A homogeneous chemical reactor analysis and design laboratory: The reaction kinetics of dye and bleach

An experimental module for senior-level reaction engineering/reactor design students is described. The module is used to characterize the kinetics of dye (food coloring) neutralization by household bleach, and the reactor system is configurable for use in either batch reactor or continuous-stirred tank reactor (CSTR) modes. The reactor temperature, volume, reactant feed rates, and reactant concentrations may be adjusted to enable students to obtain a wide range of kinetic data. Dye concentrations in the reactor are monitored by absorbance spectroscopy, and the kinetic rate law is determined directly from the batch reactor performance data. Students use the completed kinetic rate law to compare experimental steady-state CSTR performance data to the mathematical models derived from reactor design equations. Finally, the students use the kinetic behavior of the system to design a hypothetical plug-flow reactor for the same chemical reaction and a set of stated operational goals.     

Investigation of the liquid recycle in the reactor cascade of an industrial scale ebullated bed hydrocracking unit

One of the commercial means to convert heavy oil residue is hydrocracking in an ebullated bed. The ebullated bed reactor includes a complex gas–liquid–solid backmixed system which attracts the attention of many scientists and research groups. This work is aimed at the calculation of the internal recycle flow rate and understanding its effect on other parameters of the ebullated bed. Measured data were collected from an industrial scale residual hydrocracking unit consisting of a cascade of three ebullated bed reactors. A simplified block model of the ebullated bed reactors was created in Aspen Plus and fed with measured data. For reaction yield calculation, a lumped kinetic model was used. The model was verified by comparing experimental and calculated distillation curves as well as the calculated and measured reactor inlet temperature. Influence of the feed rate on the recycle ratio(recycle to feed flow rate) was estimated. A relation between the recycle flow rate, pump pressure difference and catalyst inventory has been identified. The recycle ratio also affects the temperature gradient along the reactor cascade. Influence of the recycle ratio on the temperature gradient decreased with the cascade member order.     

钯复合膜反应器中异丁烷催化脱氢反应

引　言异丁烷脱氢反应是一个受热力学平衡限制的反应 ,平衡转化率很低 ,若将膜反应器用于该反应 ,则可以通过膜不断地从反应区选择性分离出氢气 ,克服了反应受热力学平衡制约的缺点 ,这样就可降低反应温度和减压程度的要求 ,改善反应的工艺条件 ,从而达到高效和节能的目的 .文献中已分别对钯 /陶瓷复合膜[1,2 ]和钯 -钌 (钌的质量分数为 2 % )合金膜[3]反应器中的异丁烷脱氢反应进行了初步研究 .前文[4 ]已对用改进的化学镀新工艺制备的钯和钯 -银 /陶瓷复合膜进行了表征 ,本文将用钯-银 /陶瓷复合膜反应器进行异丁烷脱氢反应的研究 .本工作…     

EFFECTS OF VARIOUS PROCESS PARAMETERS ON TEMPERATURE PROFILE OF ADIABATIC FIXED BED REACTOR FOR PRODUCTION OF DIMETHYL ETHER (DME) FROM METHANOL

Catalytic dehydration of methanol for production of dimethyl ether (DME) is an exothermic reaction. Therefore, the temperature of the adiabatic reactor of DME production will be increased by the progress of the reaction. In this article, effects of various process parameters are considered on the temperature profile of a fixed catalyst bed in a laboratory-scale reactor of DME production from methanol. Acidic gamma alumina is used for DME production, and effects of inlet feed temperature, flow rate of the feed, pressure of the reactor, and catalyst particle sizes on the temperature profile of the catalyst beds are investigated.     

EFFECTS OF VARIOUS PROCESS PARAMETERS ON TEMPERATURE PROFILE OF ADIABATIC FIXED BED REACTOR FOR PRODUCTION OF DIMETHYL ETHER (DME) FROM METHANOL

Catalytic dehydration of methanol for production of dimethyl ether (DME) is an exothermic reaction. Therefore, the temperature of the adiabatic reactor of DME production will be increased by the progress of the reaction. In this article, effects of various process parameters are considered on the temperature profile of a fixed catalyst bed in a laboratory-scale reactor of DME production from methanol. Acidic gamma alumina is used for DME production, and effects of inlet feed temperature, flow rate of the feed, pressure of the reactor, and catalyst particle sizes on the temperature profile of the catalyst beds are investigated.     

