bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and mechanism of deactivation by fouling of a silica‐alumina catalyst in the gaseous phase dehydration of isoamyl alcohol
Authors: Corella Jose , Asua Jose M. 
Published: March 2009

AbstractThe kinetics and mechanism of the deactivation by fouling of a silica‐alumina catalyst in the dehydration of isoamyl alcohol in gas phase have been investigated. It has been found that deactivation takes place in series with the main reaction by coverage of active sites. The kinetic equation of deactivation is of the Langmuir‐Hinshelwood type, and the parameters have been determined from the data obtained in an isothermal reactor.
Thermal decomposition of pyrite in a fluidized bed
Authors: Monteiro J.L.F. 
Published: March 2009

AbstractThe thermal decomposition of pyrite was investigated in a silica batch fluidized bed reactor, in the temperature range 594 to 625°C. Particles were sampled during each run and those partially reacted showed a sharp reaction front. An equilibrium between pyrite and the resulting pyrrhotite is maintained until the central core of pyrite has disappeared, after which the reaction proceeds uniformly throughout the particle forming pyrrhotites with successsively lower sulfur contents. The reaction rate was sensitive to temperature, particle size and gas velocity. Application of the shrinking core model is consistent with heat transfer as the controlling step.
Wet oxidation of glucose
Authors: Skaates J. M. , Briggs B. A. , Lamparter R. A. , Baillod C. R. 
Published: March 2009

AbstractWet oxidation is used to oxidize organic substances at a controlled rate in an aqueous medium at elevated temperatures and pressures. Aqueous glucose solutions were oxidized with pure oxygen at four different temperatures in the range 176.7°C to 260.0°C, and at an oxygen pressure of 2.3 MPa. Three distinct stages of wet oxidation were found — induction, rapid oxidation, and slow oxidation. During the rapid oxidation period the reaction was assumed to be confined to a thin liquid layer next to the gas‐liquid interface. The activation energy for the rapid oxidation period was estimated to be 130 ± 20 kJ/mol. Acetic acid was found to accelerate the rate of wet oxidation of glucose only slightly.
Experimental determination of air‐h2s equilibria under claus furnace conditions
Authors: Bennett Howard A. , Meisen Axel 
Published: March 2009

AbstractSince little fundamental information is available on the Claus furnace, equilibrium compositions of air‐H2S mixtures were calculated for temperatures and O2/H2S ratios ranging from 600 to 2000°K and 0 to 1, respectively. Sulphur yields were found to increase marginally when O2/H2S ratios less than 0.5 (stoichiometric) are used. Feed impurities such as H2O, CO2 and NH3 generally diminish the sulphur yields.To determine equilibrium compositions experimentally, known air‐H2S mixtures were reacted in the range of 800 to 1500°K and the products were analyzed chromatographically. The measurements for H2S dissociation agreed well with theory and Raymont's experimental data; the results for H2S oxidation showed the same trends as theoretical predictions, but did not agree quantitatively. Reasons for the discrepancies and their practical implications are discussed.
Synergistic surfactant mixtures containing lignosulphonates
Authors: Hornof Vladimir , Neale Graham , Bourgeois Paul 
Published: March 2009

AbstractEnhanced oil recovery (EOR) schemes have been gaining importance over the past several years. Of the various methods being tested, surfactant (or micellar) flooding appears to be one of the most promising ones. It involves injecting into the well the solution of a surfactant which reduces the inter‐facial tension between the displacing aqueous solution and the oil trapped in the reservoir. Depending on the concentration of the surfactant, oil displacement proceeds either by a miscible process (surfactant concentration > 10%) or by a immiscible process (surfactant concentration = 2–3%). Miscible flooding converts to the immiscible process as the system is diluted by connate (interstitial) water. Under immiscible conditions, the most significant parameter affecting recovery is the interfacial tension(1,2). Petroleum sulfonates are perhaps the most important group of surfactants capable of producing very low interfacial tensions between crude oil and the water phase. Their relatively high cost, however, renders many potential applications uneconomical.
Three‐phase fluidization: Some knowledge gaps
Authors: Epstein Norman 
Published: March 2009

