For Fischer-Tropsch Synthesis Performance Research Articles

Modulating Co reduction degree and Fischer-Tropsch synthesis performance by reducing cobalt silicate at different conditions

It is always hard to reduce Co2SiO4 to active Co0 on supported Co-based catalyst for Fischer-Tropsch synthesis (FTS). Here, amorphous Co2SiO4 material was prepared by in-situ doping TMOS during synthesis of ZIF-67, which was then reduced at different temperature and time to obtain ReX-2h (X = 400, 450, 500, 550, 600) and Re500-Yh (Y = 2, 4, 8) catalysts. The effects of reduction temperature and time on Co reduction degree and FTS performance were investigated. Results indicated that the ReX-2h and Re500-Yh catalysts exhibited low CH4 selectivity due to no obvious Co microcrystal found. The reduction degree of ReX-2h increased with reduction temperature, which led to enhanced FTS activity. However, both Re550-2h and Re600-2h exhibited poorer stability than Re500-2h, so the effects of reduction time on Re500-Yh were done. The reduction degree and FTS activity of Re500-Yh were also promoted with extending reduction time. The Re500-8h exhibited higher FTS activity with good stability.

Delaminated and Pit-rich Nano-kaolinites obtained via an Intercalation-etching Method and their Application to Fischer–Tropsch Synthesis

AbstractModified kaolinites possess excellent adsorption properties and, therefore, are regarded widely as potential catalytic components. The use of modified kaolinites as a catalytic component for Fischer–Tropsch synthesis (FTS) has remained unexplored, however. In the current study, delaminated and pit-rich nano-kaolinite was prepared via acid treatment of N-methylformamide (NMF)-intercalated kaolinite (intercalation-etching strategy), and was used as a support to prepare a cobalt-based FTS catalyst (denoted as 15%-Co-HNKln). Compared with other FTS catalysts, the supports for which were raw kaolinite or directly acid-treated kaolinite, the 15%-Co-HNKln showed several advantages such as large specific surface area, dispersed Co particles with small particle size, more new active sites, and significant surface acidity. Given the aforementioned advantages, the 15%-Co-HNKln catalyst demonstrated very good FTS performance. Compared with that of the raw kaolinite-supported FTS catalyst, the CO conversion rate and C5–C12 hydrocarbon selectivity of 15%-Co-HNKln increased by 20% and 15%, respectively.

MOF-Derived Ru1Zr1/Co Dual-Atomic-Site Catalyst with Promoted Performance for Fischer-Tropsch Synthesis.

Cobalt-based catalysts have been widely used for Fischer-Tropsch synthesis (FTS) in industry; however, achieving rational catalyst design at the atomic level and thereby a higher activity and more long-chain-hydrocarbon products simultaneously remain an attractive and difficult challenge. The dual-atomic-site catalysts with unique electronic and geometric interface interactions offer a great opportunity for exploiting advanced FTS catalysts with improved performance. Herein, we designed a Ru1Zr1/Co catalyst with Ru and Zr dual atomic sites on the Co nanoparticle (NP) surface through a metal-organic-framework-mediated synthesis strategy which presents greatly enhanced FTS activity (high turnover frequency of 3.8 × 10-2 s-1 at 200 °C) and C5+ selectivity (80.7%). Control experiments presented a synergic effect between Ru and Zr single-atom site on Co NPs. Further density functional theory calculations of the chain growth process from C1 to C5 revealed that the designed Ru/Zr dual sites remarkably lower the rate-limiting barriers due to the significantly weakened C-O bond and promote the chain growth processes, resulting in the greatly boosted FTS performance. Therefore, our work demonstrates the effectiveness of dual-atomic-site design in promoting the FTS performance and provides new opportunities for developing efficient industrial catalysts.

