Solvent-free synthesis of alumina supported cobalt catalysts for Fischer–Tropsch synthesis

A novel mechano-synthesis method has been elaborated in this work for the design of efficient cobaltbased Fischer–Tropsch catalysts. The process aims to reduce the total number of steps involved in the synthesis of solid catalysts and thus to avoid relevant toxic solutions generated during the catalyst preparation. The mechano-synthesis of the Co/Al_2O_3 catalyst was processed in a low-energy vibratory micro mill and high energy planetary ball mill. Porous spherical γ-aluminas(1860 μm and 71 μm mean particle diameter) were used in this work as host compounds. Co_3O_4(3 μm mean particle diameter) has provided guest particles for mechano-synthesis. The catalysts were characterized by textural(surface area, porosity and particle size) and structural analyses(X-ray diffraction, TPR, SEM-EDX and microprobe). The microprobe images show deposition of Co_3O_4 on the surface of the alumina and indicated no Co_3O_4 diffusion inside the alumina pores. SEM-EDX mapping illustrated that cobalt coating tended to occur on surface of rounded shape of cracked alumina fragments. After milling, the crystallite size of Co_3O_4 decreased to 15 nm from 30 to 50 nm. The TPR profiles indicated very low concentrations of inactive cobalt aluminate mixed compounds which are usually produced during the catalyst preparation by impregnation.In Fischer–Tropsch synthesis, the catalysts prepared using mechano-synthesis methods showed catalytic performance comparable to the catalysts prepared by impregnation.     

Fischer–Tropsch synthesis over iron catalysts with corncob-derived promoters

A sustainable strategy for Fischer–Tropsch iron catalysts is successfully achieved by embedding of synergistic promoters from a renewable resource, corncob. The iron-based catalysts, named as "corncob-driven"catalysts, are composed of iron species supported on carbon as primary active components and various minerals(K, Mg, Ca, and Si, etc.) as promoters. The corncob-driven catalysts are facilely synthesized by a one-pot hydrothermal treatment under mild conditions. The characterization results indicate that the formation of iron carbides from humboldtine is clearly enhanced and the morphology of catalyst particles tends to be more regular microspheres after adding corncob. It is observed that the optimized corncob-driven catalyst exhibits a higher conversion than without promoters' catalyst in Fischer–Tropsch synthesis(ca. 73% vs. ca. 49%). More importantly, a synergistic effect exists in multiple promoters from corncob that can enhance heavy hydrocarbons selectivity and lower CO_2 selectivity, obviously different from the catalyst with promoters from chemicals. The proposed synthesis route of corncob-driven catalysts provides new strategies for the utilization of renewable resources and elimination of environmental pollutants from chemical promoters.     

Effect of introduced zeolite on the Fischer–Tropsch synthesis over a cobalt catalyst

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Controlled synthesis of cobalt nanocrystals on the carbon spheres for enhancing Fischer–Tropsch synthesis performance

Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine cobalt nano-particles was studied. Thermal decomposition synthesis method was applied to obtain cobalt catalysts with high dispersion and narrow particle size distribution. Furthermore the cobalt size can be controlled by the molar ratio of o-dichlorobenzene/benzylamine. Compared with supported cobalt catalysts prepared by incipient wetness impregnation method and ultrasonic impregnation method,the catalyst prepared by thermal decomposition method showed higher catalytic activity, higher long chain hydrocarbons selectivity and lower methane selectivity.     

Fischer–Tropsch synthesis over CNT-supported cobalt catalyst: effect of magnetic field

In the present work, the cobalt catalysts supported on carbon nanotubes (CNTs) were prepared by impregnation method in the presence and absence of magnetic field. The prepared catalysts were employed to yield higher hydrocarbons via Fischer–Tropsch synthesis. It is explored that using magnetized water can effectively change the catalyst geometry in impregnation catalyst preparation method. For the preparation of different sizes of cobalt particles on the CNTs support, the physical properties of solvent (water) in impregnation process were changed using the magnetizing process. The results showed that the average particle sizes of impregnated cobalt nanoparticles were decreased by using magnetized water in impregnation step. In addition, in the magnetized treated cobalt catalyst, the cobalt particles mostly dispersed outside the tubes because the capillary forces decreased by reducing water surface tension. Furthermore, the experimental results showed that the probability of chain growth (α) and selectivity to heavier hydrocarbons increased in magnetized water treatment catalysts.     

Fischer–Tropsch synthesis using zeolitic imidazolate framework (ZIF-7 and ZIF-8)-supported cobalt catalysts

The Fischer–Tropsch synthesis using cobalt catalysts supported on zeolitic imidazolate frameworks (ZIFs), ZIF-7 and ZIF-8, has been investigated. ZIF-7, ZIF-8 and corresponding cobalt-containing catalysts, after preparation, were characterized using various techniques. Thermogravimetric analysis results show that ZIF-7 and ZIF-8 supports have good thermal stability for the Fischer–Tropsch synthesis reaction, and weaker interaction between cobalt and zinc in the ZIF-7 and ZIF-8 supports results in more cobalt reduction. The catalytic performance was evaluated in Fischer–Tropsch synthesis and compared with that of a cobalt catalyst supported on SBA-15 promoted with zinc. The pore structure of the ZIF supports plays an essential role in product selectivity for the prepared catalysts. The carbon number in hydrocarbon products and olefin selectivity depend on cobalt dispersion and support structure owing to the impacts of site density and carrier skeleton on the speed of diffusion-enhanced olefin re-adsorption reactions.     

