Comparison of the Various Kinetic Models of TAME Formation by Simulation and Parameter Estimation

Various kinetic models proposed for the synthesis of TAME (tert-amyl methyl ether, 2-methoxy-2-methylbutane) were tested against experimental batch reactor data. The experiments were carried out with methanol/isoamylenes molar ratios varying from 0.2 to 2.0 at temperatures between 333 and 353 K. The range of validity of the various models was evaluated by simulating the experimental conditions and by comparing the adequacy of the models to predict the experimental changes of composition as a function of the catalyst contact time and composition at reaction equilibrium. Activity-based models were found to predict the experimental results better within a wider range of conditions than the concentration-based models. The activity-based models were additionally compared by estimating the values for the model parameters from the experimental data.     

MeOH to DME in bubbling fluidized bed: Experimental and modelling

Methanol dehydration over a ZSM‐5 containing catalyst was studied in a fluidized bed reactor. At temperatures ranging from 250 to 325°C, methanol conversion varied from 30% at a contact times of 0.14 s and approached 100% of the equilibrium conversion at a contact time starting from 10 s. Sequential and parallel reactions were negligible at low temperatures while hydrocarbon formation became appreciable at 325°C. Online gas analysis by mass spectrometry provided real‐time measurements at a frequency of 4.4 Hz that allowed for fast determination of steady‐state conditions. Gas phase residence time distribution (RTD) measurements indicated that axial dispersion was essentially negligible at short contact times with a shallow bed of catalyst. With longer residence times, the flow pattern could be approximated by six continuously stirred‐tank reactors (CSTR) in series. Both the simple 1D hydrodynamic model and a detailed multi‐zone fluidized model were used to interpret the experimental data to derive a kinetic expression for the dehydration of methanol to di‐methyl ether (DME). The expression includes the reverse reaction that is most often neglected in the literature. The reaction data were best fit with the kinetics based on the 1D model. The fluidized bed is a viable reactor type for kinetic measurements of highly exothermic reactions where hotspots and radial and axial temperature gradients are problematic in fixed beds.     

Prediction of spouted bed reactor performance using kinetic models

The form of the equation governing the kinetic model of a reactor depends on the mixing regime of the reacting phases and the conversion kinetics. The formation of detached flow in a spouted-bed reactor results in backmixing of the solid material. Therefore, the processes in a spouted-bed reactor can be described by a diffusion (quasihomogeneous) model equation. The paper compares the values of the production capacity of a spouted-bed reactor calculated using the diffusion model with experimental values of the efficiency of green ultramarine oxidation (kinetic region), of oxidative calcination of some metal sulphides (mixed region), and of the ion exchange extraction of copper from solutions (diffusion region). The kinetics of the corresponding conversions are also described.     

Design,optimization, and control of reactive distillation column for the synthesis of tert-amyl ethyl ether

The temperature–composition cascade strategy was proposed to control the reactive distillation (RD) process for the synthesis of tert-amyl ethyl ether. Aspen Split tool was adopted to obtain the design parameters of the column from the viewpoint of separating tert-amyl alcohol, ethanol, and water. The proposed procedure which included optimization and sensitivity analysis was implemented to optimize the design parameters of the column and obtain the sensitive variables simultaneously, without requirement to run various simulations. In those optimized conditions, the proposed control strategy was introduced to manage the RD process by changing the sensitive variables. From results of the dynamic simulation, it can be known that the proposed strategy was able to handle disturbances while maintain the tert-amyl ethyl ether product purity and quickly reach the steady state. Therefore, the proposed control strategy was regarded as the effective control structure and could successfully control this RD system.     

醋酸乙酯加氢合成乙醇反应器的模型化

根据实验室数据对醋酸乙酯加氢制乙醇宏观动力学方程进行参数估计,得到宏观动力学模型。根据动力学模型,同时考虑内扩散的影响以及物料、热量和动量衡算方程建立了醋酸乙酯加氢制乙醇固定床反应器的一维拟均相模型,并分别得到不同氢酯比、不同控制温度、不同压力下的多种工况的模拟结果。模拟结果与实际生产数据吻合。该模型可用于指导工业反应器的设计和操作优化。     

Co-Ni/y-Al2O3催化剂上乙醇催化氨化合成乙腈反应的本征动力学

引言乙腈是一种重要的溶剂和化工原料,广泛用于有机合成、农药、医药、石油化工、表面活性剂以及高分子材料等领域。此外,由于高纯乙腈对紫外线的吸收为零,并且具有独特的物理化学性质,因此,乙腈在高压液相色谱、电化学以及分光光度法分析中作为溶剂广泛使用[1]。目前,工业上主要通     

