bluuebunny/crossref_metadata_2025_split huggingface dataset:
A multi‐step kinetic model for phenol oxidation in high‐pressure water
Authors: Tufano Vincenzo 
Published: August 2005

AbstractA kinetic model for the oxidation of phenol in high‐pressure water has been developed and compared with experimental data taken from literature. The model assumes a chain reaction propagated by O⋅ and OH⋅. Production of the hydroxyl radical by the reaction of atomic oxygen and water induces a chain‐branching effect, which is particularly effective at low temperatures and high pressures. The proposed model gives a fair correlation of the experimental data in the whole examined temperature and pressure range and appears significantly better than a simpler, power‐law kinetic model. The relibility of the model is strengthened by the consideration of values obtained for the kinetic parameters (in particular for the activation energies) which compare well with the literature.
A mathematical model of dehydroisomerization of methylcyclopentane using a bifunctional catalyst blend
Authors: Dittrich Joachim , Keil Frerich J. , Luus Rein 
Published: August 2005

AbstractA mathematical model of dehydroisomerization of methylcyclopentane in presence of bifunctional catalysts under industrial operating conditions is presented. The model consists of six differential equations. The rate constants are expressed as polynomial functions of the catalyst blend, and coefficients of these polynomials were determined from numerous measurements, taken along the axis of a tubular reactor. The resulting polynomial coefficients led to reaction rate constants which yielded results close to the actual process.
Fluid phase equilibria in the system hydrogen sulphide‐water at high pressure. Application of an extended Henry's law
Authors: Carroll John J. , Mather Alan E. 
Published: August 2005

AbstractHenry's law is often used to correlate the solubility of a gas in water. Such an approach is frequently employed to calculate the solubility of hydrogen sulphide in water. However, Wright and Maass [1] clearly demonstrated that the strict Henry's law did not apply to the solubility of hydrogen sulphide in water. That is, the solubility of hydrogen sulphide is not directly proportional to its partial pressure, even at seemingly low pressures. By accounting for the non‐idealities in the vapour phase, Carroll and Mather [2] showed how a simple modification of Henry's law could be used for moderate pressures (up to 1 MPa). In this paper, a further extension of Henry's law is used to model the vapour‐liquid equilibrium at higher pressures and temperatures. It is also applied to liquid‐liquid and vapour‐liquid‐liquid equilibria, areas where Henry's law is rarely used.
A learning feedforward control strategy for the concentration control of recycle reactors. Part III: Implementation and operation
Authors: Schnitzlein Klaus , Bolze Klaus , Löwe Arno 
Published: August 2005

AbstractIn order to verify its performance, the learning feedforward control strategy was applied to the catalytic methanation of CO‐rich synthesis gas. Details of the implementation in hardware as well as in software are discussed. The experimental results confirm the functionality of the learning feedforward control. Suggestions are given for further improvement of the control strategy.
Controlled precipitation
Authors: Mersmann Alfons , Angerhöfer Martin , Franke Jürgen 
Published: August 2005

AbstractIn a process of precipitation, two or more reactants form a product. In many cases, the solubility of this product is very low and high supersaturation is generated which leads to nucleation and crystal growth. The number of the formed nuclei and their growth govern the particle size distribution of the precipitate. As a rule, the precipitate is separated from the mother liquor in a centrifuge or on a filter. This separation and the subsequent drying process of very fine particles can be very expensive with respect to investment and energy costs. Therefore, it is desirable to produce as coarse a precipitate as possible with a narrow crystal size distribution.
Kinetic studies on high temperature desulphurization of synthesis gas with zinc ferrite
Authors: Karlegärd Åsa , Bjerle Ingemar 
Published: August 2005

