Acetaldehyde dimethylacetal synthesis with Smopex 101 fibres as catalyst/adsorbent

The synthesis of dimethylacetal using acetaldehyde and methanol as raw material in the presence of Smopex 101 fibres as catalyst and adsorbent in batch reactor and in a fixed bed adsorptive reactor, respectively, was studied. In the batch reactor the determination of thermodynamic and reaction kinetics data for acetalization reaction was presented. A kinetic model based on a pseudo-homogeneous rate expression using activities was proposed to describe the experimental kinetic results. The dynamic binary adsorption experiments were carried out in the absence of reaction at 293.15 K in a laboratory scale column. The experimental results of the adsorption of binary non-reactive mixtures are reported and used to obtain multi-component adsorption equilibrium isotherms of Langmuir type. The mathematical model was proposed to describe the adsorptive reactor dynamic behaviour. The experimental results obtained for the reaction and regeneration experiments were compared with the model proposed. Model equations were solved by orthogonal collocation on finite elements (OCFE) implemented by the PDECOL package, using the measured model parameters and was validated for both reaction and regeneration steps.     

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.     

Experimental Reaction Equilibrium and Kinetics of the Liquid‐phase Butyl Acrylate Synthesis Applied to Reactive Distillation Simulations

Butyl acrylate, which can be produced in liquid phase from butanol and acrylic acid, is an important precursor for varnishes and adhesives. The reaction equilibrium and the kinetics of the butyl acrylate synthesis catalyzed by acid ion exchange resins were measured and the results are used to derive formulas for the equilibrium and the kinetics which is supposedly based on a Langmuir‐Hinshelwood‐Hougen‐Watson mechanism. Because of the highly nonideal reaction mixture, both the equilibrium and the kinetics are expressed in terms of activities. The equations are used in the modeling and simulation of a butyl acrylate production plant which consists of a catalytic tube reactor and a reactive distillation column. A column that is operated in the common manner, i.e. by heating only the reboiler, leads to a reactive azeotrope over a large part of the column. However, distributing the heat flow over the whole column improves the separation and the conversion significantly.     

吸附反应器的动态特性—非瞬时竞争吸附的影响

针对可逆催化反应Ａ－Ｂ＋Ｃ、各组分非瞬时Ｌａｎｇｍｕｉｒ吸附的情况，研究了固定床吸附反应器的动态特性，着重分析多组分非时竞争吸附的影响。对反应物阶跃输入时，吸附反应器的出口浓度响应进行了模拟分析，模拟结果预示，在一定的参数条件下，动态操作的吸附反应器有较高的反应转化率、高的产物和反应物分离度、而且产物Ｂ和Ｃ之间也能同时得到高度分离。另外，给出了Ｂ和Ｃ分离的条件及定性评价其分离程度的判据。     

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.     

Optimal separation of n-paraffins from Kuwait kerosene using a molecular sieve adsorbent

A study has been made of the vapour-phase adsorptive separation of n-alkanes from Kuwait kerosene using zeolite molecular sieves (LMS-5A). The object was to identify the optimum operating conditions, in terms of flow rate, adsorption temperature and zeolite particle size for the separation of n-alkanes from kerosene, so that the remaining stock would also be of marketable quality. The effect of these conditions on the height of the mass transfer zone (HMTZ) and the dynamic capacity (Ad) of zeolite was also investigated. The adsorptive separation process comprised one cycle of adsorption using a fixed bed of zeolite type-5A. The bed was fed with kerosene vapour until equilibrium had been achieved, whereby the n-paraffins were adsorbed and the denormalized material excluded. The processes were carried out isobarically at one atmosphere. The optimum operating conditions were found to be a feed flow rate of 33.33 × 10^?9 m³ s^?1, an adsorption temperature of 643 K and a zeolite pellet fraction size of 1.0–2.0 × 10^?3m. This yielded an HMTZ value of 0.206 m and an Ad of 9.653 × 10^?2 kg n-paraffins kg^?1 zeolite. The data will serve as a basis for the design of commercial plant.     

Analysis and performance of a countercurrent moving-bed chromatographic reactor

A theoretical and experimental investigation of a countercurrent moving-bed chromatographic reactor is the subject of this paper. In this reactor a reversible heterogeneous reaction takes place on catalyst particles passing downward through an upcoming gas stream. The behaviour of an ideal reactor model was examined for different values of feed concentrations and reactor length. It is predicted that reaction and separation can be achieved simultaneously and that under appropriate operating conditions, a reactor fed at the bottom with the species more favoured by thermodynamic equilibrium can lead to 100% product purity with overall conversions lower than a conventional fixed bed reactor. The effect of nonidealities on the reactor performance is also discussed. Finite adsorption and axial dispersion have a generally deteriorating effect on overall conversion and product purity. An improved reactor configuration with a bottom stripping section is suggested. Its operating conditions can be tailored so that predicted performance exceeds that of a fixed bed both in yield and product purity. The hydrogenation of mesitylene with excess hydrogen over a Pt on alumina catalyst was used for an experimental investigation of the reactor. The experiments, performed in a 1/2″ i.d., 7′ long column, resulted in products of higher purity than the equilibrium prediction, and overall conversions comparable to a fixed bed reactor.     

Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed‐bed column experiments

This paper evaluates the potential use of a locally available organic soil amendment as a low‐cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed‐bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo‐second‐order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow‐rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate‐controlled pore diffusion was successfully performed. The adsorption process was reversed, regenerating the columns by eluting the cadmium using 0.1 mol dm^?3 hydrochloric acid. The high retention capacity together with the favourable structural characteristics indicated that this material could be used as an effective and low‐cost adsorbent for treatment of wastewaters containing heavy metals. Copyright © 2006 Society of Chemical Industry     

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     

吸附反应器动态特性的研究

针对反应速率方程为γ_A=k_1c_A~m-k_2c_B~n的非瞬时可逆均相反应A(?)vB、液相反应或浓度很稀的气相反应和反应物A或产物B瞬时非线性Langmuir吸附的情况,研究了反应和吸附相结合的吸附反应器之动态特性.建立了平推流固定床吸附反应器的动态模型,通过数值解法获得了反应物阶跃和方波输入时,吸附反应器出口的动态响应曲线.研究结果表明,吸附反应器无需附加净化步骤就能获得高纯度的产物;吸附反应物时,反应转化率降低,吸附产物时,反应转化率提高.并讨论了吸附平衡常数和反应速率常数对吸附反应器性能的影响.     

Analysis of a discontinuously operated chromatographic reactor

The principle of a discontinuously operated chromatographic reactor was studied experimentally and theoretically. The heterogeneously catalysed hydrolysis of methyl formate was chosen as a model reaction. An acidic ion exchange resin was used as catalyst and adsorbent. The relevant adsorption equilibrium constants were available from a previous study. In this work the reaction rates were quantified on the basis of batch reactor experiments. Subsequently, systematic experiments were carried out using a fixed bed. The influence of temperature, residence time, feed concentration and cycle time on the reactor performance was studied. It was attempted to analyse the observations using a simplified pseudo-homogeneous cell model. Since the model was found to be capable of describing the reactor behaviour over a wide parameter range, it was applied to perform extensive parametric calculations. Besides the achievable conversion other objective functions such as recoveries and production rates were also analysed. From the results obtained a few generally applicable rules to evaluate the potential of discontinuously operated chromatographic reactors could be derived.     

Simulation and validation of ethanol removal from water in an adsorption packed bed: Isotherm and mass transfer parameter determination in batch studies

Preferential adsorption of ethanol from ethanol/water mixtures in batch equilibrium and kinetic experiments were carried out on a commercially available activated carbon adsorbent Filtrasorb 600 (F‐600). A model based on finite difference method was developed and employed to determine the mass transfer parameters and equilibrium behaviour for the adsorption of ethanol from simple batch systems. The estimates of the adsorption isotherm along with the mass transfer parameters were used to simulate the transient performance that could be expected in a packed bed under various operating conditions (feed flow rate, feed concentration, and particle size). The applicability of the simulation results were found to be a good match with experimental packed bed experiments over the entire range of operating conditions tested.     

A novel continuous reactor for catalytic reduction of NOx—fixed bed simulations

A novel dual‐zone fluidized bed reactor was proposed for the continuous adsorption and reduction of NO_x from combustion flue gases. The adsorption and reaction behaviour of such a reactor has been simulated in a fixed bed reactor using Fe/ZSM‐5 catalyst and propylene reductant with model flue gases. Fe/ZSM‐5 exhibited acceptable activity at T = 350°C and GHSV = 5000 h^?1 when O₂ concentration was controlled at levels lower than 1% with a HC to NO molar ratio of about 2:1. XPS and BET surface area measurement revealed the nature of the deactivation of the catalyst. Those performance data demonstrated the feasibility of a continuous dual‐zone fluidized bed reactor for catalytic reduction of NO_x under lean operating conditions.     

Valeric acid extraction with tri‐n‐butyl phosphate impregnated in a macroporous resin: II. Studies in fixed bed columns

Extraction and back‐extraction of valeric acid in a fixed bed packed with Amberlite XAD‐4 resin impregnated with tri‐n‐butyl phosphate were experimentally studied at 25 °C. The effects of the feed flow rate, acid concentration in the feed solution and extractant concentration in the impregnated resin on the breakthrough curves, were investigated. The bed saturation capacity was larger under the conditions of higher extractant concentration in the resin phase and higher acid concentration in the feed solution. A dynamic model that considers intraparticle diffusion and external liquid film diffusion as limiting steps in mass transfer rates was successfully applied. The intraparticle effective diffusivities (10^?9 dm² s^?1) were from one to three orders of magnitude lower than the diffusivities in the external liquid film (10^?8–10^?6 dm² s^?1). A fast and complete back‐extraction of valeric acid from the saturated bed was carried out with sodium hydroxide solutions. The operational life of the impregnated resin was also studied. Copyright © 2005 Society of Chemical Industry     

