For Fischer-Tropsch Synthesis Reaction Research Articles

Computational fluid dynamics simulation of Fischer-Tropsch synthesis coupled with a novel reaction kinetics using trimetallic catalyst over a biomass-based support

A mathematical modeling based on the computational fluid dynamics (CFD) was performed in this work. The reactive flow behavior in a tubular reactor was modeled for Fischer-Tropsch synthesis (FTS) using a novel trimetallic catalyst supported on a low-cost and renewable carbonaceous material. The fixed bed reactor was simulated as a porous media using a commercial software package (COMSOL Multiphysics). In this study, major attention has been paid to the species transport and reaction kinetics, as a fundamental stage in CFD simulation of FTS. The reaction kinetics was evaluated using Eley-Rideal theory assuming the molecular adsorption of CO based on the enol mechanism. Furthermore, the products distribution was accounted in the kinetics study by defining a mathematical expression and the kinetics parameters were optimized using genetic algorithm (GA). The activation energy and heat of H2 adsorption were estimated as 62.63 and −29.52 kJ/mol, respectively. The role of operational conditions was critically evaluated on the partial pressure profiles of the species, and the CFD results were validated with the experimental data. While increasing total pressure improved the partial pressure of C5+ hydrocarbons to 1.2 bar, increasing temperature to 310 °C limited the chain growth. The employed modeling and novel catalyst design can provide promising overview of the FTS reaction mechanism and products selectivity in fixed bed reactors.

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 %.

Alumina Coated Silica Nanosprings (NS) Support Based Cobalt Catalysts for Liquid Hydrocarbon Fuel Production From Syngas.

The effects of Al2O3 coating on the performance of silica nanospring (NS) supported Co catalysts for Fischer–Tropsch synthesis (FTS) were evaluated in a quartz fixed-bed microreactor. The Co/NS-Al2O3 catalysts were synthesized by coating the Co/NS and NS with Al2O3 by an alkoxide-based sol-gel method (NS-Al-A and NS-Al-B, respectively) and then by decorating them with Co. Co deposition was via an impregnation method. Catalysts were characterized before the FTS reaction by the Brunauer–Emmett–Teller (BET) method, X-ray diffraction, transmission electron microscopy, temperature programmed reduction, X-ray photoelectron spectroscopy, differential thermal analysis and thermogravimetric analysis in order to find correlations between physico-chemical properties of catalysts and catalytic performance. The products of the FTS were trapped and analyzed by GC-TCD and GC-MS to determine the CO conversion and reaction selectivity. The Al2O3 coated NS catalyst had a significant affect in FTS activity and selectivity in both Co/NS-Al2O3 catalysts. A high CO conversion (82.4%) and Σ > C6 (86.3%) yield were obtained on the Co/NS-Al-B catalyst, whereas the CO conversion was 62.8% and Σ > C6 was 58.5% on the Co/NS-Al-A catalyst under the same FTS experimental condition. The Co/NS-Al-A catalyst yielded the aromatic selectivity of 10.2% and oxygenated compounds.

Al2O3–FSM16-supported cobalt catalyst: a promising novel Fischer–Tropsch synthesis catalyst

High specific surface area ordered meso-porous solid (FSM16) was synthesized by using the organic template method. The surface acidity of solid (FSM16) was modified significantly with the addition of alumina content by impregnation of alumina nitrate aqueous solution with Si/Al molar ratios of 10. Al2O3–FSM16 and conventional γ-alumina-supported cobalt catalysts were introduced for Fischer–Tropsch synthesis (FTS). The catalysts were prepared using wet impregnation with a cobalt loading of 15.0 wt% and characterized by ICP, TPR, BET, XRD, TEM, NH3-TPD, TGA and H2 chemisorptions. Finally, the activity, selectivity and stability of the catalysts were assessed in FTS. The characterizations clearly confirmed that morphology of the Al2O3–FSM16 support (surface area, pore volume, pore size distribution and crystallite phase) can affect the catalyst performances. The proposed 15 wt% Co/Al2O3–FSM16 catalyst has shown surprising stability during 120 h continuous of FTS reaction and also at first 24 h of test run, increased the FTS rate from 0.15 to 0.34 g HC/gcat./h, CO conversion by about 68%; also the C5+ hydrocarbons increased, compared to that prepared by conventional γ-alumina support (Conndea Vista Catalox B g-alumina).

