bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of gas hold‐up in three‐phase systems by ultrasonic technique
Authors: Maezawa Akinori , Muramatsu Shingo , Uchida Shigeo , Okamura Seichi
Published: August 2005

It was established by using double impulse method that the transmission time of an ultrasonic wave, which passes near a bubble, is either shorter or longer than that in the liquid system. This is attributed to the fluid vortex originated by the bubble rising ahead of the wave. The longitudinal distribution of gas hold‐up in a three‐phase system, measured by analyzing wave shape and reduction of transmission time is in good agreement with that obtained by using the static pressure method. This indicates the possibility of application of ultrasonic techniques to the simultaneous measurement of phase hold‐ups in the three‐phase system.
Dynamics of the gas phase in bubble columns
Authors: Modak Shrikant Yadneshwar , Juvekar Vinay Anant , Rane Vishwanath Chango
Published: August 2005

The conventional two‐bubble‐class model for bubble column reactors has been modified to account for interactions between the two bubble classes. It is shown that the modified model is more consistent with the observed residence time distribution in the gas phase than the conventional model. The results indicate that there is an intensive cross‐mixing between the bubble phases. This study also reveals that the modified two‐bubble‐class model cannot be distinguished from the single‐bubble‐class model solely on the basis of the residence time distribution.
Flow regimes in circulating fluidized beds
Authors: Bai Dingrong , Jin Yong , Yu Zhiqing
Published: August 2005

Based on a comprehensive hydrodynamic analysis, a practical definition of the circulating fluidized bed (CFB) regime has been proposed. It was established that two flow regimes are involved in a CFB: fast fluidization and dense phase conveying. By demonstrating the variation of pressure gradient in both the lower and the upper section of the bed versus superficial gas velocity, the criteria for the determination of transition velocities have been obtained. Literature data which over wider operating conditions, particle properties and bed diameters from the basis of the obtained generalized correlations of transition velocities. A quantitative flow diagram is presented.
Wall factor for acceleration and terminal velocity of falling spheres at high reynolds numbers
Authors: Bougas Athanasios , Stamatoudis Michael
Published: August 2005

The wall factor for spheres in the acceleration and terminal velocity ranges was determined experimentally for very high Reynolds numbers (13 500 < Re < 70 000). Experiments were performed with 12, 15, 18, 21, 25 and 31.75 mm spheres, falling in water inside cylinders 3.4, 4.9, 7, 10, 14 and 19 cm in diameter. A published empirical equation was found to yield good results for the terminal velocity wall factor in the range of studied Reynolds numbers.
Homogenization of liquids in tanks stirred by multiple impellers
Authors: Jahoda Milan , Machoň Václav
Published: August 2005

The process of homogenization of liquids in a tall vessel equipped with a multiple impeller was studied. Up to four standard Rushton turbines and/or six pitched‐blade turbines were used. The mixing time in the system was measured by the conductivity method. A continuous time history of the tracer concentration at several points in the system was recorded. The data were interpreted by means of an adapted cell model of the flow within the stirred vessel with several impellers based on the assumption of well mixed cells and intercellular flow of liquid. The liquid transfer flow rate between the cells, as a parameter of the model, was calculated from experimental data. A good agreement between the time dependence of concentration obtained experimentally and that calculated from theory was obtained. A direct relationship between the flow numbers between cells and those of impellers was established.
Influence of viscosity on product distribution of fast competitive chemical reactions
Authors: Gholap Raghuraj V. , Petrozzi Sergio , Bourne John R.
Published: August 2005

The objective of this study was to determine the influence of viscosity on micromixing in turbulent flow. It was first necessary to find a suitable viscosity‐raising additive. HEC (hydroxyethyl cellulose) proved to be better than previously studied additives [sorbitol and carboxymethylcellulose (CMC)]. In concentrations up to 1 wt‐%, HEC solutions are almost Newtonian with viscosities independent of pH over the range 2 to 10. HEC had no effect on the reaction rate constants and the spectrophotometric analysis of the fast, competing reactions used – the diazo coupling between 1‐naphthol and diazotized sulphanilic acid. The viscosity can then be raised by around an order of magnitude by adding less than 1 wt‐% HEC to this reaction system.