Development of an Iron-Based Fischer—Tropsch Catalyst with High Attrition Resistance and Stability for Industrial Application

In order to develop an iron-based catalyst with high attrition resistance and stability for Fischer–Tropsch synthesis (FTS), a series of experiments were carried out to investigate the effects of SiO2 and its hydroxyl content and a boron promoter on the attrition resistance and catalytic behavior of spray-dried precipitated Fe/Cu/K/SiO2 catalysts. The catalysts were characterized by means of N2 physisorption, nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS), H2-thermogravimetric analysis (H2-TGA), temperature-programmed reduction and hydrogenation (TPR and TPH), and scanning and transmission electron microscopy (SEM and TEM). The FTS performance of the catalysts was tested in a slurry-phase continuously stirred tank reactor (CSTR), while the attrition resistance study included a physical test with the standard method and a chemical attrition test under simulated reaction conditions. The results indicated that the increase in SiO2 content enhances catalysts’ attrition resistance and FTS stability, but decreases activity due to the suppression of further reduction of the catalysts. Moreover, the attrition resistance of the catalysts with the same silica content was greatly improved with an increase in hydroxyl number within silica sources, as well as the FTS activity and stability to some degree. Furthermore, the boron element was found to show remarkable promotion of FTS stability, and the promotion mechanism was discussed with regard to probable interactions between Fe and B, K and B, and SiO2 and B, etc. An optimized catalyst based on the results of this study was finalized, scaled up, and successfully applied in a megaton industrial slurry bubble FTS unit, exhibiting excellent FTS performance.

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

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

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

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

Enhanced Fischer-Tropsch synthesis performances of Fe/h-BN catalysts by Cu and Mn

A series of Fe/h-BN catalysts promoted with Cu or Mn were prepared for Fischer-Tropsch synthesis (FTS). The physicochemical properties, crystal structures and morphologies of the catalysts were characterized by N2 physisorption, FT-IR, TPR, XPS, XRD, MES and TEM. It is found that iron oxide nanoparticles are highly dispersed on h-BN matrix due to the anchoring effect of surface defects and the accommodation of porous structures of h-BN. The characterization results indicate that strong interaction between iron oxide and h-BN is present on un-promoted catalyst, which endows the h-BN supported iron catalyst with stable properties under FTS conditions but severely retards reduction of the catalyst. The addition of Cu to Fe/h-BN can to some extent overcome the strong interaction by introducing more sites for dissociating H2. It is observed that Cu promoter can increase the reduction or carburization degree and thus enhance the FTS activity. The addition of Mn to Fe/h-BN can weaken the strong interaction by altering the electron structure of iron species. And the electron-rich Fe species are responsible for easy reduction and the enhanced FTS performance. Besides, a higher activity can be realized by co-adding Cu and Mn to the Fe/h-BN catalyst. These results suggest that the synergistic effect of Mn and Cu can largely improve the performance of Fe/h-BN catalyst without impairing the stability of the catalyst. The present study paves a way to tailor the performances of FTS catalysts with h-BN as support.

Controlled formation of iron carbides and their performance in Fischer-Tropsch synthesis

Iron carbides are unmistakably associated with the active phase for Fischer-Tropsch synthesis (FTS). The formation of these carbides is highly dependent on the catalyst formulation, the activation method and the operational conditions. Because of this highly dynamic behavior, studies on active phase performance often lack the direct correlation between catalyst performance and iron carbide phase. For the above reasons, an extensive in situ Mössbauer spectroscopy study on highly dispersed Fe on carbon catalysts (Fe@C) produced through pyrolysis of a Metal Organic Framework was coupled to their FTS performance testing. The preparation of Fe@C catalysts via this MOF mediated synthesis allows control over the active phase formation and therefore provides an ideal model system to study the performance of different iron carbides. Reduction of fresh Fe@C followed by low-temperature Fischer-Tropsch (LTFT) conditions resulted in the formation of the ε′-Fe2.2C, whereas carburization of the fresh catalysts under high-temperature Fischer-Tropsch (HTFT) resulted in the formation of χ-Fe5C2. Furthermore, the different activation methods did not alter other important catalyst properties, as pre- and post-reaction transmission electron microscopy (TEM) characterization confirmed that the iron nanoparticle dispersion was preserved. The weight normalized activities (FTY) of χ-Fe5C2 and ε′-Fe2.2C are virtually identical, whilst it is found that ε′-Fe2.2C is a better hydrogenation catalyst than χ-Fe5C2. The absence of differences under subsequent HTFT experiments, where χ-Fe5C2 is the dominating phase, is a strong indication that the iron carbide phase is responsible for the differences in selectivity.

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.

