer-Tropsch synthesis

Alkalis (Li, Na, and K) decorated FeMnZr catalysts prepared by coprecipitation and impregnation methods were used to investigate the effects of three alkali metal promoters and promoter loading (for Na and K) on the iron-based catalyst for high-temperature Fischer-Tropsch synthesis (HTFT). The results showed that alkalis donated electrons to iron species, which promoted CO dissociative adsorption while suppressing hydrogen adsorption, then boosted the selectivity to light olefins and the improvement was enhanced with the increase of the atomic number of alkali metals and the content of alkali metals. Moreover, compared to alkalis-free catalysts, alkalis-promoted catalysts facilitated the formation of χ-Fe5C2 and ɛ’-Fe2.2C. In alkalis decorated catalysts, the χ-Fe5C2 content decreased and the ɛ’-Fe2.2C content increased with increasing basicity of the catalyst surface. In addition, compared with χ-Fe5C2, ɛ’-Fe2.2C has a stronger CC coupling ability and promotes chain growth more. Compared to Li and Na promoters, K was easier to facilitate the formation of ɛ’-Fe2.2C due to its strongest basicity and CO dissociative adsorption ability. The lowest CH4 and highest C5+ selectivity were accompanied by the highest content of ɛ’-Fe2.2C on K-promoted catalysts, which suggested that ɛ’-Fe2.2C had outstanding CC coupling ability.

Effect of Preparation Conditions on Precipitated Iron-Based Catalysts for High-Temperature Fischer–Tropsch Synthesis of Light Olefins

Effect of Preparation Conditions on Precipitated Iron-Based Catalysts for High-Temperature Fischer–Tropsch Synthesis of Light Olefins

High-temperature Fischer–Tropsch synthesis over the Li-promoted FeMnMgOx catalysts

Fischer–Tropsch-to-Olefins (FTO) over iron-based catalysts is a promising process for the production of light olefins from a non-petroleum source. However, the catalytic mechanism is unclear because of the variation in the iron phase during the reduction and activation processes and the complex iron phase composition under the reaction conditions. A series of Li-promoted FeMnMgOx catalysts is synthesized using co-precipitation and impregnation methods, after which the effect of promoters on the evolution of the iron phase, chemisorption, and FTO performance are analyzed. The results demonstrate that Mg enhances dissociative CO adsorption and hydrogen adsorption, improving the FTO activity. Mg facilitates the dispersion of α-Fe2O3 and suppresses the carbonization, which weakens the chain propagation, encourages the formation of short-chain hydrocarbons, and increases the selectivity of light olefins. Li also enhances dissociative CO adsorption and increases CO conversion. Moreover, Li facilitates the formation of the ε'-Fe2.2C phase, which reveals a higher FTS activity and better C–C coupling ability than the χ-Fe5C2 phase. This results in a decrease in CO2 and increase in light olefins. At the optimal Li loading, the FeMnMg-0.75Li sample displays the highest space time yield of light olefins at 355 g/(kgcat·h).

Effect of the Zr promoter on precipitated iron-based catalysts for high-temperature Fischer–Tropsch synthesis of light olefins

FeMnxZr and FeMnxZr2Na catalysts prepared by coprecipitation and impregnation methods were applied to investigate the promoting effects of Zr on iron-based catalysts for high-temperature Fischer–Tropsch synthesis (HTFT).

Catalytic Activity of Thermolyzed [Co(NH3)6][Fe(CN)6] in CO Hydrogenation Reaction.

Currently, the processes of obtaining synthetic liquid hydrocarbons and oxygenates are very relevant. Fischer-Tropsch synthesis (FTS) is the most important step in these processes. The products of thermal destruction in argon of the mixture [Co(NH3)6][Fe(CN)6] and Al(OH)3 were used as catalysts for CO hydrogenation. The resulting compositions were studied using powder X-ray diffraction, IR spectroscopy, elemental analysis, SEM micrographs. The specific surface area, pore and particle size distributions were determined. It was determined that the DCS-based catalysts were active in the high-temperature Fischer-Tropsch synthesis. The effect of aluminum in the catalyst composition on the distribution of reaction products was revealed.