Diazo couplings were conducted in a 20 1 semi‐batch tank reactor stirred by a Rushton turbine at two viscosity levels (0.9 and 6.2 mPa s). Long feed times ensured that micromixing was controlling. More bisazo dye was formed in the more viscous solution, all other conditions being unchanged, indicating more intense segregation and slower micromixing.

This was also shown by visualizing the extent of neutralisation zones, with more spreading and slower micromixing being observed in viscous solution. Higher turbine speeds reduced this spreading. One feed point near and one far from the turbine were employed: the strong inhomogeneity of the turbulence led to smaller amounts of bisazo dye when the feed was added to the turbine suction, irrespective of the viscosity. All results agreed with the trends predicted by the engulfment model of micromixing. Its simplest form assigns an average energy dissipation rate to the reaction zone: the values obtained are of similar magnitude to those measured by physical techniques and were related to the spreading of the reaction zone.
Heterogeneous catalytic methylation of catechol
Authors: Porchet Stéphane , Su Shoujin , Doepper Ralf , Renken Albert
Published: August 2005

It has been shown that, after a partial deactivation, γ‐alumina (γ‐Al2O3) is a good catalyst for selective methylation of 1,2‐benzenediol in the temperature range of 260–310°C. The main products are the desired 3‐methyl‐1,2‐benzenediol and 2‐methoxyphenol, which may be converted in another step into 3‐methyl‐1,2‐benzenediol, giving an overall selectivity for the desired products of 80 to 90%. The catechol forms a strongly chemisorbed surface species on γ‐alumina and its steric adsorption model correlates with the kinetic data.
A mathematical model describing the ARI “autocirculation reactor” for low temperature conversion of H2S into sulphur
Authors: Abedinzadegan M. , Nasr M. R. Jaffari
Published: August 2005

A prototype “autocirculation”‐type reactor has been designed and constructed at the N.I.O.C. Research Institute, Tehran and a mathematical model describing the concentration versus time profile subsequently developed. The model encompasses mass transfer considerations and kinetic studies of the regeneration reaction. For this purpose, the rate equation for iron complex oxidation, proposed by Japanese researchers, was modified and a new rate equation presented. This rate equation has been widely used in the above mentioned mathematical model. With this model, the vessel volume for a time‐dependent H2S feed has been calculated for a “ZDDP” production unit.
Conversion of ethanol over zeolite H‐ZSM‐5
Authors: Schulz Jürgen , Bandermann Friedhelm
Published: August 2005

The conversion of ethanol over H‐ZSM‐5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and Si/Al ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H‐ZSM‐5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.
Kinetic modelling of zinc liberation from zinc sulphide‐containing sludges in the viscose industry
Authors: Hofmann Hanns , Glöckl Steffen
Published: August 2005

Large quantities of sludge containing considerable amounts of zinc are obtained on treatment of waste water from the production of viscose fibres for textiles and industrial applications. A process has been proposed [7, 10] for the recovery of zinc from one such sludge, in the first step of which zinc is transferred to the liquid phase with liberation of hydrogen sulphide. In connection with this work a model was developed which provides a kinetic description of zinc liberation from various sludges and the parameters of this model fitted to the measured data by means of linear regression.
Mass transfer effects on kinetics of nonideal liquid phase ethyl tert‐butyl ether formation
Authors: Sundmacher Kai , Zhang Rui‐Sheng , Hoffmann Ulrich
Published: August 2005

Ethyl tert‐butyl ether (ETBE) is an alternative fuel oxygenate that can be produced in the liquid phase by addition of ethanol to isobutene catalyzed by sulfonic acid ion exchange resins. A generalized Langmuir‐Hinshelwood rate expression is formulated in terms of the liquid phase activities of the reactants that is quasi‐autocatalytic due to ethanol. This microkinetic model is combined with the generalized Maxwell‐Stefan equations for a detailed investigation of the influence of multicomponent mass transfer limitations inside the macropores of the heterogeneous catalyst. The model is used for revision of experimental rate data for ETBE synthesis in the literature. The analysis reveals that reverse diffusion of isobutene can occur by strong interaction with ethanol and the catalyst effectiveness factor can exceed unity.
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