AbstractThe most recent review by østergaard — on the fluid mechanics of three‐phase fluidized beds — is updated and broadened, and the more manifest knowledge gaps are identified. A systematic classification of the various modes of three‐phase fluidization is presented in order to provide some perspective on the research which has been done and on that which has yet to be done.
Entrained coal gasifiers: Modeling the particle acceleration
Authors: De Lasa H. , Mok L. K. 
Published: March 2009

AbstractA conceptual model for the design of an entrained bed reactor is proposed in this article. This mathematical model simulates the continuous changes on the properties of both solid and gas phases inside the reactor. The model also computes the required reactor length for a specific coal conversion. Furthermore, a computer simulation is presented to illustrate the crucial continuous particle acceleration resulting of the coal gasification. We believe this effect must be considered for any appropriate particle residence time definition.
Dispersion of aqueous polymer solutions injected from a point source into turbulent water flows
Authors: El Riedy O. K. , Latto B. 
Published: March 2009

AbstractThe dispersion of water and aqueous polymer, when injected from a point source along the flow centre line into two‐dimensional, fully developed and uniform turbulent flows with flow Reynolds numbers of the order of 4.6 × 105, have been studied experimentally. Concentration profiles at five locations were obtained for injection concentrations and velocities in the ranges 0 to 1000 w.p.p.m. and equal to or less than the local flow velocity. The concentrations were assessed using a fluorescing dye technique.Empirical equations describing the radial and longitudinal concentration field as a function of the injection and flow parameter are given. A universal concentration profile, independent of the injection flow rate and concentration and length of injection source tube, and valid for water and for polymer solution, under both fully developed and uniform flow, is also presented. The results indicate that the turbulent dispersion of polymer solution is suppressed compared to that of water.
Co‐current stratified flow of immiscible liquids: Velocity distribution and pressure gradient in the laminar‐laminar and laminar‐turbulent regimes
Authors: Wang Chester C‐C , Charles M. E. 
Published: March 2009

AbstractFurther studies on the co‐current stratified flow of two immiscible liquids in closed conduits with emphasis on the laminar‐laminar and laminar‐turbulent regimes are reported. Experimental velocity distributions obtained using a photo‐chromic dye technique and pressure gradients for the flow of oil/water and oil/ethanol‐water systems in a rectangular conduit are compared with predictions developed from fundamental concepts. The agreement between the experimental data and the predictions are very satisfactory in both flow regimes. As a consequence, further work should now be focussed on the turbulent‐turbulent regime.
The plug flow model for mass transfer in three‐phase fluidized beds and bubble columns
Authors: Alvarez‐Cuenca M. , Nerenberg M. A. 
Published: March 2009

AbstractThe plug flow model (PFM), overwhelmingly used to describe mass transfer in bubble columns and three‐phase fluidized beds, has never been critically tested. This study analyzes the PFM single parameter, KLa, to quantify mass transfer in the forementioned systems.Particular attention is paid to the mass transfer features of the zone near the distributor (grid zone) largely ignored until now. This study, carried out under the largest gas and liquid flow rates ever published, for similar types of systems, indicates the presence of two well defined mass transfer zones. These features invalidate, for design purposes, the use of the PFM. However, it still can be used as a qualitative mass transfer indicator. This has permitted a comparison between the mass transfer efficiency of bubble columns and three‐phase fluidized beds with the conclusion that three‐phase fluidized bed of 0.5 cm particles can compete successfully with bubble columns.
Hierarchical control of a train of continuous polymerization reactors
Authors: Kiparissides C. , Ponnuswamy S. R. 
Published: March 2009

AbstractA multilayer control scheme is synthesized for a series of polymerization stirred tank reactors to control the monomer conversion over the reactor line. In this work two layers of control are implemented. In the' first level digital PI or self‐tuning regulators (STR) are used to control the reaction temperature of each reactor in the series by manipulating the flowrates of the coolant streams. In the second layer, a locally linear state space model, that can predict the monomer concentration in each reactor, is derived based on steady‐state energy balances. A quadratic performance index is then minimized to obtain the optimal reaction profile that will bring the monomer distribution over the reactor line to its desired target value.
Examination of a model for oscillating heterogeneously catalyzed reactions
Authors: Lynch David T. , Wanke Sieghard E. 
Published: March 2009

