bluuebunny/crossref_metadata_2025_split huggingface dataset:
The catalyzed dehydrogenation of methanol to formaldehyde at high temperatures: New insights by modelling of transport phenomena and reaction
Authors: Sauer Jörg , Emig Gerhard 
Published: August 2005

AbstractAn experimental investigation in a tube wall reactor with catalyst‐coated inner wall is presented. Yields of formaldehyde of more than 70% can be obtained in the selective methanol dehydrogenation over alkalialuminate. Models for the reactor and the system of most important homogeneous reactions are derived. Different models describing the catalytic action are proposed. The results can only be explained by a new type of catalytic reaction, not described so far in the literature. Reducing gases like hydrogen and methanol lead to a volatilization of material from alkalialuminate which apparently catalyzes the dehydrogenation in the gas phase. Calculations and experimental evidence lead to the conclusion that this material should be sodium atoms. These are engaged in the homogeneous radical chain reaction by regulating the concentration of hydrogen atoms.
Law of substance separation on cross‐flow filtration in turbulent flow
Authors: Fuitz Andreas , Pahl Manfred H. 
Published: August 2005

AbstractCross‐flow filtration is a filtration process for separation of a disperse phase from liquids. Suspension flows tangentially to a membrane and the filtrate is drawn off perpendicular to the direction of flow. Formation of a filter cake on the membrane is thus prevented, reduced, or its composition, modified. The principle of the separation is based on tow opposing effects: on the one hand, the particles are transported by the filtration flux to the membrane where they cause and increase in concentration; on the other hand, concentration differences are again reduced by the turbulence of the cross‐flow and by Brownian motion of the particles. The two mechanisms compete with each other and depend upon particle size in different ways. An energetic comparison of the two effects yields the separation law of cross‐flow filtration as a steady state solution of the Fokker‐Planck equation. The separation law has an exponential form and assigns each particle size a separation probability with which it reaches the membrane. Once on the membrane the particles may form a filter cake, flow through the pores or return to the bulk flow. If the particles remain on the membrane the ranges of layer‐free and cake‐forming filtration can be calculated from the hydro‐dynamic and geometric conditions of the cross‐flow filter. Conventional cake filtration is regarded as limiting case. In continuous cross‐flow filtration process a low separation probability through the filtration pressure on selection of the filter medium resistance.
A study of oxygen absorption kinetics in ionic Cu(I) aqueous solutions
Authors: Benadda Belkacem , Prost Michel , Otterbein Michel 
Published: August 2005

AbstractWe developed the oxidation reaction of Cu(I) ion in aqueous hydrochloric solution by oxygen in a gas‐lift capillary bubble column. The method of gas‐liquid absorption with chemical reaction was used. Test data confirmed that the rate constant of the reaction is strongly affected by solution compositions, and that chloride ions induce an inhibition effect. The kinetical orders found are equal to 1 and 2 for oxygen and Cu(I) respectively. The influence of temperature on reaction rate constant showed the existence of a maximum value between 303 and 313K. The effect of gas‐liquid of gas‐liquid system on the liquid‐side mass transfer coefficient kL was also investigated.
Effect of sinusoidal variation of feed concentration and temperature on the performance of a packed‐bed biological reactor – a theoretical study
Authors: Beg Shafkat Ali , Hassan Mirza Manirul , Chaudhary Muhammad Arshad Seed 
Published: August 2005

AbstractThe performance of a packed‐bed biological reactor has been analysed under sinusoidal variations of substrate concentration and temperature for zero‐order, first‐order and Michaelis‐Menten kinetics. The model equations were solved by the method of orthogonal collocation. The results show that the cyclic steady‐state conversion is not affected by cyclic variations in the feed concentration. However, cyclic temperature variations with an amplitude of 20°C significantly decrease the mean exit concentration for zero‐order and Michaelis‐Menten kinetics compared to the constant‐temperature case. The approach to cyclic steady‐state conditions is estimated to be somewhat flower for zero‐order kinetics than for the other kinetics models investigated. We conclude that temperature variations during the day or changes in the performance of upstream plant will not adversely affect the performance of a packed‐bed biological reactor.
Scaling up the styrene butyl methacrylate copolymerisation reaction
Authors: Joshi M. V. , Mukesh D. 
Published: August 2005