An 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

Cross‐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

We 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

The 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

The 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

Distillation 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

Carefully 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

Exergy 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

A 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

The 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

Hydrodynamic 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

The 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

New 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

A 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

An 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

When 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

Electrochemical 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

Errors 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

The 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

A 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

Two 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

A 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

Two 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

When 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.
Coordination of Li+, Ca+, V+, and Cu+ to the Molecules S8 and S4 — A Computational Study
Authors: Steudel Yana , Wong Ming Wah , Steudel Ralf
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis, Crystal Structure Determination from X‐Ray Powder Diffractometry and Vibrational Spectroscopic Properties of Mg[N(CN)2]2×4H2O.
Authors: Irran Elisabeth , Juergens Barbara , Schmid Sabine , Schnick Wolfgang
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Crystallographic Properties of ErFe6Sn6‐xGax Compounds (0 < x < 6).
Authors: Ihou‐Mouko H. , Venturini G.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Ag3.5Bi7.5S13, a New Member (N = 8) of the Homologous Series [Bi2S3]2× [AgBiS2](N—1)/2.
Authors: Poudeu Poudeu Pierre F. , Ruck Michael
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
The Twofold Superstructure of Titanium(III) Oxybromide at T = 17.5 K.
Authors: Palatinus Lukas , Schoenleber Andreas , van Smaalen Sander
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Barium Chlorite Hydrate, Ba(ClO2)2×3.5H2O.
Authors: Smolentsev Anton I. , Naumov Dmitry Yu.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Crystal Structures of the Ln3.33CuPb1.5Se7 (Ln: Tb, Dy, Ho, Er, Tm, Yb and Lu) Compounds.
Authors: Gulay L. D. , Olekseyuk I. D.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Thermochemistry of Binary Liquid Gd—Ti and Tb—Ti Alloys.
Authors: Tedenac J.‐C. , Ivanov M. I. , Bulanova M. V. , Berezutski V. V.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Isothermal Section of the Dy—Fe—Sn Phase Diagram at 800 °C.
Authors: Pereira L. C. J. , Rojas D. P. , Waerenborgh J. C.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
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

For Abstract see ChemInform Abstract in Full Text.
Facile Desulfurization of Thioamides and Thioureas with Tetrabutylammonium Periodate under Mild Conditions.
Authors: Pourali Ali Reza
Published: August 2005

For 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

For Abstract see ChemInform Abstract in Full Text.
Reactions of Heteroaryl Substituted Propenones.
Authors: Greiner‐Bechert Lutz , Sprang Thomas , Otto Hans‐Hartwig
Published: August 2005

For 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

For Abstract see ChemInform Abstract in Full Text.
An Expedient One‐Pot Entry Catecholestrogens and Other Catechol Compounds via IBX‐Mediated Phenolic Oxygenation.
Authors: Pezzella Alessandro , Lista Liliana , Napolitano Alessandra , d'Ischia Marco
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
A Facile Stereoselective Synthesis of (E)‐2,3‐Disubstituted Allylic Alcohols via Hydromagnesiation of Alkylarylacetylenes.
Authors: Cai Mingzhong , Xia Jun
Published: August 2005

For 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

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Catalytic Friedel—Crafts Acylation of Aromatic Ethers Using SmI3.
Authors: Chen Xiaohang , Yu Mingxin , Wang Meijun
Published: August 2005

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Carbonic Anhydrase Inhibitors: Synthesis and Inhibition of Cytosolic/Tumor‐Associated Carbonic Anhydrase Isozymes I, II, IX, and XII with N‐Hydroxysulfamides — A New Zinc‐Binding Function in the Design of Inhibitors.
Authors: Winum Jean‐Yves , Innocenti Alessio , Nasr Jihane , Montero Jean‐Louis , Scozzafava Andrea , Vullo Daniela , Supuran Claudiu T.
Published: August 2005

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Homogeneous and Heterogenized Au(III) Schiff Base‐Complexes as Selective and General Catalysts for Self‐Coupling of Aryl Boronic Acids.
Authors: Gonzalez‐Arellano C. , Corma A. , Iglesias M. , Sanchez F.
Published: August 2005

