For Fischer–Tropsch Research Articles

Sonochemical and mechanochemical synthesis of iron-based nano-hydrotalcites promoted with Cu and K as catalysts for CO and CO2 Fischer-Tropsch synthesis

A novel class of Fe-based nano hydrotalcites as catalysts for Fischer-Tropsch (FT) synthesis, with a focus on CO2 hydrogenation have been prepared, characterized and tested. These catalysts were synthesized using two green, energy- and time-saving synthesis methods: ultrasound-assisted co-precipitation and solvent-free mechanochemical syntesis. The catalysts demonstrate very satisfactory CO and CO2 conversion capacities, in particular with good selectivities towards heavy hydrocarbons. The ultrasound-processed variant is particularly noteworthy, displaying about 10 % higher activity under specific conditions. The unique physicochemical properties of these catalysts, which were extensively characterized by XRD, TGA, (ATR) FT-IR, ICP-OES, SEM, TEM, BET, and TPR, are responsible for their remarkable potential for CO and CO2 conversion with varied product distribution. These findings highlight as these iron-based hydrotalcites can be considered as a new promising class of catalyst for CO and CO2 conversion by Fischer-Tropsch reaction.

Liquid fuel production from syngas: Simulation and optimization using artificial neural network

This study aimed to increase liquid fuel (C5+) product selectivity from CO and H2 conversion over a Cu/Fe-based catalyst and followed by artificial neural network simulation to enable a profound visualization strategy for Fischer–Tropsch (FT) process. The experiments were performed in a fixed-bed reactor over temperatures (T) of 483–553 K, pressures (P) of 14.5–203 psig, space velocities (SV) of 1000–2900 hr−1, and H₂/CO feed ratios of 1–6.2. Mathematical modeling (MM) and artificial neural network (ANN) were utilized to simulate the nonlinear CO conversion and product selectivity of the FT process. Nine simultaneous reaction pathway was developed to evaluate the reactant and product behaviors under varying FT conditions. In addition, a multilayered parameter processed by a neural network was used to predict the performance of the CO hydrogenation process. A comparison between these two approaches demonstrated that ANN more closely mimicked the nonlinear conversion and selectivity of the FT process than MM, and the correlation coefficients for the predicted mole fractions and CO conversion were 0.991 and 0.986, respectively. A hybrid Genetic Algorithm–ANN procedure was constructed to predict the optimum operating conditions to increase liquid fuel over the catalyst. The optimum C5+ selectivity (75.1 %), which meets the FT process objective, was achieved under operating conditions of T = 483 K, P = 203 psig, SV = 1303 hr−1, and H₂/CO feed ratio = 1.01 for process design optimization.

Optimization of Syngas Quality for Fischer-Tropsch Synthesis

While fossil oil reserves have been receding, the demand for diesel and gasoline has been growing. In recent years, syngas of biomass origin has been emerging as a viable feedstock for Fischer-Tropsch (FT) synthesis, a process for manufacturing synthetic gasoline and diesel. This paper reports the optimization of syngas quality to match the FT synthesis requirement. The optimization model maximizes the thermal efficiency under the constraint of H 2 / C O ≥ 2.15 and operating conditions of equivalent ratio ( E R = 0.0 -1.0), steam to biomass ratio ( S B = 0.0 -5.0), and gasification temperature ( T g = 500 °C-1300°C). The optimization model is executed using the optimization section of the Model Analysis Tools of the Aspen Plus simulator. The model is tested using eleven (11) types of municipal solid waste (MSW). The optimum operating conditions under which the objective function and the constraint are satisfied are E R = 0 , S B = 0.66 -1.22, and T g = 679 -763°C. Under optimal operating conditions, the syngas quality is H 2 = 52.38 -58.67 mole percent, lower heating value L H V = 12.55 -17.15 MJ/kg, and N 2 = 0.38 -2.33 mole percent. From an economic point of view, 12.98% to 33.12% of biomass is used as fuel for steam generation, drying, and pyrolysis. The generalized optimization model reported could be extended to any other type of biomass and coal.