Rapid Online Fischer–Tropsch Reaction Monitoring using a Modified Frontier Tandem Micro‐Reactor GC–MS System

Conventional laboratory facilities used for Fischer–Tropsch (FT) catalyst evaluation usually consist of a reactor that is connected to an online gas chromatograph (GS). This arrangement is characterized by longer response times that make it difficult to acquire early reaction dynamics, which are crucial to the understanding of long‐term catalyst performance. This article describes how the modification of a Frontier Single micro‐Reactor, interfaced to a gas chromatograph–mass spectrometer (GC–MS) system, can facilitate rapid evaluation of catalysts for FT synthesis reaction. The study has been performed using an Ru/SBA‐15 catalyst prepared by reduction of RuCl3 using NaBH4 and deposition on a synthesized mesoporous SBA‐15 support and characterized using Brunauer–Emmett–Teller, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, temperature‐programmed reduction, and X‐ray diffraction techniques. The system was successfully modified to perform catalyst evaluation in batch and real‐time modes. Unlike conventional FT setups, which require extended reaction times to generate the Anderson–Schulz–Flory plot and the chain growth probability (α), the modified system in this study allows the determination of product distribution and alpha value in less than 30 min from the start of the reaction. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13079, 2019

Investigations on the effect of reaction parameters over Fe/Cu/K catalyst for the production of selective range of liquid hydrocarbon

Effect of reaction conditions were investigated for Fischer-Tropsch (FT) synthesis process over Fe/Cu/K./ $$\hbox {SiO}_{2}$$ catalyst for maximization of a selective range of liquid hydrocarbon $$(\hbox {C}_{5-20})$$ . Operating conditions of the reaction have a strong impact on the activity and selectivity of the process. The parameters that influence the FT synthesis reaction and product distribution include the reactor temperature, pressure, space velocity, the $$\hbox {H}_{2}/\hbox {CO}$$ molar ratio in the feed syngas and the catalyst. Experiments were performed at varying range of temperature, pressure, Space velocity and $$\hbox {H}_{2}/\hbox {CO}$$ molar ratio. Variation in $$\hbox {C}_{5+}$$ selectivity and (olefin/paraffin) O/P ratio were observed and analyzed to select the optimum values. Reaction conditions affect the $$\hbox {H}_{2}$$ and CO surface coverage and re-adsorption of olefins which play a crucial role in altering overall product selectivity. Reaction rates for FT and water gas shift (WGS) reactions were compared at different conditions. At optimum conditions, CO conversion and $$\hbox {C}_{5+}$$ selectivity were 45.9% and 77.4%, respectively. Synopsis. The reaction conditions for Fischer-Tropsch synthesis were optimized for maximum $$\hbox {C}_{5+}$$ yield over Fe/Cu/K/ $$\hbox {SiO}_{2}$$ catalyst. At optimized operating conditions (T – 225 $$^{\circ }\hbox {C}$$ , P - 25 bar, $$\hbox {H}_{2}/\hbox {CO}$$ molar ratio - 1 and GHSV - 2000 cc/gcat-h), % CO conversion and $$\hbox {C}_{5+}$$ selectivity were observed to be 45.9% and 77.4%, respectively.