AbstractThe desulphurization of synthesis gas with zinc ferrite was studied in a laboratory‐scale fixed‐bed reactor. Desulphurization efficiency of 97–99% was obtained. The inlet hydrogen sulphide concentration was about 2600 ppm. A flat breakthrough curve showed that diffusion through the sulphide layer controlled the rate of sulphidization. The degrees of utilization varied between 5 and 11%. Experimental data formed the basis of a kinetic evaluation with the fixed bed model and the unreacted core model. Rate constants, reaction orders, and effective diffusion constants were calculated. When chemical reaction controlled the rate, the order of reaction was between zero and unity. The rate of reaction increased with temperature. Effective diffusivities were of the order of 10−5 m2 s−1, increasing slightly in the temperature range between 500 and 600°C. The activation energy was determined as 54 kJ mol−1, which corresponds to an unexpectedly strong temperature dependence of the diffusion‐controlled reaction. The low degrees of utilization, and also the strong temperature dependence, are explained by sintering of the sulphidized zinc ferrite.
HCl formation via pyrolytic degradation of polyvinyl chloride (PVC): An empirical approach to kinetic modelling
Authors: Bisi Marco , Nicolella Cristiano , Palazzi Emilio , Rovatti Mauro , Ferraiolo Giuseppe 
Published: August 2005

AbstractThe pyrolysis of polyvinyl chloride (PVC) has been described in terms of a relatively simple kinetic model, based on a large number of laboratory tests. The model predictions are in a good agreement with experimental data, regarding hydrochloric acid and non‐condensable combustible gases. Therefore, the proposed model can be used to predict with good approximation the distributions of the above classes of compounds, in the whole range of applied experimental conditions.
Estimation of the drying rate and moisture profiles in an industrial spray dryer by means of experimental investigations and a simulation study
Authors: Fieg Georg , Wozny Günter , Buick Kurt , Jeromin Lutz 
Published: August 2005

AbstractA spray dryer simulation program is described. It is based on the known conservation laws and permits determination of temperature and moisture profiles and droplet trajectories inside spray dryers. An industrial spray dryer used in the manufacture of detergents serves as an example to demonstrate the applicability of the program; this approach required prior experimental determination of the flow field and an axial temperature profile. On the basis of a rough estimate of the drying rate in the spray dryer, good agreement was observed between experiment and simulation.
Study of drop‐interface coalescence: Drainage time measurement
Authors: Kourio Maria Julia , Gourdon Christophe , Casamatta Gilbert 
Published: August 2005

AbstractAn automatic apparatus has been developed and set up for the study of drop‐interface coalescence. Most other studies have concentrated on events when the drop arrives at the interface with its terminal velocity. In our case, the drop is maintained fixed at the tip of a needle, and the interface is moved towards the drop at a controlled speed. The coalescence times are measured by means of a vectorial video camera focused on the drop. Several times are measured by means of a vectorial video camera focused on the drop. Several parameters have been investigated, such as the drop diameter, the relative drop‐interface velocity, the phase system, the presence and the direction of mass transfer.
A general simulation model of batch chemical reactors for thermal control investigations
Authors: Cabassud Michel , Lann Marie‐Véronique Le , Ettedgui Boaz , Casamatta Gilbert 
Published: August 2005

AbstractThis paper describes the development of a dynamic simulation model for stirred tank batch or semi‐batch chemical reactors fitted with an alternative heating‐cooling system. Heat and mass balances are established for the reactor and its jacket. Since the general purpose of our research is the thermal control of these reactors, special attention is devoted to the behaviour of the heating‐cooling system. In this article, we are particularly concerned with an alternative system, i.e. different fluids at a constant temperature can be alternatively delivered to the jacket. The computer simulation programme is flexible, enabling simulation of a batch or semi‐batch reaction vessel, ranging from a laboratory pilot plant to a full‐scale production plant. A control algorithm is included which allows reactor operation with open or closed‐loop temperature control. To demonstrate the good performance of the simulation model, experimental results are presented for both a pilot plant and an industrial reactor.
Crystallization process optimization using artificial neural networks
Authors: Woinaroschy Alexandru , Isopescu Raluca , Filipescu Laurentiu 
Published: August 2005

AbstractThis paper presents a new procedure for optimization of continuous mixed suspensionmixed product removal (MSMPR) crystallizing systems. Owing to the difficulties of theoretical modelling, simulation of the MSMPR crystallization process is based on the use of artificial neural networks (ANN). The optimization criterion is a compound objective function corresponding to an intended mean crystal size dimension and a minimal dispersion. The presence of multiple local minima has called for investigation by several optimization techniques. Ultimately, Luus' and Jaakola's random adaptive method proved to be most effective. The results obtained lend support to the general procedure proposed.
Unsteady two‐film model for mass transfer
Authors: Wang Jinfu , Langemann Horst 
Published: August 2005