芳烃催化加氢交叉流反应器模型

提出了一种抗硫中毒的芳烃加氢催化反应器模型,称之为交叉流反应器模型,把反应物料分为两股,其中含有噻吩的乙苯物料采用轴向连续流动方式由反应器进口进入催化剂床层,而氢气由铅直导管直接进入催化剂床层中,然后与乙苯物料混合。在氢气导管出口处形成含硫乙苯浓度低而氢气浓度高的特殊区域,因而硫对催化剂的中毒效应大幅度降低,整体上提高了乙苯加氢饱和反应效率。与传统轴向混合流反应器进行比较,在相同条件下交叉流反应器具有更好的整体加氢反应性能。分别建立了交叉流反应器与传统轴向混合流反应器模型,提出了两种反应器的催化反应转化率方程;利用此转化率方程,对实验数据进行处理,得到动力学参数,模型的计算结果与实验数据相吻合,也验证了在交叉流反应器中,硫的中毒效应明显减弱。     

Determination of process parameters and modelling of lipase-catalyzed transesterification in a fixed bed reactor

Chemical transesterification is of major importance to the edible oil industry. While alkali catalysts randomize all the fatty acids in a triglyceride mixture, the use of a 1,3 specific lipase causes a more selective exchange of fatty acid residues. Basic process parameters for the development of a continuous solvent-free process in a fixed bed reactor have been determined. The kinetics of the transesterfication reaction and the influence of particle diameter, substrate and water concentration on the effective reaction rate were examined in batchwise experiments. Residence time distribution and parameters of inter- and intraparticle mass transfer were determined by modelling of experiments carried out in a fixed bed reactor under transient conditions. Fixed bed reactors with side stream analysis were used for continuous transesterification. A kinetic model was developed for the enzyme catalyzed reaction, thereby showing the analogy between heterogeneous catalytic and enzyme catalyzed reactions. A one-dimensional heterogeneous reactor model was formulated on the basis of the kinetic equation and different process parameters. For numerical calculations, an exponential enzyme distribution inside the carrier was assumed. The simulation of experimental results indicates that they are well described by the developed model. Water concentration and presence of other substances strongly influence the stability of the immobilized enzyme.     

Kinetic study of ethyl octyl ether formation from ethanol and 1‐octanol on Amberlyst 70

An option to introduce bioethanol to diesel, improving at the same time its fuel quality, is by adding ethyl octyl ether (EOE). It can be obtained successfully by the dehydration reaction between ethanol and 1‐octanol over acidic ion‐exchange resins. In the present work, the kinetic study of EOE synthesis on Amberlyst 70 in the liquid phase is performed in a 20‐cm³ fixed‐bed reactor and in a 100‐cm³ batch reactor at 423–463 K and 2.5 MPa. EOE synthesis takes place together with diethyl ether (DEE) formation as main side reaction. A mechanistic kinetic model in terms of component activities is proposed for EOE synthesis (E_a=105 ± 4 kJ/mol) and for DEE formation (E_a =100 ± 5 kJ/mol). Reaction rates were highly inhibited by the adsorption of the formed water on Amberlyst 70. The inhibitor effect of water is well represented as a competitive adsorption with alcohols reactants on the catalysts surface. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2918–2928, 2014     

Direct Synthesis of 1-Butanol from Ethanol in a Plug Flow Reactor: Reactor and Reaction Kinetics Modeling

Bio-ethanol is well known for its use as a gasoline additive. However, it can be blended in low portions to traditional gasoline although it has a corrosive nature. By taking advantage of modern continuous reactor technology and heterogeneous alumina catalysts, ethanol can be upgraded to 1-butanol in fixed beds. Butanol has more feasible properties as fuel component in comparison to ethanol. Mathematical modeling of reaction kinetics revealed a simple kinetic model could be used to describe the complex reaction process on a Cu/alumina catalyst. The reaction kinetics model is based on five parallel reactions in which ethanol reacts to 1-butanol, acetealdehyde, ethyl acetate, diethyl ether and diethoxyethane, respectively.

     

Combined experimental and kinetic modeling studies for the conversion of gasoline range hydrocarbons from methanol over modified HZSM-5 catalyst

The reaction was carried out in fixed bed reactor. The effect of process variables on the activity of oxalic acid treated 0.5 wt% ZnO/7 wt% CuO/HZSM5 catalyst for the conversion of methanol to gasoline range hydrocarbons was studied. The catalyst was prepared by incipient wetness impregnation method. After impregnation the catalyst was treated with oxalic acid. The validity of kinetic model proposed for the methanol to gasoline range hydrocarbon process at zero time on stream was studied, from the experimental results obtained in a wide range of operating conditions. The kinetic parameters for various models were calculated by solving the equation of mass conservation in the reactor for the lumps of the kinetic models. The kinetic model fitted well for simulating the operation in the fixed bed reactor in the range of 635 to 673 K, with regression coefficient (R²) higher than 0.96.     

Mechanistic Modelling of the Catalytic Pyrolysis of Methylcyclohexane

A detailed chemical kinetic mechanism describing the thermal and catalytic cracking of methylcyclohexane over a 12CaO.7Al₂O₃ catalyst is presented. The model is based on balanced equations for both molecular and radical species describing an experimental fixed‐bed reactor system. The mechanistic model is based on overall first‐order decomposition kinetics, which satisfactorily describes experimental data. The simulated product distributions show a reasonably good agreement with the experimental results and confirm the hypothesis that the catalyst does not affect the pyrolysis mechanism and only increases the rate of the initiation steps.     