AbstractNumerous cases of self‐sustained oscillations have been reported for heterogeneously catalyzed oxidation reactions. For these self‐sustained oscillations, the conversion of reactants varies with time in the absence of external perturbations. Several models have been proposed for these systems. One of these models is based on Langmuir‐Hinshelwood mechanisms involving an adsorbed species which acts as a buffer. Previous predictions based on this model have involved simplifying assumptions. Model predictions without these assumptions are presented in this paper. These results are compared with previously reported simulations.
Some ideas on cracking catalyst design
Authors: Corma A. , Wojciechowski B. W. 
Published: March 2009

AbstractProgress in understanding the nature of cracking catalysts has led from the early recognition of the carbonium ion intermediate to the current view which ascribes cracking activity to the acidic nature of active sites. Here we develop the concept of acid catalysis to include the specific effects of Bronsted and Lewis acid sites on gas oil cracking. It is shown that these two types of sites react with specific substrates and that each has a characteristic kinetic behaviour. This leads us to suggest that careful control of the total site density and of the proportion of Bronsted/Lewis sites can result in a catalyst which is optimized for the feedstock, reactor configuration, and product distribution desired.
Photocatalytic oxidation of various compounds over TiO2 and other semiconductor oxides; Mechanistic considerations
Authors: Pichat P. , Herrmann J.‐M. , Courbon H. , Disdier J. , Mozzanega M.‐N. 
Published: March 2009

AbstractA synthesis of studies on the photocatalytic oxidation of various compounds (isobutane, propene, alkyltoluenes, butanols, ammonia, halide ions in aqueous solution) is presented, TiO2 being the main photocatalyst. Comparisons are also made with other n‐type semiconductors: ZrO2, V2O5, Sb2O4, ZnO, SnO2, CeO2, WO3. Information about the mechanism has been obtained by (i) an examination of the photocatalytic isotopic exchange of oxygen in competition with the oxidation of a hydrocarbon, (ii) kinetics and photoconductivity measurements, and (iii) oxidation of butanols by NO. The main conclusions are that these reactions proceed in an adsorbed phase and that dissociated oxygen species play an essential role.
Synergetic effect of molybdenum dioxide on nickel in the catalytic hydrogenation of benzene
Authors: Astier M. , Bertrand A. , Teichner S. J. 
Published: March 2009

AbstractMolybdenum dioxide is deposited on the form of an aerogel (in the autoclave) on nickel Mond. The catalytic activity for the hydrogenation of benzene into cyclohexane at 100°C depends on the proportion of MoO2 and on the temperature of a pretreatment in hydrogen. When this temperature is 440°C, the catalytic activity exceeds that of pure nickel Mond and exhibits a maximum for about 10% of MoO2. This synergetic effect, which is an exemple of a strong metal‐support interaction (SMSI), is explained by the incorporation into the surface of nickel Mond crystals of molybdenum produced by partial reduction of MoO2, with the formation of an inter‐metallic compound MoNi4.
Optimization of copper chloride based catalysts for ethylene oxyhydrochlorination
Authors: Arcoya Adolfo , Cortes Antonio , Seoane Xose L. 
Published: March 2009

AbstractIn this work we have studied the effect of adding Li, Na or K chloride to CuCl2 supported on α‐Al2O3, on its catalytic activity for the oxyhydrochlorination of ethylene to dichloroethane in a fixed bed reactor, at 573 K and atmospheric pressure. Both NaCl and KCl show a strong promoting effect. For the case of KCl, this effect has been further examined for a wide range of concentrations and a fixed amount of CuCl2 supported on either α‐Al2O3, γ‐Al2O3 or SiO2 gel. The catalytic and thermogravimetric results obtained indicate that KCl is very effective on the overall rate, even at low concentrations, particularly because it increases considerably the rate of reoxidation of the reduced form of the catalyst. In the case of the γ‐Al2O3 series, the promoting effect is only moderate.Ethylene oxyhydrochlorination data for a series of α‐Al2O3 supported catalysts containing a constant K+/Cu2+ atomic ratio and increasing total amount of KCl + CuCl2 are shown. The activity curve shows a maximum for about 18 wt % total active phase.Finally, the influence of Ce, Nd and Pr chlorides on the activity of CuCl2 + KCl supported on α‐Al2O3 is also shown. In the case of Pr, the entire range of Pr3+/Cu2+ atomic ratios has been examined. The results indicate that the rare earths, especially praseodymium, also have an additional positive effect on activity.
Estimation of liquid film mass transfer coefficients for columns randomly packed with partially wetted rings
Authors: Ponter Anthony B. , Au‐Yeung Patrick H. 
Published: March 2009