AbstractThe scale‐up of benzoyl peroxide initiated copolymerisation of styrene and butyl methacrylate is studied here. The reaction is carried out in reactors of 3, 10 and 100 1 volume. Increasing the reactor size increase the weight average molecular weight and broadens the molecular weight distribution. Reducing the agitator diameter broadens the molecular weight distribution.
Exergy analysis of distillation processes
Authors: Le Goff Pierre , Cachot Thiery , Rivero Ricardo 
Published: August 2005

AbstractDistillation is a unit operation in which two main processes are involved: heat transfer for vaporizing and condensing and mass transfer for the separation of the mixture. A distillation unit can be described as an exergy converter: that is a unit which converts thermal exergy into chemical exergy. To obtain a complete graphical representation of mass, enthalpy and exergy balances in a fractional distillation, we propose the use of a diagram: the specific enthalpy (in KJ/ Kg of mixture) is plotted against the Carnot factor θ to show the heat and mass transfer effects simultaneously. The application of the methodology to the distillation of an ammonia‐water mixture is presented. Conventional fractional distillation consumes a lot of exergy. We propose a new type of distillation in which the reboiler and the condenser normally located at the bottom and at the top of distillation column, are replaced by two heat exchangers integrated in the column itself. The exchanger integrated in the bottom of the column inputs heat to the column, and the other exchanger located in the upper part of the column removes heat. This arrangement minimizes the creation of entropy in the column and therefore maximizes the exegetic effectiveness. This new process, called:“diabatic” or “quasi‐reversible” distillation should bring important improvement to conventional distillation, not only from the point of view of energy use (large reduction in the consumption of heat carriers fluids for heating and cooling), but also in terms of capital investment as the cost of fitting a heat exchanger in the destillation column will probably be less than the cost of reboiler or condenser and reflux head.
Reduction of investment costs by improvement of thermodynamic efficiency in cryogenic systems
Authors: Quack Hans , Philipp Jens 
Published: August 2005

AbstractCarefully directed investments to reduce the thermodynamic losses in critical subsystems often leads to a reduction of the overall investment costs. This is demonstrated by recent developments in the technology of low temperature refrigeration. By replacing the Joule‐Thomson valve by a work extracting expander and other modifications of the cycle, operating costs are reduced by 40% and investment costs by 20%.
Opportunities and limits for exergy analysis in cryogenics
Authors: Streich Martin 
Published: August 2005

AbstractExergy analysis is an excellent tool for locating weak spots in a process. Purposefully applied, it improve our insight and allow us to design processes systematically. Yet for many engineers exergy remains a difficult subjects. To make analysis easier and the results easier to interpret, therefore, we need the best possible exergy analysis tools. The commercial performance of both plant suppliers and operating companies depends heavily on optimization to reduce plant costs (in the widest sense) to a minimum. As an optimization tool in plant design, exergy analysis has to compete with parametric studied and, increasingly, with equation‐based optimization programs.
Comparison study of lewis acid type catalysts on the esterification of octanoic acid and n‐octyl alcohol
Authors: Santos Ana María Bahamonde , Martínez Mercedes , Mira José Aracil 
Published: August 2005

AbstractA Comparative study of different Lewis acids (metal chlorides of valences, I, II, III, IV) has been made. These catalysts are used in the synthesis of a high molecular weight ester in a stirred tank reactor using octanoic acid and n‐octyl alcohol as reactants. It was found that the best efficiency of the formatted ester (n‐octyl octanoate) was obtained with ferric chloride. This could be explained by the high electronegativity and the existence of free d orbitals in the Lewis acid.
Formation of emulsions in a screw loop reactor
Authors: Ludwig Alfons , Flechtner Ulrich , Prüss Jan , Warnecke Hans‐Joachim 
Published: August 2005

