Slurry Phase Fischer Tropsch Synthesis Research Articles

The value-added of dual-stage entrained flow gasification and CO2 cycling in biomass-to-gasoline/diesel: Design and techno-economic analysis

Interests in securing alternatives to oil have been intensified in recent years. This work provides a conceptual design of a highly efficient Biomass-to-Liquid (BTL) fuels process that produces gasoline and diesel. It incorporated the configuration of biomass pre-pyrolysis followed by entrained flow gasification, which avoided separate torrefaction of feedstock and provided more syngas with a higher cold gas efficiency. The application of Fe-based slurry-phase Fischer-Tropsch synthesis further improved the gasoline/diesel yield to 10.2 GJ/t dry biomass with an overall energy efficiency of 58%, which is higher than current reports. However, the water consumption of BTL was much more than that of conventional petroleum refinery. A CO2 cycling scheme was developed in this design to reduce water consumption. The value-added of these features and performance of this BTL system are revealed. The production cost of this BTL was approximately 5,115∼5,683 CNY/t with a breakeven crude oil price of 83∼93 $/bbl.

Precisely designing bimodal catalyst structure to trap cobalt nanoparticles inside mesopores and its application in Fischer-Tropsch synthesis

Bimodal catalyst support is a widely applied concept in solid catalysts but until now the supported metal on the bimodal support has no satisfied dispersion and the average metal particle size is generally larger than the pore size of small pores (mesopores) of the bimodal structure, lowering the power and significance of the bimodal structure. To overcome this problem, a novel ZrO2SiO2 bimodal pore support with enlarged depth of small pores, was successfully fabricated though self-assembly of nanosized ZrSiO4 inside pore of silica gel. Cobalt was finely dispersed on bimodal support by incipient-wetness impregnation. The bimodal support and catalyst were characterized by various techniques, such as BET, TEM, XRD, and TPR and H2-chemisorpion. The bimodal catalyst was applied in slurry-phase Fischer-Tropsch synthesis. Characterization results suggested that bimodal pore support processed larger BET surface than pristine silica gel, due to the newly formed small pores organized by packing of the ZrSiO4 nanoparticles. The enlarged BET surface area leaded to good dispersion of cobalt species. More importantly, it was observed that the deep small pores could serve as traps for Co nanoparticles, preventing sintering and agglomeration due to confinement effect. Co/30wt%ZrO2-Q-50 and Co/20wt%ZrO2-Q-100 bimodal catalyst with large BET surface and deep small pores exhibited excellent catalytic activity, and selectivity to heavy hydrocarbons due to high dispersion of cobalt and unique pore structure, while coexisting ZrO2 promoted the reduction of finely-dispersed cobalt oxide nanoparticles. It is interesting to find that different from the conventional theory where small metallic particle lowers chain-growth probability, the trapped smaller Co particles inside deep small pores achieved higher chain-growth probability due to the facilitated re-adsorption of olefinic intermediates happening inside deep small pores.

Expanding Small Pore Size of the Bimodal Catalyst with Surfactant and Its Application in Slurry-phase Fischer-Tropsch Synthesis

The pore size effect on the reaction activity and hydrocarbon selectivities of Fischer-Tropsch synthesis (FTS) is investigated on the Co-based bimodal catalysts with tunable small pores and large pores, prepared by employing various surfactants, such as PEG400, PEG600 and P123. The small pore size is enlarged to 4–10 nm, higher than conventional bimodal catalysts prepared by nanoparticles from sol or solution of support precursor. The depth of small pores can also be enlarged by increasing the ZrSiO4 loading amount of the Zr−Si bimodal support, promoting dispersion of cobalt nano-crystallite. The higher cobalt reduction degree is achieved on these small pore enlarged catalysts, enhancing the activity of FTS. The P123-assisted one exhibits the highest CO conversion owing to its largest small pore size. The enlarged small pore of 5 nm prepared with PEG400 is the optimized pore size to accelerate the carbon chain growth reaction, producing more heavy hydrocarbons compared to the others.