Active phases for high temperature Fischer-Tropsch synthesis in the silica supported iron catalysts promoted with antimony and tin

Fischer-Tropsch synthesis provides an important opportunity for utilization of biomass and plastic waste. Iron catalysts are the catalysts of choice for light olefin synthesis using Fischer-Tropsch reaction. In this paper, we investigate strong promoting effects of antimony and tin on the catalytic performance of silica supported iron Fischer-Tropsch catalysts using a combination of advanced and in-situ techniques. The catalyst doping with these elements added via impregnation results in a major increase in the reaction rate and much better catalyst stability. No enhancement of iron dispersion was observed after the promotion, while somewhat higher extent of iron carbidization was observed in the antimony promoted catalysts. Iron-bismuth bimetallic nanoparticles are detected by several techniques. In the working catalysts, the promoters are located in close proximity to the iron nanoparticles. The promotion leads to the 7–10 times increase in the intrinsic activity of iron surface sites due to their interaction with the promoters.

Direct Conversion of Syngas to Light Olefins through Fischer-Tropsch Synthesis over Fe-Zr Catalysts Modified with Sodium.

Fe–Zr–Na catalysts synthesized by coprecipitation and impregnation methods were implemented to investigate the promoting effects of Na and Zr on the iron-based catalyst for high-temperature Fischer–Tropsch synthesis (HTFT). The catalysts were characterized by Ar adsorption–desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, CO temperature-programmed desorption, H2 temperature-programmed desorption, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy (MES). The results indicated that Na changed the active sites on the catalyst surface for the CO and hydrogen adsorption, owing to the electron migration from Na to Fe atoms, which resulted in an enhanced CO dissociative adsorption and a decrease in hydrogen adsorption on the metallic Fe surface. The decreased H/C ratio on the catalyst surface accounted for the increased chain propagation and weakened hydrogenation of light olefins. Besides, Na could also facilitate the carbonization of catalysts and protect the iron carbide against oxidation, which provides more active sites for HTFT reaction and is beneficial to the C–C coupling. Zr could decrease the hematite crystallite size and stabilize the active phase to improve the HTFT activity. At an optimal Na loading of 1.0 wt %, the Fe–Zr–1.0Na catalyst exhibited the highest light olefin selectivity of 35.8% in the hydrocarbon distribution at a CO conversion of 95.2%.

Mn-Decorated CeO2 nanorod supported iron-based catalyst for high-temperature Fischer–Tropsch synthesis of light olefins

The synergistic effect between Mn and Ce can improve electrons transfer from Ce to Fe and the oxygen migration. The remarkable properties promote the dissociation of CO, suppress the hydrogenation, and improve the selectivity of light olefins.

Identification of efficient promoters and selectivity trends in high temperature Fischer-Tropsch synthesis over supported iron catalysts

In this work, 29 elements were evaluated as promoters for silica supported iron catalysts for high temperature Fischer-Tropsch synthesis using a high-throughput experimentation unit. The selected promoters include alkali/alkaline metals, transition metals, precious metals and lanthanides. Several general selectivity trends were observed and discussed. The selectivity enhancement to light olefins requires maintaining low selectivity to methane and light paraffins and at the same time, slowing the chain growth to the C5+ hydrocarbons.A major increase in Fischer-Tropsch rate principally due to higher intrinsic site activity, was observed over the catalysts promoted with metals with low melting points such as tin, antimony, bismuth and lead. These promoted catalysts also exhibited better stability. The effect of the promotion with tin and antimony on the olefin selectivity was not noticeable, while the presence of bismuth and lead results in the major enhancement of the selectivity to light olefins, lower methane and C2-C4 paraffin selectivities.

Effect of Operating Conditions of High-Temperature Three-Phase Fischer-Tropsh Synthesis Pilot Plant on Key Process Parameters

The possibility, in principle, of high-temperature three-phase Fischer-Tropsch synthesis, which is implemented in the presence of iron-containing catalytic dispersions in a bubble column reactor, is demonstrated. The catalytic system is activated in situ in a CO stream. It is proved that the particle size of the iron-containing dispersion used as the catalyst for this process depends on the precursor solution injection technique and in no case does it exceed 50 nm. It is shown that the described three-phase high-temperature Fischer-Tropsch synthesis method makes it possible to achieve high process parameters, such as target products yield up to 138 g/m3 with 90% selectivity of products formation. The properties of the developed catalyst enable it to perform for a prolonged period with high conversions without impairment of process selectivity.

