bluuebunny/crossref_metadata_2025_split huggingface dataset:
Limitation by zeolite protons of the oxygenate yield in syngas conversion over RhMn/NaY catalysts
Authors: Treviño Horacio , Sachtler Wolfgang M. H. 
Published: August 2005

AbstractCO hydrogenation over Mn‐promoted Rh/NaY catalysts was studied at 1 MPa and 250°C. Significant selectivity to ethanol and ethyl acetate was obtained only after neutralising the protons formed on reduction of Rh ions. Layered bed experiments show that protons act as Brønsted acid sites catalysing secondary reactions that convert the oxygenates to hydrocarbons and coke.
Modification of the catalytic properties of supported noble metal catalysts by carrier doping
Authors: Ioannides Theophilos , Verykios Xenophon E. 
Published: August 2005

AbstractThe influence of altervalent cation doping of TiO2 carriers on the chemisorptive and catalytic properties of supported Pt and Rh crystallites has been investigated. It was observed that doping of the carrier with higher valence cations leads to suppression of the H2 and CO chemisorption capacity of Pt catalysts, while their activity in hydrogenation and oxidation reactions is significantly reduced. The opposite effects were observed in the case of Rh catalysts supported on higher valence doped TiO2. These catalysts were found to possess higher activity in CO and CO2 hydrogenation, in aromatics hydrogenation and in CO and C2H4 oxidation. Their stability characteristics were also found to be superior to those of the undoped Rh/TiO2 catalyst. These effects are believed to originate from an electronic type interaction at the metal‐support interface, induced by doping, which results in electron transfer from the support to the metal crystallites.
Single liquid drop velocities and breakage mechanism in sections of structured packings
Authors: Mao Z.‐Q. , Godfrey J. C. , Slater M. J. 
Published: August 2005

AbstractSingle liquid drop velocities in structured packings have been measured to aid calculation of throughput of liquid extraction columns using characteristic (single drop) velocities. Solvent drops were passed through two types of glass and two types of steel structured packing and further work was done using sloping glass tubes. Existing wall‐effect equations for drop velocity reduction in vertical tubes were considered and that given by Clift et al. [1] was used as a basis for correlation of structured packing data. Drop breakage was studied in order to improve understanding of drop size distribution development in packed columns. Drops broke only rarely within the structured packing; most of the breakage occurred as a drop hit the exposed edges on entry to a piece of packing. An energy balance equation was used to correlate critical conditions for breakage of drops hitting glass blades at various angles. Under the conditions used all those drops moving at terminal velocity had enough energy to break but a condition exists when drops may be small enough to have insufficient energy to break.
Single liquid drop breakage probabilities and characteristic velocities in Kühni columns
Authors: Fang J. , Godfrey J. C. , Mao Z.‐Q. , Slater M. J. , Gourdon C. 
Published: August 2005

AbstractStudies have been made on the extent and mechanism of breakage of single liquid drops of organic liquids immiscible in water rising through short sections of Kühni liquid‐liquid extraction columns. Information on drop breakage probabilities is required for calculation of drop size distributions developed under counter‐current column operating conditions. The breakage probability data from two small diameter Kühni columns containing one, three or five stages have been correlated as a function of a modified Weber number based on the shearing forces on drops. The critical condition for breakage, giving a maximum stable drop size, is based on an impeller Weber number. Characteristic velocities of drops were measured relative to terminal velocity and the ratio was tentatively correlated with a function of an impeller Reynolds number together with the fractional free area of the perforated plates used to separate compartments. The drops were found to break predominantly at the holes in the plates, not at the turbine, in the region of transitional Reynolds number used in this work. The results apply only to non‐turbulent conditions so further work on larger diameter equipment is called for.
Synthesis of tertiary amyl methyl ether (TAME): Equilibrium of the multiple reactions
Authors: Oost Carsten , Sundmacher Kai , Hoffmann Ulrich 
Published: August 2005