Effect of synthesis and activation methods on the catalytic properties of silica nanospring (NS)-supported iron catalyst for Fischer-Tropsch synthesis

A nanostructured iron (Fe) catalyst for Fischer-Tropsch synthesis (FTS) was prepared and evaluated using a silica nanospring (NS) support. FTS offers an approach of producing biofuels from synthesis gas (syngas) produced via biomass gasification. The Fe/NS catalysts were prepared using three different methods: (i) incipient wetness impregnation, (ii) precipitation and (iii) modified sol-gel, in order to obtain different sizes of deposited Fe nanoparticles on the NS support and investigate the influence of particle size on FTS. The Fe decorated catalysts were calcined and then activated with either H2, CO or H2+CO mixture. The prepared Fe/NS catalysts were characterized before the FT reaction by BET surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) in order to find correlations between physico-chemical properties of catalysts and catalytic performance. The decoration of Fe nanoparticles of different sizes onto NS using the various methods ranged from 1.7 to 10nm. The FTS performance was also evaluated in a quartz fixed-bed microreactor (H2/CO of 2:1, 270°C) and the products trapped and analyzed by GC-TCD and GC–MS to determine CO conversion and reaction selectivity. These results show that the highest CO conversion (76.6%) and a wide distribution of light hydrocarbon (C6 to C14) were obtained for Fe/NS catalyst prepared by impregnation and activated with CO after 12h of the FT reaction.

Effect of confinement of TiO2 nanotubes over the Ru nanoparticles on Fischer-Tropsch synthesis

Ru nanoparticles (NPs) have been successfully deposited in the inner pores of TiO2 nanotubes (TNTs), denoted as Ru-in/TNT, by vacuum assisted impregnation method for Fischer-Tropsch synthesis (FTS). The composition, morphology and electronic properties have been characterized by the XRD, TEM, N2-sorption, H2-TPR/TPD and XPS, investigating the confinement effect of TNT on the entrapped Ru NPs’ FTS performance. The Ru-in/TNT exhibits high CO conversion activity and superior deactivation-resist ability over the Ru-out/TNT (with most of Ru NPs deposited on the outer surface of TNT) and Ru/P25 (using commercial P25 powder as support) catalysts. Besides above superiority, the Ru-in/TNT facilitates the formation of long chain (C19+) products as well. The enhanced activity and selectivity can be ascribed to the confinement effect of TNT: (i) strengthen charge transfer and modulate the electronic properties of Ru species resulting in more active center site; (ii) constrain the metal sintering and metal leaching to resist deactivation during FTS; (iii) facilitate the re-adsorption of α-olefin leading to long-chain product.

Enhanced Fischer–Tropsch synthesis performance of iron-based catalysts supported on nitric acid treated N-doped CNTs

Iron-based catalysts supported on N-doped CNTs (NCNTs) treated by various concentrations of nitric acid for Fischer–Tropsch synthesis (FTS) were investigated. An improved catalytic performance for the iron catalyst supported on acid treated NCNTs was obtained and the suitable nitric acid concentration was 10M. The physiochemical properties of the NCNTs and the corresponding catalysts were characterized by BET, TEM, XRD, XPS, TGA and H2-TPR. The acid treatment removed the impurity and amorphous carbon, damaged the bamboo-like structure and increased the number of oxygen-containing functional groups and graphitization degree on the NCNTs. The more iron particles located inside the channels of NCNTs, the better catalytic FTS performance due to high dispersion and reducibility.

Highly dispersed cobalt on N-doped carbon nanotubes with improved Fischer–Tropsch synthesis activity

N-doped carbon nanotubes (NCNTs) were used as the support for a Co catalyst (Co/A-NCNTs). After acid treatment, the bamboo-like structure of the NCNTs disappeared and more defects were formed on the surface of the NCNTs; however there was little change in the inner diameter and N content of the nanotubes. This resulted in an improved dispersion of Co inside the cavities of the NCNTs. The Co/A-NCNT catalyst was compared with Co supported on acid treated CNTs, and the Co/A-NCNT catalyst had a smaller surface area and for Fischer–Tropsch (FT) synthesis, it had a higher CO conversion with producing a narrower distribution of low carbon number hydrocarbons. The high Co dispersion in the Co/A-NCNTs is the main reason for the improved FT synthesis performance.