Mn and Zr modified Co/SiO2 catalysts development in slurry-phase Fischer–Tropsch synthesis

A series of SiO2-supported, Mn- and Zr-modified Co catalysts were synthesized using different preparation methods and varying Mn and Zr loadings. The effects of these variations on the applicability of the resulting catalysts to the Fischer–Tropsch synthesis reaction were subsequently investigated. The coimpregnation of the SiO2 support with Co, Mn and Zr produced the most attractive catalytic properties among the three synthetic methods of coimpregnation, sequential impregnation and reverse sequential impregnation. The addition of moderate amount of Mn and Zr affected both the Co reducibility and dispersion. Based on the results of various characterizations, we conclude that the enhanced Fischer–Tropsch synthesis activity of the coimpregnation Mn+Zr+Co/SiO2 catalyst can be attributed to the formation of highly dispersed Co metal particles which have interacted with Mn species.

A comparison of cobalt and iron based slurry phase Fischer–Tropsch synthesis

This article provides a comparison between cobalt and iron catalysts for use in the slurry phase Fischer–Tropsch synthesis. The themes covered include the typical catalyst preparation methods and properties, catalyst deactivation behaviour, reaction kinetic considerations and the effect of metal crystallite size on catalytic performance. Finally, the implications of catalyst choice for application in different reactors are discussed, paying specific attention to the maximum production capacity of a single reactor.

Evaluation of Laboratory Methods for the Acquisition of Catalyst from Fischer–Tropsch Wax/Catalyst Mixtures

Catalyst breakdown by physical attrition and chemical stresses is a problem of great and continuing concern in the slurry phase Fischer–Tropsch Synthesis. To reach a better understanding of the morphology and composition of a working catalyst, it requires first the removal of wax from the catalyst. In this work, Improved Soxhlet Extraction (ISE) in comparison of Standard Soxhlet Extraction was evaluated concerning their separation efficiency and relevancy for characterization of working catalysts. ISE extracted a greater amount of wax and recovered nearly all of the catalyst. In addition, ISE does not change the morphology and particle size distribution of working catalysts whereas Soxhlet extraction fails to reflect the actual information on the catalyst. The ISE is appropriate for the rapid and accurate analysis in plant operation.

A Study on Vapour-Liquid Equilibria in Fischer-Tropsch Synthesis

Slurry phase Fischer-Tropsch synthesis is an important and promising route to produce clean fuels and valuable long chain hydrocarbons from synthesis gas. An important phenomenon in these kinds of reactors is the vapour-liquid equilibrium. Due to the complexity both in the reaction and hydrodynamics of these reactors, most of the reported work are on hydrodynamics and then on reaction and less attention has been paid to the vapour-liquid equilibria. This work shows an effort to present a reliable method for phase equilibria in slurry reactor for Fischer-Tropsch Synthesis. Different equation of states, and the empirical Henry's correlation have been applied to a set of experimental data in non-reactive environment and it was tried to get a good fit, by introducing some adjustable parameters. It was shown that a modified SRK equation of state is the most appropriate for prediction the phase equilibria in Fischer-Tropsch synthesis reactor.

Crucial factors for catalyst aggregation and deactivation on Co/Al 2O 3 in a slurry-phase Fischer–Tropsch synthesis

The different behaviors for catalyst deactivation by forming aggregated catalyst lumps were investigated on the phosphorous-modified Co/P–Al 2O 3 and the unmodified Co/Al 2O 3 Fischer–Tropsch synthesis (FTS) catalysts in a slurry-phase continuous stirred tank reactor. The lower catalytic activity at steady-state with a fast deactivation rate was observed on the phosphorous-unmodified Co/Al 2O 3 catalyst due to the facile formation of aggregated catalyst lump with a high hydrophilic property of support and a significant hydrocarbon deposition on catalyst surface. The amount of adsorbed water and the deposited hydrocarbons are strongly related with aggregated catalyst lump formation. The adsorbed water could possibly transform the local γ-Al 2O 3 surface to pseudo-boehmite (Bronsted acidic Al 2OH sites) material which is characterized as a low attrition resistance and accelerates the formation of fine powders during FTS reaction. The formed fine powder during FTS reaction could be easily aggregated and it is resulted in catalyst deactivation due to the difficult intraparticular diffusion of reactants. The possible mechanisms of phase transformation of γ-Al 2O 3 to pseudo-boehmite and formation of aggregated catalyst lump were suggested by measuring the deposited hydrocarbons and the concentration of adsorbed water on catalyst surface with the help of the characterizations such as X-ray photoelectron spectroscopy, temperature-programmed surface reaction, diffuse reflectance infrared Fourier transform and water-sorption method.