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Rearrangement of Bromo‐acenaphtheno‐norbornanes on Silver Bromide. Pure exo‐Acenaphtheno‐norbornene Synthesis.
Authors: Leu Rodica , Chiraleu Filip , Draghici Constantin , Enescu Lucian
Published: August 2005

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One‐Pot Synthesis of Tetrahydro‐2‐methylidenefurans.
Authors: Okabe Fumi , Tagawa Yoshinobu , Yamagata Kenji
Published: August 2005

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Palladium‐Catalyzed Cyclization Reactions of Propargylic Carbonates with Nucleophiles: A Methodology for the Syntheses of Substitued 2,3‐Dihydrofurans and Benzofurans.
Authors: Yoshida Masahiro , Morishita Yukio , Fujita Mika , Ihara Masataka
Published: August 2005

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Fe3+‐Montmorillonite as Effective, Recyclable Catalyst for Paal—Knorr Pyrrole Synthesis under Mild Conditions.
Authors: Song Guoyong , Wang Bo , Wang Guang , Kang Yuru , Yang Tao , Yang Liming
Published: August 2005

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Reactions of Substituted 2,3,7‐Triazabicyclo[3.3.0]oct‐2‐enes and 1,2,7‐Triazaspiro[4.4]non‐1‐enes with Halogens.
Authors: Molchanov A. P. , Stepakov A. V. , Kostikov R. R.
Published: August 2005

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Synthesis of New Aromatic Isatin Derivatives.
Authors: Mesropyan E. G. , Ambartsumyan G. B. , Avetisyan A. A. , Sargsyan M. G. , Galstyan A. S.
Published: August 2005

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Synthesis of Benzoylmethylpyrazolidine Regioisomers on the Surface of Basic Adsorbents: A Competitive Attack of Crotonaldehyde at the Two Nitrogen Atoms of 1,2‐Acetylphenylhydrazine.
Authors: Sviridova Lyudmila A. , Golubeva Galina A. , Tavtorkin Aleksandr N.
Published: August 2005

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4‐Functionally Substituted 3‐Heterylpyrazoles. Part 14. N‐Benzyl‐N‐[3‐aryl(heteryl)‐4‐pyrazolylmethylene]amines and Their Derivatives.
Authors: Bratenko M. K. , Panimarchuk O. I. , Chornous V. A. , Vovk M. V.
Published: August 2005

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A New Method for the Preparation of 1,2‐Benzisoxazole‐3‐carboxaldehyde.
Authors: Kalkote Uttam R. , Panchgalle Sharad P. , Mahakal Kumodini K. , Choudhary Suman M. , Chavan Subhash P.
Published: August 2005

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The Development of New Isoxazolone Based Inhibitors of Tumor Necrosis Factor‐Alpha (TNF‐α) Production.
Authors: Clark Michael P. , et al. et al.
Published: August 2005

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Synthesis and Biological Screening of New 2‐Azetidinones and 4‐Thiazolidinones.
Authors: Patel K. D. , Mistry B. D. , Desai K. R.
Published: August 2005

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Tetramethylguanidine‐[bmim][BF4]. An Efficient and Recyclable Catalytic System for One‐Pot Synthesis of 4H‐Pyrans.
Authors: Peng Yanqing , Song Gonghua , Huang Feifei
Published: August 2005

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Behavior of o‐Hydroxyacetophenones Towards Action of POCl3/DMF (Vilsmeier Reagent) in the Presence of BF3×Et2O: A Novel Observation in the Synthesis of Chromones.
Authors: Prakash Om , Kumar Ravi , Sharma Deepak , Bhardwaj Vikas
Published: August 2005

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α‐Cleavage During the Oxidation of Benzazolyl‐4‐coumarinomethyl Sulfides.
Authors: Adavi H. H. , Kusanur R. A. , Kulkarni M. V.
Published: August 2005

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Cyclopropanation of 3‐(2‐Oxo‐2H‐chromen‐3‐yl‐carbonyl)‐2H‐chromen‐2‐one with Zinc Enolates Derived from 1‐Aryl‐2,2‐dibromoalkanones.
Authors: Shchepin V. V. , Russkikh N. Yu. , Uzun D. V. , Silaichev P. S.
Published: August 2005