Influences of ordered mesoporous silica on product distribution over Nb-promoted cobalt catalyst for Fischer-Tropsch synthesis

Nb-promoted cobalt catalysts supported on ordered mesoporous silica were prepared by sequential impregnation method and characterized by N2 physisorption, XRD, TEM, EDS-Mapping, H2-TPR, and CO-TPD. The performance of samples and the product distribution were investigated on a fixed bed reactor for Fischer-Tropsch synthesis (FTS). In respect of porous properties, the modification of supports with Nb can reduce the BET surface areas, pore volume, and pore size, possibly owing to the fact that the pore of ordered mesoporous silica was covered partially by NbOx. After the modification of Nb, both the structures of SBA-15 and KIT-6 are very stable as a catalyst support, but that of Co/Nb-MCM-41 was obviously distorted. The formation of smaller cobalt particles occurs in the narrow pore size of support. The presence of NbOx on catalyst surface can significantly weaken the cobalt-support, and accelerate the reduction of cobalt oxides. Meanwhile, NbOx can significantly enhance the adsorption stability and amount of CO adsorbed at FTS reaction condition for Co/Nb-KIT-6 sample. The CO conversion and C5+ selectivity for Co/Nb-KIT-6 sample are 92.1% and 85.1%, which are all higher than other samples supported on SBA-15 and MCM-41, and Co/Nb-KIT-6 sample has a lower CH4 selectivity up to 7.7%. Therefore, the supports with larger pore size are in favour of the formation of larger Co particles, resulting in higher FTS reaction activity. In addition, the introduction of Nb into cobalt catalysts can accelerate FTS activity and the growth of hydrocarbon chains. However, Co/Nb-MCM-41 sample with smaller pores is beneficial to the formation of oxy-compound and its selectivity to alcohols is 4.5%. Wherein, Co/Nb-KIT-6 sample has a higher selectivity to C2+-OH up to 75%. Thus, KIT-6 modified by Nb can be applied as a promising support for FTS catalysts in terms of enriching the range of FTS products.

Active Fischer-Tropsch synthesis Fe-Cu-K/SiO2 catalysts prepared by autocombustion method without a reduction step

ABSTRACT The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer–Tropsch synthesis (FTS) without a reduction step. The effect of different citric acid (CA):iron nitrate (N) molar ratios and acid types on the FTS performance of catalysts were investigated. The CA:N molar ratios had an important influence on the formation of iron active phases and FTS activity. The iron carbide (FexC), which is known to be one of the iron active phases, was demonstrated by the X-ray diffraction and X-ray photoelectron spectroscopy. Increasing the CA:N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA:N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst (CA:N molar ratio = 0.1) achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to FexC. But here, even if without reduction, FexC was formed directly by autocombustion and induction period was eliminated during FTS reaction.

Co-Promoted Cu/ZnO Catalysts for Fischer-Tropsch Synthesis

Co-promoted Cu/ZnO catalysts were studied for Fischer-Tropsch synthesis (FTS). All catalysts were prepared by the co-precipitation method, having the mass ratio of Co:Cu:Zn=0 (unpromoted), 0.05, 0.5:1:1, and characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). From XRD and XAS, the results confirmed the phase transformation of CuO to Cu foil and Co3O4 to Co foil in Co-promoted catalysts after reduction. After FTS reaction testing, the Co-promoted catalysts showed the decrease in methanol selectivity of 15 and 1.6% for 0.05Co-Cu/ZnO and 0.5Co-Cu/ZnO, respectively, and the increase in C5-C15 selectivity during 30 h of reaction.

Fe-containing carbon obtained from ferrocene: Influence of the preparation procedure on the catalytic performance in FTS reaction