Surface Impregnation Combustion Method to Prepare Nanostructured Metallic Catalysts without Further Reduction: As-Burnt Co/SiO2 Catalysts for Fischer–Tropsch Synthesis

A series of the as-burnt supported metallic catalysts (Co/SiO2) were prepared by a novel surface impregnation combustion method using cobalt nitrates (noted as M) and citric acid (noted as CA), and burnt in the argon atmosphere. H2 and CH4 which were derived from the decomposition of the CA, acted as the reducing agents for synthesizing metallic Co from Co2+ in the chelated compounds. The X-ray diffraction (XRD) patterns revealed that all the as-burnt catalysts with different M/CA molar ratios were converted into Co and CoO species supported on SiO2 (Q-50). The as-burnt catalyst C1.5, with M/CA = 1/1.5, was almost fully converted to metallic Co species and amorphous carbon supported on SiO2. With increase of the content of CA in the initial precursors, the reduction degree of the as-burnt catalysts which was measured by temperature-programmed reduction (TPR) and the dispersion of metallic cobalt increased gradually. The as-burnt catalysts were used directly in slurry-phase Fischer-Tropsch synthesis (FTS) ...

Deactivation behaviors of Pt or Ru promoted Co/P-Al2O3 catalysts during slurry-phase Fischer–Tropsch synthesis

The catalytic stability of cobalt-based catalyst using phosphorous-modified alumina support (P-Al2O3), promoted with Pt or Ru, during Fischer–Tropsch synthesis (FTS) has been investigated for 1000 h on stream using a slurry-phase continuous-stirred tank reactor. Although catalytic properties such as surface area and particle size of metallic cobalt are similar for both the catalysts, the different deactivation behaviors were observed with respect to the kind of noble metal addition. The slower catalyst deactivation was observed on Pt promoted Co/P-Al2O3 catalyst than Ru promoted one, which seems to be owing to small deposition of polymeric carbons on the surface, confirmed by hydrogenation of surface carbons, and suppressed formation of aggregated catalyst lump at the beginning of FTS reaction.

Catalytic performance and attrition strength of spray-dried iron catalysts for slurry phase Fischer–Tropsch synthesis

Three iron Fischer–Tropsch (F–T) catalysts (100 Fe/3 Cu/5 K/16 SiO 2 in parts by weight) in the form of micro-spherical particles were prepared by spray drying. Their particle size distribution was rather broad, ranging from 5 to 40 μm in diameter, regardless of the source of silica (colloidal silica, tetraethyl orthosilicate, or potassium silicate) employed in their preparation. Catalyst prepared employing colloidal silica had the highest attrition strength among all catalysts studied. After 345 h of testing in a stirred tank slurry reactor its morphology remained essentially unchanged, and it experienced small reductions in the volume mean diameter (5.4%) and generation of particles smaller than 10 μm in diameter was very small (0.7%). Catalytic performance of these catalysts during F–T synthesis was excellent. Syngas conversion was between 71 and 76%, whereas methane selectivity was between 2.0 and 3.5% and that of C 5 + hydrocarbons was 78–89% (on C-atom basis).

One-Step Preparation of Bimodal Fe–Mn–K/SiO2 Catalyst and its Catalytic Performance of Slurry Phase Fischer–Tropsch Synthesis

Bimodal pore Fe–Mn–K catalysts supported onto SiO2 pellet were prepared by a one-step incipient wetness impregnation method. In this method, the active component and promoters were used as the “bricks” to directly build up the small pores inside the large pores of silica gel. The catalysts were applied to catalyze Fischer–Tropsch synthesis in slurry phase. Compared with the SiO2 supported non-bimodal catalysts, the bimodal catalysts exhibited excellent activity due to the improved active metal dispersion and the fastened diffusion efficiency. The preparation method was much more feasible than the previous two-step method, and can be extended to prepare bimodal catalysts with different active components. Bimodal pore Fe–Mn–K catalysts were prepared by a one-step incipient wetness impregnation method using the active component and promoters as the “bricks” to directly build up the small pores inside the large pores of silica gel. The prepared catalyst exhibited excellent activity in slurry phase Fischer–Tropsch synthesis.

