Influence of Reaction Conditions on the Conversion of Methane‐Rich Gases to Fischer‐Tropsch Products

Evidence is provided that stable operation of a microstructured reactor for steam‐assisted catalytic partial oxidation (sCPOX) and its subsequent coupling with a Fischer‐Tropsch synthesis (FTS) reactor is possible at pressures up to 25 bar. The product composition of the sCPOX was determined and subsequently used as feed composition for a downstream FTS reactor to prove the possibility of coupling with syngas generation. After stable operation was proven in both setups, they were coupled and operated together, feeding the product gas stream of the sCPOX to the FTS. In addition, the negative influence of sulfur in the sCPOX‐gas feed was evaluated.     

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

A 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.     

Multidimensional modeling of a microfibrous entrapped cobalt catalyst Fischer‐Tropsch reactor bed

Thermal management of highly exothermic Fischer‐Tropsch synthesis (FTS) has been a challenging bottleneck limiting the radial dimension of the packed‐bed (PB) reactor tube to 1.5 in. ID. A computational demonstration of a novel microfibrous entrapped cobalt catalyst (MFECC) in mitigating hot spot formation has been evaluated. Specifically, a two‐dimensional (2‐D) model was developed in COMSOL^®, validated with experimental data and subsequently employed to demonstrate scale‐up of the FTS bed from 0.59 to 4 in. ID. Significant hot spot of 102.39 K in PB was reduced to 9.4 K in MFECC bed under gas phase at 528.15 K and 2 MPa. Improvement in heat transfer within the MFECC bed facilitates higher productivities at low space velocities (≥1000 h^?1) corresponding to high CO conversion (≥90%). Additionally, the MFECC reactor provides an eightfold increase in the reactor ID at hot spots ≤ 30 K with CO% conversions ≥ 90%. This model was developed for a typical FTS cobalt‐based catalyst where CO₂ production is negligible. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1723–1731, 2018     

Parametric analysis of Fischer‐tropsch synthesis in a catalytic microchannel reactor

Fischer‐Tropsch synthesis (FTS) involves highly exothermic conversion of syngas to a wide range of hydrocarbons, but demands isothermal conditions due to the strong dependence of product distribution on temperature. Running FTS in microchannel reactors is promising, as the sub‐millimeter dimensions can lead to significant intensification that inherently favors robust temperature control. This study involves computer‐based FTS simulations in a heat‐exchange integrated microchannel network composed of horizontal groups of square‐shaped cooling and wall‐coated, catalytic reaction channels. Effects of material type and thickness of the wall separating the channels, side length of the cooling channel, coolant flow rate, and channel wall texture on reaction temperature are investigated. Use of thicker walls with high thermal conductivities and micro‐baffles on the catalytic reaction channel wall favor near‐isothermal conditions. Response of reaction temperature against coolant flow rate is significant. Using cooling channels with smaller side lengths, however, is shown to be insufficient for temperature control. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Dynamic modeling and simulations of the behavior of a fixed‐bed reactor‐exchanger used for CO2 methanation

A multidimensional heterogeneous and dynamic model of a fixed‐bed heat exchanger reactor used for CO₂ methanation has been developed in this work that is based on mass, energy and momentum balances in the gas phase and mass and energy balances for the catalyst phase. The dynamic behavior of this reactor is simulated for transient variations in inlet gas temperature, cooling temperature, gas inlet flow rate, and outlet pressure. Simulation results showed that wrong‐way behaviors can occur for any abrupt temperature changes. Conversely, temperature ramp changes enable to attenuate and even fade the wrong‐way behavior. Traveling hot spots appear only when the change of an operating condition shifts the reactor from an ignited steady state to a non‐ignited one. Inlet gas flow rate variations reveal overshoots and undershoots of the reactor maximum temperature. © 2017 American Institute of Chemical Engineers AIChE J, 64: 468–480, 2018     

High‐Pressure High‐Temperature Transparent Fixed‐Bed Reactor for Operando Gas‐Liquid Reaction Follow‐up

A 3‐MPa, 350 °C fixed‐bed reactor was designed to follow‐up gas‐liquid‐solid reactions on a millimetric size heterogeneous catalyst with Raman spectroscopy. The transparent reactor is a quartz cylinder enclosed in a Joule effect heated stainless‐steel tube. A methodology to determine how to focus the microscope for liquid and solid phase characterization is presented. The setup was validated by performing diesel hydrodesulfurization on a CoMo/alumina extrudate catalyst with a conversion very close to expected values along with the acquisition of Raman spectra of the solid catalyst showing an evolution of the catalyst phase during sulfidation.     

