bluuebunny/crossref_metadata_2025_split huggingface dataset:
Agriculture wastes. A source of bulk products?
Authors: Schügerl Karl 
Published: August 2005

AbstractBiotechnological production processes for low‐molecular bulk chemicals can only compete with their petrochemical counterparts on using inexpensive raw materials, e.g., agricultural by‐products or wastes, otherwise requiring disposal. The upgrading of by‐products/wastes of potato starch production and the use of potato protein liquor and potato pulp for the production of bulk chemicals were investigated. It transpired that the economy of these processes depends on the waste disposal costs of the upgrading processes. In addition, it is shown that specialty chemicals can be produced economically from wastes. However, since they are produced in a large quantities, the upgraded product cannot be put on the market without ruining existing prices.
Comparison of the dynamic behaviour of packed and plate distillation columns
Authors: Fieg Georg , Wozny Günter , Jeromin Lutz , Kruse Christopher 
Published: August 2005

AbstractThe results of experimental investigations on distillation columns operating on a lab and on a production scale are presented and compared with the results obtained by simulation. There is good agreement between experiment and simulation. On the basis of these results a dynamic analysis was carried out. It compares the dynamic behaviour of packed and plate distillation columns of the same diameter and same number of theoretical plates. This reflects the influence of the different hold‐ups of the two columns.
On the para/ortho product ratio of phenol and anisole hydroxylation over titanium silicalite‐1
Authors: Vetter Sabina , Schulz‐Ekloff Günter , Kulawik Kornelia , Jaeger Nils I. 
Published: August 2005

AbstractTitanium silicalite‐1 samples of different particle size are synthesised and characterised by X‐ray diffraction (XRD), photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), Raman and infrared spectroscopy. Size histograms are taken from transmission electron micrographs. Temporal changes of activity and selectivity for the hydroxylation of phenol and anisole are monitored. It is postulated that the p/o product ratios are due to the greater chemisorption of the ortho molecule.
Process for production of pure 4‐methyl‐1‐pentene
Authors: Yankov Marin , Ninov Jordan , Petrov Peter 
Published: August 2005

AbstractA process for the manufacture of pure 4‐methyl‐1‐pentene by catalytic dimerization of propylene has been developed in three stages. The first stage involves preparation of a new process catalyst, which contains metallic sodium and potassium deposited on a Bulgarian natural zeolite, the support having been passivated previously by potassium carbonate. The experimental results demonstrate the advantages of the resulting catalyst over exisisting technology, namely 36% conversion and 92% selectivity relevant to liquid isomers. The second development stage concerns the technological regime of chemical reaction for production of 4‐methyl‐1‐pentene. In the third stage, the regime conditions and equipment ensuring desired quality of the product and utilization of the unreacted propylene returned to the reactor are determined. Based on the studies of all stages, a flowsheet is proposed for synthesis and separation of the reaction mixture of isomeric hexenes to give pure 4‐methyl‐1‐pentene.
Hydrogen consuming anodes for energy saving in sodium sulphate electrolysis
Authors: Holze Stephan , Jörissen Jakob , Fischer Christian , Kalvelage Heinrich 
Published: August 2005

AbstractGas diffusion electrodes, made of PTFE‐bonded carbon with precious metal catalysts, were investigated as hydrogen consuming anodes in sodium sulphate electrolysis. The catalysts used were platinum and palladium and mixtures of both metals, prepared by two different methods. Various metal meshes were used as current collector. The electrodes performed well in pure sulphuric acid (5–15 wt‐%) and in mixtures with sodium sulphate (10 wt‐%) at temperatures of 30 to 70°C and current densities up to 5 kA/m2. In long‐term experiments, at a current density of 2.6 kA/m2, the electrodes were stable over three months. The electrodes were characterised by stationary current density/potential curves and by galvanostatic current interruption measurements.
Hydrogenation of carbon dioxide on cobalt catalysts – activation, deactivation, influence of carbon monoxide
Authors: Kestel Ulrich , Fröhlich Gerd , Borgmann Dieter , Wedler Gerd 
Published: August 2005