AbstractThe classical two‐film model for mass transfer between two fluid phases can only be used to describe the steady state mass transfer mechanism. Both the penetration and the film‐penetration model are also valid solely when only one diffusion boundary layer exists at the interface between the phases. With a view to surmounting the limitations of the above models a new model has been developed for the mass transfer between two fluid phases with two diffusion boundary layers at the interface. The new model is based on the two‐film concept and the Danckwerts distribution function, and is also able to simulate the unsteady state mass transfer mechanism between two fluid phases with two different boundary layers.
The cocurrent downflow contactor–a novel reactor for gas‐liquid‐solid catalysed reactions
Authors: Boyes Adrian P. , Raymahasay Sugat , Tilston Mike W. , Lu Xia X. , Sarmento Sandra , Chugtai Arshad , Winterbottom John M. 
Published: August 2005

AbstractThe Cocurrent Downflow Contactor (CDC) has been developed as a mass transfer and reactor device, with and without addition of tangential (swirl) flow, giving gas hold‐up (Eg) values of 0.5–0.75, interfacial areas in the range 1000–6000 m2m−3 liquid and kLa values in the range of 0.15–1.55 s−1 for absorption using the O2/H2O system. It has been studied as a catalytic slurry reactor for the hydrogenation of (i) itaconic acid and (ii) triglycerides catalysed by Pd and Ni catalysts. The reactions were observed to be largely surface‐reaction rate controlled, due to the very efficient mass transfer (kLa up to 11.75 s−1 under reaction conditions) and application of swirl flow‐enhanced reaction rates. The CDC has recently been found to be capable of operating as a fixed bed reactor, thus eliminating a downstream catalyst separation problem (therefore more cost effective), and is superior in its mass transfer characteristics to other known devices. Scale‐up can be undertaken without loss of performance efficiency.
Basic characteristics of spinel type manganese mixed oxide/titanium composite anodes for electroorganic redox catalysis
Authors: Lodowicks Egbert , Beck Fritz 
Published: August 2005

AbstractManganese mixed oxide composite layers of about 1 μm thickness on titanium sheet as substrate were fabricated by firing of the corresponding nitrates at a typical temperature of 400°C in air. The activity of these anodes was evaluated by cyclic voltammetry (10 mV/s) and the stability was determined by chronopotentiometry (2.5 mA/cm2) in 1M H2SO4. The oxidation of 2‐propanol was examined as a simple electroorganic model reaction. The quality of a first category of mixed oxides with general composition MnMe2O4 decresed in the order Me = Co, Ni, Fe. In a second group with the general formula MeMn2O4 a decrease in the order Me = Co, Cu, Fe, Ni, Ti, Zn, Cd, Ca, Mg, (Zn, Ge), Li was observed. The corresponding candidates of the second group were superior to those of the first. The anode service life τ of the optimum spinel anode CoMn2O4/Ti is dependent on the current density, according to jλ τ = const. (λ = 1.7). Thus high current densities are precluded. The mechanism has been discussed in terms of a heterogeneous redox catalysis: surface Mn(VII) states are formed in a slow electrochemical step. In a subsequent fast chemical oxidation of the organic molecule the original reduced state is regenerated. This also explains the comparatively good service life of these anodes.
Recovery of zinc from pickling baths with amberlite LA‐2. Influence of modifier on the extraction equilibrium
Authors: Martín Marta San , Bart Hans‐Jörg 
Published: August 2005

AbstractThe extraction of zinc chloride by Amberlite LA‐2, a long chain secondary alkylamine, dissolved in Shellsol K, a naphthenic solvent, has been studied at room temperature. Isodecanol was used as modifier. The aqueous phases were chloride solutions of Zn(II) and Fe(II) in the concentration range commonly encountered in pickling baths, viz. about 1 and 1.5 mol/l, respectively. The ionic strength was kept constant at 4 mol/l in all experiments. Measurement of the distribution equilibrium of zinc chloride was carried out over wide concentration ranges of amine, zinc chloride, free chloride and isodecanol. It was assumed that the zinc chloride was extracted according to the following reaction