Fischer‐Tropsch Synthesis Over Co‐Ru/γ‐Al2O3 Catalyst in Supercritical Media

The Fischer‐Tropsch synthesis (FTS) in gaseous and supercritical phases was examined in a continuous, high‐pressure fixed‐bed reactor by employing a cobalt catalyst (Co‐Ru/γ‐Al₂O₃). The kinetic modeling of the FTS was investigated in the reactor over a 60–80 mesh cobalt catalyst. The Langmuir‐Hinshelwood kinetic equation was used for both the Fisher‐Tropsch (FT) and water gas shift (WGS) reactions. The kinetic model was applied for simulation of the reactor with 16–20 mesh cobalt catalyst. The simulation results showed a good agreement with the experimental data. The experimental data showed that higher CO conversion and lower CH₄ and CO₂ selectivities were achieved in supercritical media compared to the gaseous phase. The BET surface area and pore volume enhancement results provided evidence of the higher in situ extraction and greater solubility of heavy hydrocarbons in supercritical media than in gaseous phases. Furthermore, the effects of supercritical solvent such as n‐pentane, n‐hexane, n‐heptane and their mixtures were studied. Moreover, the influence of reaction temperature, H₂/CO ratio, W/F_(CO+H2) and pressure tuning in the supercritical media FT synthesis were investigated, as well as the effect of the supercritical fluid on the heat transfer within the reactor. The product carbon distribution had a similar shape for all types of solvents and shifted to lighter molar mass compounds with increasing temperature, H₂/CO ratio, and W/F_(CO+H2). Finally, the product distribution shifted to higher molar mass hydrocarbons with increasing pressure. As a result, one may conclude that a mixture of hydrocarbon products of the FTS can be used as a solvent for supercritical media in Fischer‐Tropsch synthesis.     

Influence of ash agglomerating fluidized bed reactor scale‐up on coal gasification characteristics

To study the influence of fluidized‐bed reactor scale‐up on coal gasification characteristics, a model of the ash agglomerating fluidized‐bed reactor has been developed using an equivalent reactor network method. With the reactor network model, the scale‐up effects of a gasifier were studied in terms of the characteristics of the chemical reactions in the jet zone, the annulus dense‐phase zone and the freeboard zone. Results showed that the changes occurred in the inequality proportion of the volume of the jet zone during the reactor scale‐up. Taking into consideration the utilization of a portion of the backflow gas, the expansion of the jet zone volume and the coal particle residence time, the temperature of the jet zone was increased from 1592 to 1662 K. Also, both the annulus dense‐phase zone temperature and the freeboard zone temperature decreased, causing subsequent decrease in the carbon conversion efficiency. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1821–1829, 2014     

Multistage rotor‐stator spinning disc reactor

The scale up of a rotor‐stator spinning disc reactor by stacking single stage rotor‐stator units in series is demonstrated. The gas‐liquid mass transfer per stage is equal to the mass transfer in a single stage spinning disc reactor. The pressure drop per stage increases with increasing rotational disc speed and liquid flow rate. The pressure drop is more than a factor 2 higher for gas‐liquid flow than for liquid flow only, and is up to 0.64 bar at 459 rad s^?1. The high mass and heat transfer coefficients in the (multistage) rotor‐stator spinning disc reactor make it especially suitable for reactions with dangerous reactants, highly exothermic reactions and reactions where selectivity issues can be solved by high mass transfer rates. Additionally, the multistage rotor‐stator spinning disc reactor mimics plug flow behavior, which is beneficial for most processes. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Fixed‐Bed Multi‐Tubular Reactors for Oxidative Dehydrogenation in Ethylene Process

An industrial‐scale reactor for ethylene production was modeled using the oxidative dehydrogenation of ethane (ODHE) in a multi‐tubular reactor system, examining a variety of parameters affecting reactor performance. The model showed that a double‐bed multi‐tubular reactor with intermediate air injection scheme was superior to a single‐bed design, due to the increased ethylene selectivity while operating under lower oxygen partial pressures. The optimized reactor length for 100 % oxygen conversion was theoretically determined for both reactor designs. The use of a distributed oxygen feed with a limited number of injection points indicated a significant improvement on the reactor performance in terms of ethane conversion and ethylene selectivity. This concept also overcame the reactor runaway temperature problem and enabled operations over a wider range of conditions to obtain enhanced ethylene production.     