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Ring Opening Reactions of 1,2‐Didehydroprolines. Part 2. Synthesis of 5‐Amino‐2,4‐dihydroxypentanoic Acids, Their 2‐Piperidones and Pentanolides.
Authors: Haeusler Johannes , Kaehlig Hanspeter
Published: August 2005

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Copper(I) Complexes of Fesulphos Ligands: Highly Efficient Chiral Lewis Acids for the Formal Aza Diels—Alder Reaction of N‐Sulfonyl Imines
Authors: Garcia Mancheno Olga , Gomez Arrayas Ramon , Carretero Juan C.
Published: August 2005

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Synthesis of N‐(4‐Methyl‐1,2,3,4‐tetrahydro‐2 quinolinyl)‐N‐aryl Amines
Authors: Piri Farideh , Zalfard Hojat Allah , Gahramani Agdas , Yavari Issa
Published: August 2005

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Synthesis, Structure, and Fluorescence of Isomeric Indolizinediones. Carbonyl‐Bridged Isodipyrrinones.
Authors: Boiadjiev Stefan E. , Lightner David A.
Published: August 2005

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Design and Synthesis of Potent Pyridazine Inhibitors of p38 MAP Kinase.
Authors: Tamayo Nuria , et al. et al.
Published: August 2005

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A New Approach to the Synthesis of Biginelli Compounds.
Authors: Shutalev Anatoly D. , Kurochkin Nikolay N.
Published: August 2005

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Simple Synthesis of 4‐Aryl‐6‐styryl‐1,2,3,4‐tetrahydropyrimidin‐2‐ones by the Alkaline Hydrolysis of Biginelli Compounds.
Authors: Shutalev Anatoly D. , Aksionov Alexey N.
Published: August 2005

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4‐Functionally Substituted 3‐Heterylpyrazoles. Part 13. 3‐Aryl(heteryl)‐4‐(4‐pyrazolyl)‐1,2,3,4‐tetrahydropyrimidin‐2‐ones (thiones).
Authors: Bratenko M. K. , Chornous V. A. , Vovk M. V.
Published: August 2005

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Microwave‐Assisted Synthesis and Antibacterial Activity of Some 2‐Amino‐6‐aryl‐4‐(2‐thienyl)pyrimidines.
Authors: Chandrasekaran S. , Nagarajan S.
Published: August 2005

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Synthesis and Rearrangement of Cycloalkyl[1,2‐e]oxazolo[3,2‐a]pyrimidin‐8/9‐ones: An Access to Cycloalkyl[1,2‐d]oxazolo[3,2‐a]pyrimidin‐5‐ones.
Authors: Adetchessi Ouru‐Sama , Leger Jean‐Michel , Guillon Jean , Forfar‐Bares Isabelle , Bosc Jean‐Jacques , Jarry Christian
Published: August 2005

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Novel 4‐Amino‐furo[2,3‐d]pyrimidines as Tie‐2 and VEGFR2 Dual Inhibitors.
Authors: Miyazaki Yasushi , et al. et al.
Published: August 2005

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Novel 2‐Amino‐4‐oxo‐5‐arylthio‐substituted‐pyrrolo[2,3‐d]pyrimidines as Nonclassical Antifolate Inhibitors of Thymidylate Synthase.
Authors: Gangjee Aleem , Jain Hiteshkumar D. , Kisliuk Roy L.
Published: August 2005

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New Pyrazolo[1′,5′:1,6]pyrimido[4,5‐d]pyridazin‐4(3H)‐ones as Potent and Selective PDE5 Inhibitors.
Authors: Feixas Joan , Giovannoni Maria Paola , Vergelli Claudia , Gavalda Amadeu , Cesari Nicoletta , Graziano Alessia , Piaz Vittorio Dal
Published: August 2005

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Synthesis of Partially Hydrogenated 1,2,4‐Triazoloquinazolines by Condensation of 3,5‐Diamino‐1,2,4‐triazole with Aromatic Aldehydes and Dimedone.
Authors: Lipson V. V. , Desenko S. M. , Borodina V. V. , Shirobokova M. G. , Musatov V. I.
Published: August 2005