AbstractA batch reactor directly combined with an ultrahigh vacuum apparatus, which is equipped with facilities for catalyst preparation and Auger electron spectroscopy, was used to answer some questions which had arisen in recent studies concerning carbon dioxide hydrogenation on pure metallic and supported Co catalysts. Both oxygen incorporated during oxidation/reduction cycles and carbon deposited when CO2 is hydrogenated penetrate deep into the bulk. This kind of carbon can easily be hydrogenated. CO strongly hinders the reduction of the oxidized Co surface in the H2/CO2 reaction mixture (4 : 1). CO hydrogenation is favoured over CO2 hydrogenation and leads to a higher percentage of C2 to C4 hydrocarbons as compared with CH4 formation.
Gas mixing in the cocurrent downflow circulating fluidised bed
Authors: Wei Fei , Jin Yong , Yu Zhiqing , Liu Jinzhong 
Published: August 2005

AbstractAn experimental study on the gas dispersion behaviour of a cocurrent downflow gas‐solids suspension in a 140 mm i.d. circulating fluidised bed (CDCFB) using the steady‐state tracer method is presented. The influence of gas velocity, solids circulating rate and particle density on radial gas dispersion has been examined. Gas dispersion can well be described by an eddy diffusion mechanism and a proposed two dimensional dispersed plug‐flow model can fit the experimental data very well. Correlations of the radial diffusion coefficient were obtained. It is found that the axial diffusion coefficient obtained in the CDCFB is much lower than that in conventional circulating fluidised beds.
Influence of hydrodynamics of rotary dynamic filters on separation processes
Authors: Rudniak Leszek , Wroński Stanisław 
Published: August 2005

AbstractThe fluid flow in a filter chamber, consisting of a rotating disk and a stationary plate, has been numerically investigated. A proposed model provided acceptable predictions for shear rate and frictional torque in laminar and turbulent flow regimes. Owing to the pronounced effect of the shear stress on the filtration rate, the data obtained were used in analysis of the influence of hydrodynamics on the shear stress field in the filter chamber.
Modelling of pressures and flow in silos
Authors: Schwedes Jörg , Feise Hermann 
Published: August 2005

AbstractThe modelling of pressures in silos has been attempted by numerous researchers using a variety of different methods. Starting with the work of Janssen, the slice element method, the method of characteristics, the finite element method and the method of granular dynamics are reviewed. Every model needs constitutive parameters which have to be found from experiments. A method to calibrate the more recent – and highly complex – constitutive models from general tests is presented. Besides the models for silo pressures, several models of flow in silos are considered.
CO hydrogenation over supported cobalt catalysts: FTIR and gravimetric studies
Authors: Fredriksen Geir R. , Blekkan Edd A. , Schanke Dag , Holmen Anders 
Published: August 2005

AbstractThe hydrogenation of CO over supported cobalt catalysts has been studied using in situ FTIR spectroscopy and gravimetry at P = 6 bar, T = 473–723 K and H2/CO = 2–3. On both silica‐ and alumina‐supported catalysts IR absorption bands corresponding to linearly adsorbed CO on metallic cobalt were observed. On alumina an additional pair of bands at lower frequencies was attributed to bridge‐bonded CO. Absorption bands corresponding to adsorbed hydrocarbons (3050–2700 cm−1) and to oxygen containing species (1800–1200 cm−1) were found to correspond to adsorbed products or unreactive species. The gravimetric studies showed a significant difference between the supports. On the silica‐supported catalyst the weight uptake decreased with increasing temperature (473–573 K). The weight increase during reaction was attributed to adsorbed hydrocarbon reaction products. On the alumina‐supported catalyst the weight uptake increased with increasing temperature, and there was also a significant weight increase with the support alone. Most of the weight uptake can be attributed to the formation of stable formate and carbonate species on the alumina support. At 723 K the deposits formed were stable in H2, and the shape of the curves indicated different mechanisms for deposition of material. In particular the Co/Al2O3 sample showed a very high and linear rate of weight gain, which was an order of magnitude higher than for the other samples.
Kinetic modelling of the oxidative coupling of methane over lanthanum oxide in connection with mechanistic studies
Authors: Lacombe Sylvie , Durjanova Zuzana , Mleczko Lezlaw , Mirodatos Claude 
Published: August 2005