Progress in membrane gas–liquid reactors

Gas–liquid reactions are crucially important in chemical synthesis and industries. In recent years, membrane gas–liquid reactors have attracted great attentions due to their high selectivity, productivity and efficiency, and easy process control and scale‐up. Membrane gas–liquid reactors can be divided into three categories: dispersive membrane reactor, non‐dispersive membrane reactor and pore flowthrough reactor. The progress in membrane gas–liquid reactors, including features, applications, advantages and limits, is briefly reviewed. © 2012 Society of Chemical Industry     

Investigation of Fischer-Tropsch synthesis performance and its intrinsic reaction behavior in a bench scale slurry bubble column reactor

A bench scale slurry bubble column reactor (SBCR) with active-Fe based catalyst was developed for the Fischer-Tropsch synthesis (FTS) reaction. Considering the highly exothermic reaction heat generated in the bench scale SBCR, an effective cooling system was devised consisting of a U-type dip tube submerged in the reactor. Also, the physical and chemical properties of the catalyst were controlled so as to achieve high activity for the CO conversion and liquid oil (C₅₊) production. Firstly, the FTS performance of the FeCuK/SiO₂ catalyst in the SBCR under reaction conditions of 265 °C, 2.5 MPa, and H₂/CO = 1 was investigated. The CO conversion and liquid oil (C₅₊) productivity in the reaction were 88.6% and 0.226 g/g_cat-h, respectively, corresponding to a liquid oil (C₅₊) production rate of 0.03 bbl/day. To investigate the FTS reaction behavior in the bench scale SBCR, the effects of the space velocity and superficial velocity of the synthesis gas and reaction temperature were also studied. The liquid oil production rate increased up to 0.057 bbl/day with increasing space velocity from 2.61 to 3.92 SL/h-g_Fe and it was confirmed that the SBCR bench system developed in this research precisely simulated the FTS reaction behavior reported in the small scale slurry reactor.     

Continuous‐Flow Di‐N‐Alkylation of 1H‐Benzimidazole in a Fixed‐Bed Reactor

A new process for a continuous‐flow di‐N‐alkylation of 1H‐benzimidazole to 1H‐benzimidazole‐3‐ium iodide by methylene iodide in the presence of potassium carbonate in a fixed‐bed reactor is presented. The synthesis was transferred from batch to continuous operation with similar yields and conversion rates. Moreover, the influence of temperature and residence time in the continuous flow setup was characterized; optimized conditions led to a doubling of yield. In addition, the continuous flow allowed for a better control of the two‐step reaction by adding an additional tube reactor after the fixed bed that further enhanced the overall performance. With this, the continuous‐flow system presented itself as superior due to higher available temperatures and a better controllability.     

Importance of proper hydrodynamics modelling in fixed‐bed reactors: Fischer‐Tropsch synthesis study case

The importance of hydrodynamics, particularly gas density, superficial gas velocity, and total pressure in axial and radial directions, was analyzed for the modelling of a catalytic reactor using a non‐isothermal pseudo‐homogeneous approach. The modelling of a fixed‐bed reactor in one and two stages for CO conversion by Fischer‐Tropsch synthesis was taken as a study case. For the validation of the proposed model, the results of the simulations for the CO conversion and temperature profiles were compared with experimental data reported in the literature. Simulations for CO conversion and reactor temperature profiles confirmed the model's ability to predict the selectivity of the liquid products in the Fischer‐Tropsch synthesis reactor in one and two stages. The proposed model predicts more suitable profiles of CO conversion and temperature along the reactor, which makes it a more robust and efficient tool for design, optimization, and control purposes.     

CO2 methanation: Optimal start‐up control of a fixed‐bed reactor for power‐to‐gas applications

Utilizing volatile renewable energy sources (e.g., solar, wind) for chemical production systems requires a deeper understanding of their dynamic operation modes. Taking the example of a methanation reactor in the context of power‐to‐gas applications, a dynamic optimization approach is used to identify control trajectories for a time optimal reactor start‐up avoiding distinct hot spot formation. For the optimization, we develop a dynamic, two‐dimensional model of a fixed‐bed tube reactor for carbon dioxide methanation which is based on the reaction scheme of the underlying exothermic Sabatier reaction mechanism. While controlling dynamic hot spot formation inside the catalyst bed, we prove the applicability of our methodology and investigate the feasibility of dynamic carbon dioxide methanation. © 2016 American Institute of Chemical Engineers AIChE J, 63: 23–31, 2017     