AbstractThe octane enhancer tertiary amyl methyl ether (TAME) is produced by liquid phase synthesis from methanol and a mixture of isoamylenes, namely 2‐methyl‐1‐butene and 2‐methyl‐2‐butene, using a sulfonic acid ion exchange resin as catalyst. Three reactions take place simultaneously in TAME synthesis: etherification of the two methylbutenes and their isomerisation. In order to study the equilibrium of the multiple reactions in TAME synthesis, the thermodynamic properties of the compounds in the liquid phase and equilibrium constants were calculated using a modified UNIFAC method to describe the nonideality of the system. Four parameters influencing the equilibrium conversion were derived and discussed in detail. Supplemental experiments were performed at three temperatures in the range from 303 to 343 K and at different initial molar ratios of educts. Equilibrium conversions of methanol were determined from these experiments and compared with calculated values. At 298 K the predicted activity based equilibrium constant was 22.9 for TAME synthesis from 2‐methyl‐1‐butene and 1.6 for TAME synthesis from 2‐methyl‐2‐butene; for isomerisation of 2‐methyl‐1‐butene to 2‐methyl‐2‐butene a value of 14.3 was obtained.
Oxidation of methane on a Au + SrFeO3−δ//YSZ electrode characterised by mass spectroscopy and 18O2 pulses
Authors: Norby Truls , Middleton Peter Hugh , Hansen Eddy W. , Dahl Ivar , Andersen Arnfinn G. 
Published: August 2005

AbstractA solid state electrochemical reactor is described in which reactants can be oxidised at high temperatures over an anode/catalyst using co‐fed oxygen gas as well as electrochemically supplied oxygen. The setup permits injection of isotopic pulses in the reactant streams. The composition and isotopic distribution in the products are recorded with a quadrupole mass spectrometer. The use of the system is exemplified by oxidation of methane over a Au + SrFeO3−δ//YSZ anode at 800–850°C. Pulses of 18O2 in the stream of co‐fed O2 were used to study the reactivity and products of gaseous oxygen as distinguished from the electrochemically supplied oxygen. The results indicate that the anode used supports oxygen pumping, but is only moderately active for methane oxidation. The products are mainly CO and CO2. The content of 18O in the products is low, indicating that methane oxidation takes place by 16O‐rich lattice oxygen. In comparison, a reference Au//YSZ electrode was found to be a slower anode for oxygen pumping, but a better catalyst for the reaction between CH4 and gaseous O2, seemingly involving adsorbed oxygen.
Air stripping – a method for treatment of wastewater
Authors: Kutzer Stephan , Wintrich Hans , Mersmann Alfons 
Published: August 2005

AbstractDuring recent years the air stripping process has been increasingly applied to the cleaning of water contaminated by volatile organic compounds (VOC). The present contribution compares various methods of treating VOC‐contaminated water, with a special focus on removal efficiency and economic aspects. In particular, air stripping, a universally used cleaning method, is described in greater detail. Design and operational aspects are worked out for packed stripping towers for the special case of water contaminated with chlorinated hydrocarbons. Experimental results substantiate predictions of various operating conditions, packing types and scale‐up effects.
Nonlinear model‐based feedforward control of distillation columns
Authors: Broll Johannes , Rix Armin , Gelbe Horst 
Published: August 2005

AbstractAn approach to feedforward distillation control based on inverse computation of nonlinear stage models is presented. The feedforward model calculates dynamic trajectories of manipulated variables from measured disturbances and product purity set points independently of the control configuration. Because the model includes the dominant dynamics and nonlinearities of the column, dynamic decoupling of the control loops is achieved. A superimposed linear controller only has to compensate model uncertainties and disturbances that cannot be measured. The proposed approach improves the control performance. Simulation studies show the applicability of the method to multicomponent distillation as well as to distillation trains. Experiments on a pilot plant scale binary distillation column verify the simulation results.
The vapour‐liquid equilibria of several binary systems of fluorocarbons and hydrocarbons, part II
Authors: Kramp Sabine , Wagner Heinz Georg 
Published: August 2005

AbstractThe vapour‐liquid equilibria of the binary systems perfluoromethylcyclohexane‐pentafluorobenzene, benzene‐pentafluorobenzene, benzene‐methylperfluorobutanoate and perfluoromethylcyclohexane‐methylperfluorobutanoate have been measured at 333.07 K and 343.12 K using a dynamic circulation still of the Sieg‐Röck type. The thermodynamic consistency of the measurements was tested by two different methods. New UNIFAC interaction parameters [1] were calculated for the following groups: ACH‐ACF, ACF‐CF2, CF2‐COO, ACCH2‐ACF, ACH‐CF2. The abbreviations stand for the following increments: ACH = aromatic CH group, ACF = aromatic CF group, CF2 = aliphatic CF2 group, COO = ester group and ACCH2 = side chain CH group.
Application of fuzzy relational modelling to industrial product quality control
Authors: Qian Yu , Tessier Patrick J. C. 
Published: August 2005

