Fischer–Tropsch Synthesis Rate Research Articles

Design and Technoeconomic Analysis of Fischer–Tropsch Fixed‐Bed Synthesis with Cobalt‐Based Catalysts

A multitubular Fischer–Tropsch (FT) reactor with gas recycle and a cobalt‐based catalyst is simulated by a 2D fixed‐bed model that considers the complex kinetics, all relevant mass and heat transfer aspects, and also the influence of the changing molar flow rate by the FT reaction, of pressure drop, and of formation of steam, which decreases the reaction rate of FT synthesis. Optimal values of gas velocity and single‐tube diameter and length are determined by a technoeconomic analysis. The comparison of the data of the FT reactor modeled in this work with data of commercial reactors indicates that the used model reflects reality well and is reliable. A superficial gas velocity of 0.5 m s−1, a tube diameter of 3 cm, and a length in a range of 12–20 m are appropriate for a high production rate of C2+‐hydrocarbons with minimal operating costs of the FT unit, even for a large range of the electricity price from 0.06 to 0.3 € kWh−1.

Pyrolysis of Rice husk, Coconut shell, and Cladophora glomerata algae and application of the produced biochars as support for cobalt catalyst in Fischer–Tropsch synthesis

The performance of bio chars prepared from Rice husk, Coconut shell, and Cladophora glomerata algae as Fischer–Tropsch synthesis (FTS) cobalt catalyst support is investigated. The biochars are synthesized through the pyrolysis process. The three substrates were activated precisely at a specific temperature and time. 15 wt% cobalt catalysts were prepared by impregnation method. The physicochemical properties of catalysts were assessed using different techniques. The activity and selectivity of catalysts were studied in a fixed bed micro reactor at 220 °C, H2/CO ratio of 2, feed flow rate of 60 mL/min, 2 MP pressure and 14–16 h reduction on 400 °C. The catalytic performance of biochars supported cobalt catalysts was evaluated and compared with a γ-Alumina supported industrial catalyst. The modified algae biochar supported cobalt catalyst showed the highest FTS rate of 0.345 g HC/(g cat. h) and 67% CO conversion. While, C5+ liquid hydrocarbons selectivity showed a slight decrease.

Loading and promoter effects on the performance of nitrogen functionalized graphene nanosheets supported cobalt Fischer-Tropsch synthesis catalysts

The effects of nitrogen functional groups on graphene surface and also the effects of cobalt loading and ruthenium promoter on the performance of nitrogen functionalized graphene nanosheets (N-GNS) supported cobalt catalysts in Fischer–Tropsch synthesis (FTS) are investigated. A 15 wt% Co/PGNS catalyst, a series of Co/N-GNS (15–30 wt% loading) and ruthenium promoted catalysts (25 wt% Co,0.5 wt% Ru/N-GNS and 25 wt% Co,0.5 wt% Ru/PGNS) were prepared by impregnation method. The purified GNS and functionalized GNS and all catalysts were characterized by Raman spectroscopy, FTIR, SEM, EDS, ICP, BET, TEM, XRD and TPR. The catalysts assessed in FTS in a fixed bed micro-reactor at 220 °C, 1.8 Mpa and H2/CO ratio of 2. Functionalization of GNS shifted the TPR reduction peaks to lower temperature, increased the dispersion of cobalt particles and increased the percentage CO conversion from 70.6% to 74.5%. Increasing the cobalt loading resulted in increasing the average cobalt cluster size, improvements in the reducibility of Co3O4. The maximum FTS activity for N-GNS supported catalyst is achieved at 30 wt % cobalt loading. The C5+ selectivity for the 30 wt % cobalt catalyst was higher than that of the 15 wt % Cobalt catalyst. Addition of 0.5 wt%Ru increased the FTS rate (gCH/(gcat·h)) from 0.377 to 0.412 and the liquid products selectivity from 86.5% to 91.2%.