Carbon capture and utilization: More than hiding CO2 for some time

Carbon capture and utilization: More than hiding CO2 for some time

The water assisted vinylene mechanism for cobalt Fischer-Tropsch synthesis assessed by multi-catalyst modelling of kinetics and deactivation

The paper describes development of a mechanism and a consistent rate expression for Fischer-Tropsch (FT) synthesis over cobalt-based catalysts. The developed mechanism relies on a two-step hydrogen assisted activation of CO. The carbon atom of CO is first hydrogenated by surface hydrogen to formyl; followed by the rate-limiting step whereby the oxygen atom is hydrogenated by adsorbed water. The produced CH* monomer is incorporated into the growing chain giving vinylene intermediate. The vinylene intermediate is either terminated to an olefin by adding hydrogen to the α-carbon atom or propagates by adding hydrogen to the β-carbon position. The resulting expression for CO consumption, the Fischer-Tropsch rate, can respond positively or negatively to the partial pressure of water, in agreement with experimental observations. A special feature is that the chain propagation probability does not depend on the partial pressure of hydrogen. The resulting kinetic model is tested on several cobalt catalysts supported on alumina; spanning from γ-alumina with average pore sizes ranging from 6.1 to 18.3 nm to α-alumina with a wide pore structure; and with cobalt particle sizes from 8 to 19 nm. Water was added sequentially to the syngas feed, causing enhanced deactivation, for testing the water response on activity and selectivity. A deactivation model comprising sintering and cobalt oxidation, and the FT-kinetics, describe the observed CO conversions with great precision for all catalysts. Selectivities are also well described, but with slight deviations at least partly due the effect of deactivation. Trends in some of the kinetic parameters are rationalized in terms of cobalt crystallite and pore sizes.

Dynamic process simulations and control of a lignite/waste to Fischer Tropsch liquids plant

This study comprises the dynamic process simulations of a HTW gasification plant for Fischer-Tropsch (FT) liquids production under transient feedstock of lignite and solid recovered fuel (SRF) as well as load variations. Main objective of the current study is the proof of concept in unsteady conditions and the effective plant wide control of a novel gasification-driven liquid fuels production pathway. Therefore, the dynamic analysis of all sub-units in an integrated simulation scheme by means of Aspen Plus Dynamics (APD) and MATLAB/Simulink interference is attempted. In this way, it is possible to evaluate the impact of system disturbances on every process stage and apply the required control strategies to ensure system stability. Another aspect addressed within this work is the alternative management of solid materials in APD environment, which is an inherent drawback of this otherwise appropriate software as mentioned in previous studies. The performed dynamic simulations revealed that the proposed value chain seems to have a respectable potential in terms of operational flexibility and performance stability, always in relation to the gasification-based chemical plants and the constraints that accompany them.

Activation of Cobalt Foil Catalysts for CO Hydrogenation

CO hydrogenation has been studied on cobalt foils as model catalysts for Fischer–Tropsch (FT) synthesis. The effect of pretreatment (number of calcinations and different reduction times) for cobalt foil catalysts at 220 °C, 1 bar, and H2/CO = 3 has been studied in a microreactor. The foils were examined by scanning electron microscopy (SEM). It was found that the catalytic activity of the cobalt foil increases with the number of pretreatments. The mechanism is likely an increase in the available cobalt surface area from progressively deeper oxidation of the foil, supported by surface roughness detected by SEM. The highest FT activity was obtained using a reduction time of only 5 min (compared to 1 and 30 min). Prolonged reduction caused the sintering of cobalt crystallites, while too short of a reduction time led to incomplete reduction and small crystallites susceptible to low turn-over frequency from structure sensitivity. Larger crystals from longer reduction times gave increased selectivity to heavier components. The paraffin/olefin ratio increased with the increasing number of pretreatments due to olefin hydrogenation favored by enhanced cobalt site density. From the results, it is suggested that olefin hydrogenation is not structure sensitive, and that mass transfer limitations may occur depending on the pretreatment procedure. Produced water did not influence the results for the low conversions experienced in the present study (<6%).

Study of the detailed catalyst hydrodynamics using radioactive particle tracking technique in a mimicked Fischer-Tropsch slurry bubble column

Slurry bubble column reactor (SBCR) is the preferred choice of reactor for Fischer – Tropsch (FT) synthesis. However, the understanding of the catalyst flow dynamics in FT-SBCR is still lacking. In this work, hydrodynamics of the FT catalyst were studied using computer aided radioactive particle tracking (CARPT) technique at the mimicked conditions of FT synthesis for the first time. Solids ensemble averaged velocity, turbulent kinetic energy, Reynolds normal and shear stresses were experimentally obtained. Effect of operating conditions on the velocity flow field were investigated. Further, studies were conducted to quantify the difference in flow field due to the change in the liquid and solid phases. It was found that the change of solids turbulence is insignificant with pressure and solids loading at the studied operating conditions. Further, it was found that the surface tension of the fluid and the solid properties plays a dominant role on the turbulence.