AbstractIndustrial product quality control is a typical mathematical programming and optimization problem. Unfortunately, complete and precise models are not always available for many industrial processes. A fuzzy relation modelling approach is proposed to describe approximate relationships among system variables and reconcile empirical equations. Symmetric fuzzy decision‐making is transformed into a non‐linear function maximization problem. The approach is applied to optimization of a wood chip refining process. It is used either to improve pulp quality within the refiner operation range, or to reduce operation costs while maintaining an acceptable pulp quality.
Pyrolysis of methane in the presence of hydrogen
Authors: Olsvik Ola , Rokstad Odd A. , Holmen Anders 
Published: August 2005

AbstractThe kinetics of methane pyrolysis were studied in a tubular flow reactor in the temperature range 1200 to 1500°C at atmospheric pressure. To avoid excessive carbon formation the reaction time was short and the methane feed was diluted with hydrogen. Ethene, ethyne, benzene and hydrogen were the main gaseous products. Ethane was observed as a product at very low conversions of methane. More than 90% selectivity was obtained for C2 products. The ratio of ethyne to ethene increased with increasing temperature. The yield of C2 products is limited by gas‐phase equilibrium at lower temperatures. Formation of carbon was strongly depressed by hydrogen at higher temperatures. The maximum yield of ethyne was found to increase from about 10% to about 50% when the temperature was increased from 1200 to 1500°C, with hydrogen dilution H2: CH4 = 2: 1. A mechanistic reaction model was used to simulate the pyrolysis of methane at the actual conditions. A sensitivity analysis was performed to evaluate the elementary reactions which influence the formation and consumption of the species in the model system.
Kinetics of thermal decomposition of hydromagnesite
Authors: Rao T. Rajeswara , Chohan V. S. 
Published: August 2005

AbstractThe thermal decomposition of hydromagnesite has been studied using thermogravimetric analysis. The experiments were conducted in a nitrogen atmosphere with pellets of hydromagnesite in the temperature range 300 to 550°C, and also with powder samples under non‐isothermal conditions at a heating rate of 10°C/min. It is found that the reaction proceeds in two stages: dehydration followed by decomposition. The dehydration reaction is controlled by external mass transfer whilst the decomposition reaction is controlled by both external and internal mass transfer. The activation energy for the dehydration reaction was found to be 2.67 × 107 J/kmol. From the non‐isothermal analysis the activation energy for the decomposition of magnesium carbonate was found to be 1.62 × 108 J/kmol.
Fluid catalytic cracking: Selectivity and product yield patterns
Authors: Hari C. , Balaraman K. S. , Balakrishnan A. R. 
Published: August 2005

AbstractFluid catalytic cracking, a common secondary process employed in the petroleum industry, is used to convert heavier feedstocks into products such as liquefied Petroleum Gas (LPG), motor gasoline, diesel etc. The present study focuses on developing a three lump fraction kinetic model to estimate the yield of C5 up to 370°C cut (motor gasoline and middle distillates). A Micro Activity Test (MAT) apparatus was used to estimate the parameters in the kinetic model. The study is useful in evolving a procedure to simulate plant performance using experimental data obtained in the MAT apparatus for a particular catalyst and feedstock in terms of the product yield pattern.
Mass transfer coefficients for arranged packings with vertical walls under gas film control
Authors: Kolev Nikolai , Nakov Svetoslav , Djonova‐Atanassova Daniela 
Published: August 2005

AbstractPackings with vertical walls, especially structured packings, are distinguished by their high efficiency and low pressure drop per mass transfer unit. Yet for these types of packings there is still no universal relationship for calculating gas‐film‐controlled mass transfer coefficients. The present work proposes such an equation. For arranged and structured packings the new equation fits the experimental data, both new results and those taken from the literature, with a mean error of 9%.
Inulin hydrolysis to fructose by a novel catalyst
Authors: Abasaeed A. E. , Lee Y. Y. 
Published: August 2005