Contribution to emission reduction of CO2 by a fluidized-bed membrane dual-type reactor in methanol synthesis process

In this work, a fluidized-bed membrane dual-type reactor was evaluated for CO₂ removal in methanol synthesis process. The feed synthesis gas is preheated in the tubes of the gas-cooled reactor and flowing in a counter-current mode with reacting gas mixture in the shell side. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas into the reaction side through the membrane. The outlet synthesis gas from this reactor is fed to tubes of the water-cooled packed-bed reactor and the chemical reaction is initiated by the catalyst. The methanol-containing gas leaving this reactor is directed into the shell of the gas-cooled reactor and the reactions are completed in this fluidized-bed side. A two-phase dynamic model in bubbling regime of fluidization was developed in the presence of long-term catalyst deactivation. This model is used to compare the removal of CO₂ in a FBMDMR with a conventional dual-type methanol synthesis reactor (CDMR) and a membrane dual-type methanol synthesis reactor (MDMR). The simulation results show a considerable enhancement in the CO₂ conversion due to have a favourable profile of temperature and activity along the fluidized-bed membrane dual-type reactor relative to membrane and conventional dual-type reactor systems.     

整体式新型生物质气化催化反应器的实验研究

在现有生物质气化反应器及焦油处理方法的基础上,开发出一种整体式新型生物质气化催化反应器,并对该反应器进行相关的实验研究。实验研究结果表明:当木粉进料速率为6.48 g/min,空燃比RE为0.23,气化温度在500—670℃,这种整体式新型生物质气化催化反应器内有、无催化剂时对木粉气化产生的燃气中焦油的含量以及气体组分有明显影响;当采用钴与氧化钴的质量分数为20%,氧化钙的质量分数为80%的钴基催化剂作为焦油裂解催化剂,裂解温度为800℃,标态下体积空时为1.8 s的情况下,燃气中夹带的焦油可完全被催化裂解,同时燃气中的气体成分氢体积分数可从无催化剂时的15%提高到有催化剂时的35%,净提高20%。同时也对使用前后的钴基催化剂进行了XRD表征分析,发现氧化钙在生物质气化过程中具有一定的CO2捕集能力。     

Potential catalyst savings in heterogeneous gaseous spiral coiled reactor utilizing selective wall coating – A computational study

This study numerically evaluates the effect of secondary flow on the reaction performance in heterogeneous gaseous spiral coiled reactor utilizing selective wall coatings. Laminar multispecies gas flow in spiral coiled reactor with circular and square cross-section is investigated using a validated three-dimensional computational fluid dynamics (CFD) model. Various selective wall coating strategies are evaluated within a range of Reynolds number. The reactor performance is measured not only based on the conversion rate but also in terms of figure of merit (FoM) defined as reaction throughput per unit pumping power and catalyst coating active area. The results indicate that secondary flow enhance reaction performance and improve catalyst utilization, especially at the outer wall. By maximizing this effect, the requirement of expensive catalyst materials can be minimized. This study highlight the potential of selective catalyst coating in coiled reactor for process intensification and cost reduction in various applications.     

A recycle reactor for measuring hydrogen isotope exchange kinetics under vapour phase and trickle bed conditions

A recycle reactor system has been developed to measure the activities of catalysts for isotope exchange between hydrogen gas and water vapour. To allow testing of reasonably large quantities of catalysts, the reactor was operated with a high recirculating flow of hydrogen gas passing through a saturator to provide the water vapour required for the reaction. In this mode of operation, only a small spiking gas flow was required as feed compared to the very high feed flow that would be required for once-through operation. The reactor was also operated as a trickle bed by recirculating the saturator water. By testing catalysts under both vapour and trickle bed modes, it was possible to investigate the effect of trickling water over the catalyst on the catalytic activity. Kinetic exchange rates under vapour phase operation were calculated from both plug flow and well-mixed reactor models. The former model was found to be the appropriate one for the ranges of operating conditions investigated. However, for trickle bed operation, the well-mixed reactor model was found to be the suitable one. Vapour phase and trickle bed tests done with random bed and structured bed catalysts indicated that the gas phase isotope exchange reaction was not impaired by the presence of liquid water in the reactor.     