On the basis of this reaction, an easy to use model was developed to describe the extraction behaviour of Zn in typical pickling baths. Prediction and optimization of a solvent extraction plant performance under changing industrial feed conditions is then possible. This model takes account of the influence of isodecanol used as modifier.
Liquid velocity and dispersion coefficient in an airlift reactor with inverse internal loop
Authors: Kochbeck Birgit , Hempel Dietmar C. 
Published: August 2005

AbstractAn airlift reactor with inverse internal loop (annulus sparged) is investigated with regard to liquid velocity and dispersion coefficient for the purpose of reactor design. To distinguish between the influence of the individual parts of the reactor (downcomer, riser, bottom) on the liquid velocity and mixing, several draft tubes with different geometries and draft tube bottom clearances are successively installed.
Mathematical simulation of bioseparation in an affinity packed column
Authors: Sridhar P. , Sastri N. V. S. , Modak J. M. , Mukherjee A. K. 
Published: August 2005

AbstractAffinity chromatography (biospecific adsorption) relies on specific interactions of biological molecules such as enzymes, antigens, antibodies, and proteins. The process consists of three steps: adsorption, washing, and elution. A mathematical model including convection, diffusion, and reversible reaction is formulated to analyse the breakthrough behaviour of the solute. A moving finite element orthogonal collocation method is applied with respect to the space variables of the governing partial differential equations of the model to evaluate the breakthrough of the solute. Danckwerts' boundary conditions are considered for the column. The validity of the numerical scheme is checked by comparison with an analytical solution for a simplified model. The results obtained from model simulation show that the breakthrough time of the solute is significantly influenced by the axial dispersion coefficient, solute concentration, ligand content, reaction kinetics, particle porosity, particle size, and flow rate. Solute recovery and bed utilisation efficiencies are evaluated for different values of the above parameters.
Economics of the oxidative coupling of methane as an add‐on unit for naphtha cracking
Authors: Hoebink Jozef H. B. J. , Venderbosch Henny M. , van Geem Paul C. , Van den Oosterkamp Paul F. , Marin Guy B. 
Published: August 2005

AbstractThe feasibility of methane coupling as an add‐on unit to a naphtha cracker was studied. The existing cold box was used for separation of ethylene and unconverted methane, but arrangements were made for separation of the coupling by‐products. The cracker's methane was used as a feedstock. The concept is technically and economically feasible at spring 1992 prices, provided the catalyst meets the assumed 30% conversion and 80% C2 selectivity.
Selective oxidation of o‐xylene to phthalic anhydride over vanadia/titania: A comparative study of integral and recycle reactor operation
Authors: Nobbenhuis Marc G. , Barnickel Peter , Wokaun Alexander , Baiker Alfons 
Published: August 2005

AbstractTwo vanadia/titania catalysts, containing 1 and 8 wt% vanadia on anatase, have been investigated for the selective oxidation of o‐xylene to phthalic anhydride. In a comparative study, activity and selectivity in o‐xylene oxidation were measured using an integral reactor and a reactor with external product recirculation, with the objective of studying the influence of backmixing in the latter on the reaction behaviour. Adsorbed surface species were investigated by means of in‐situ diffuse reflectance FT‐IR spectroscopy, using an environmental chamber which corresponds to an integral reactor. No difference in activity and selectivity in o‐xylene oxidation was observed between the two catalysts. FT‐IR studies showed adsorbed o‐xylene, benzoate and a high concentration of phthalic anhydride on the surface of both catalysts. o‐Xylene oxidation follows a sequential reaction path, with o‐tolualdehyde as the first intermediate and phthalide, phthalic anhydride and maleic anhydride as sequential products. No evidence was found for a direct oxidation‐path of o‐xylene to phthalic anhydride. Total oxidation products CO and CO2 are formed by direct oxidation of the o‐xylene and by oxidation of the reaction products. Due to greatly reduced concentration and temperature gradients, the recycle reactor proved to be highly suitable for studying the extremely exothermic oxidation of o‐xylene.
Three‐Stage wiped‐film molecular evaporator: Design and application
Authors: Cvengroš Ján 
Published: August 2005

