Fixed-bed Fischer-Tropsch Synthesis Research Articles

Dynamic one-dimensional pseudohomogeneous model for Fischer-Tropsch fixed-bed reactors

A dynamic one-dimensional pseudohomogeneous fixed-bed Fischer-Tropsch synthesis (FTS) reactor model in a non-isothermal regime is developed. The proposed dynamic model is validated with experimental data obtained from the literature and is compared with simulations of a steady-state one-dimensional isothermal fixed-bed FTS reactor model recently reported. The best set of initial operating conditions showing highest syngas conversions (CO and H2) and high heavy hydrocarbons (C5+) selectivities correspond to temperature, pressure and gas hourly spaces velocity (GHSV) of 503 and 518 K, 1.0 and 1.5 MPa, and 1800 NmL/gcat·h respectively. The proposed model is able to accurately predict the CO conversion experimental data and products selectivity. Furthermore, it allows to evaluate the thermal behavior of the reactor, as well as to analyze the hot-spot generation typically observed in highly exothermic reactions such as in the case of the FTS reaction.

Optimizing the Preparation Conditions of Silica Supported Fe-Co-Ce Ternary Catalyst for the Fixed-bed Fischer-Tropsch Synthesis: Taguchi Experimental Design Approach

Using wet impregnation method, a novel ternary system of silica supported Fe-Co-Ce catalyst was prepared. Preparation conditions such as impregnation time and temperature, drying time and temperature, were optimized by the L9 Taguchi experimental design to achieve a light olefin selective catalyst with maximum CO conversion in a fixed bed micro-reactor. It was found that the best conditions to maximize the responses were obtained at 4h impregnation time, 60°C impregnation temperature, 6h drying time, 90°C drying temperature and 350°C of reaction’s temperature. Characterization of the optimal catalyst precursors and calcined samples before, and after the Fischer-Tropsch reaction was carried out using various techniques.

Parametric Study and Multiobjective Optimization of Fixed-Bed Fischer–Tropsch (FT) Reactor: The Improvement of FT Synthesis Product Formation and Synthetic Conversion

A mathematical model of a fixed-bed reactor for Fischer–Tropsch synthesis (FTS) over 37% Co/SiO2 catalyst was developed to investigate the performance of the whole process for products’ selectivity and syngas conversion. The model was capable of calculating the changes of reactant and products’ concentrations, partial pressures, conversion, and selectivity. In a previous study, a series of combined novel FT and water gas shift (WGS) reaction mechanisms (eight elementary FT reaction pathways along with seven WGS kinetics models) were developed in order to calibrate and validate the mathematical model along with reaction kinetics at different experimental conditions. Such mathematical models with reaction networks can be used as a key tool to emphasize the most significant facts of FTS catalysis and chemistry. Integration of the global search optimization algorithm with the developed model was explained for estimation of kinetics parameters. Data analyses were carried out to ensure that the predicted model ...

One-dimensional heterogeneous model of a Fischer-Tropsch synthesis reactor with a fixed catalyst bed in the isothermal granules approximation

A one-dimensional heterogeneous model has been developed for a cat6alytic fixed-bed Fischer-Tropsch (FT) synthesis reactor in the isothermal granules approximation. The FT process has been simulated for a laboratory-scale reactor. The effects of the linear gas velocity and of the inner diameter of the reactor on the thermal stability of the process are considered. The size of the reactor is limited by the possibility of a “thermal explosion” occurring in the frontal layer of the catalyst. Raising the linear gas velocity enhances heat transfer, thereby reducing the overheating of the catalyst bed. The synthesis of solid hydrocarbons can be conducted in reactors no larger than 18 mm in diameter. According to calculations, the maximum temperature drop in a 3-, 4-, and 6-m-long reactor is 4.7, 4.2, and 3.6°C, respectively. The corresponding CO conversion is 35.0, 34.4, and 33.9%, respectively. For producing liquid hydrocarbons in a high-performance reactor, it is necessary to decrease its inner diameter to 12 mm. In this case, the maximum temperature drop at a reactor length of 3, 4, and 6 m is 9.6, 8.7, and 7.6°C, and the CO conversion is 78.0, 77.4, and 76.7%, respectively. The mathematical model devised here provides means to estimate the necessary design parameters of the reactor and the appropriate FT synthesis conditions for producing liquid or solid hydrocarbons.