Effects of Functionalization of Carbon Nanotubes on Activity and Selectivity of Co/CNT Catalysts in Fischer-Tropsch Synthesis

The Fischer–Tropsch Synthesis (FTS) activities of cobalt-based catalysts supported on carbon nanotubes (CNTs) and functionalized carbon nanotubes (FCNTs) are investigated in this work. The cobalt-based catalysts are synthesized by the reverse micro-emulsion technique using a non-ionic surfactant, and characterized by the Brunauer-Emmett-Teller, X-ray diffraction, H2 chemisorption, temperature program reduction, and transmission electron microscopy techniques. The activities of the synthesized catalysts are evaluated in terms of the FTS production rate (g produced hydrocarbons /g.cat./h) and selectivity (percentage of the CO converted to hydrocarbon products). According to the TEM results, the synthesized cobalt nanoparticles have a narrow size distribution and are mostly confined inside the functionalized CNTs (FCNTs) . These nanoparticles are highly reducible as evidenced by the reduction peaks of the FCNT catalyst shifting to low temperatures. In comparison to non-functionalized CNT, FCNT increases the FTS rate and CH4 selectivity and decreases the C5+ selectivity as a catalytic support. In addition, the FCNT support preserves the high dispersion and reducibility of cobalt, which can be attributed to the hydrogen spill-over effect of the functional groups present on the CNT surface.

Design of ultra-active iron-based Fischer-Tropsch synthesis catalysts over spherical mesoporous carbon with developed porosity

Iron-based Fischer-Tropsch synthesis (FTS) has received renewable interests due to the gradual depletion of crude oil resources and its flexible product adjustment from lower olefins to long-chain hydrocarbons. However, one of the main challenges of iron-based FTS catalysts is the relative lower activity or productivity (per gram catalyst) at low or middle temperature. In this work, ultra-active iron-based FTS catalysts (Fe/SMC) were developed by loading iron over spherical mesoporous carbon (SMC) with huge porosity. The large pore volume (2.22 cm3/g) and high specific surface area (767 m2/g) of SMC allowed the high iron loading (up to 50 wt%) with proper dispersion. Weak C-Fe interaction was observed in the Fe/SMC catalysts, which was favorable for the reduction of iron and its further carburization to form more active sites of FTS. Activity tests showed that the Fe/SMC catalysts exhibited ultra-high activities in FTS. With the increase of iron loadings (30–50 wt%), the FTS rates (FTY, mmol CO/(h·g cat.)) of Fe/SMC catalysts increased due to the larger iron surfaces exposed at higher iron loadings. Small amount of K promoter significantly enhanced the FTY and apparent turnover frequency (TOF, S−1) of the Fe/SMC catalysts. The hydrocarbon productivity of K-promoted catalyst (40FeK/SMC) was up to 0.91 g HC/(h·g cat.) (260 °C, H2/CO = 1, 2 MPa), much higher than that of any other supported or unsupported iron-based FTS catalysts reported at similar reaction conditions. The results obtained in this work will open a new avenue for the development of highly active iron-based FTS catalysts.

Effect of Drying Temperature on Iron Fischer-Tropsch Catalysts Prepared by Solvent Deficient Precipitation

A novel solvent deficient precipitation (SDP) method to produce nanoparticles was studied for its potential in Fischer-Tropsch synthesis (FTS) catalysis. Using Fe(NO3)3·9H2O as the iron-containing precursor, this method produces ferrihydrite particles which are then dried, calcined, reduced, and carbidized to form the active catalytic phase for FTS. Six different drying profiles, including final drying temperatures ranging between 80 and 150°C, were used to investigate the effect of ammonium nitrate (AN), a major by-product of reaction between Fe(NO3)3·9H2O and NH4HCO3 in the SDP method. Since AN has two phase-transitions within this range of drying temperatures, three different AN phases can exist during the drying of the catalyst precursors. These AN phases, along with physical changes occurring during the phase transitions, may affect the pore structure and the agglomeration of ferrihydrite crystallites, suggesting possible reasons for the observed differences in catalytic performance. Catalysts dried at 130°C showed the highest FTS rate and the lowest methane selectivity. In general, better catalytic performance is related to the AN phase present during drying as follows: phase III > phase II > phase I. However, within each AN phase, lower drying temperatures led to better catalytic properties.