Direct Synthesis of 1-Butanol from Ethanol in a Plug Flow Reactor: Reactor and Reaction Kinetics Modeling

Bio-ethanol is well known for its use as a gasoline additive. However, it can be blended in low portions to traditional gasoline although it has a corrosive nature. By taking advantage of modern continuous reactor technology and heterogeneous alumina catalysts, ethanol can be upgraded to 1-butanol in fixed beds. Butanol has more feasible properties as fuel component in comparison to ethanol. Mathematical modeling of reaction kinetics revealed a simple kinetic model could be used to describe the complex reaction process on a Cu/alumina catalyst. The reaction kinetics model is based on five parallel reactions in which ethanol reacts to 1-butanol, acetealdehyde, ethyl acetate, diethyl ether and diethoxyethane, respectively.     

Enantioselective Hydrogenation of Ethyl Benzoylformate,from Mechanism and Kinetics to Continuous Reactor Technology

The enantioselective hydrogenation of ethyl benzoylformate over (?)-cinchonidine (CD)-modified Pt/Al₂O₃ catalyst in semi-batch and continuous fixed bed reactors was studied as a function of the modifier concentration and reaction temperature. The kinetic results from the semibatch reactor showed a higher enantioselectivity and lower initial rate as the amount of modifier was increased. The results from the fixed bed reactor demonstrates that continuous enantioselective hydrogenation is possible and that continuous feeding of (?)-CD is needed to maintain a high steady-state enantioselectivity.     

ROLE OF SUPPORT STRUCTURE ON KINETIC PARAMETER ESTIMATIONS IN A SHELL CATALYST

The kinetic parameters for VOC oxidation by a shell catalyst are generally obtained from the experimental data of conversion-temperature in a laboratory scale isothermal fixed bed reactor. The kinetics of these reactions are often represented by a bi-molecular Langmuir-Hinshelwood expresion. With the help of experimental data for n-hexane, the present study showed that the values of the kinetic parameters estimated depend significantly upon the location and width of the active catalyst layer as well as value of the effective diffusivity of the reactant within the porous structure. The present analysis showed that accurate a priori assessment of these parameters is very important for the reliable estimations of the kinetic parameters.     

Mathematical modeling and simulation of steady state plug flow for lactose-lactase hydrolysis in fixed bed

A detailed mathematical model for evaluating lactose hydrolysis with immobilized enzyme in a packed bed tubular reactor is presented. The model accounts for axial and radial dispersion effects, chemical reaction and external mass transfer resistances but is void of significant internal diffusion resistances of the particles. The comprehensive model was then simplified to a plug flow model for lactose-lactose hydrolysis in fixed bed. The resulting plug flow model was solved by using Runge-Kutta-Gill method via employing different kinetics for lactose hydrolysis. The reliability of model simulations was tested using experimental data from a laboratory packed bed column, where the β-galactosidase of Kluyveromyces fragilis was immobilized on spherical chitosan beads. Comparison of the simulated results with experimental exit conversion show that the plug flow model incorporating Michaelis-Menten kinetics with competitive product (galactose) inhibition are appropriate to interpret the experimental results and simulate the process of lactose hydrolysis in a fixed bed when the mass transfer resistance was reduced by a factor of 34.5.     

Oxidative dehydrogenation of butenes over Bi‐Mo and Mo‐V based catalysts in a two‐zone fluidized bed reactor

The oxidative dehydrogenation of a 1‐butene/trans‐butene (1:1) mixture to 1,3‐butadiene was carried out in a two‐zone fluidized bed reactor using a Mo‐V‐MgO and a γ‐Bi₂MoO₆ catalyst. The significant operating conditions temperature, oxygen/butene molar ratio, butene inlet height, and flow velocity were varied to gain high 1,3‐butadiene selectivity and yield. Furthermore, axial concentration profiles were measured inside the fluidized bed to gain insight into the reaction network in the two zones. For optimized conditions and with a suitable catalyst, the two‐zone fluidized bed reactor makes catalyst regeneration and catalytic reaction possible in a single vessel. In the lower part of the fluidized bed, the oxidation of coke deposits on the catalyst as well as the filling of oxygen vacancies in the lattice can occur. The oxidative dehydrogenation reaction takes place in the upper zone. Thorough particle mixing inside fluidized beds causes permanent particle exchange between both zones. © 2016 American Institute of Chemical Engineers AIChE J, 63: 43–50, 2017     

The catalytic dehydrogenation of isobutane to isobutene in a palladium/silver composite membrane reactor

Isobutane dehydrogenation to isobutene has been investigated experimentally and by modelling for a membrane reactor and a fixed bed reactor under similar operating conditions using a Pt/alumina catalyst. Reaction kinetics were obtained from experiments in the fixed bed reactor. Comparative tests showed that the membrane reactor achieved much higher yields of isobutene and also gave higher selectivities, with less by-products than the fixed bed system.

Using the kinetic data, the simulations gave good agreement with the fixed bed experiments, but over predicted the yields from the membrane reactor. Analysis of these results indicated that in the membrane reactor the hydrogen permeability of the membrane was much greater than its hydrogen transfer requirement and that the reaction rate was the determining factor for isobutene yield.