Four different preparation routes were applied to obtain Fe-containing carbon catalysts for Fischer Tropsch Synthesis (FTS) including copolymer assisted co-precipitation of iron precursor, chemical modification of ferrocene, sol-gel and wetness impregnation of iron on polymeric carbon. The effects of the FTS reaction temperature and pressure were also examined. Using ferrocene as a starting precursor and applying sol-gel method to prepare the solid, the syngas is readily converted to C10+ hydrocarbons with a conversion of up to 56% and a productivity of 34mg hydrocarbon.gcat−1.h−1 at 240°C and 20atm. Impregnation method gave a Fe/C based catalyst with the highest exposure of active sites, including surface Fe3+ and Fe2+ redox sites with great properties in FTS. Chemical modification of ferrocene route enables the formation of hematite and maghemite nanoparticles on carbon, which were in situ reduced to magnetite and iron carbides, being the latter mostly active for the water gas shift reaction. It is found that copolymer assisted co-precipitation of ferrocene facilitates the production of large crystals of magnetite, which suffered from sintering and coking exhibiting low performance in FTS. Among these methods, sol-gel based catalyst proved to have superior performance due to the good dispersion of Fe, stable magnetite and iron carbide and Fe-doped nitrogen carbon phases production. Based on spent catalysts characterizations, the synergetic effect between magnetite and the iron carbides phases in the sol-gel based catalyst plays an important role in heavy hydrocarbon formation.

Low‐temperature Fischer‐Tropsch synthesis using plasma‐synthesized nanometric Co/C and Fe/C catalysts

AbstractIn this study, two analogous nanometric catalysts consisting of carbon‐supported cobalt or iron (Co/C and Fe/C) were synthesized by plasma and tested for Fischer‐Tropsch synthesis (FTS) in a continuously‐stirred tank slurry reactor (CSTSR). Being pyrophoric in nature, these new materials were reduced in situ at 673 K (400 °C) for 24 h using pure H2 gas. The FTS reaction was conducted at 493 K (220 °C), 2000 kPa pressure, and gas hourly space velocity (GHSV) of 3600 mL · for 24 h, using a feed stream of 0.6 L/L (60 vol %) H2 and 0.3 L/L (30 vol %) CO, with 0.1 L/L (10 vol %) Ar for mass balance determination. Devoid of promoters and under similar reaction conditions, the Co/C catalyst showed higher CO conversion (42 %) than the Fe/C (25 %), benchmarked against the commercial Fe‐NanoCat® (32 %). Co/C was more selective toward gasoline production, while Fe/C was more selective toward the diesel fraction. From transmission electron microscopy (TEM) analysis, no significant change in the mean particle size (∼12 nm) was observed in the plasma‐synthesized catalysts before and after FTS reaction, implying that the catalysts did not sinter. Additionally, there were no internal mass transport limitations in these catalysts, making them favourable for FTS. Besides metallic species, X‐ray diffraction (XRD) analysis indicated the presence of carbides in fresh catalysts (Fe3C in Fe/C and Co3C in Co/C). Magnetite (Fe3O4) was the most prevalent phase in the used Fe‐NanoCat® sample, a phase that was below the detection limits of XRD in the used plasma‐synthesized Fe/C sample.

Effect of preparation methods on activation of cobalt catalyst supported on silica fiber for Fischer–Tropsch synthesis

Silica fibers (SF) have been synthesized by facile combination of a sol–gel method and electrospinning technique and investigated as supports of cobalt catalysts for Fischer–Tropsch synthesis (FTS). Tetraethyl orthosilicate (TEOS) was used as precursors for the production of silica fibers. The cobalt supported on silica fibers (Co/SF) catalysts were prepared with the impregnation (IM), strong electrostatic adsorption (SEA), deposition precipitation (DP), and hydrothermal synthesis (HT) method and characterized by N2 adsorption, SEM, TEM, XRD, EDX, H2-TPR and H2-chemisorption. The results showed that the preparation methods significant affected the catalytic activity of Co/SF catalyst. The catalyst prepared by the SEA method showed the highest catalytic activity for FTS reaction, and their catalytic activities were varied in the order of SEA>DP>IM≫HT. The XRD analysis showed that the Co3O4 particles on the Co/SF catalyst prepared by SEA method (9nm) were smaller than those on catalyst prepared by IM method (30nm). The size of the Co3O4 particles was controlled by the preparation method, with small particles formed in catalyst prepared by SEA, DP and HT method. The excellent catalytic activity of Co/SF-SEA may be attributed to the smaller size of cobalt particles and higher cobalt dispersion on this catalyst.