Fischer–Tropsch synthesis and water gas shift kinetics for a precipitated iron catalyst

A large number of kinetic data points (83 sets) was obtained over a wide range of CO conversion (7–90%), pressure (1.3–2.5MPa) and H2/CO ratio (0.67–1.5) with an iron catalyst (100 Fe/5.1 Si/1.25K). The kinetics of the catalyst in the low (XCO<70%) and high conversion (XCO>70%) regions were studied separately. Twenty six Fischer–Tropsch synthesis (FTS) and water gas shift (WGS) kinetic models were tested and discriminated. Water and CO2 inhibition was evaluated. While all thirteen FTS models gave a satisfactory fit, the new FTS models that included CO2 inhibition surpassed the others. Water inhibition of the FTS rate was insignificant over both low and high conversion ranges. For the WGS kinetics of the iron catalyst, a newly constructed empirical model and one from the literature provided the best fits of the WGS rates, while nine mechanistic models and one power law WGS model were unable to satisfactorily fit the WGS kinetic data. Water did not significantly limit the WGS rate and CO2 only inhibited the rate at high CO conversions. The equations obtained for the low and high CO conversion ranges varied greatly. The errors for the models for 85% of the FTS and WGS data points were less than 10%, and the errors of the remaining points fell in the range of 10–15%.

Effect of H2S in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst

The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270°C, 1.3MPa, H2/CO=0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase reactor. The used Fe catalysts were characterized by XRD, Mössbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1ppm H2S in the feed. Co-feeding of 0.1ppm H2S in syngas for 70h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270°C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260°C and increased further to 13.5 at 230°C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mössbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230°C), and similar M/S ratios (13.5–15.0) were obtained.

Role of water-gas-shift reaction in Fischer–Tropsch synthesis on iron catalysts: A review

Water-gas-shift (WGS) reaction plays a significant role in industrial application of Fischer–Tropsch synthesis (FTS) for coal-to-liquid (CTL) processes with iron-based catalysts. This reaction provides necessary hydrogen for synthesis gas with low H2/CO molar ratio, and has influence on concentrations of reactants, water and carbon dioxide, which in turn has effect on product distribution, rate of FTS and catalyst deactivation. We provide information on the effect of process conditions (H2/CO feed ratio, reaction temperature and pressure), syngas conversion, and catalyst composition and activation procedure on the WGS activity. H2/CO consumption (or usage) ratio and the exit H2/CO ratio vary with conversion and the extent of WGS reaction. The extent of variation is much greater for H2/CO feed ratios greater than 1.7, than it is for the CO rich syngas (H2/CO=0.5–1). This in turn places limits on maximum practical single pass conversion which can be achieved with different feed compositions and results in different types of operation (low single pass conversion with tail gas recycle, and high once through single pass conversion).

Role of ZrO2 in Promoting the Activity and Selectivity of Co-Based Fischer–Tropsch Synthesis Catalysts

The effects of Zr promotion on the structure and performance of Co-based Fischer–Tropsch synthesis (FTS) catalysts were investigated. Inclusion of Zr in the catalysts was found to increase the FTS turnover frequency and the selectivity to C5+ hydrocarbons and to decrease the selectivity to methane under most operating conditions. These improvements to the catalytic performance are a function of Zr loading up to an atomic ratio of Zr/Co = 1.0, above which the product selectivity is insensitive to higher concentrations of the promoter. Characterization of the Co nanoparticles by different methods demonstrated that the optimal Zr loading corresponds to half monolayer coverage of the Co surface by the promoter. Measurements of the rate of FTS at different pressures and temperatures established that the kinetics data for both the Zr-promoted and unpromoted catalysts are described by a two-parameter Langmuir–Hinshelwood expression. The parameters used to fit this rate law to the experimental data indicate that ...