A preliminary evaluation of a continuous‐flow reactor for liquid–liquid–solid phase‐transfer catalyzed synthesis of n‐butyl phenyl ether

This study evaluates the feasibility of using a continuous‐flow stirred vessel reactor (CFSVR) to synthesize n‐butyl phenyl ether (ROPh) from n‐butyl bromide (RBr) and sodium phenolate (NaOPh) by liquid–liquid–solid phase‐transfer catalysis (triphase catalysis). The factors affecting the preparation of triphase catalysts, the etherification reaction in a batch reactor, and the performance in a CFSVR were investigated. The kinetic study with a batch reactor indicated that when the initial concentration of NaOPh or RBr was high, the conversion of RBr would depend on the initial concentration of both RBr and NaOPh. The reaction can be represented by a pseudo‐first‐order kinetic model when the concentration of NaOPh is in proper excess to that of RBr, and the apparent activation energy is 87.8 kJ mol^?1. When the etherification reaction was carried out in the CFSVR, the catalyst particles did not flow out of the reactor, even at a high agitation speed. The conversion of RBr in the CFSVR was, as predicted, lower than that in the batch reactor, but was higher than the theoretical value because the dispersed phase is not completely mixed. Copyright © 2004 Society of Chemical Industry     

A Laboratory Reactor for Gas‐Phase Olefin Polymerization

A new reactor system for gas‐phase ethylene/α‐olefin polymerization is described. Good gas‐phase temperature control at high polymerization rates was achieved with the 2‐L semi‐batch reactor. Ethylene/1‐hexene and ethylene polymerization results showing the effects of operating conditions on temperature profiles are presented. Good gas‐phase temperature control is required to obtain reliable activity profiles. A gas‐sampling and analysis system, which allows relatively rapid (< 3 min) and accurate determination of ethylene/1‐hexene contents in the gas‐phase of the reactor, is also described. Rapid and reliable hydrogen contents were also measured with this relatively inexpensive system.     

A novel slurry bubble column membrane reactor concept for Fischer–Tropsch synthesis in GTL technology

Fischer–Tropsch synthesis (FTS) plays an important role in the production of ultra-clean transportation fuels, chemicals, and other hydrocarbon products. In this work, a novel combination of fixed-bed and slurry bubble column membrane reactor for Fischer–Tropsch synthesis has been proposed. In the first catalyst bed, the synthesis gas is partially converted to hydrocarbons in a water-cooled reactor which is fixed bed. In the second bed which is a membrane assisted slurry bubble column reactor, the heat of reaction is used to preheat the feed synthesis gas to the first reactor. Due to the decrease of H₂/CO to values far from optimum reactants ratio, the membrane concept is suggested to control hydrogen addition. A one-dimensional packed-bed model has been used for modeling of fixed-bed reactor. Also a one-dimensional model with plug flow pattern for gas phase and an axial dispersion pattern for liquid-solid suspension have been developed for modeling of slurry bubble column reactor. Proficiency of a membrane FTS reactor (MR) and a conventional FTS reactor (CR) at identical process conditions has been used as a basis for comparison in terms of temperature, gasoline yield, H₂ and CO conversion as well as selectivity. Results show a favorable temperature profile along the proposed concept, an enhancement in the gasoline yield and, thus a main decrease in undesirable product formation. The results suggest that utilizing this type of reactor could be feasible and beneficial. Experimental proof of concept is needed to establish the validity and safe operation of the proposed reactor.     

Transient Effects during Dynamic Operation of a Wall‐Cooled Fixed‐Bed Reactor for CO2 Methanation

The power‐to‐gas process is an option to transform fluctuating renewable electric energy into methane via water electrolysis and subsequent conversion of H₂ by methanation with CO₂. The dynamic behavior of the methanation reactor may then be a critical aspect. The kinetics of CO₂ methanation on a Ni‐catalyst were determined under isothermal and stationary conditions. Transient isothermal kinetic experiments showed a fast response of the rate on step changes of the concentrations of H₂, CO₂; in case of H₂O, the response was delayed. Non‐isothermal experiments were conducted in a wall‐cooled fixed‐bed reactor. Temperature profiles were measured and the effect of a changing volumetric flow was studied. The experimental data were compared with simulations by a transient reactor model.