Synthesis of Dimethyl Carbonate from Methyl Carbamate and Methanol Using a Fixed‐Bed Reactor

Several mixed oxide catalysts were prepared by coprecipitation for dimethyl carbonate (DMC) synthesis from methyl carbamate and methanol. During the batch process, the DMC yield was below 35 %. In order to minimize the unfavorable thermodynamic equilibrium and side reactions for the DMC synthesis, a fixed‐bed reactor was designed. A maximum DMC yield of ～ 73 % could be realized over a ZnO‐Al₂O₃ catalyst. The effects of reaction conditions for this type of reactor were investigated in detail.     

Modeling of a Reverse Flow Reactor for Methanol Synthesis Modeling of a Reverse Flow Reactor for Methanol Synthesis

An accurate one-dimensional, heterogeneous model taking account of axial dispersion and heat transfer to the reactor wall, and heat conduction through the reactor wall for methanol synthesis in a bench scale reactor under periodic reversal of flow direction is presented. Adjustable parameters in this model are the effectiveness factors for each of the three reactions occurring in the synthesis and a factor for the bed to wall heat transfer coefficient correlation. Experimental data were used to evaluate these parameters and reasonable values of these parameters were obtained. The model was found to closely predict the reactor performance under a wide range of operating conditions, such as carbon oxide concentrations, volumetric flow rate, and cyclic period.     

径向流动甲醇合成反应器的数学模型与优化设计

以ＣＯ、ＣＯ２加氢合成甲醇平行反应为独立反应，ＣＯ和ＣＯ２为关键组分，建立了径向流动甲醇合成反应器的一维非均相数学模型，描述气相和催化剂颗粒表面气体组成、温度随径向距离的分布。     

Modeling of Multi‐Tubular Reactors for Fischer‐Tropsch Synthesis

The results of the simulation of multi‐tubular Fischer‐Tropsch reactors based on a two‐dimensional pseudo‐homogeneous model are presented. The model takes into account the intrinsic kinetics of two commercial iron and cobalt catalysts, intraparticle mass transfer limitations, and the radial heat transfer within the fixed bed and to the cooling medium (boiling water). The effective rate with Co is slightly higher than with Fe. Hence, a temperature level can be used for Co that is 20 °C lower compared to Fe. The conversion and product selectivies are then almost the same and the reactor can be operated safely without a temperature runaway. The results of the simulations are consistent with literature data and show that there is still room for improvement of fixed bed FT reactors, e.g., by an enhanced heat transfer.     

Kinetics and Reactor Modeling of the Steam Reforming of Methanol over a Mn‐Promoted Cu/Al Catalyst

The kinetics of the steam reforming of methanol (SRM) was studied in a packed‐bed reactor over a Mn‐promoted Cu/Al₂O₃ catalyst under defined conditions. A Langmuir‐Hinshelwood‐Hogan‐Watson (LHHW)‐type mechanism that assumes the dissociative adsorption of methanol on two distinct active sites as the rate‐controlling step was found to satisfactorily describe the SRM reaction with activation energies of 77.3 and 64.5 kJ mol^?1 at low and high temperature, respectively. No mass or heat transfer limitations were observed under the experimental conditions used in this study. A reactor model was also developed, validated, and employed to predict the conversion, temperature, and concentration profiles. The axial dispersion had no influence on the temperature distribution but the effect was more pronounced on the methanol conversion.     

Study of the Characteristics of Methanol Synthesis in a Recirculation Slurry Reactor – A Novel Three‐Phase Synthesis Reactor

A process feasibility analysis on the liquid phase methanol synthesis (LPMeOH^TM) process was performed in a recirculation slurry reactor (RSR). In the three‐phase RSR system, a fine catalyst is slurried in the paraffin and this catalyst slurry is continuously recirculated through the nozzle from the slurry sector to the entrained sector by a pump. The syngas is fed concurrently with the downward flow of slurry to form the methanol product. A laboratory scale mini‐pilot plant version of a recirculation slurry reactor system was successfully designed and built to carry out process engineering research, and in addition, an identical cold model was built to measure the mass transfer coefficient in the recirculation slurry reactor. The effects of operating conditions, including temperature, pressure, gas flow rate and catalyst slurry recirculation flow rate on the productivity of methanol were studied. This experimental data helps the scale‐up and commercialization of the methanol synthesis process in recirculation slurry reactors.     