AbstractThe following article concerns emulsification reaction in a continuous screw loop reactor. The influence of hydrodynamics on the emulsification process as well as the influence of some specific substances were examined. We produced oil/water model emulsions under different test conditions and we determined the correlations between the mixing behavior of the reactor and the characteristic features of the obtained emulsion. Special consideration was given to the droplet size and its distribution. Variable operating conditions of the reactor are the residence time and the rotational speed of the screw, both of which have a decisive influence on the recycle factor and the number of passages through the rotor/stator system. In addition we determined the dependence of the obtained droplet size distribution on the viscosity of the continuous and dispersed phase, on the interfacial surface tension and on the phase proportions. The influence of the specific type of emulsifying agent and its concentration has been examined as well. The positive effect of the mixing and of the recirculation on the emulsification in the screw loop reactor was particularly evident with low emulsifier concentrations and with emulsifiers with slow adsorption kinetics. The established theories for emulsion formation (Kolmogoroff, Taylor) were used for a quantitative description of the experimental results. The screw loop reactor was compared to an agitated tank reactor and a toothed‐ring dispersing machine (Ultra Turrax) based on the comminution energy which is produced per unit volume of emulsion. The agitated tank reactor produced only coarsely dispersed emulsions through the entire rotational speed range, wheras the screw loop reactor and the Ultra Turrax, particularly at high rotational speeds and, therefore, high power densities, showed a similar emulsification and produced much finer dispersed emulsions.
Comparison of hydrodynamic parameters for countercurrent and cocurrent flow through packed beds
Authors: Iliuta Ion , Thyrion Fernand C. , Bolle Leon , Giot Michel 
Published: August 2005

AbstractHydrodynamic parameters have been determined in common equipment, i.e., same column and liquid and gas distributors, for cocurrent and countercurrent two‐phase flow through fixed beds. The piston/dispersion exchange model (PDE) with usual Danckwerts' boundary conditions (closed/closed system) has been used to describe the liquid flow. A new imperfect pulse method has been used to estimate the PDE model parameters directly from the experimentally nonideal input and output response. The transition between trickle flow and pulse flow, for two‐phase downflow, and the occurrence of flooding, for countercurrent flow, has been investigated using a macroscopic model for the two‐phase flow.
Modeling and simulation of dynamics of chemical reactors
Authors: Halder Raghunath , Rao D. Phaneswara , Varadarajan R. 
Published: August 2005

AbstractThe rate of the homogenous exothermic hydrolysis reaction of acetic anhydride catalyzed by sulfric acid in solvent acetic acid was estimated from nonisothermal experimental batch reactor transient temperature data. Rate equations based on three different reaction mechanisms of hydrolysis published in the literature were fitted to the experimental rate data. The experimental results on runaway and limit cycle behavior obtained with this reaction were explained by using the mechanism‐based rate equations for hydrolysis in the reactor dynamic models, and good agreement was obtained between the predicted and the experimental dynamic data.
Ion‐Exchange membrane processes for clean industrial chemistry
Authors: Audinos R. 
Published: August 2005

AbstractNew uses of artificial selective membranes, particularly ion‐exchange membranes, improve on traditional methods of treating liquid mixtures before, during or after chemical or biochemical reactions. With the correct choice of ion‐exchange membrane in a membrane reactor, reactions can be performed in such a way that the main product is not contaminated by undesired byproducts. Recent examples, mainly in organic chemistry, are given for eight typical ion‐exchange membrane reactors: electrodialysis (ED), electrometathesis (EMT), electro‐ion substitution (EIS), electro‐ion injection‐extraction (EIIE), coupled counter‐transport (CCT), electro‐electrodialysis (EED), electrohydrolysis with bipolar membranes (EHBM), and catalysis with ion‐exchange membrane (IEMC).
Hydrodynamic method for cleaning inner surfaces of pipes
Authors: Grinis Lionid , Korin Eli 
Published: August 2005

AbstractA new method for cleaning inner surfaces of pipes was studied both theoretically and experimentally. The method is based on the phenomenon of a sphere rotating in a pipe (levitation), when the translational movement of the sphere is restricted and the sphere is subjected to fluid flow in the pipe. The high rotation velocity causes a vibration process, which may be exploited for cleaning sediments or rust from the inner surfaces of pipes. A simplified theoretical model for the determination of the relationships among the dimensionless parameters governing the rotation phenomenon was developed. The model was validated with experimental data and found to be appropriate for engineering design of the system. Application of the cleaning method was demonstrated by cleaning the sediments and rust off the inner surface of a one‐inch nominal diameter pipe.
Ortho‐experiment study on formation of potassium sulfate from the system of K+, Ca2+, NH4+ ‖ Cl−, SO42− in H2O
Authors: Kai He , Wang Xiang‐Rong 
Published: August 2005