AbstractA semitheoretical correlation based on an extension of the random length, random angle statistical model of Davidson (1959) is developed which predicts liquid film mass transfer coefficients in a column packed with partially wetted Raschig rings.The method takes into account the ring size and the mixing which occurs at the packing junctions and allows an estimation of the effective length of a packing piece for a particular liquid viscosity. Predicted values of mass transfer coefficients are in good agreement with the experimental values obtained for the carbon dioxide‐water and carbon dioxide‐aqueous glycerol systems at 25°C reported by Mangers and Ponter (1980b) and other systems reported by Sherwood and Holloway (1940).
Étude des Caractéristiques de l'Ecoulement créé par une Turbine à Barreaux croisés dans une Cellule de Flottation — Influence du Nombre de Barreaux et de la Viscosité du Liquide I. • Détermination de la Capacité de Pompage et de l'Intensité de Turbulence
Authors: Costes J. , Alran C. , Couderc J.P. 
Published: March 2009

AbstractLes vitesses moyennes, les fluctuations de vitesse, la capacité de pompage, les intensités de turbulence du courant de refoulement d'une turbine à barreaux croisés dans une cellule de flottation ont été déterminés par anémométrie à film chaud à différentes vitesses de rotation. Les influences du nombre de barreaux de la turbine et de la viscosité du liquide ont été étudiées.
Heterogeneous catalysis rate parameters in a gradientless reactor by the method of moments
Authors: Garza‐Tobias G. , Jimenez‐Ocana J. , Rosales M.A. 
Published: March 2009

AbstractThe transient behaviour of an internally‐recycled catalytic reactor has been studied accounting for the contributions from intraparticle diffusion, adsorption and surface reaction. Equations for the zeroth, first and second absolute moments of the break‐through curves are given in terms of the rate constants for the three elementary steps (first order processes are assumed throughout). The moments can be obtained from experimental break‐through curves and the rate parameters for adsorption and surface reaction then evaluated from such data. Simplified equations also are derived for the case of insignificant chemical reaction and this case is used to test the method experimentally. Values of the hydrogen adsorption equilibrium constant for γ‐alumina supported Co Mo‐Ni catalyst are reported.
The chemistry of catalyst poisoning and the time on stream theory
Authors: Viner M. R. , Wojciechowski B. W. 
Published: March 2009

AbstractIt is shown that concentration‐independent decay functions apply over a fairly wide range of poisoning mechanisms in which both products and reactants take some part in poisoning the active sites. The Time on Stream theory is therefore applicable to a wide range of decay mechanisms. In particular, it appears to be ideally suited to catalytic cracking, where the same intermediate carbonium ions are thought to lead to cracking as a main reaction or to poisoning as a side reaction.Our considerations of the chemistry of poisoning and simulation of catalyst decay behaviour lend credence to the earlier analyses of various kinetic parameters which have been obtained from experimental data using the Time on Stream theory.
Simulation d'un réacteur catalytique à lit fixe (Oxydation du propène)
Authors: Djelveh G. , Gros J. B. , Bugarel R. 
Published: March 2009

AbstractUn modèle bidimensionnel pseudo‐homogène est utilisé pour l'étude de comportement d'un réacteur catalytique à lit fixe d'oxydation du propène en acroléine. Les lois de vitesses utilisées sont les fonctions puissance de pressions partielles en oxygène et en propène. Les valeurs des paramètres thermiques Pehr et Bi nécessaires à la simulation sont obtenues directement à l'aide des profils de température en l'absence de réaction. Le modèle est intégré par une méthode de collocation orthogonale. Les résultats du modèle, à savoir les profils de températures et la concentration à la sortie du réacteur, sont comparés avec ceux obtenus expérimentalement.
Evaluation of capital cost data: Onsite utilities (industrial gases)
Authors: Woods Donald R. , Anderson Susan J. , Norman SILLS Suzanne L. 
Published: March 2009

AbstractCapital cost correlations with capacity or with total investment are given for units supplying onsite industrial gases: compressed air, oxygen, nitrogen, inert atmospheres, high purity hydrogen, synthesis gas, ozone and acetylene. Costs are also given for units to remove carbon dioxide and water from gas streams. Correlations available in the literature and current data are compared. Graphs show the relative magnitudes of the different correlations, and the recommended correlation for each type of equipment is given. Some unit usages are given for producing some of the gases.
La flottation de spheres et de cylindres
Authors: Gapany P. , Leidi M. , Hartland S. 
Published: March 2009