AbstractThis paper describes the design principles of multistage molecular evaporators with a wiped film which are used for gentle distillation of low‐volatility blends of thermolabile materials. The conditions of distillation in an evaporator with a convex evaporation surface are discussed, along with problems relating to the function of the segmented wiper in the formation of the retarded liquid film and the functional principles of closing elements in a multistage evaporator with a single evaporating cylinder and of the built‐in entrainment separator in the distillation space, which is designed to retain splashing spray. A TMO 65 three‐stage molecular evaporator is described, with an evaporating cylinder having a diameter of 65 mm and a total evaporating area of 0.19 m2. This pilot‐plant evaporator can be used in the small‐capacity production of specialty chemicals or in technological research as a verification unit for establishing data necessary for the operation of large evaporators. These possible applications are documented by the results obtained on fractionation of various important materials. Fractional distillation of crude monoacylglycerols (M) containing 35 to 55% M afforded concentrates containing over 90% M, at yields of 78 – 95% M in the product fraction. Fractionation of oligomers of higher α‐olefins gave distillate cuts with high contents of the respective n‐mer, suitable for use as synthetic lubricating oils. Fractionation of polyalkylaromatic residue from the production of monoalkylbenzenes produced a distillate fraction with excellent electrical insulation properties. Finally, purification of technical diane‐bis‐glycidyl ether yielded over 75% of a product fraction which was found suitable for production of insulating material for electrical equipment operating at voltages of 6 to 15 kV.
Vortex depth in unbaffled single and multiple impeller agitated vessels
Authors: Markopoulos Joannis , Kontogeorgaki Eleni 
Published: August 2005

AbstractAlthough vortex formation is usually an undesirable phenomenon in the process industry, satisfactory process conditions and results can also be obtained in unbaffled agitated vessels in the presence of a vortex. This fact and especially the low power requirements in these systems, with their immediate relevance to the energy problem in the process industry, show the true importance of vortex formation in agitated vessels. This article reviews the literature results and the correlations proposed for the prediction of vortex depth in unbaffled agitated vessels with various types of single and multiple impeller systems and presents a critical discussion on the basis of a theoretical analysis.
New and efficient high‐temperature processes with circulating fluid bed reactors
Authors: Reh Lothar 
Published: August 2005

AbstractStarting with a brief review of the development of the circulating fluid bed (CFB) reactor principle, its main features as an important tool for efficient and thus environmentally acceptable processing of fine particulate solids, typically less than 150 μm diameter, are discussed. Various new industrial processes and high temperature process options starting with alumina calcination are described. Developing applications in the cement, metallurgical and chemical industries are approaching large‐scale industrial importance. Efficient combustion or pressure gasification of fossil fuels and carbon‐containing residues, fulfilling increasingly strict environmental legislation, is by far the most rapidly expanding field of application. In support of these developments our fundamental understanding of the fluid dynamics of CFB riser and of cyclone precipitation at high solid loadings has to be steadily improved. The reaction behaviour of aggregating fine particulate solids of varying size distributions also remains an open question.
The role of Cl− in a Li+‐ZnO‐Cl− catalyst on the oxidative coupling of methane and the oxidative dehydrogenation of ethane
Authors: Wang Dingjun , Rosynek Michael P. , Lunsford Jack H. 
Published: August 2005

AbstractThe effect of Cl− ion addition to a Li+‐ZnO catalyst has been studied with respect to the oxidative coupling of CH4 and the oxidative dehydrogenation (OXD) of C2H6. Increasing the Cl/Li ratio from 0.65 to 0.90 had relatively little effect on the CH4 conversion, whereas the C2H4/C2H6 ratio was enhanced significantly as a result of an increase in the OXD reaction rate. Conversely, loss of Cl− from the catalyst during the reaction had a much more deleterious effect on ethane OXD activity than on methane coupling activity. Addition of Cl− ions at a Cl/Li ratio of 0.9 caused a decrease both in the number of basic sites and in the basic strength of these sites, as determined by temperature‐programmed desorption of CO2. The similarities between the results obtained over Li+‐ZnO‐Cl− catalysts and those previously reported for Li+‐MgO‐Cl− catalysts confirm that basicity of the host oxide plays only a minor role in determining the properties of these chlorided catalysts.