A comparison of auto-thermal and conventional methanol synthesis reactor in the presence of catalyst deactivation

This study proposed a one-dimensional dynamic plug flow model to analyze and compare the performance of an auto-thermal and a conversional methanol synthesis reactor in the presence of catalyst deactivation. An auto-thermal two-stage industrial methanol reactor type is a system with two catalyst beds instead of one single catalyst bed. In the first catalyst bed, the synthesis gas is partly converted to methanol in a water-cooled reactor. In the second bed which is a gas-cooled reactor, the reaction heat is used to preheat the feed gas to the first bed. To analyze the effect of important control variables on the rector performance, steady state and dynamic simulations are utilized to investigate effect of operating parameters on the performance of reactors. The simulation results show that there is a favorable profile of temperature along the two-stage auto-thermal reactor type in comparison with conventional single stage reactor type. In this way the catalysts are exposed to less extreme temperatures and, catalyst deactivation via sintering is reduced. Overall, this study resulted in beneficial information about the performance of the reactor over catalyst life-time.     

全混流反应器内流动规律模拟研究

研究了一种接近全混流的小型气固相反应器,可以用于在实验室研究时需要实现全混流接触状态的气固相反应的研究.采用计算流体力学软件(CFD)进行模拟得到最优结构,其结构包括1个圆锥形反应器主体,4个连接在反应器主体底部的进料口,1个连接在反应器主体上部的出料口.气体从4个进料口进入,催化剂在流动过程中从中部掉落,形成气体水平...     

ON THE EFFECTS OF SYNGAS COMPOSITION AND WATER-GAS-SHIFT REACTION RATE ON FT SYNTHESIS OVER IRON BASED CATALYST IN A SLURRY REACTOR

Water gas shift reaction plays an important role in the Fischer-Tropsch synthesis reaction over iron-based catalysts. A slurry reactor model which accounted for the kinetics of both Fischer-Tropsch synthesis and water gas shift reaction was used to investigate the effects of hydrogen to carbon monoxide ratio, water vapor concentration and reactor temperature on synthesis gas conversion. The model was used to determine optimum concentration of water in the feed gas. For a given reactor temperature, the optimum concentration of water in the feed gas was found to increase with decreasing hydrogen to carbon monoxide ratio. The optimum concentration of water in the feed gas was found to decrease with increasing reactor temperature. Increasing the water gas shift reaction rate improved syngas conversion for low reaction temperatures.     

Dynamic behavior of trickle-bed reactors

An analysis is given for the transient behavior of a trickle-bed reactor in which gas and liquid streams flow downwards through a bed of catalyst particles. Equations are given for the zero and first moments of the response, in either the gas or liquid effluent, to a pulse input of concentration in either the liquid or gas feed. First-order, reversible adsorption, and adsorption plus first-order irreversible reaction are considered.Procedures are discussed and illustrated for evaluating equilibrium, mass transfer, and reaction rate constants from the moment equations. Also, the dependency of the moments on the rate and equilibrium constants are summarized for various reactor arrangements and chemical processes. This information is useful in designing experiments to give data suitable for evaluating such constants.     

Co‐current and Countercurrent Configurations for a Membrane Dual Type Methanol Reactor

A dynamic model for a membrane dual‐type methanol reactor was developed in the presence of catalyst deactivation. This reactor is a shell and tube type where the first reactor is cooled with cooling water and the second one with feed synthesis gas. In this reactor system, the wall of the tubes in the gas‐cooled reactor is covered with a palladium‐silver membrane which is only permeable to hydrogen. Hydrogen can penetrate from the feed synthesis gas side into the reaction side due to the hydrogen partial pressure driving force. Hydrogen permeation through the membrane shifts the reaction towards the product side according to the thermodynamic equilibrium. Moreover, the performance of the reactor was investigated when the reaction gas side and feed gas side streams are continuously either co‐current or countercurrent. Comparison between co‐current and countercurrent mode in terms of temperature, activity, methanol production rate as well as permeation rate of hydrogen through the membrane shows that the reactor in co‐current configuration operates with lower conversion and also lower permeation rate of hydrogen but with longer catalyst life than does the reactor in countercurrent configuration.     

Continuous Neutralization of NaOH Solution with CO2 in an Internal‐Loop Airlift Reactor

The neutralization of NaOH with CO₂ in a continuously operated airlift reactor with gas flow rates up to 10 NL min^?1 and gas phase recycle was investigated. Neutralization experiments were performed at 25 °C and the amount of absorbed CO₂, as well as the NaOH feed rate, were recorded. The reaction rate was calculated based on the two‐film theory and empirical equations for several parameters. The calculations of the volumetric mass transfer coefficient, the liquid phase circulation velocity, and the gas holdup were experimentally validated. The reaction rate and the process efficiency were modeled with a deviation of 5 %.     