AbstractA study is made of the maximum weight of spherical and cylindrical particles which can be supported by a pendant bubble and at an infinite fluid/liquid interface. The maximum weight increases with the radius, the contact angle (measured through the lower fluid), the density difference between the two fluids and the interfacial tension. It follows that to ensure good flotation suface active agents must be added to increase the contact angle. The maximum particle weight which can be supported at an infinite interface is always greater than that which can be transported there by the pendant bubble.
Reacteur a electrode volumique a lit fixe: Taux de conversion et selectivite
Authors: Ratel A. , Routie R. , Lacoste G. 
Published: March 2009

AbstractFor the purpose of recovering silver from sulfuric acid solution, performance problems of a three‐dimensional electrode operating at sublimiting current are discussed here. Material and charge balances in the reactor lead to three differential equations for concentration, potential and current density, which are solved by a numerical method. In the case of flow from cathode to anode the kinetic term has been found to be constant. Design equations for this kind of reactor have also been established.
Effect of liquid wetting on catalyst effectiveness in trickle‐bed reactors
Authors: Capra V. , Sicardi S. , Gianetto A. , Smith J. M. 
Published: March 2009

AbstractThe liquid in trickle‐bed reactors falls in rivulets down over the catalyst particles. Heretofore, studies of the effect of fractional liquid coverage of the outer surface of the particle on reaction rate have ignored the distribution of the rivulets. A model has been developed in this paper for predicting the effect of number and size of the liquid rivulets. The system of equations has been solved numerically for a first order reaction for two types of reactions: a), one where the rate is determined by the reactant concentration in the liquid, and b), a reaction where the rate is controlled by reactant concentration in the gas phase, as in some hydrogenations.The results show that intraparticle concentration profiles are strongly affected by the distribution and size of the rivulets. However, for both types of reactions the overall rate, as measured by an overall effectiveness factor, is not significantly affected. This result is important since it suggests that distribution and size of the liquid rivulets may be safely ignored in evaluating the effect of liquid coverage, or wetting efficiency, on the rate of reaction
Flow of stratified slurries through horizontal venturi meters
Authors: Shook C. A. 
Published: March 2009

AbstractStratified slurries flowing through horizontal venturi meters are shown to have discharge coefficients higher than values for homogeneous fluids. This effect increases with slurry concentration and decreases as the velocity increases. Predictions using a two‐layer model are qualitatively reasonable but inadequate knowledge of the effect of fluid lift forces makes quantitative prediction difficult.
Hydrodynamic and mass transfer characteristics of bubble and packed bubble columns with downcomer
Authors: Gopal J. S. , Sharma M. M. 
Published: March 2009

AbstractThe hydrodynamic and mass transfer characteristics of bubble and packed bubble columns with downcomer were investigated. The contactor consisted of two concentric columns of 0.11 and 0.2 m i.d., with the annulus acting as the downcomer. The packing used in this investigation was standard 16 mm stainless steel Pall rings. The superficial gas and liquid velocities, VG and VL, were varied from 0.01 to 0.09 and 1 × 10−3 to 8.8 × 10−3 m s−1 respectively.Two flow patterns, namely the bubble and pulse flows were observed in the packed bubble column with downcomer, as shown by a flow map.The liquid circulation velocity in both the contactors was observed to be constant throughout the ranges of VG and VL covered in this work. The effect of liquid viscosity (0.8 to 9.5 mPa ṁ s) and surface tension (45 to 72 mN m−1) on the flow pattern, liquid circulation, gas hold‐up and pressure drop was investigated. The pressure drop characteristics across the two contactors have been compared with those across a bubble column.Values of the effective interfacial area, a, and the volumetric mass transfer coefficient, kL a, were measured by using chemical methods. Values of a as high as 180 and 700 m−1 and kL a as high as 0.075 and 0.22 s−1, in the bubble and packed bubble columns with downcomer, respectively, were obtained. The values of true liquid‐side mass transfer coefficient, kL, were found to be independent of VG and were of the order of 5.5 × 10−4 and 3.5 × 10−4 m s−1, respectively, in the two contactors.