Emulsion copolymerization in a tubular reactor

A study was conducted on the emulsion copolymerization of vinyl acetate and butyl acrylate in a tubular reactor. It was performed at a constant temperature of 60°C and at different fluid velocities and feed compositions. Conversion, particle size distribution, and copolymer composition were measured, respectively, with gravimetric method, laser light scattering, and nuclear magnetic resonance. Maximum conversions were found for each of the monomer compositions; this maximum conversion varied, however, with the recipe used. The amount of butyl acrylate has a direct effect on the number of particles and on the final conversion. In lower levels of butyl acrylate particle size distribution is wide and bimodal. High levels of butyl acrylate leads to narrow and monomodal particle size distribution. Therefore the level of butyl acrylate and the velocity of fluid flowing inside the tube have strong effects on the shape (monomodal‐bimodal) and the width of particle size distributions. This effect may vary at different levels of butyl acrylate and flow rate. The results obtained from copolymer composition show that an alternating block copolymer is made during the reaction. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 833–842, 2000     

A Novel Fluidized‐Bed Membrane Dual‐Type Reactor Concept for Methanol Synthesis

A novel fluidized‐bed membrane dual‐type methanol reactor (FBMDMR) concept is proposed in this paper. In this proposed reactor, the cold feed synthesis gas is fed to the tubes of the gas‐cooled reactor and flows in counter‐current mode with a reacting gas mixture in the shell side of the reactor, which is a novel membrane‐assisted fluidized bed. In this way, the synthesis gas is heated by heat of reaction which is produced in the reaction side. Hydrogen can penetrate from the feed synthesis gas side into the reaction side as a result of a hydrogen partial pressure difference between both sides. 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 partially converted gas leaving this reactor is directed into the shell of the gas‐cooled reactor and the reactions are completed in this fluidized‐bed side. This reactor configuration solves some drawbacks observed from the new conventional dual‐type methanol reactor, such as pressure drop, internal mass transfer limitations, radial gradient of concentration, and temperature in the gas‐cooled reactor. The two‐phase theory of fluidization is used to model and simulate the proposed reactor. An industrial dual‐type methanol reactor (IDMR) and a fluidized‐bed dual‐type methanol reactor (FBDMR) are used as a basis for comparison. This comparison shows enhancement in the yield of methanol production in the fluidized‐bed membrane dual‐type methanol reactor (FBMDMR).     

Kinetics of the liquid phase esterification of acrylic acid with butanol catalysed by cation exchange resin

Esterification of butyl alcohol with acrylic acid catalysed by Amberlyst-15 cation exchange resin was carried out in a batch reactor in the liquid phase in the temperature range 333 to 364 K and 1 atm. The reaction rate increased with an increase in catalyst concentration and decreased with an increase in water concentration. The rate data were correlated with a kinetic model based on inhibition by water. The apparent activation energy was found to be 59.5 kJ mol^?1 for the formation of butyl acrylate.     

Adsorptive reactors for enhancing equilibrium gas-phase reactions—two case studies

The conversion enhancement potential of fixed-bed adsorptive reactors has been evaluated for two heterogeneously catalysed gas-phase equilibrium reactions: the Claus reaction used in sulphur recovery and the direct synthesis of hydrogen cyanide from carbon monoxide and ammonia. It was found that kinetics of both reaction and adsorption as well as adsorbent capacity have to be very compatible to achieve high conversions. The specific parameters of the reaction/catalyst system, such as the deposition of solids (e.g. sulphur, coke) or the formation of undesirable by-products have to be taken into account for the successful application of adsorptive reactor concepts. A crucial point is the selection of the reaction conditions (i.e. temperature), since the occurrence of side reactions may be enhanced in adsorptive reactor operation due to the inherently distorted concentration profiles.     

Dynamic Study of the Synthesis of 1,1-Dibutoxyethane in a Fixed-Bed Adsorptive Reactor

The synthesis of 1,1-Dibutoxyethane in a fixed-bed adsorptive reactor using Amberlyst 15 was studied for the first time. The adsorption of non-reactive pairs was investigated experimentally, at 25°C, by frontal chromatography in a fixed-bed adsorber. In order to avoid the immiscibility of the liquid phase, the liquid-liquid equilibrium for the mixture 1-butanol/water was studied. The multicomponent equilibrium adsorption data was assumed to follow the modified Langmuir type isotherm. Reaction experiments of 1,1-Dibutoxyethane production and column regeneration were performed in the fixed-bed adsorptive reactor. This work will enable further developments in chromatographic reactors aiming at the 1,1-Dibutoxyethane process intensification.