AbstractAcidic zeolite LZ‐M‐8 was used to catalyse the hydrolysis reaction of inulin into fructose. Fructose contents of 96% and 75% were obtained when commercial inulin and Jerusalem artichoke extract were used respectively as substrates. Zeolite LZ‐M‐8 was found to be extremely selective towards inulin hydrolysis as compared to fructose decomposition. Formation of hydroxymethyl furfural (HmF) was not detected and it was confirmed that zeolite LZ‐M‐8 does not adsorb HMF. The catalytic activity of the zeolite remained intact upon repeated use of the catalyst. The superiority of the zeolite over other catalysts used in inulin hydrolysis was demonstrated experimentally.
Effect of double agitation on particle size in suspension polymerization of styrene with a loop reactor
Authors: Tanaka Masato , Takahashi Tohru , Kimura Isao 
Published: August 2005

AbstractSuspension polymerization of styrene was performed in the loop reactor. In order to allow wide change to the polymer particle size, a sub impeller was included within the main impeller. The sub impeller served to increase the fluid velocity and to uniformly disperse the polymer droplets during polymerization.It was investigated how the double agitation method by the main and the sub impellers affected the transient droplet diameter distribution and the final particle size distribution. The particle size could be changed widely by the double agitation method without the decrease in degree of the uniformity of the particle size.
Kinetics of vanillin oxidation
Authors: Fargues Claire , Mathias Álvaro , Silva José , Rodrigues Alírio 
Published: August 2005

AbstractVanillin can be produced by oxidation of kraft lignin, with air, in alkaline medium. The optimal conditions for vanillin production strongly depend on pH and temperature. This paper addresses the effect of temperature and pH on vanillin degradation by oxidation. Experiments were carried out in a wide range of vanillin concentration, oxygen partial pressure, temperature and pH. Simple models are proposed to explain the observed rate of vanillin consumption under conditions of high alkalinity (pH>12) and lower alkalinity (pH<12). At pH>12,the reaction rate of vanillin oxidation is first order in dissolved oxygen concentration [O2] and in vanillin concentration [C], i.e., (−rC) ∝[O2][C]; at pH<12, the rate is zero order in oxygen concentration and second order in vanillin concentration, i.e., (−rC)∝f(pH)[C]2.
Determination of lumped rate coefficients of proteins: Effect of adsorption
Authors: Hashim Mohd. Ali , Chu Khim Hoong , Tsan Peh Sim 
Published: August 2005

AbstractThe equilibria and kinetics of adsorption of lysozyme and bovine serum albumin on the Fractogel‐EMD tentacle‐type cation exchanger and the Fractogel‐TSK conventional cation exchanger have been studied experimentally by batch stirred‐tank method. Adsorption equilibrium data corresponded well to the Langmuir isotherm. For both proteins, the tentacle‐type exchanger exhibited a higher binding capacity than the conventional exchanger. This is attributed to the flexibility of the functional groups in the tentacle‐type exchanger which enhance optimal electrostatic interactions. The dynamic data were analyzed by a simplified data model which lumped mass transfer resistances and intrinsic adsorption kinetics into a single rate constant. For both proteins, it was found that the tentacle‐type exchanger showed a smaller lumped rate coefficient than the conventional exchanger. The difference in the values of the lumped rate coefficients was shown to be due to the influence of nonlinear equilibrium constants rather than due to any difference in rate of adsorption.
Interfacial tension of fluid system considering the nonstationary case with respect of mass transfer
Authors: Jaeger Philip T. , Schnitzler Joachim V. , Eggers Rudolf 
Published: August 2005

AbstractInterfacial properties exert a fundamental influence on fluid/liquid separation processes, with the interfacial tension being an important quantity associated with mass transfer and mutual solubility of participating compounds. A better understanding of transport phenomena is achieved by obtaining interfacial tension data under different conditions of pressure and temperature and as a function of time. Generally, interfacial tension decreases with increasing pressure due to increased adsorption of the compressed fluid at the interface. In the case of considerable mutual solubility, interfacial tension further decreases with time as mass transfer into the bulk phase proceeds. Prediction of colloidal behaviour in a separation process requires acquisition of additional information on the presence of surfactants.
Two‐dimensional motion of spherical particles
Authors: Michalski Jacek A. 
Published: August 2005