Design and Determination of New Bimodal Pore Catalyst Structure with Hetero Atom Combination by Inside-Pore Organization of Nano-Particles from Sol

A catalyst support with spatially-connected small pores and large pores, as a distinct bimodal pore structure, has been developed, which has excellent advantages in solid-catalysis reactions because the large pores provide pathways for rapid molecular transportation and the small pores serve a large area of active surface. The obtained ZrO2-SiO2 bimodal support loaded with cobalt was applied in slurry-phase Fischer-Tropsch synthesis (FTS). The bimodal catalyst presented the best reaction performance in slurry-phase FTS as higher reaction rate and lower methane selectivity, because the spatially promotional effect of bimodal structure and the chemically promotional effect of the porous zirconia were available at the same time inside the large pores of original silica gel.

Slurry-Phase Fischer–Tropsch Synthesis Using Co/γ-Al2O3, Co/SiO2 and Co/TiO2: Effect of Support on Catalyst Aggregation

The catalytic performance of Co/γ-Al2O3, Co/SiO2 and Co/TiO2 catalysts has been investigated in a slurry-phase Fischer–Tropsch Synthesis (FTS). Although Co/SiO2 catalyst shows higher CO conversion than the other catalysts, the intrinsic activity is much higher on Co/TiO2 due to large pore size and low deactivation of large cobalt particles by reoxidation mechanism. Co/γ-Al2O3 catalyst confirms low formation rate of oxygenates and C5+ selectivity because of deactivation of catalyst due to catalyst aggregation and reoxidation by the in situ generated water during the FTS reaction. Long-chain hydrocarbons such as wax formed during FTS reaction generally contains water and trace amount of oxygenate which are conducive to the formation of a macro-emulsion of wax products. Formation of such macro-emulsion on the catalyst suggests that the presence of proper amount of alcohol content derived FTS reaction on large pore of catalyst inhibits the catalyst aggregation. The intrinsic activity (turn-over frequency; TOF) of cobalt-based catalysts, in a slurry-phase FTS reaction, is affected by the average pore size of catalyst, cobalt particle size, degree of reduction of cobalt species and possible reoxidation by in situ generated water.

Kinetic modeling of Fischer–Tropsch synthesis over [formula omitted] catalyst in slurry phase reactor

Comprehensive kinetics of slurry phase Fischer–Tropsch synthesis (FTS) on an industrial Fe – Cu – K – SiO 2 catalyst, in the presence of water–gas shift (WGS), is studied using a stirred tank slurry reactor. A series of rival models for FTS and WGS reaction are derived using Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach. In order to describe the deviation from ideal hydrocarbon distribution, secondary reactions of primary olefin on a separated active site and its chain length dependent solubility in slurry phase are taken into account. It is found that the optimal model is based on the mechanism that the rates of FTS are determined by insertion of methylene ( CH 2 ) via the alkylidene propagation mechanism and the rate of WGS reaction is controlled by the desorption of CO 2 via formate intermediate mechanism. Present model can describe the CO conversions and hydrocarbon distributions consistently and accurately over large interval of reaction conditions ( 523 – 563 K , 1.0 – 2.5 MPa , H 2 / CO ratio: 0.67 – 1.5 , and space velocity: 1000 – 2500 ml g cat - 1 h - 1 ) . On the other hand, the success predictions of the deviation from ideal distribution suggest the strong influence on the secondary reactions by the chain length dependent solubility of olefins.

An active and selective production of gasoline-range hydrocarbons over bifunctional Co-based catalysts

Catalytic performance of several bifunctional cobalt-based catalysts in slurry-phase Fischer–Tropsch synthesis has been investigated at 1 MPa and 230 °C. The catalysts were prepared according to the conventional impregnation method using SiO 2, Al 2O 3, montmorillonite (K10 ®), and various zeolites (USY, ZSM-5 and MCM-22) as a support. When an acidic support was applied, the formation of heavier hydrocarbons was retarded and the carbon number distribution was shifted to gasoline range (C 4–C 12). Montmorillonite loaded with Co (Co/MONT) was a good catalyst, showing higher the CO conversion than Co/SiO 2 and Co/Al 2O 3. MCM-22 exhibited a superior performance to other zeolitic supports. With decreasing aluminum content, the activity of Co/MCM-22 catalysts was remarkably enhanced and the selectivity to methane and isoparaffins decreased. Besides the high CO conversion (55–60%), C 4 + isoparaffins were produced more selectively over Co/MCM-22 (43–53%) than Co/USY (43.5%) and Co/ZSM-5 (36%). Compared to the results under supercritical conditions, the slurry-phase conditions are more suitable for an active and selective production of gasoline-range hydrocarbons through the Fischer–Tropsch synthesis over MCM-22 supported Co catalysts.