Stabilization of \u03b5-iron carbide as high-temperature catalyst under realistic Fischer\u2013Tropsch synthesis conditions

The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. ε-Iron carbide (ε-Fe2C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K). Here, we succeed in stabilizing pure-phase ε-Fe2C nanocrystals by confining them into graphene layers and obtain an iron-time yield of 1258 μmolCO gFe−1s−1 under realistic FT synthesis conditions, one order of magnitude higher than that of the conventional carbon-supported Fe catalyst. The ε-Fe2C@graphene catalyst is stable at least for 400 h under high-temperature conditions. Density functional theory (DFT) calculations reveal the feasible formation of ε-Fe2C by carburization of α-Fe precursor through interfacial interactions of ε-Fe2C@graphene. This work provides a promising strategy to design highly active and stable Fe-based FT catalysts.

Impact of Coordination Features of Co(II)-Glycine Complex on the Surface Sites of Co/SiO2 for Fischer–Tropsch Synthesis

To investigate the effect of coordination features of Co(II)-glycine complex on the performance of Co/SiO2 for Fischer–Tropsch (FT) synthesis, Co(II)-glycine complex precursors were prepared by the conventional method, i.e., simply adding glycine to the solution of Co nitrate and novel route, i.e., reaction of glycine with cobalt hydroxide. The SiO2-supported Co catalysts were prepared by using the different Co(II)-glycine complexes. It is found that glycine is an effective chelating agent for improving the dispersion of Co and the mass-specific activity in FT synthesis when the molar ratio of glycine/Co2+ = 3, which is independent to the preparation method in this study. Significantly, the surface Co properties were significantly influenced by the coordination features of the Co2+ and the molar ratio of glycine to Co2+ in the Co(II)-glycine complex. Specifically, the Co(3gly)/SiO2 catalyst prepared by the novel route exhibits smaller and homogenous Co nanoparticles, which result in improved stability compared to Co-3gly/SiO2 prepared by the conventional method. Thus, the newly developed method is more controllable and promising for the synthesis of Co-based catalysts for FT synthesis.

Co-Ru catalysts with different composite oxide supports for Fischer–Tropsch studies in 3D-printed stainless steel microreactors

Bimetallic Co-Ru on different mesoporous composite oxides (m-SiO2-Al2O3, m-SiO2-TiO2, m-TiO2-Al2O3) and CoRu-m-SiO2-TiO2 were synthesized by incipient wet-impregnation (IWI) and one-pot (OP) hydrothermal methods, respectively. Bimetallic catalysts were coated in the microchannels of 3D-printed stainless steel (SS) microreactors for Fischer-Tropsch (FT) studies. The physiochemical properties of the catalysts were examined by BET, XRD, SEM, TEM, TPR, TGA-DSC and XPS techniques. The TPR results showed that the method and the composite support had a profound effect on the reducibility of the active sites. All the catalysts resisted deactivation for first 50 h and 10Co5Ru/m-SiO2-TiO2 (IWI) was most stable with ∼80 % CO conversion at the end of 60 h. The stability and activity of the catalysts were observed in the order: 10Co5Ru/m-SiO2-TiO2 (IWI) >10Co5Ru/m-SiO2-Al2O3 (IWI) >10Co5Ru/m-Al2O3-TiO2 (IWI) >10Co5Ru-m-SiO2-TiO2 (OP). The TPO and XRD analyses of the spent catalysts confirmed coking as a potential factor but not the only cause of catalyst deactivation over time.

Preparation of Synthesis Gas from CO2 for Fischer–Tropsch Synthesis—Comparison of Alternative Process Configurations

We compare different approaches for the preparation of carbon monoxide-rich synthesis gas (syngas) for Fischer–Tropsch (FT) synthesis from carbon dioxide (CO2) using a self-consistent design and process simulation framework. Three alternative methods for suppling heat to the syngas preparation step are investigated, namely: allothermal from combustion (COMB), autothermal from partial oxidation (POX) and autothermal from electric resistance (ER) heating. In addition, two alternative design approaches for the syngas preparation step are investigated, namely: once-through (OT) and recycle (RC). The combination of these alternatives gives six basic configurations, each characterized by distinctive plant designs that have been individually modelled and analyzed. Carbon efficiencies (from CO2 to FT syncrude) are 50–55% for the OT designs and 65–89% for the RC designs, depending on the heat supply method. Thermal efficiencies (from electricity to FT syncrude) are 33–41% for configurations when using low temperature electrolyzer, and 48–59% when using high temperature electrolyzer. Of the RC designs, both the highest carbon efficiency and thermal efficiency was observed for the ER configuration, followed by POX and COMB configurations.