AbstractA method for the prediction of velocity and path length components for two‐dimensional particle motion is developed for stagnant and slowly moving gas. The numerical algorithm appears much more straightforward and more efficient than those previously developed on the basis of simplified analytical methods. In the case of particle motion in a flowing gas, several limitations of the method occur. The method of limit estimation is briefly described.
Measurement of pumping characteristics of agitators in tubes
Authors: Rieger František 
Published: August 2005

AbstractThe Pumping characteristic of an agitator in a tube is necessary of the calculation of its pumping capacity in configuration in the vessel with a draught tube. The general dimensionless equation of the pumping characteristic suitable for the higher Reynolds number region was derived by inspection analysis of basic equations. The new dynamic experimental method for determination of pumping characteristics is put forward. The application of this method is illustrated on a special three‐blade axial‐flow impeller.
About the possibility of a direct concentration control for distillation columns
Authors: Fieg Georg , Landwehr Birgitta , Wozny Günter 
Published: August 2005

AbstractThe results of simulations of direct concentration control of a distillation column in industrial scale are presented. Both controlled variables, the two product concentrations, are determined by on‐line gas chromatographs and are characterised by high dead times of about 30 min. For the resulting scanning control of the product concentrations corresponding decentralised PI controllers were developed and applied. The control of the product concentrations developed presents a conventional DV structure and was exemplarily tested for disturbances in feed flow and feed concentrations. The calculations carried out exhibit a good time behaviour of the whole system. On this occasion it can be stated that the control quality could be clearly improved if a steady‐state decoupling by output transformation was employed. In this case the results achieved are totally comparable to those of internal model control (IMC), which was in use at the production plant for over two years.
Simulation of hydrodynamic behaviour and mass transfer efficiency of reduced pressure distillation
Authors: Benadda Belkacem , Moszkowicz Pierre , Prost Michel , Otterbein Michel , Mohammedi Kamal 
Published: August 2005

AbstractA random packing hydrodynamic simulator is designed specially to carry out experiments under reduced pressures with a counter‐current flow air/water system. The simulator results (air/water system) compared to those obtained in a real packed distillation column (benzylchloride/ ethylbenzene system) show a good agreement between hydrodynamic parameters like pressure drop, flooding flow rate, and total liquid hold‐up. Empirical relationships derived from the simulator experimental results are proposed allowing the calculation of the pressure drop in a packed distillation column, operating in the pressure range between 10 kPa and atmospheric pressure. The influence of reduced pressure on the HETP in the distillation column and interfacial area in the simulator was also investigated.
A comparison of cavern development in mixing a yield stress fluid by rushton and intermig impellers
Authors: Galindo Enrique , Argüello Martha A. , Velasco David , Albiter Verónica , Martínez Alfredo 
Published: August 2005

AbstractIntermig impellers have been postulated as very efficient for mixing highly viscous non‐Newtonian fluids (such as xanthan and mycelial broths). However, no formal characterisation has been published and no fair comparisons have been made, based on accurate power drawn measurements and using equal number of impeller stages and equal diameter, if compared (for example) with the performance of Rushton turbines. Characterisation of the shape, size, and evolution of the well‐mixed zones or “caverns” were correlated with power drawn, for single and dual Rushton turbines and for one‐ as well as two‐stage Intermig unslotted impellers. Cavern evolution studies were carried out in a mixing tank (diameter=0.205 m, H/T=1.6) equipped with an accurate air bearing dynamometer. Carbopol 940 (0.25 wt.‐%) was used as a model, transparent fluid. Impeller to tank diameter ratio was 0.53 for both impellers. Caverns were visualised by injecting methylene blue in the well‐mixed zones. A single Rushton turbine developed larger caverns if compared with one‐stage Intermig of the same diameter under power drawn below 1.5 kW m−3. At higher power drawn, both impellers behaved very similarly, reaching a limit in cavern volume of about 40% of the total liquid volume, even at very high (20 kW m03) power drawn. A similar trend characterised dual combinations: below 3 kW m−3, dual Rushtons gave larger cavern volume if compared with the performance of two‐stage Intermigs. In either case, power drawn higher than 3 kW m03 was sufficient to mix more than 90% of the liquid volume. The presence or absence of the slot in the Intermig did not influence cavern development. Experiments with a smaller if compared with those obtained with the larger Intermig (D/T = 0.53).