Carbon nanotubes decorated α-Al2O3 containing cobalt nanoparticles for Fischer-Tropsch reaction

A new hierarchical composite consisted of multi-walled carbon nanotubes (CNTs) layer anchored on macroscopic α-Al2O3 host matrix was synthesized and used as support for Fischer-Tropsch synthesis (FTS). The composite constituted by a thin shell of a homogeneous, highly entangled and structure-opened carbon nanotubes network and it exhibited a relatively high and fully accessible specific surface area of 76 m2·g−1, compared with that of 5 m2·g−1 of the original α-Al2O3 support. The metal-support interaction between carbon nanotubes surface and cobalt precursor and high effective surface area led to a relatively high dispersion of cobalt nanoparticles. This hierarchically supported cobalt catalyst exhibited a high FTS activity along with an extremely high selectivity towards liquid hydrocarbons compared with the cobalt-based catalyst supported on pristine α-Al2O3 or on CNTs carriers. This improvement can attribute to the high accessibility of composite surface area comparing with the macroscopic host structure alone or to the bulk CNTs where the nanoscopic dimension induced a dense packing with low mass transfer which favoured the problem of reactants competitive diffusion towards the cobalt active site. In addition, intrinsic thermal conductivity of decorated CNTs could help the heat dissipating throughout the catalyst body, thus avoiding the formation of local hot spots which appeared in high CO conversion under pure syngas feed in FTS reaction. Cobalt supported on CNTs decorated α-Al2O3 catalyst also exhibited satisfied high stability during more than 200 h on stream under relatively severe conditions compared with other catalysts reported in the literature. Finally, the macroscopic shape of such composite easily rendered its usage as catalyst support in a fixed-bed configuration without facing problems of transport and pressure drop as encountered with the bulk CNTs.

Preparation and characterization of stable Ru nanoparticles embedded on the ordered mesoporous carbon material for applications in Fischer–Tropsch synthesis

A novel Ru–OMC catalyst was prepared by autoreduction reaction between a ruthenium precursor and a carbon source at 1123 K. Ruthenium nanoparticles were embedded on the carbon walls of the ordered mesoporous carbon material. Characterization tools including power X-ray diffraction (XRD), nitrogen adsorption–desorption, and transmission electron microscopy (TEM) were used to scrutinize the catalysts. The catalyst activity for Fischer–Tropsch synthesis (FTS) was carried out in a fixed bed reactor. For comparison, Ru catalysts supported on ordered mesoporous carbon (OMC), active carbon (AC), and carbon nanotubes (CNT) were prepared using conventional impregnation method and evaluated at the same FTS reaction conditions. The Ru–OMC catalyst exhibited highly ordered mesoporous structure and large surface area, indistinguishable with those of the OMC material. On this catalyst, Ru nanoparticles were actually embedded on the carbon walls, forming an intimate contact with the carbon supports. It is proposed that this feature might create certain electron-deficient sheets on the interfacial contact, which facilitates the transfer of spilled-over hydrogen and improves hydrogen disassociation on the catalyst surface.