AbstractAn ortho‐experiment design and the analysis method of mathematical statistics are adopted to study the conversion of gypsum and potassium chloride to potassium sulfate in the system of K+, Ca2+, NH4+ ‖ Cl−, SO42− in H2O. Optimal reaction parameters and engineering mean are acquired to attain a conversion yield of potassium chloride of 94.52%.
Bubble growth in secondary foams
Authors: Gutwald Stefan , Mersmann Alfons 
Published: August 2005

AbstractWhen mechanical foambreakers are used in chemical engineering processes to control an undesired primary foam, a secondary foam is often produced. Secondary foams consist of small bubbles, have a high liquid hold‐up, and cannot be condensed further by mechanical foambreakers. Secondary foams can be converted into liquid and gas in a coalescence column by drainage, diffusion, and breakage of the lamellas. This paper presents a new model to determine the velocity of bubble growth and the time of coalescence of secondary foams. The experimental investigations have been carried out with surfactants in aqueous solutions.
Gas holdup and mass transfer in solid suspended bubble columns in presence of structured packings
Authors: Neme Favio , Coppola Liliana , Böhm Ursula 
Published: August 2005

AbstractElectrochemical gas absorption or biotechnical purification processes using structured packing as electrode or as biological support, respectively, may operate in bubble columns in presence of suspended solids. In both systems the knowledge of mass transfer rates from the liquid to the packing is important for the design of equipment. In the present investigation, the fluid dynamic behavior of a simple bubble column and a bubble column containing small size particles, both in presence of structured packing, was studied. Furthermore, mass transfer coefficients between the liquid and the structured packing were obtained by the electrochemical method. The influence of physical properties of the liquid phase, gas flow rate, kind and concentration of the suspended particles on both gas holdup and mass transfer was investigated. Correlations of the experimental data of mass transfer using dimensionless groups were derived and compared to previous correlations. Similarity with a heat transfer expression already used in two‐phase systems was found.
An improved approach to the design of flexible heat exchanger networks
Authors: Wang Pu , Hua Ben , Qian Yu 
Published: August 2005

AbstractErrors caused by the use of sensitivity tables may become very large in some cases because of the tables' total disregard of nonlinearities and interaction effects. We introduce a new and improved approach which calculates the effect of disturbances simultaneously by solving a set of linear equations. The approach offers simplicity, speed, insight and accuracy.
Impact of accessibility and acidity on novel molecular sieves for catalytic cracking of hydrocarbons
Authors: Roos Klaus , Liepold Armin , Koch Heico , Reschetilowski Wladimir 
Published: August 2005

AbstractThe catalytic properties of extra‐large pore aluminosilicate MCM‐41, silicon containing VPI‐5 and aluminium containing ETS‐10 were investigated by MAT (Micro Activity Test) using n‐hexadecane and 1,3,5‐triisopropylbenzene as the model feeds and were then compared with the results obtained from Y zeolite in the H‐form and a commercial FCC (Fluid Catalytic Cracking) catalyst. It could be demonstrated that not only the acidic properties of the investigated materials, but also the accessibility to the internal active sites of the investigated materials have a significant influence on activity and selectivity. It can be assumed that, by optimising structural and chemical properties, the mesoporously organised MCM‐41 and related materials are suitable as active components in cracking catalysts for “deeper” cracking of high boiling hydrocarbons.
Extraction of Fe(III) from phosphoric acid by HDDNSA
Authors: El‐Khaiary Mohammad I. 
Published: August 2005

AbstractA study was conducted on the stoichiometry of the reaction that takes place on the extraction of ferric ions by didodecyl naphthalene sulphonic acid (HDDNSA) from phosphoric acid solutions. The experimental results were numerically analyzed by nonlinear regression. It was found that ferric forms two compounds with HDDNSA, namely Fe(DDNSA)3, and FeHPO4‐DDNSA. The values of the equilibrium constants of the reactions involved were also calculated.
Removal of sulfur compounds from naphtha solutions using solid adsorbents
Authors: Salem Abu Bakr S. H. , Hamid Halim S. 
Published: August 2005