Photocatalytic Fischer–Tropsch Synthesis on Graphene-Supported Worm-Like Ruthenium Nanostructures

Fischer–Tropsch synthesis (FTS) converts carbon monoxide and hydrogen to liquid fuels and chemicals and is usually operated under high temperature ranges, which results in an evident increase of energy consumption and CO2 emission. A photocatalytic FTS route was proposed to efficiently harvest solar energy. Worm-like ruthenium nanostructures dispersed on graphene sheets can effectively catalyze FTS at mild conditions (150 °C, 2.0 MPa H2, and 1.0 MPa CO) under irradiation of visible light and achieve a catalytic activity as high as 14.4 molCO·molRu–1·h–1. The reaction rate of FTS can be enhanced by increasing the irradiation intensity or decreasing the irradiation wavelength. The work provides a green and efficient photocatalytic route for FTS.

Efficient hierarchically structured composites containing cobalt catalyst for clean synthetic fuel production from Fischer–Tropsch synthesis

We report a straightforward preparation method to synthesize hierarchical composite consisting of TiO2-coated multi-walled carbon nanotubes (CNTs) decorating a macroscopic host structure of α-Al2O3. The obtained composite possesses moderate specific surface area and very open porous structure, as well as moderate interaction with active sites, which significantly improve the cobalt nanoparticles dispersion and the mass diffusion during the reaction. The Co/TiO2/CNT-α-Al2O3 (CoTiCNTA) catalyst is then used in the Fischer–Tropsch synthesis (FTS) process. This hierarchical catalyst achieves a FTS rate to C5+ of 0.80gC5+gcat−1h−1 along with a long-chain hydrocarbons (C5+) selectivity of 85%, which can be pointed out as the most outstanding noble promoter-free catalyst for the FTS process. The as-synthesized catalyst also exhibits an extremely high stability as a function of time on stream which is also one of the prerequisites for the development of future FTS catalysts, especially for the Biomass-to-Liquids process where trace amount of impurities and/or moisture could have an impact on the catalyst stability. The present work also introduces a new investigation methodology based on the use of zero field 59Co NMR, which allows one to map in a precise manner the cobalt active phase distribution and to correlate it with the FTS performance. It is expected that such technique would be extremely helpful for the understanding of the catalyst structure–performance relationship and for future optimization in the FTS process as well as in other fields of investigation where cobalt particles are involved.

Enhancement of activity, selectivity and stability of CNTs-supported cobalt catalyst in Fischer–Tropsch via CNTs functionalization

Functionalization of carbon nanotubes (CNTs) was performed, during preparation of Fischer–Tropsch synthesis (FTS) cobalt nanocatalysts, to modify the surface properties of CNTs support. Common CNTs and functionalized CNTs supported cobalt nanocatalysts were prepared using microemulsion technique with cobalt loading of 15wt%. The catalysts were characterized by Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), temperature program reduction (TPR), H2 chemisorption, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. Most of the cobalt particles were homogeneously distributed inside the tubes and the rest on the outer surface of the functionalized CNTs. Functionalization of CNTs shifted the TPR reduction peaks to lower temperatures, improved the reduction degree, and increased the dispersion of cobalt particles. The proposed cobalt catalyst supported on functionalized CNTs increased the FTS rate (g HC/gcat./h), and percentage CO conversion from 0.1476, and 32.4% to 0.24, and 54%, respectively. Catalysts supported on functionalized CNTs showed better stability.