AbstractA kinetic model of the oxidative coupling of methane (OCM) over lanthanum oxide is developed on the basis of mechanistic conclusions obtained elsewhere. A reaction scheme is proposed, and the kinetic parameters corresponding to the different kinetic equation are optimized. Experimental and calculated reaction rates are compared with the aim of testing the proposed scheme and validating the basic mechanistic assumptions.
Modeling of sulphur retention in atmospheric fluidized bed combustors. Sensitivity analysis and simulation
Authors: Adánez Juan , García‐Labiano Francisco 
Published: August 2005

AbstractFor the design, simulation and optimization of sulphur retention in atmospheric fluidized bed coal combustors, a mathematical model is needed that would be able to predict the behaviour of the combustor in a wide range of operating conditions. In this work, a sensitivity analysis of the sulphur retention predictions of the different hypotheses, equations and parameters, which define the different submodels and phenomena occurring in the combustor, has been carried out. It has been found that the hypotheses related to the gas flow, devolatilization type and sulphur distribution in the pyrolysis products imply an important division among models. The greatest effect on sulphur retention predictions is exercised by the parameters defining the fines elutriation and sorbent sulphation capacity. However, those corresponding to the bed hydrodynamics (minimum fluidization velocity and bed expansion) do not have a significant effect on the sulphur retention predictions.The sulphur retentions obtained in the combustion of high sulphur lignites with eight different limestones were used for model validation. A good fit of the experimental sulphur retentions was found, without using any adjustable parameter. Finally, a simulation of the process was made. The great effect of the bed height, air velocity and the particle size distribution of the limestone must be pointed out, as well as the effect of its reactivity through the maximum conversion attainable by each particle size.
Crystallization of potassium chloride: The additives ZnCl2, Na6 [(PO3)6] and K4 [Fe(CN)6]
Authors: Behrens Marcus A. H. , Lacmann Rolf , Schröder Wolfgang 
Published: August 2005

AbstractThe batch crystallization of potassium chloride from aqueous solution is investigated without impurities, with zinc chloride I (30, 100, 1000 ppm), with sodium hexametaphosphate II (100 ppm) and potassium hexacyanoferrate (II) III (100, 500, 1000, 16 × 25 ppm). The dominant particle size of the pure system LN, D = 427 μm increases by 40% by addition of I and by 250% by addition of II. While I does not affect the habit II changes it from cubes to octahedrons. In cases of low concentration, III leads to dendrites.It is shown that addition of III decelerates growth and increases the metastable zone width. Hence a high supersaturation is formed, the solution impoverishes fast while III gets incorporated and therefore a strong nucleation starts in a relatively pure solution. By quasi‐continuously adding 16 × 25 ppm of III the dominant particle size increases by 160% with little fines. In this case the content of III in the product is relatively low.
Latex characterization by atomic force microscopy
Authors: Nick Leo , Lämmel Ralf , Fuhrmann Jürgen 
Published: August 2005

AbstractWays, benefits and limitations of extracting the form and size of single latex particles or particle size distributions out of the surface topography of non‐coalesced latex films obtained by atomic force microscopy (AFM) are discussed. The general ways to generate the desired information out of topographical information in terms of height, surface curvature and lateral extensions are shown for idealized particles and measurement conditions. The different sources of information are evaluated for practical use and the analysis of particle size distributions is demonstrated by practical examples. The information content in lateral particle dimensions is shown to be the most advantageous for practical use.Determination of latex particle size distributions by AFM is shown to be an interesting alternative to the arsenal of available methods with respect to exactness of results, time consummation and instrumentation costs.
Circulating fluid‐bed reactor for coal pyrolysis
Authors: Ścia̧żko Marek , Zieliński Henryk 
Published: August 2005