Studies on KIT-6 Supported Cobalt Catalyst for Fischer–Tropsch Synthesis

KIT-6 molecular sieve was used as a support to prepare cobalt catalyst for Fischer–Tropsch synthesis (FTS) using an incipient wetness impregnation method to produce cobalt loadings of 15 and 25 wt%. The catalysts were characterized by BET surface area, X-ray diffraction, scanning transmission election microscopy (STEM), extended X-ray absorption fine spectroscopy and X-ray absorption near edge spectroscopy. The catalytic properties for FTS were evaluated using a 1L CSTR reactor. XRD, pore size distribution, and STEM analysis indicate that the KIT-6 mesostructure remains stable during and after cobalt impregnation and tends to form smaller cobalt particles, probably located inside the mesopores. The mesoporous KIT-6 exhibited a slightly higher cobalt dispersion compared to amorphous SiO2 supported catalyst. With the higher Co loading (25 wt%) on KIT-6, partial structural collapse was observed after the FTS reaction. Compared to an amorphous SiO2 supported cobalt catalyst, KIT-6 supported cobalt catalyst displayed higher methane selectivity at a similar Co loading, likely due to diffusion effects. KIT-6 molecular sieve was used as a support to prepare cobalt catalyst for Fischer–Tropsch synthesis (FTS) using an incipient wetness impregnation method to produce cobalt loadings of 15 and 25 wt%. The catalysts were characterized by BET surface area, X-ray diffraction (XRD), scanning transmission election microscopy (STEM), extended X-ray absorption fine spectroscopy (EXAFS) and X-ray absorption near edge spectroscopy (XANES). The catalytic properties for FTS were evaluated using a 1L CSTR reactor. The mesoporous KIT-6 exhibited a slightly higher cobalt dispersion compared to amorphous SiO2 supported catalyst. With the higher Co loading (25 wt%) on KIT-6, partial structural collapse was observed after the FTS reaction. XRD, pore size distribution, and STEM analysis indicate that the KIT-6 mesostructure remains stable during and after cobalt impregnation and tends to form smaller cobalt particles, probably located inside the mesopores. Compared to an amorphous SiO2 supported cobalt catalyst, KIT-6 supported cobalt catalyst displayed higher methane selectivity at a similar Co loading, likely due to diffusion effects.

Nanosized cobalt-based catalyst prepared by supercritical phase condition for Fischer-Tropsch synthesis

A series of nanosized Co/Zn/Mn/K composite catalysts for Fischer-Tropsch synthesis (FTS) were prepared by supercritical fluid drying (SCFD) method and common drying (CD) method. The nanosized cobalt-based catalysts were characterized by XRD, TEM and BET techniques. Their catalytic performances were tested in a slurry-bed reactor under FTS reaction conditions. The drying and crystallization were carried out simultaneously during SCFD, therefore, the catalysts prepared by SCFD method have ideal structure and show the FTS performance superior to the others prepared by CD method. The FTS activity and selectivity were improved via adding Zn, Mn and K promoters, and less CH 4 and CO 2 as well as higher yield of C 5+ products were achieved. The optimal performance of a 92% CO conversion and a 65% C 5+ product yield was obtained over a catalyst with the component of Co/Zn/Mn/K = 100/50/10/7. Furthermore, the catalytic performance was studied under the conditions of liquid-phase and supercritical phase slurry-bed, and C 5+ product yield were 57.4% and 65.4%, respectively. In summary, better catalytic performance was obtained using the nanosized catalyst prepared by SCFD method under supercritical reaction conditions, resulting in higher conversion of CO, less CO 2 byproduct, and higher yield of C 5+ products.

Effect of SiO 2 content on iron-based catalysts for slurry Fischer–Tropsch synthesis

A study has been carried out to investigate the effects of binder SiO 2 content on catalytic behavior of spray-dried precipitated Fe/Cu/K/SiO 2 catalysts for Fischer–Tropsch synthesis (FTS). The catalysts were characterized by means of N 2 physisorption, H 2 temperature-programmed reduction (TPR), scanning electron microscopy (SEM), and Mössbauer effect spectroscopy (MES). The Fischer–Tropsch synthesis performances (activity, selectivity and stability) of the catalysts were studied in a slurry-phase continuously stirred tank reactor (CSTR). The results indicated that the increase of SiO 2 content stabilizes Fe 3O 4 phase and suppresses the further reduction and carburization of the catalysts in syngas. Long time on stream FTS performances showed that the catalyst with SiO 2 improves its reaction stability. The selectivities to light hydrocarbons (methane, C 2–C 4, C 5–C 11) are enhanced whereas those to heavy hydrocarbons (C 12 +) are suppressed with increasing SiO 2 content. The results were explained to the interactions of Fe–SiO 2 and K–SiO 2. From the present study, it is found that a catalyst with composition of 100Fe/5Cu/4.2K/25SiO 2 on mass basis displays both better FTS performances and a good attrition resistance, which is suitable for the use in CSTRs or SBCRs (Slurry Bubble Column Reactors) for FTS reaction.