Fischer–Tropsch catalyst testing in a continuous bench-scale coal gasification system

A bench-scale oxygen-blown fluid-bed gasifier was coupled to a modular fixed-bed Fischer–Tropsch (FT) reactor system for testing an FT catalyst under syngas. Various blends of subbituminous coal, torrefied biomass, and untreated biomass were gasified at 22 bar absolute, 800°–860 °C, and 4 kg/h. Syngas exiting the fluid bed passed through a cyclone, candle filter, and sulfur sorbent to reduce fine particulate and H 2S to levels well below 1 ppmv. The syngas was cooled to condense out moisture and volatiles and then reheated to temperatures required for FT synthesis. The clean syngas then flowed into the FT reactor with a 5:1 ratio of recycled FT product gas-to-fresh syngas feed. A 70% overall conversion of CO and H 2 was achieved at 269 °C and 18.9 bar over an iron-based catalyst supported on gamma-alumina pellets.

Simulation and Analysis of a Tubular Fixed‐Bed Fischer‐Tropsch Synthesis Reactor with Co‐Based Catalyst

AbstractA two‐dimensional pseudohomogeneous reactor model is proposed to simulate the performance of fixed‐bed Fischer‐Tropsch synthesis (FTS) reactors by lumped thought. A CO consumption kinetics equation and a carbon chain growth probability model were incorporated into the reactor model. The model equations discretized by a two‐dimensional orthogonal collocation method were solved by the Broyden method. Concentration and temperature profiles were obtained. The validity of the reactor model against the pilot plant test data was investigated. Satisfactory agreements between model prediction values and experiment results were obtained. Further simulations were carried out to investigate the effect of operating conditions on the reaction behavior of the fixed‐bed FTS reactor.

Fischer-Tropsch Catalysts Based on Zr-Fe Intermetallides Encapsulated in an Al2O3/Al Matrix

ZrFe and ZrFe2 intermetallides in an Al2O3/Al cermet matrix are reported as catalysts for the fixed-bed Fischer-Tropsch synthesis, and the effects of some preparation conditions on their texture, structural, mechanical, and catalytic properties are discussed. A nonmonotonic dependence of their catalytic activity on the size of interametallide particles is observed. The selectivity, activity, and mechanical strength of the composites depend on the calcination temperature and on the place of the hydriding step in the catalyst preparation procedure. In terms of volumetric efficiency, the catalysts prepared are comparable with bulk, unencapsulated intermetallides and are among the most efficient iron-containing catalysts known to date.

Heterogeneous modeling for fixed-bed Fischer–Tropsch synthesis: Reactor model and its applications

A comprehensive one-dimensional heterogeneous reactor model is developed to simulate the performance of fixed-bed Fischer–Tropsch reactors for hydrocarbon production. The detailed mechanistic kinetics is combined into the reactor model along with considering the fact that the catalyst pores are filled with liquid wax under realistic conditions. The equilibrium between the gases in the bulk and the wax in the catalyst pores is correlated by using a modified SRK equation of state (MSRK EOS). The model is solved by using Gear method to integrate the reactor model with the embedded pellet model discretized by orthogonal collocation on finite elements. The validity of the reactor model is tested against the measured data from different-scale demonstration processes. Satisfactory agreements between model predictions and experiment results are obtained. Detailed numerical simulations are performed to investigate the effect of major process parameters on the reaction behavior of fixed-bed FTS systems with recycle operation.