AbstractTwo types of solid adsorbents, activated carbon and zeolite 13X, were used at 80°C to remove sulfur compounds from naphtha solutions. Adsorption isotherms have been determined in a pressure vessel. This investigation indicated that activated carbon is superior to zeolite 13X at such high temperatures. A new formula based on the Langmuir model has been found to fit the experimental data satisfactorily. Comparison of the findings of this study with those of a previous one conducted at ambient temperatures in this department indicates that such treatment generally gives better results at low temperature where almost complete recovery of the sulfur compounds can be performed by using zeolite 13X.
Continuous citric acid fermentation in a supported biomass reactor
Authors: Sommariva Corrado , Zilli Mario , Converti Attilio , Del Borghi Marco 
Published: August 2005

AbstractA semi‐submerged biodisk apparatus provided with inert matrix for cell entrapment, previously employed with success for alcohol fermentation, is proposed in this study to overwhelm the well‐known problems related to the continuous citric acid production. This immobilized‐mycelium system shows at the same time a remarkable increase in citric acid volumetric productivity, with respect to a Continuous Stirred Tank Reactor, but the same progressive activity loss evidenced in the past with comparable immobilized‐cell reactors.
Kinetics of xanthan gum production from whey by constructed strains of Xanthomonas campestris in batch fermentations
Authors: Liakopoulou‐Kyriakides Maria , Tzanakakis Emanuel S. , Kiparissidis Costas , Ekaterianiadou Lukia V. , Kyriakidis Dimitrios A. 
Published: August 2005

AbstractTwo new constructed strains of X. campestris XLM1521 and XMT1, either alone or in mixed cultures were used for the production of xanthan gum in batch fermentations from whey. Fermentations were carried out at three different pH levels of 6.0, 7.0 and 8.0 and the results were compared with those previously reported for fermentations in Erlenmeyer flasks without controlling the pH. The kinetics of cultures of the strain X. campestris XLM1521 were studied in a batch reactor at constant pH values. A mathematical model, based on the Luedeking‐Piret equation, was used and experimental design was employed in order to correlate model's parameters with pH variation. The highest xanthan gum concentration, 17.3 g/l, was observed at pH 8.0. This is the largest amount of xanthan gum reported so far.
Continuous preparation of porous organofunctionalized (Hetero‐)polysiloxane spheres
Authors: Witossek Herbert , Bratz Ernst 
Published: August 2005

AbstractWhen in contact with water, organoalkoxysilanes and other alkoxy metal compounds react to organofunctionalized polysiloxanes or heteropolysiloxanes. A new method for the continuous preparation of porous organopolysiloxane spheres was developed. Droplets of the precursor mixture are injected into the vertical reactor column. Movement of the gelating droplets is controlled by flow of the aqueous reaction medium. Advantages are adjustable residence time, minimized coalescence and low reactor height. An example shows typical product characteristics like narrow particle size distribution and macroporosity.
Low‐Temperature Polyol Synthesis of AuCuSn2 and AuNiSn2: Using Solution Chemistry to Access Ternary Intermetallic Compounds as Nanocrystals.
Authors: Leonard Brian M. , Bhuvanesh Nattamai S. P. , Schaak Raymond E. 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Reaction of Magnesium Alkylidene Carbenoids with Lithium Acetylides and Lithium Thiolates: A Novel Synthesis of Conjugated Enynes and Vinyl Sulfides.
Authors: Watanabe Masanori , Nakamura Masatomo , Satoh Tsuyoshi 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
A Novel Synthesis of Bicyclo[3.3.0]oct‐1‐en‐3‐ones from Cyclobutanones Through [Chloro(p‐tolylsulfinyl)methylidene]cyclobutanes with Ring Expansion.
Authors: Kawashima Tadashi , Kashima Hiroaki , Wakasugi Daisuke , Satoh Tsuyoshi 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Synthesis of 4‐Substituted Homoallylic Alcohols via a One‐Pot Tandem Lewis‐Acid Catalyzed Crotylboration‐[3,3]‐sigmatropic Rearrangement.
Authors: Ramachandran P. Veeraraghavan , Pratihar Debarshi , Biswas Debanjan 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.