AbstractA high temperature coal pyrolysis reactor was developed and its operation demonstrated on a scale of 8 t/h. Pyrolysis is performed in a circulating fluidized bed reactor at 850–950°C. The developed process was integrated into smokeless fuel production technology and tested. Experimental data and reactor performance are presented.
Fluid dynamics and mass transfer in the total capacity range of packed columns up to the flood point
Authors: Billet R. , Schultes M. 
Published: August 2005

AbstractUp to now, the only equations that were known for calculating mass transfer during two‐phase countercurrent flow in packed columns were those that apply to the range extending up to the loading point. The gas and liquid streams flow separately through the column below but not above this point. Above it, the shear stress in the gas stream supports an increasing quantity of liquid in the column, with the result that the liquid holdup greatly increases. Finally, at the flood point, the liquid accumulates to such an extent that column instability occurs. Mass transfer in this upper loading range can be described if these fluid dynamic relationships are taken into consideration. The algorithm that is presented here for its prediction is based on theoretical and experimental studies.
Mass‐ and momentum transfer in hydrogen/air and methane/air mixtures
Authors: Metz Stefan W. , Aretz Wilfried , Wilhelmi Herbert 
Published: August 2005

AbstractIn this article we present results for the viscosity and the mass transfer rates of hydrogen/air, hydrogen/oxygen, methane/air and methane/oxygen mixtures in the temperature range from 1000 to 7000 K and a pressure range from 103 to 106 Pa. In addition, the combustion ratio is varied from 0 to ∞. The transport properties are calculated from the first order solution of the Chapman Enskog approach to the Boltzmann equation, assuming chemical equilibrium composition. An extensive literature study was performed to derive experimental and/or theoretically based data for the respective binary interaction potentials. The values of the collision integrals, as derived from a complex numerical integration procedure, are correlated to an approximation formula. In addition, the exact solutions of the kinetic theory are compared to frequently used empirical mixture rules. For the mixture viscosity an easy approximation formula is deduced from the gas‐kinetic theory.
A model for the rate of hydrodesulfurization of thiophene in a continuous catalytic fixed bed reactor
Authors: Sohrabi Morteza , Zahedi Marganeh 
Published: August 2005

AbstractHydrodesulfurization of thiophene in n‐heptane, using a mixture of cobalt and molybdenum oxides as catalyst, has been studied in a fixed bed integral reactor, 200 mm long, 30 mm outer diameter and 20 mm inner diameter. It has been shown that, under experimental conditions employed in this study, neither external nor internal diffusion had been effective in the process and isothermal conditions prevailed in both gas and solid phases. A three step mechanism has been proposed for the hydrodesulfurization of thiophene. According to such a mechanism the diluent (n‐heptane) acts as an inhibitor by occupying free active sites. In further steps, thiophene is adsorbed on the catalyst surface and then undergoes reaction with hydrogen gas. Based on this scheme a rate model has been derived and verified by experimental results.
Agglomeration of alumina powders: A turbidimetric study
Authors: Masy Jean‐Claude , Cournil Michel , Lance Michel 
Published: August 2005

AbstractTurbidimetry has proved to be an efficient method for the quantitative study of powder agglomeration for particle sizes in the region of 1 μm. This work presents a new application of the technique for the agglomeration of α‐alumina in water and in n‐heptane. The method of determining the kinetic parameters of agglomeration from the initial time‐evolution of turbidity is explained.Turbulent flow in the reactor has also been characterised by laser anemometry. From the turbulence intensity, the number of collisions per unit time is calculated and the agglomeration rate can therefore be determined.Good agreement is found between the values obtained respectively from turbidimetric and hydrodynamic measurements. Addition of KOH modifies the zeta potential of alumina in water and influences the agglomeration kinetics. This can also be quantitatively characterised by turbidimetry. The experimental results obtained for alumina particles of diameter 0.3 μm and 1 μm are interpreted according to the DLVO model of interaction between particles.
Vertical motion of spherical particles
Authors: Michalski Jacek A. 
Published: August 2005