Effects of glow discharge plasma on Cu–Co–Al-based supported catalysts for higher alcohol synthesis

The novel plasma assisted Cu–Co/γ-Al₂O₃ catalysts were prepared by incipient impregnation method for CO hydrogenation to higher alcohols and characterized by means of scanning electron microscopy (SEM), N₂ adsorption, X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that introduction of plasma significantly improved the specific surface area, dispersion of catalyst and the enrichment of active species on the surface of catalysts. Under the conditions of P = 5.0 MPa, GHSV = 6,000 h⁻¹, V(H₂)/V(CO) = 2, T = 573 K, the conversion of carbon monoxide over the plasma enhanced catalyst increased by 41.9% compared with that of the conventional sample, and the space time yield reached 337.1 g kg⁻¹ h⁻¹.     

Effect of preparation methods on Co/ZrO2 catalysts in Fischer–Tropsch synthesis

Cobalt was incorporated into the zirconia support by different methods. The reducibility and activity of the catalysts was directly related to the preparation methods. Impregnated Co/ZrO₂ catalyst showed the highest reduction degree and the highest CO hydrogenation activity.     

Dynamics of carbide formation in iron-supported catalysts of the Fischer–Tropsch process promoted by copper and potassium

The kinetics of the formation of iron carbides during the activation of iron-coated catalyst for Fischer–Tropsch synthesis promoted by copper and potassium, and by carbon monoxide and syngas, is studied. It is established that the presence of copper lowers the initial temperature of hematite reduction to magnetite and leads to the formation of carbide in both CO and СО/Н₂. Potassium slows the rate of magnetite formation, but it accelerates the formation of iron oxide. It is shown that the rate of carbide formation during magnetite reduction for catalysts is half that in the reaction of hematite reduction to magnetite in both CO and СО/Н₂.     

Promotion of cobalt catalyst for Fischer–Tropsch synthesis by molybdenum as protection against sulfur poisoning

Molybdenum promotion was used to increase the resistance of a cobalt catalyst for the Fischer–Tropsch synthesis to sulfur poisoning. A series of experiments on adding 1,3,5-trithiane to synthesis gas (sulfur content of 1 ppm) showed that the Co–Mo /Al₂O₃ catalyst regained its initial activity after 8 h of operation. In comparison, catalysts not containing molybdenum experienced a significant irreversible loss of activity that was not recovered after stopping the addition of 1,3,5-trithiane to the feed.     

Promotion of lanthanum-supported cobalt-based catalysts for the Fischer–Tropsch reaction

This paper focuses on the effect of the La/Co ratio on the structure of alumina cobalt supported catalysts for Fischer–Tropsch synthesis. Catalysts are prepared by wetness impregnation of alumina followed by calcination in air. The catalysts contain 10 wt% of cobalt and between 0 and 20 wt% of La (0, 5, 10, 15, 20). The catalysts were activated by reduction in hydrogen at 673 K and the catalytic performance was evaluated in a fixed bed reactor at 20 bar and 493 K. A wide range of techniques (BET, XRD, TPR, and XPS) were used for catalyst characterization at each preparation step and showed strong impact of the La/Co ratio on the structure, reducibility of supported cobalt phases. It was shown that 10 wt% of lanthanum allows reducing cobalt aluminate and improving catalytic performances.     

Fischer–Tropsch synthesis on potassium-modified Fe3O4 nanoparticles

Research on Chemical Intermediates - Synthesized magnetite (Fe3O4) nanoparticles, with an average crystallite size of 8 and 22 nm, were investigated for Fischer–Tropsch synthesis...     

Cobalt–copper based catalysts for higher terminal alcohols synthesis via Fischer–Tropsch reaction

The production of higher terminal alcohols through CO hydrogenation according to the Fischer–Tropsch(F–T) process has been a topic of interest since the Institut Fran?ais du Pétrole(IFP) demonstrated shortchain C_1–C_6mixed alcohols production over cobalt–copper based catalysts. A number of catalyst formulations were screened for their suitability at that time. In particular, the addition of Cr, Zn, Al, Mn and V to Co Cu was investigated. In a number of patents, it was shown that catalyst preparation is crucial in these catalyst formulations and that high alcohols selectivity can only be achieved by carefully respecting the procedures and recipes. This short critical review highlights recent developments in Co Cu-based catalysts for higher terminal alcohols synthesis via F–T synthesis. Special attention will be given to catalyst preparation which according to developments in our group is based on oxalate precipitation. This way we show that the close association of Co and Cu on the one hand and promoter/dispersant on the other are of utmost importance to ensure high performance of the catalysts. We shall concentrate on "Co Cu Mn","Co Cu Mo" and "Co Cu Nb" catalyst formulations, all prepared via oxalate precipitation and combined with"entrainment techniques" if necessary, and show high total alcohols selectivity can be obtained with tunable Anderson-Schulz-Flory chain-lengthening probability. Either long-chain C_8–C_(14)terminal alcohols as feedstock for plasticizers, lubricants and detergents, or short-chain C_2–C_5alcohols as "alkanol" fuels or fuel additives can be formed this way.     