Microwave Assisted Co/SiO2 preparation for Fischer-Tropsch synthesis

Cobalt catalyst has been widely used for Fischer-Tropsch (FT) Synthesis in Industry. The most common method to prepare cobalt catalyst is impregnations. Metal is deposited on porous support by contacting dry support with solution containing dissolved cobalt precursor. This step will follow by drying, calcination and reduction. The heating step used in this conventional method, however, may lead to the formation of metal silicate which is inactive site for catalysis. In this study, author explore the use of microwave to prepare catalyst compared to conventional drying method. Cobalt catalyst with SiO2 support was prepared and characterized. Particle size, surface area, and cobalt content were investigated. Crystallite size of 3-8 nm was formed which was reported to be the optimum size for cobalt catalyst in FT Synthesis. Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM) image revealed that microwave catalyst showed better uniformity and cobalt dispersion on silica support. Thermo-Gravimetric Analysis (TGA) study also indicated that this catalyst has good stability at Low Temperature Fischer-Tropsch Synthesis. The catalysts were then applied plasma assisted FT process over a range of power plasma (20-60W) to investigate the effect on the conversion and selectivity. The results showed that microwave catalyst exhibit lower CO conversion at 42.06% compared to conventional method at 68.32%. However, microwave catalyst is more favourable for long chain hydrocarbon selectivity.

Composite mesoporous SiO2-Al2O3 supported Fe, FeCo and FeRu catalysts for Fischer-Tropsch studies in a 3-D printed stainless-steel microreactor

Composite oxide support, SiO2-Al2O3, with high surface area, was prepared by one-pot procedure, and 10 wt%Fe, 10%Fe5%Co, and 10%Fe5%Ru were impregnated for Fischer-Tropsch (FT) studies. BET studies show the hysteresis loop for mesoporous (m) structure of the composite. H2-TPR studies showed the effect of Ru and Co on iron oxide reduction at lower temperature and XPS studies confirmed two oxidation states for cobalt and iron with different binding energies. The FT studies in a 3D printed stainless steel (SS) microchannel microreactor were performed at 1 atm at 300 °C. 10Fe5Ru catalyst showed better CO conversion and higher selectivity to C1–C3 hydrocarbons.

Removal of sodium compounds from Co/SBA-15 catalysts for Fischer-Tropsch Synthesis

In the present work, the synthesis of Co/SBA-15 catalysts intended for Fischer-Tropsch (FT) synthesis was performed. During the synthesis of catalysts there was contamination of samples with sodium nitrate due to the nature of the reducing agent used for the synthesis of metallic phase. This kind of impurity is not advantageous for the FT reaction. Attempts at removal of sodium compounds were carried out by means of simple leaching treatments, using ethanol and acid ethylenediaminetetraacetic (EDTA) as solvent and complexing agent, respectively, followed by heat treatment at temperatures of 150 or 300°C. It was possible to conclude that the treatment using EDTA was more effective in removing almost all the alkaline phase of samples, despite the occurrence of oxidation, agglomeration, and removal of the metal nanoparticles in this process. In addition, there were no significant differences in the product selectivity of FT synthesis of the catalysts after sodium removal, although the nanoparticles were larger than 10 nm.

A simple coupled ANNs‐RSM approach in modeling product distribution of Fischer‐Tropsch synthesis using a microchannel reactor with Ru‐promoted Co/Al 2 O 3 catalyst

A simple approach using hybrid artificial neural networks (ANNs)-response surface methodology (RSM) was developed to model the detailed product distribution using Ru-promoted cobalt-based catalyst with Al2O3 as the support in a microchannel reactor for Fischer-Tropsch (FT) synthesis. Using the independent process parameters for training, the established model is capable of predicting hydrocarbon production distributions, ie, paraffin formation rate (C2-C15) and olefin to paraffin ratio (OPR C2-C15) within acceptable uncertainties. The ANNs-RSM model and comprehensive mechanistic model using the Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach were compared to identify a few inherent advantages of the proposed model in modeling complex FT synthesis. The proposed ANNs-RSM model shows its appealing merits, ie, faster converge and higher accuracy (less than ±10% uncertainties was achieved from ANNs-RSM model, while LHHW model achieved less than ±15% uncertainties except a few exceptional high errors uncertainties at certain experimental conditions). The statistical significances to the product distributions and hydrocarbon formation rate during FT synthesis could be easily identified and quantitatively analyzed by the established ANNs-RSM model. The future effective alternative of kinetic study of the complex system such as FT synthesis in the microstructured reactor might follow the methods of using empirical reliable approach for process optimization together with mechanistic kinetic study for detailed reaction pathway discrimination.