Enhancement of ruthenium-promoted Co/CNTs nanocatalyst performance using microemulsion technique

BackgroundRuthenium-promoted cobalt nanocatalysts that are supported by carbon nanotubes (CNTs) are prepared using impregnation and microemulsion techniques. Ruthenium loadings were varied from 0 to 1 wt% while the amount of cobalt was fixed at 15 wt%. The nanocatalysts were extensively characterized by different methods and their activity and selectivity in Fischer–Tropsch synthesis (FTS) have been assessed in a fixed-bed microreactor. The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method.ResultsVery narrow particle size distribution has been produced by the microemulsion technique. According to the transmission electron microscopy, pictures small Co particles (2–7 nm) are mostly confined inside the CNTs. Ruthenium increased the percentage reduction of the unpromoted catalyst by a factor of 25. Compared with the catalysts prepared by impregnation, using microemulsion technique with water-to-surfactant ratio of 0.5 which decreased the average cobalt oxide particle sizes to 4.8 nm, the percentage of dispersion is almost doubled and the percentage of reduction is increased by 28.ConclusionsAddition of ruthenium increased the percentage conversion and C5+ selectivity of the unpromoted catalyst by a factor of 22.6 and 7, respectively. Activity and selectivity were found to be dependent on the catalyst preparation method and water-to-surfactant ratio (as well as on cobalt particle sizes). The percentage of CO conversion and FTS rate increased from 59.09 to 75.05 and 0.291 to 0.372 g HC/g cat/h, respectively, while the C5+ liquid hydrocarbons selectivity decreased slightly.

Enhancement of bimetallic Fe-Mn/CNTs nano catalyst activity and product selectivity using microemulsion technique

Bimetallic Fe-Mn nano catalysts supported on carbon nanotubes (CNTs) were prepared using microemulsion technique with water-to-surfactant ratios of 0.4–1.6. The nano catalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis (FTS) have been assessed in a fixed-bed microreactor. The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method. Very narrow particle size distribution has been produced by the microemulsion technique at relatively high loading of active metal. TEM images showed that small metal nano particles in the range of 3–7 nm were not only confined inside the CNTs but also located on the outer surface of the CNTs. Using microemulsion technique with water to surfactant ratio of 0.4 decreased the average iron particle sizes to 5.1 nm. The reduction percentage and dispersion percentage were almost doubled. Activity and selectivity were found to be dependent on the catalyst preparation method and average iron particle size. CO conversion and FTS rate increased from 49.1% to 71.0% and 0.144 to 0.289 gHC/(gcat·h), respectively. While the WGS rate decreased from 0.097 to 0.056 gCO2/(gcat·h). C5+ liquid hydrocarbons selectivity decreased slightly and olefins selectivity almost doubled.

Enhancement of ruthenium-promoted Co/CNT nanocatalyst performance using microemulsion technique

Background: Ruthenium-promoted cobalt nanocatalysts that are supported by carbon nanotubes (CNTs) are prepared using impregnation and microemulsion techniques. Ruthenium loadings were varied from 0 to 1 wt.% while the amount of cobalt was fixed at 15 wt.%. The nanocatalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis (FTS) have been assessed in a fixed-bed microreactor. The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method. Results: Very narrow particle size distribution has been produced by the microemulsion technique. According to the transmission electron microscopy, pictures small Co particles (2 to 7 nm) are mostly confined inside the CNTs. Ruthenium increased the percentage reduction of the unpromoted catalyst by a factor of 25. Compared with the catalysts prepared by impregnation, using microemulsion technique with water-to-surfactant ratio of 0.5 which decreased the average cobalt oxide particle sizes to 4.8 nm, the percentage of dispersion is almost doubled and the percentage of reduction is increased by 28. Conclusions: Addition of ruthenium increased the percentage conversion and C5 selectivity of the unpromoted catalyst by a factor of 22.6 and 7, respectively. Activity and selectivity were found to be dependent on the catalyst preparation method and water-to-surfactant ratio (as well as on cobalt particle sizes). The percentage of CO conversion and FTS rate increased from 59.09 to 75.05 and 0.291 to 0.372 gr HC/gr cat/h, respectively, while the C5 liquid

Rate Expression of Fischer-Tropsch Synthesis Over Co-Mn Nanocatalyst by Response Surface Methodology (RSM)