Equilibrium calculations for direct synthesis of dimethyl ether from syngas

Thermodynamic analysis of single‐step synthesis of dimethyl ether (DME) from syngas over a bi‐functional catalyst (BFC) in a slurry bed reactor has been investigated as a function of temperature (200–240°C), pressure (20–50 bar), and composition feed ratio (H₂/CO: 1–2). The BFC was prepared by physical mixing of CuO/ZnO/Al₂O₃ as a methanol synthesis catalyst and H‐ZSM‐5 as a methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H₂, methanol dehydration to DME and water–gas shift reaction were chosen as the independent reactions. The equilibrium thermodynamic analysis includes a theoretical model predicting the behaviour and a comparison to experimental results. Theoretical model calculations of thermodynamic equilibrium constants of the reactions and equilibrium composition of all components at different reaction temperature, pressure, and H₂/CO ratio in feed are in good accordance with experimental values.     

Dynamic mathematical modeling of a novel dual-type industrial ethylene oxide (EO) reactor

In this paper, the dynamic behavior of a novel dual-type industrial ethylene oxide reactor has been proposed with taking catalyst deactivation into account. The configuration of two catalyst beds instead of one single catalyst bed is developed for conversion of ethylene to ethylene oxide. In the first reactor which is an industrial fixed-bed water-cooled reactor, the feed gas is partly converted to ethylene oxide. This reactor functions at very high yield and at a higher than normal operating temperature. In the second converter, the reaction heat is used to preheat the feed gas to the first reactor and a milder temperature profile is observed. The potential possibilities of a two-stage catalyst bed system are analyzed using a 1D heterogeneous dynamic model to obtain necessary comparative estimates. A differential evolution (DE) algorithm is applied as an effective and robust method to optimize the reactors length ratio. The results obtained from the simulation demonstrate that there is a desirable catalyst temperature profile along the dual-type reactor (DR) compared with the conventional single-type reactor (SR). In this way, the catalysts are exposed to less extreme temperatures and thus, diminishing the catalyst deactivation via sintering. Results from this study provided beneficial information about the effects of reactors configuration on catalyst lifetime and ethylene oxide production rate simultaneously.     

A study of hydrodenitrogenation of pyridine over molybdenum nitride catalysts and their characterization

A series of molybdenum nitride (Mo₂N) catalysts were prepared by a topotactic synthesis method using a TPR (Temperature Programmed Reaction) at various conditions (temperature ramping rate, NH₃ gas flow rate, final preparation temperature). The surface property and acidity of Mo₂N catalysts prepared at various prepared conditions were studied by SEM, XRD, BET, FTTR and TGA. The hydrodenitrogenation (HDN) of pyridine in n-heptane over Mo₂N catalyst (Al) was studied in a fixed bed continuous flow reactor (CATATEST) at the temperatures between 250–450°C , the pressure at 20–40 X 10₅ Pa and the contact time between 0.01-0.05 g cat.hr./ml feed. The microstructure of M0₂N catalyst was not changed at various preparation conditions by topotactic reaction. The XRD and BET studies showed that the extent of the crystallinity and the surface area of the prepared Mo₂N catalysts increased when the final preparation temperature increased and the temperature ramping rate was lowered. In addition, from the TGA curve, the acid strength increased with the increase of the NH₃ gas flow rate. The results of pyridine hydrodenitrogenation (HDN) over Mo₂N catalyst showed that the catalytic activity (conversion % ) increased as reaction temperature, reaction pressure, and contact time increases. The selectivity for piperidine possessed a maximum at 350°C regardless of the reaction pressure. Also, the selectivity for cracked products increased as reaction temperature and pressure increased. The activation energy was determined 7.16 kcal/mol by Arrehenius plot.     

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.     

对撞流反应器甲醇合成实验研究

液相法甲醇合成由于有惰性液体介质的存在,气液相间传质对反应起到了一定的阻碍作用,对撞流反应器使用喷嘴将催化剂浆料雾化从而强化了气液相间传质。文中在对撞流反应器内对甲醇合成温度、合成气比例、气流量、浆料循环量以及喷嘴个数进行了考察,结果表明,温度控制在230℃左右操作比较适宜,二氧化碳参与反应对甲醇合成较为有利,合成气流量在22.4 L/min以后时空产率几乎不再增加,增加浆料循环量和采用对置式二喷嘴或四喷嘴比单喷嘴时空产率和出口甲醇体积分数都有所增加。由结果可知,利用喷嘴雾化和液体对撞可以显著地增强气液传质从而达到增加液相甲醇合成时空产率的目的。