Attrition studies with catalysts and supports for slurry phase Fischer–Tropsch synthesis

Attrition properties of several oxide supports and precipitated iron-based F–T catalyst (100Fe/3Cu/4K/16SiO 2 in parts by weight) were evaluated using ultrasound irradiation test and stirred tank slurry reactor (STSR) test under non-reactive conditions. Attrition by fracture and erosion of the iron-based catalyst was small in both types of tests and its overall attrition strength was better than that of the alumina and silica supports, which were evaluated under the same conditions. Also, attrition studies with four iron-based F–T catalysts were conducted under reaction conditions in the STSR. Catalyst of similar composition, as that used in non-reactive studies, prepared by spray drying technique had the highest attrition strength among all catalysts tested.

Multi-functional alumina–silica bimodal pore catalyst and its application for Fischer-Tropsch synthesis

A multi-functional bimodal pore catalyst support, alumina–silica bimodal pore support, was prepared from a polymer complex solution and silica gel. The obtained bimodal pore support had two kinds of main pores; the pore volume was decreased and the specific surface area was enlarged, comparing with the original silica gel. This kind of bimodal pore support was applied in slurry phase Fischer-Tropsch synthesis, where cobalt was supported as active metal. Alumina–silica bimodal pore catalyst exhibited high catalytic activity and favorite selectivity, due to the spatial effects of bimodal pore structure and chemical effects of coexisting alumina, which formed the new small pores inside SiO 2 large pores. Alumina–silica bimodal pore catalyst showed higher activity than silica–silica bimodal pore catalyst with similar pore structure, proving that hetero-atom bond between alumina and silica was important to promote the performance of the dispersed cobalt. The various catalysts were characterized by XRD, chemisorption, in situ DRIFT, TPR, and TPSR. It was found that alumina in alumina–silica bimodal structure improved cobalt dispersion significantly while keeping the reduction degree almost the same. TOF of alumina–silica bimodal catalysts was the highest, supported by the largest bridge-type adsorbed CO peak in DRIFT observation of this catalyst, as bridge-type adsorbed CO was the active intermediate in FTS.

Preparation of alumina?silica bimodal pore catalysts for Fischer-Tropsch synthesis

The bimodal pore structure support has excellent advantages in solid catalysis reaction because the large pores provide pathways for rapid molecular transportation and small pores provide a large active surface, contributing to high diffusion efficiency and high dispersion of supported metal simultaneously, A multi-functional bimodal pore catalyst support, alumina-silica bimodal pore support, was prepared from polymer complex solution and silica gel. The obtained bimodal pore support had two kinds of main pores, decreased pore volume and enlarged specific surface area, comparing the original silica gel. This kind of bimodal pore support was applied in slurry phase Fischer-Tropsch synthesis, where cobalt was supported as active metal. Alumina-silica bimodal pore catalyst exhibited high catalytic activity and favorite selectivity, due to the spatial effects of bimodal pore structure and chemical effects of coexisting alumina, which formed the new small pores of bimodal pore support.

Calcination of Co-Based Fischer–Tropsch Synthesis Catalysts

The calcination of Co-based slurry-phase Fischer–Tropsch synthesis catalysts was investigated. Fischer–Tropsch synthesis is part of the gas-to-liquids (GTL) process that produces gas oil and naphtha from natural gas. For the GTL process, the preparation of highly active Co-based catalysts is of utmost importance. This paper shows that the conditions during the calcination of impregnated cobalt precursors have a significant influence on the performance of the final catalyst. The options of calcination in rotary kilns, furnaces and fluidized-bed reactors were considered. It was found that the catalyst performance is strongly dependent on the heating rate and the air-space velocity during the preferred option of fluidized bed calcination. The postulation that Co3O4 is not the preferred oxide phase of the calcined intermediate catalyst is supported by a temperature-programmed reduction (TPR) study.