Investigating the feasibility of valorizing residual char from biomass gasification as catalyst support in Fischer-Tropsch synthesis

In spite of its remarkable properties and similarities to more traditional activated carbon (AC), biomass gasification char is considered a worthless material and treated as an industrial waste. However, similar to AC, char could be valorized in several applications. This study investigates the application of char as catalyst support for Fischer-Tropsch (FT) synthesis. For this purpose, char derived from a biomass gasifier operating in South Tyrol, Italy, was collected, characterized, acid treated and used as support for the catalysts preparation. Cobalt and iron were used as active metals and impregnated on char with a 10% metal loading (10Co and 10Fe). Catalysts were characterized through different techniques. FT tests were run in a fixed bed reactor operating at T = 240 °C, p = 1.6 MPa, H2/CO = 2, WHSV = 3600 mL g−1 h−1.10Fe was also tested at 250 °C. Catalysts performances in terms of CO conversion, CH4 and CO2 selectivity, and product distribution were analyzed and compared. The highest CO conversion (26%) was measured for 10Fe at 250 °C. For 10Fe, C1 - C22 hydrocarbons were detected, while for 10Co also C22 - C24. Only production of C13 - C19 was superior for 10Fe than 10Co.

Boosting carbon efficiency of the biomass to liquid process with hydrogen from power: The effect of H2/CO ratio to the Fischer-Tropsch reactors on the production and power consumption

Carbon efficiency of a biomass to liquid process can be increased from ca. 30 to more than 90% by adding hydrogen generated from renewable power. The main reason is that in order to increase the H2/CO ratio after gasification to the value required for Fischer-Tropsch (FT) synthesis, the water gas shift reaction step can be avoided; instead a reversed water gas shift reactor is introduced to convert produced CO2 to CO. Process simulations are done for a 46 t/h FT biofuel production unit. Previous results are confirmed, and it is shown how the process can be further improved. The effect of changing the H2/CO ratio to the Fischer-Tropsch synthesis reactors is studied with the use of three different kinetic models. Keeping the CO conversion in the reactors constant at 55%, the volume of the reactors decreases with increasing H2/CO ratio because the reaction rates increase with the partial pressure of hydrogen. Concurrently, the production of C5+ products and the consumption of hydrogen increases. However, the power required per extra produced liter fuel also increases pointing at optimum conditions at a H2/CO feed ratio significantly lower than 2. The trends are the same for all three kinetic models, although one of the models is less sensitive to the hydrogen partial pressure. Finally, excess renewable energy can be transformed to FT syncrude with an efficiency of 0.8–0.88 on energy basis.

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

Flame-spray-pyrolysis amorphous alumina-silica for tailoring the product distribution of Fischer-Tropsch synthesis

Abstract The solid acid in metal-acid bifunctional catalysts for Fischer-Tropsch (FT) synthesis plays a crucial role for one-step selective synthesis of liquid fuels such as gasoline or diesel. In this work, the amorphous silica-alumina (ASA) synthesized by a one-step flame spray pyrolysis method (FSP) was demonstrated for the first time as an efficient solid acid for regulating the product distribution of FT synthesis. The 3 wt.% Ru impregnated ASA with different Al/(Al+Si) ratios was comparatively investigated for FT synthesis under typical conditions. The materials were characterized by XRD, STEM, H2-TPR, NH3-TPD, and N2 adsorption/desorption at low temperatures. In comparison with the ASA synthesized by the traditional sol-gel method, the ASA prepared by the FSP method showed clearly increased acidity. As a result, the selectivity of C13+ hydrocarbons was decreased while the selectivity of C5-12 hydrocarbons was increased, the extent of which is clearly dependent on the Al/(Al+Si) ratio of ASA. Moreover, both the carbon-chain length and the composition of olefins, normal and branched alkanes of FT products were easily regulated in a certain extent by simply changing the Al/(Al+Si) ratio of ASA. Thus, the enhanced and easily regulated acidity, rich porous structure, and available large-scale production of the ASA originated from FSP method make it an important solid acid for selective synthesis of liquid fuels via FT route.