流向变换强制周期操作合成甲醇反应器的模型化

An accurate one-dimensional,heterogeneous model taking account of axial dispersion and heat transfer to the reactor wall,and heat conduction through the reactor wall for methanol synthesis in a bench scale reactor under periodic reversal of flow direction is presented.Adjustable parameters in this model are the effectiveness factors for each of the three reactions occurring in the synthesis and a factor for the bed to wall heat transfer coefficient correlation.Experimental data were used to evaluate these parameters and reasonable values of these parameters were obtained.The model was found to closely predict the reactor performance under a wide range of parameters were obtained.The model was found to closely predict the reactor preformance under a wide range of operating conditions,such as carbon oxide concentrations,volumetric flow rate,and cyclic period.     

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.     

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.     

Influence of Particle Size and Single‐Tube Diameter on Thermal Behavior of Fischer‐Tropsch Reactors. Part I. Particle Size Variation for Constant Tube Size and Vice Versa

Simulation of a single tube of a wall‐cooled multitubular Fischer‐Tropsch (FT) reactor with a cobalt catalyst indicates that the reactor performance is improved by enlarging the catalyst particle diameter. This aspect is studied for variation of the particle size for a fixed tube diameter and vice versa. For a syngas conversion per pass of about 30 % as target and a typical industrially used single‐tube diameter of 40 mm, a particle size of > 3 mm is appropriate with regard to a high production rate of higher hydrocarbons. For a particle diameter of < 3 mm, a temperature runaway can only be avoided by rather low cooling temperatures, and the target conversion cannot be reached. In addition, the pressure drop then gets rather high. The reasons for this behavior are: (i) the heat transfer to the cooled tube wall for a given tube size is considerably enhanced by increasing the particle size; (ii) the influence of pore diffusion on the effective rate gets stronger with rising particle size which decreases the danger of temperature runaway.     

Improved Design of the Lurgi Reactor for Methanol Synthesis Industry

Current studies are devoted to promote the production yield of the methanol synthesis process for treating large feed capacities in Algerian methanol manufacture industry by designing new reactor technologies. In order to achieve a high yield of methanol, the performance of methanol synthesis is improved by substituting the quench reactor by a new Lurgi reactor. The design of operating parameters of the Lurgi reactor involves the effect of CO₂ injection on methanol production yield and the catalyst deactivation. The simulation results demonstrate that under the same industrial operating conditions the conversion rate of reactants increases from 23 % in the quench reactor to 37 % in the Lurgi reactor and the methanol yield can be increased by 33 % when substituting the quench reactor by the Lurgi reactor     

Synthesis of the Biofuel Additive 1,1‐Diethoxybutane in a Fixed‐Bed Column with Amberlyst‐15 Wet

The synthesis of 1,1‐diethoxybutane (DEB) through the acetalization reaction between ethanol and butyraldehyde was studied in a fixed‐bed adsorptive reactor packed with Amberlyst‐15 wet. The miscibilities of reactants and water were evaluated and breakthrough experiments with nonreactive pairs of ethanol‐water and ethanol‐DEB were performed. The parameters of the isotherms were fitted by a Langmuir competitive model. Synthesis of the acetal was carried out with mixtures of ethanol and butyraldehyde at different molar ratios. The dynamic behavior of the fixed‐bed adsorptive reactor was described by a mathematical model developed taking into account the reaction kinetics, adsorption mechanisms, mass transfer resistances, and velocity variations.     