Fischer–Tropsch synthesis on impregnated cobalt-based catalysts:New insights into the effect of impregnation solutions and pH value

The Co-based catalysts were prepared with different cobalt acetate solutions. Effects of p H value were studied deeply on Fischer–Tropsch synthesis(FTS) through a semi-batch reactor. Among all impregnation solutions(water, butanol, amyl alcohol, acetic acid, nitric acid and ammonium nitrate), the catalyst prepared by NH_4NO_3 solution showed the highest catalytic activity due to its small particle size and high reduction degree. However, the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS. According to FT-IR spectra results, the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity. Whereas, the high activity of catalysts prepared from NH_4NO_3 solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower p H conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher p H value.     

Fabrication of K-promoted iron/carbon nanotubes composite catalysts for the Fischer–Tropsch synthesis of lower olefins

K-promoted iron/carbon nanotubes composite(i.e., Fe K-OX) was prepared by a redox reaction between carbon nanotubes and K_2FeO_4followed by thermal treatments on a purpose as the Fischer–Tropsch catalyst for the direct conversion of syngas to lower olefins. Its catalytic behaviors were compared with those of the other two Fe-IM and Fe K-IM catalysts prepared by impregnation method followed by thermal treatments. The novel Fe K-OX composite catalyst is found to exhibit higher hydrocarbon selectivity,lower olefins selectivity and chain growth probability as well as better stability. The catalyst structureperformance relationship has been established using multiple techniques including XRD, Raman, TEM and EDS elemental mapping. In addition, effects of additional potassium into the Fe K-OX composite catalyst on the FTO performance were also investigated and discussed. Additional potassium promoters further endow the catalysts with higher yield of lower olefins. These results demonstrated that the introduction method of promoters and iron species plays a crucial role in the design and fabrication of highly active,selective and stable iron-based composite catalysts for the FTO reaction.     

β-Cyclodextrin for design of alumina supported cobalt catalysts efficient in Fischer-Tropsch synthesis

Addition of β-cyclodextrin during catalyst preparation strongly affects the structure and catalytic performance of alumina supported cobalt catalysts for Fischer-Tropsch synthesis. Impregnation of the support with solutions containing β-cyclodextrin leads to higher metal dispersion and spectacularly enhances both reaction rate and heavy hydrocarbons productivity in Fischer-Tropsch synthesis.     

Industrial catalyst for the selective Fischer–Tropsch synthesis of long-chain hydrocarbons

The results of development of an industrial supported cobalt–silica gel catalyst for the Fischer–Tropsch synthesis are reported. The studies included the selection of a support and the determination of an optimum active component content, a calcination temperature, and the effect of doping with aluminum oxide on the physicochemical and catalytic properties of the Co–SiO₂ system. The catalyst samples were characterized by a set of physicochemical methods. The on-stream stability of the supported cobalt–silica gel catalyst was tested in the continuous mode for 1000 h. In the course of the entire test cycle, the catalyst exhibited stable operation under varied synthesis temperature and gas space velocity, and it can be recommended for industrial applications. The experimental results were used for the preparation of a pilot batch of the catalyst.     

Fischer–Tropsch Synthesis on Bifunctional Cobalt Catalysts with the Use of Hierarchical Zeolite HBeta

Kinetics and Catalysis - The production of fuel components in the integrated Fischer–Tropsch synthesis on bifunctional cobalt catalysts in the form of a mixture of the cobalt catalyst...     

Deactivation behaviors of hybrid Fischer–Tropsch catalysts in the production of middle distillate from synthesis gas in a dual-bed reactor

Production of middle distillate (C₁₀–C₂₀) from synthesis gas (CO + H₂) through hydrocracking of wax (>C₂₁₊) was carried out in a dual-bed reactor. Fischer–Tropsch catalyst (Co/TiO₂) was used in the first-bed reactor to produce wax from synthesis gas, and a mesoporous Pd–alumina composite catalyst (Pd–Al₂O₃) was used in the second-bed reactor to produce middle distillate through hydrocracking of wax. Both Fischer–Tropsch synthesis function of Co/TiO₂ catalyst and hydrocracking function of Pd–Al₂O₃ catalyst were deactivated during 100 h-hybrid Fischer–Tropsch synthesis reaction. It was revealed that deactivation behaviors of Co/TiO₂ and Pd–Al₂O₃ catalysts were governed by different factors. Wax accumulation and Co sintering were responsible for deactivation of Co/TiO₂ catalyst in the Fischer–Tropsch synthesis reaction. Loss of Pd dispersion and Pd surface area of Pd–Al₂O₃ catalyst was responsible for its decreased catalytic performance in the production of middle distillate through hydrocracking of wax.