Li-decorated Fe-Mn nanocatalyst for high-temperature Fischer–Tropsch synthesis of light olefins

Fe-Mn-Li nanocomposite particles were prepared using the combined urea hydrolysis and incipient wetness impregnation method. No surfactant or capping agents were involved in the preparation process, which ensured that this was low-cost and environmentally friendly method. In this study, the effects of urea hydrolysis temperature and Li amount on the catalyst structure, morphology, and particle size were analyzed combining various characterization techniques, including N2 adsorption–desorption, X-ray diffraction (XRD), H2 temperature-programmed reduction, CO2 temperature programmed desorption, CO temperature programmed desorption, X-ray photoelectron spectroscopy, scanning electron microscopy, and Mössbauer spectroscopy. The nanocatalyst synthesized at 140 °C (Fe-Mn-140) presented the largest specific surface area and highest selectivity for light olefins and the lowest selectivity for CO2 and CH4 of all Fe-Mn-x samples in this study. These findings were consistent with the results of the Mössbauer spectroscopy and XRD testing, where Fe-Mn-140 was determined to contain the maximum amount of χ-Fe5C2 and minimum amount of Fe3O4 after reaction of all Fe-Mn-x samples in this study. It was also determined that Li slightly restrained the reduction of iron oxides. In addition, Li increased the surface basicity of the catalysts, which reduced their selectivity for CH4 and light alkanes while increases those for light olefins and heavier hydrocarbons. Therefore, this study could lead to developing a facile and environmentally-friendly method for synthesizing iron-based nanocatalysts that present high activity and selectivity for light olefins for high-temperature Fischer–Tropsch synthesis processes.

Phase-controlled synthesis of thermally stable nitrogen-doped carbon supported iron catalysts for highly efficient Fischer-Tropsch synthesis

Iron-based nanoparticles with uniform and high particle dispersion, which are supported on carbon structures, have been used for various applications. However, their preparation still suffers from complicated synthesis involving multiple steps and from the high price of precursors and solvents. In the present work, a new carbon encapsulated iron-carbide nanoparticle supported on nitrogen-doped porous carbon (Fe5C2@C/NPC) structure was introduced. It was made using a simple solid-state reaction with sequential thermal treatments. Fe5C2@C/NPC is a highly active and stable catalyst for the high-temperature Fischer-Tropsch synthesis reaction. It showed very high hydrocarbon productivity (4.71 gHC·gcat−1·h−1) with high CO conversions (up to 96%).

Synergy of nanoconfinement and promotion in the design of efficient supported iron catalysts for direct olefin synthesis from syngas

Light olefins are important building blocks in chemical industry. High temperature Fischer-Tropsch synthesis provides a remarkable opportunity for direct synthesis of light olefins from syngas derived from a wide range of alternative feedstocks (biomass, organic or plastic wastes, natural gas, shale gas or coal). The present work focuses on the combined effects of the iron nanoconfinement, on the one hand, and promotion with bismuth and lead, on the other hand, on the structure and catalytic performance of iron catalysts supported by carbon nanotubes in high temperature Fischer-Tropsch synthesis. A wide range of techniques (TEM, XRD, TPR, synchrotron-based XPS, in-situ XANES and in-situ magnetic measurements) was used to characterize the catalysts. Iron carbidization proceeds much easier for iron species confined inside carbon nanotubes and promoted with Bi and Pb. Iron nanoconfinement inside carbon nanotubes combined with the promotion with Bi or Pb result in a 10-fold higher yield of light olefins. Nanoconfinement in carbon nanotubes mostly leads to better iron dispersion and stability, while the intrinsic activity is only slightly affected. Promotion with Bi and Pb results in a major increase in the site intrinsic activity in both confined and non-confined catalysts. Moreover, over the optimised promoted and confined catalysts, Fischer-Tropsch synthesis occurs even under atmospheric pressure with high conversion and enhanced selectivity to light olefins.