The effect of operating conditions (temperature and the partial pressures of H2 and CO) on the reaction rate of Fischer-Tropsch synthesis (FTS) were investigated by carrying out experiments according to a Box-Behnken design (BBD), and were mathematically modeled by using response surface methodology (RSM). The catalyst used was a nano-structured cobalt/manganese oxide catalyst, which was prepared by thermal decomposition. The rate of synthesis was measured in a fixed-bed micro reactor with <TEX>$H_2/CO$</TEX> molar feed ratio of 0.32-3.11 and reactor pressure in the range of 3-9.33 bar at space velocity of <TEX>$3600h^{-1}$</TEX> and a temperature range of 463.15-503.15 K, under differential conditions (CO conversion below 2%). The results indicated that in the present experimental setup, the temperature and the partial pressure of CO were the most significant variables affecting reaction rate. Based on statistical analysis the quadratic model of reaction rate of FTS was highly significant as p-value 0.0002.

Thermodynamic analysis of nanoparticle size effect on kinetics in Fischer–Tropsch synthesis by lanthanum promoted iron catalyst

The kinetic parameters of the Fischer–Tropsch synthesis (FTS) on iron catalyst are analyzed by size-dependent thermodynamic method. A Langmuir–Hinshelwood kinetic equation is considered for evaluation of catalytic activity of lanthanum promoted iron catalyst. A series of unsupported iron catalysts with different particle sizes were prepared via microemulsion method. The experimental results showed that catalyst activity pass from a maximum value by increasing the iron particle size. Also, data presented that iron particle size has considerable effects on adsorption parameters and FTS rates. The ratio of surface tension (σ) to nanoparticle radius (r) is important in FTS reaction on iron catalyst. Finally, the results showed that by increasing of iron particle size from 18 to 45 nm the activation energies of catalysts and heats of adsorption of catalysts as two main parameters of FTS reaction increased from 89 to 114 kJ/mol and from 51 to 71 kJ/mol, respectively.

Functional group effect on carbon nanotube (CNT)-supported cobalt catalysts in Fischer–Tropsch synthesis activity, selectivity and stability

The influence of cobalt crystallite size on catalyst performance in Fischer–Tropsch synthesis (FTS) has been investigated using functionalized carbon nanotube (CNT)-supported catalyst. The catalysts were synthesized by the core reverse micelle reactions with cobalt crystallites of various sizes. It has been shown that crystallite size is dependent to the water-to-surfactant ratio (3–10) used for the catalyst preparation. The catalysts were characterized by Brunauer–Emmett–Teller method (BET), X-ray diffraction (XRD), H2 chemisorption, temperature program reduction (TPR), and transmission electron microscopy (TEM). According to TEM analysis, small cobalt crystallites size (3–8nm) synthesized by microemulsion technique have a very narrow size distributions, and they were mostly confined inside the functionalized CNT. The deposition of cobalt nanoclusters synthesized by microemulsion technique on the functionalized CNT, shift the reduction peaks to a low temperature, indicating higher reducibility for uniform cobalt crystallites. The catalyst prepared with functionalized CNT using proposed microemulsion technique, increased the FTS rate from 0.64 to 0.78g HC/g cat./h, C5+ selectivity increased 7.4% and CH4 selectivity decreased 44%, compared to that catalyst prepared on common CNT.

Size-dependent studies of Fischer–Tropsch synthesis on iron based catalyst: New kinetic model

In this study the effect of catalyst nanoparticle size on the Fischer–Tropsch synthesis (FTS) activity is investigated on iron catalyst. A series of iron oxide particles doped by adding cupper and lanthanum were prepared as a catalyst via precipitation by microemulsion method. Because of the role of iron carbide in FTS reaction by iron catalysts, the iron carbide particle sizes was evaluated after activation and considered as active phase in this paper. The catalytic results indicated that FTS activity increased and passed through a maximum when the iron particle size increased. A size-dependent kinetic model for FTS rates was developed using a thermodynamic analysis method. The model parameters measured by experimental results and the effect of various active sizes on these parameters was evaluated. Calculated size dependent model parameters were employed for evaluation of surface tension energy (σ) for iron catalyst and size-independent activation energy for FTS reaction.