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Efficient Synthesis of Novel Pentacyclic 6,7‐Dihydro‐5a,7a,13,14‐tetraaza‐pentaphene‐5,8‐diones.
Authors: Pereira Maria de Fatima , Picot Laurent , Guillon Jean , Leger Jean‐Michel , Jarry Christian , Thiery Valerie , Besson Thierry
Published: August 2005

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First Selective Lithiation of Pyridylpiperazines: Straightforward Access to Potent Pharmacophores.
Authors: Louerat Frederic , Gros Philippe , Fort Yves
Published: August 2005

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Double Nucleophilic Addition of Bis(trimethylsilyl)ketene Acetals to Carbon—Carbon Double Bonds of Pyrazines: Formation of Polycyclic γ‐Lactones.
Authors: Rudler Henri , Denise Bernard , Xu Yiming , Vaissermann Jacqueline
Published: August 2005

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Synthesis and Transformations of 5‐Substituted 2‐Aryl‐7H‐[1,2,4]triazolo[3,2‐b][1,3]thiazin‐7‐ones and 2‐Aryl‐2,3‐dihydro‐4H‐[1,3]thiazino[3,2‐a]benzimidazol‐4‐ones.
Authors: Britsun V. N. , Esipenko A. N. , Chernega A. N. , Lozinskii M. O.
Published: August 2005

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Synthesis, Molecular Structure, and in vitro Antitumor Activity of New 4‐Chloro‐2‐mercaptobenzenesulfonamide Derivatives.
Authors: Slawinski Jaroslaw , Gdaniec Maria
Published: August 2005

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Synthesis and Antitumor Activity of N,N′‐Bis(substitutedphenyl) ‐3,6‐dialkyl‐1,4‐dihydro‐s‐tetrazine‐1,4‐dicarboxamide.
Authors: Hu Weixiao , Shi Haibo , Yuan Qing , Sun Yaquan
Published: August 2005

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Stereoselective Synthesis of Tri‐ and Tetrasubstituted Oxepanes via n‐Bu3SnH Mediated 7‐endo‐trig Vinyl Radical Cyclization.
Authors: Shanmugam Ponnusamy , Rajasingh Paramasivan
Published: August 2005

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Synthesis and Conformations of Novel Diamide‐Bridged Homooxacalix[3]arenes.
Authors: Liu Shilan , Gong Shuling , Zheng Qin , Chen Yuanyin , Wu Xiaojun
Published: August 2005

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Nucleophilic Aromatic Substitution Reactions of Fluorobenzenechromium Complexes with P‐Chiral Secondary Phosphine—Boranes: Synthesis of Optically Pure P‐Chiral (Dialkyl)arylphosphine—Boranes.
Authors: Katagiri Kosuke , Danjo Hiroshi , Yamaguchi Kentaro , Imamoto Tsuneo
Published: August 2005

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Reaction of Active Methylene Groups with 1,2‐Di(bromoseleno)benzene Toward Benzo‐1,3(2H)‐diselenoles.
Authors: Potaczek Piotr , Kloc Krystian , Mlochowski Jacek
Published: August 2005

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Stereoselective Synthesis of (3E)‐2‐Stannyl‐1,3‐dienes via Palladium Catalyzed Cross‐Coupling Reactions.
Authors: Cai Mingzhong , Li Haigen , Hao Wenyan
Published: August 2005

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Synthesis of New Ferrocenyl‐Substituted Aziridines via the Gabriel—Cromwell Reaction.
Authors: Dogan Oezdemir , Zeytinci Serhat , Bulut Adnan
Published: August 2005

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Improved Synthesis of Thiofluorescein.
Authors: Russkikh V. V. , Konstantinova A. V. , Berezhnaya V. N. , Gerasimova T. N. , Shelkovnikov V. V.
Published: August 2005

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PtCl2‐Mediated Cycloisomerization of Unsaturated Propargylic Carboxylates.
Authors: Anjum Shazia , Marco‐Contelles Jose
Published: August 2005

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