Size and promoter effects on iron nanoparticles confined in carbon nanotubes and their catalytic performance in light olefin synthesis from syngas

Light olefins are important products of high temperature Fischer-Tropsch synthesis over iron catalysts. In this paper, we found that the catalytic performance of iron catalysts was strongly affected by iron nanoparticle size, their encapsulation inside of carbon nanotubes and promotion with bismuth or lead. The presence of promoters and iron nanoparticle confinement leads to a major increase in the reaction rate. A gradual increase in the TOF numbers with the increase in the iron nanoparticle sizes from 2.5 to 12 nm was observed at both 1 and 10 bar over the carbon nanotubes containing encapsulated monometallic or Bi- or Pb-promoted iron nanoparticles. The size of monometallic iron nanoparticles encapsulated in carbon nanotubes does not show any noticeable effect on the light olefin selectivity, while in the Bi- and Pb-promoted catalysts, the light olefin selectivity was higher over smaller encapsulated iron nanoparticles and decreased with the increase in the nanoparticle size. The stability of iron nanoparticles versus sintering was also improved by the encapsulation.

Preparation of Iron Carbides Formed by Iron Oxalate Carburization for Fischer–Tropsch Synthesis

Different iron carbides were synthesized from the iron oxalate precursor by varying the CO carburization temperature between 320 and 450 °C. These iron carbides were applied to the high-temperature Fischer–Tropsch synthesis (FTS) without in situ activation treatment directly. The iron oxalate as a precursor was prepared using a solid-state reaction treatment at room temperature. Pure Fe5C2 was formed at a carburization temperature of 320 °C, whereas pure Fe3C was formed at 450 °C. Interestingly, at intermediate carburization temperatures (350–375 °C), these two phases coexisted at the same time although in different proportions, and 360 °C was the transition temperature at which the iron carbide phase transformed from the Fe5C2 phase to the Fe3C phase. The results showed that CO conversions and products selectivity were affected by both the iron carbide phases and the surface carbon layer. CO conversion was higher (75–96%) when Fe5C2 was the dominant iron carbide. The selectivity to C5+ products was higher when Fe3C was alone, while the light olefins selectivity was higher when the two components (Fe5C2 and Fe3C phases) co-existed, but the quantity of Fe3C was small.

Light hydrocarbons to BTEX aromatics over hierarchical HZSM-5: Effects of alkali treatment on catalytic performance

Abstract Three HZSM-5 zeolites with initial Si/Al ratios of 15, 25, and 40 were treated using an alkali solution to establish a hierarchical micropore-mesopore interconnected structure in alkali-treated zeolite samples Z15-AT, Z25-AT, and Z40-AT, respectively. The aim of the present work is to improve the catalytic stability in the aromatization of ethylene, a model compound representing the light hydrocarbons produced by the high-temperature Fischer‒Tropsch synthesis. By using characterization techniques, such as XRD, ICP, N2 adsorption/desorption, TEM, 27Al and 29Si MAS/NMR, NH3-TPD, Pyridine-IR, and TGA, we analyzed the textural property and acidity of the fresh catalysts, as well as the coke formation rate of the spent catalysts. The catalytic stability was shown to be successfully enhanced in the light hydrocarbon aromatization and the initial Si/Al ratio is a crucial factor for the mesopore formation and the catalytic performance. Among the prepared zeolite samples, the Z25-AT sample seemed to be the most suitable catalyst owing to its significant enhancement in the catalytic stability. The main reason for the improved stability by alkali treatment seems to be that the hierarchical pore structure facilitates the mass transfer and provides the additional space for carbon deposition as well, thus weakening the pore blocking and prolongs the lifetime of the catalyst.

A durable nanocatalyst of potassium-doped iron-carbide/alumina for significant production of linear alpha olefins via Fischer-Tropsch synthesis

Improvement of activity, selectivity, and stability of the catalyst used in Fischer-Tropsch synthesis (FTS) to produce targeted hydrocarbon products has been a major challenge. In this work, the potassium-doped iron-carbide/alumina (K-Fe5C2/Al2O3), as a durable nanocatalyst containing small iron-carbide particles (∼ 10 nm), was applied to high-temperature Fischer-Tropsch synthesis (HT-FTS) to optimize the production of linear alpha olefins. The catalyst, suitable under high space velocity reaction conditions (14–36 N L gcat−1 h−1) based on the well-dispersed potassium as an efficient base promoter on the active iron-carbide surface, shows very high CO conversion (up to ∼90%) with extremely high activity (1.41 mmolCO gFe−1 s−1) and selectivity for C5–C13 linear alpha olefins.