Effect of reaction conditions on the catalytic performance of Fe-Mn catalyst for Fischer-Tropsch synthesis

The effects of reaction conditions on the performance of an Fe-Mn catalyst for Fischer-Tropsch synthesis (FTS) have been investigated in a continuous spinning basket reactor. Experiments were carried out under a wide range of industrially relevant reaction conditions including reaction temperature of 533–573 K, pressure of 0.93–2.96 MPa, inlet H 2/CO molar ratio of 0.80–2.50 and space velocity of (0.46–1.85) × 10 −3 N m 3 kg cat −1 s −1. The selectivities to low molecular weight hydrocarbons basically increased with the increase of reaction temperature, total pressure and inlet H 2/CO ratio, except for ethylene. The FTS reaction rate and the overall oxygenates formation rate increased with increasing reaction temperature, pressure, space velocity and H 2/CO ratio on the whole. It was found that the catalyst has relatively high activity and selectivity in producing light alkenes. It also exhibited excellent stability during the 700 h run at H 2/CO ratio of 1.00, which indicates that the catalyst has good longevity and is suitable for syngas derived from coal with low H 2/CO ratio to produce light olefins and high-quality liquid fuels. Meanwhile, it may have potential promising applications in advanced stirred tank slurry reactors. In addition, the detailed investigation of FTS reaction performance for the Fe-Mn catalyst can provide full and accurate basic information for industrial scale-up.

Preparation of a multilayered composite catalyst for Fischer–Tropsch synthesis in a micro-chamber reactor

A 20 wt% Co/SiO2 catalyst grafted on a stainless steel substrate was used for Fischer–Tropsch synthesis (FTS) in a micro-chamber reactor. The fabrication of the catalyst was a complex process involving several steps. The first one, the pre-treatment of the AISI316L substrate through a plasma assisted chemical vapour deposition process (PACVD), allowed the formation of a silicon based polymer. This thin polymeric film was thermally degraded into a silicon oxide bonding layer. The coating of this bonding layer with sol–gel precursor of the Co/SiO2 catalysts was done with a spray coating process. The sequential combination of these steps led to a multilayered catalyst with a complex morphology. This material demonstrated high activity under FTS reaction. Activity and selectivity were higher under micro-chamber conditions than in a classical fixed-bed catalytic test. This was attributed to the increase of mass and heat transfers within the micro-device. Moreover distribution of metallic masses within the catalyst showed significant evolutions post FTS, including steel compound migrations and possible cobalt segregation.

Effects of Cu and K on Co-precipitated FeMn/SiO 2 Catalysts for Fischer-Tropsch Synthesis

The effects of copper and potassium on the activity and selectivity of coprecipitated Fe-Mn/SiO 2 catalysts for Fischer-Tropsch synthesis (FTS) were studied in a slurry phase continuous stirred tank reactor. The reduction and adsorption behaviors of the catalysts were investigated using temperature-programmed reduction/temperature-programmed desorption (TPR/TPD) methods. It was found that copper improves the reduction of the catalyst in H 2 or CO. Potassium improves the reduction of the catalyst in CO, whereas it suppresses the reduction of the catalyst in H 2. Copper enhances the H 2 adsorption, whereas potassium has no influence on the H 2 adsorption. In the FTS reaction, copper shortens the induction period required for reaching the steady state activity, whereas potassium prolongs the induction period. The potassium promoter increases the activity and decreases the selectivity of methane. The promotion effects of Cu and K on the activity and selectivity is more obvious than that of Cu, that is, the activity is higher and the methane selectivity is lower on the doubly promoted catalyst.