乙炔法合成氯乙烯固定床反应器的数学模拟和工况分析

根据对乙炔，氯化氢在ＨｇＣｌ_２－活性碳催化剂上合成氯乙烯反应动力学、失活动力学及固定床反应器的分析，建立拟均相二维有效扩散模型以描述氯乙烯合成固定床反应器的特性，用此模型对现有生产中的工况进行定量分析，并提出改进操作的方案。     

Experimental studies and modeling of a fixed bed reactor for Fischer-Tropsch synthesis using biosyngas

The aim of this work was to study the Fischer-Tropsch (FT) synthesis of a model biosyngas (33% H₂, 17% CO and 50% N₂) in a single tube fixed-bed FT reactor. The FT reactor consisted of a shell and tube with high-pressure boiling water circulating throughout the shell. A spherical unpromoted cobalt catalyst was used with the following reaction conditions: a wall temperature of 473 K, a pressure of 20 bars and a gas hour space velocity (GHSV) of 37 to 180 NmL.g_cat^− 1.h^− 1. The performance of the FT reactor was also validated by developing a 2D pseudo-homogeneous model that includes transport equations and reaction rate equations. Good agreement between the model predictions and experimental results were obtained. This developed model was extended to predict and quantify the influence of the FT kinetics as well as determine the influence of the tube diameter and the wall temperature. The predicted behaviors for CO and H₂ conversion, productivity of hydrocarbons (mainly CH₄ and C₅₊) and fluid temperature along the axis of the reactor have been analyzed.     

Optimization of Fischer‐Tropsch Process in a Fixed‐Bed Reactor Using Non‐uniform Catalysts

Optimization of Fischer‐Tropsch (FT) process in a fixed‐bed reactor is carried out using non‐uniform catalysts. The C₅⁺ yield of the reactions is maximized utilizing a combination of non‐uniform catalysts across the bed. A 1D heterogeneous model is developed to simulate the bed containing uniform and non‐uniform catalysts. It is found that the egg‐shell and surface‐layered catalysts result in higher C₅⁺ yield. Moreover, effects of cooling temperature are studied. Genetic Algorithm (GA) and Successive Quadratic Programming (SQP) methods are applied. Feed and cooling temperature are selected as decision variables together with distribution of non‐uniform catalysts along the bed. The optimization result shows 14.47 % increase in the C₅⁺ yield with respect to the base condition.     

Heterogeneous Modeling Approach for Gas‐Limited Reactions in an Inclined Rotating Fixed Bed Reactor

A heterogeneous modeling approach for an inclined rotating fixed bed reactor with concentric internal tube is introduced. The novel reactor is designed to intensify the mass transfer of gas‐limited heterogeneous catalyzed reactions by intermittent catalyst wetting, which is enabled exposing the packed bed to rotation and inclination. A simulation study for the hydrogenation of α‐methylstyrene is presented. In particular, the influence of period length and different wetting‐draining cycles on the space‐time yield of the reactor is analyzed.     

Fixed‐Bed Heat Storage – Mathematical Modeling Approaches

While renewable heat makes up only 13 % of overall German heat consumption, the share of renewable electricity produced from wind, solar, water, and geothermal power already reached 36 % of overall electricity consumption in 2017. One measure to support the integration of renewable heat in the German energy system is the use of heat storage systems. Although water‐based heat storage systems for temperatures up to 100 °C are state of the art, systems for temperatures up to several hundred degrees Celsius are still under investigation or in the demonstration phase. Therefore, this work focuses on the development of a simulation model for analyzing and engineering fixed‐bed thermal storage systems that are filled with an inert bulk material such as stone fragments.     

Modeling of a novel membrane reactor to integrate dehydrogenation of ethylbenzene to styrene with hydrogenation of nitrobenzene to aniline

The catalytic dehydrogenation of ethylbenzene to styrene is coupled with the catalytic hydrogenation of nitrobenzene to aniline in a simulated integrated reactor formed of two fixed beds separated by a hydrogen-selective membrane, where both hydrogen and heat are transferred across the surface of membrane tubes. A pseudo-homogeneous model of the two fixed beds predicts the performance of this novel configuration first proposed by Moustafa and Elnashaie [Simultaneous production of styrene and cyclohexane in an integrated membrane reactor. Journal of Membrane Science 178 (1), 171-184]. Both co-current and counter-current operating modes are investigated and the simulation results are compared with corresponding predictions for an industrial adiabatic fixed bed reactor operated at the same feed conditions. The conversion of ethylbenzene and the yield of styrene in the membrane reactor are predicted to exceed by a wide margin those in the industrial adiabatic fixed bed reactor. Aniline is also produced as an additional valuable product in a favorable manner, and autothermality is achieved within the reactor. The results suggest that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel 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.