A novel nano fischer‐tropsch catalyst for the production of hydrocarbons

A novel silica nanospring (NS) supported cobalt catalyst for Fischer‐Tropsch synthesis (FTS) was synthesized and investigated, and the results were compared with those of a conventional cobalt catalyst. The NS catalyst was prepared using deposition of Co followed by thermal assisted reduction and characterized by scanning electron microscopy‐energy dispersive spectroscopy, transmission electron microscopy, N2 physisorption, X‐ray powder diffraction, X‐ray photoelectron spectroscopy, and H2‐temperature programmed reduction. FTS performance was evaluated in a quartz fixed‐bed microreactor (230°C, H2:CO ratio 2:1), and the products were trapped and analyzed with gas chromatography‐thermal conductivity detector (GC‐TCD, gases) and gas chromatography‐mass spectrometry (GC‐MS, semivolatiles) to determine the percentage of CO conversion and selectivity. Semivolatile products from both catalysts were C6‐C18 hydrocarbons. Even though the NS FTS catalyst was not fully reduced during the activation period it still showed higher FTS activity than the conventional catalyst, which is attributed to the higher accessibility of the gases to the Co on the NS surface. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 693–698, 2014

The effect of surface acidic and basic properties of highly loaded Co catalysts on the Fischer–Tropsch synthesis

Highly loaded cobalt catalysts (80% by weight) with different supports (SiO2, Al2O3, ZrO2 and MgO) were prepared by the co-precipitation technique for Fischer–Tropsch synthesis (FTS). Microcalorimetric adsorptions of NH3, CO2, CO and H2 showed that the surface acidity/basicity significantly affected the surface properties of supported Co, as evidenced by the changes of strengths of adsorption of CO and H2 on Co, which in turn affected the FTS performance. The appropriate ratio (~ 1.2) of heats for the adsorption of CO and H2 on Co seemed important in determining the FTS activity.

Fischer–Tropsch synthesis over one eggshell-type Co/SiO 2 catalyst in a slurry phase reactor

The eggshell type cobalt catalyst (Co/SiO 2) was prepared via a spray method. Characterization of surface information between cobalt and the support of silica gel was obtained by SEM and EPMA techniques. The discrete cobalt particle sizes were calculated based on XRD analysis. The prepared eggshell Co/SiO 2 catalysts were investigated for Fischer–Tropsch (FT) synthesis in a slurry-phase reactor and compared with conventional impregnated catalyst under the conditions of P = 1.0 MPa, T = 503 K, W/ F = 5.0 g-cat h/mol and H 2/CO = 2. Results indicated that eggshell Co/SiO 2 catalyst was inclined to generate long chain hydrocarbons and had relatively low CH 4 selectivity. The parameters that respond to the performance of FT synthesis had been upgraded when compared with those of a conventional impregnated catalyst. In generated hydrocarbons for 1800 μm supported catalyst, CH 4 selectivity decreased from 22.98% to 9.68%, and C 5+ selectivity increased from 61.66% to 79.45%. Meanwhile, the chain growth probabilities ( α) also increased from 0.84 to 0.90. According to H 2-chemisorption and space-time yield (STY), the turnover frequency (TOF) of each catalyst was calculated. The higher TOF value of eggshell catalyst means better FT synthesis performance than is available using conventional impregnated catalyst.

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.

Novel precipitated iron Fischer–Tropsch catalysts with Fe3O4 coexisting with α-Fe2O3

The present study was undertaken to investigate the catalytic behavior of an industrial iron catalyst (Fe/Cu/K/SiO2) prepared from ferrous sulfate precursor for Fischer–Tropsch (FT) synthesis, in which different amount of Fe3O4 coexist with α-Fe2O3. The catalyst samples were characterized by BET, XRD, H2-TPR and Mossbauer effect spectroscopy (MES). The FT synthesis performance of the catalysts were carried out in a fixed bed reactor (FBR) under reaction conditions of 250 °C, 1.5 MPa, 2.0 nL/g-cat/h, and H2/CO=2/1 for 200 h. The results from XRD and MES for the catalyst samples of pre- and post-reduction indicate that more iron carbides form in the catalysts that have lower Fe3O4 contents. H2-TPR for the catalysts displays that Fe3O4 may facilitate the reduction of catalysts only when it was highly dispersed. FT reaction study in the FBR shows that the catalysts become more active with the decrease of Fe3O4 contents in the catalysts. However, the catalyst with certain amount of highly dispersed Fe3O4 exhibited high FT synthesis activity with CO conversion more than 75%. The catalyst also displayed much less olefins selectivity. A comparison of FTS performances of one of these catalysts with some known catalysts was also made in this paper.