AbstractA theoretical analysis is presented for the time‐dependent vertical motion of spherical particles in a gas stream. Laminar, transitional and turbulent flows are considered, and equations are developed to predict particle velocity and distance travelled as functions of time in both stagnant and slowly‐moving gases. In both cases the equations are shown not to be universally applicable, and algorithms for estimating the limits within which they remain valid are briefly presented.
Design of conical and toriconical shells under internal pressure based on finite‐elements‐analyses
Authors: Weiß Eckart , Lietzmann Andreas , Rudolph Jürgen 
Published: August 2005

AbstractExisting design codes propose different methods for the analysis for the junction region of conical and toriconical shells (limit analysis, shake down analysis, Kellog design approach, area replacement method) submitted to internal pressure load. However, now it is possible to develop generally valid an very precise guidelines based on linear and nonlinear Finite Elements‐Analyses. A clear difference is made between design with respect to fatigue strength and design according to load carrying capacity criteria. A. Major advantage of the Finite‐Elements‐Method(FEM) is the opportunity of its adaptation to given design criteria such as a strain limit or a plastification limit. It shown how design curves can be directly derived from the FE‐analysis with respect to fatigue strength (stress concentration factors) and load carrying capacity (design factors for the calculation of a required wall thickness). The materials behavior in the plastic region is considered with an without strain hardening. Large deformation effects as geometric nonlinearities can be involved in the analysis. The method can easily be applied for the analysis of other pressure vessel components.
Kinetic of a liquid/liquid/solid fine chemicals reactions – modelling of a continuous pilot plant reactor
Authors: Chamayou Alain , Delmas Henri , Casamatta Gilbert 
Published: August 2005

AbstractIn the field of fine chemicals batch process the implementation of synthesis paths results most often in the determination of the optimal operating conditions on a bench scale apparatus; successive scale‐ups are then handled in an empirical way.For multi‐phase reactions, this approach can be limited due to the coupling between the chemical kinetics and the physical kinetics of the mass transfer. This work proposes a more rational approach for the overall synthesis of Amiodarone, a widely used anti‐arrhythmic drug produced by a liquid/liquid/solid reaction. After analysing the reaction scheme and identifying the limiting steps of the process, a simplified model is proposed to describe the overall process kinetics. The latter is used to model a continuous pilot loop‐reactor packed with static mixers.
Biotechnological H2S gas treatment with Thiobacillus ferrooxidans
Authors: Pagella Claudio , Perego Patrizia , Zilli Mario 
Published: August 2005

AbstractIn this paper a novel process for biotechnological abatement of hydrogen sulphide is presented which details the fundamentals of chemical and biological phenomena involved. The process is based on the combination of two steps to form a closed cycle which has special enviornmental advantages. The chemical step corresponds to the abatement reaction itself with absorption of the gas in a ferric solution. The biological step is related to the regeneration of the absorbing solution by means of specific bacterial strains. Particular interest is devoted to the biological kinetics of the regeneration stage, where several inhibition phenomena appear, and are also related to parameters such as temperature and pH. Results of experimental runs of gas absorption in a laboratory scale plant are also described.
Membrane reactors in chemical production processes and the application to the pervaporation‐assisted esterification
Authors: Waldburger Raoul M. , Widmer Fritz 
Published: August 2005

AbstractWhen appropriate membrane was used for the assistance of chemical and biochemical equilibrium reactions, it is possible to enhance the yield and the purity of the reaction product by selectively adding educts or selectively removing products and to a lower the energy input and the reaction time compared to conventional process.In this paper a review on membrane reactors with special emphasis on membrane‐assistance of esterification reactions and a continuous tube membrane reactor for the pervaporation‐assistance of the esterification are presented. The heterogeneously catalyzed esterification of ethanol and acetic acid to ethyl acetate and water was investigated as a typical chemical equilibrium reaction.The selective and simultaneous water separation from the reaction mixture of the esterification with polyvinyl alcohol pervaporation membranes is considered to be an interesting process alternative to the conventional distillation process. Compared to the distillation process, for the pervaporation‐assisted process a decrease of the energy input of over 75% and of the investment and operating coasts of over 50% each was calculated.