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Volume 16, Issue 1, 2009
Transactions on Chemistry and Chemical Engineering


Lewis Acid Catalyzed Synthesis of Quinophthalone Pigments Under Solvent-Free Conditions
 
        J. Safari (PhD.)
  • S. Dehghan Khalili [PhD.]
  • S. H. Banitabai koupaie [PhD.]

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Abstract:
A simple and very efficient synthesis of quinophthalones has been achieved with using of phthalic anhydride and 2-methylquinoline derivatives as starting materials and BF3/Et2O as catalyst under solvent-free and reflux conditions. Keywords. Quinophthalone, Quinoline yellow, Pigments, Solvent-free conditions, Lewis acid


Study of non-catalyzed molecular reaction of reducing sugars
 
        T. Mahmood (PhD.)
  • Q. Haque [PhD.]
  • I. Mahmood [PhD.]
  • S. AsgharAli [PhD.]
  • Z.T. Maqsood [PhD.]

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Abstract The study of non-catalyzed molecular reaction of reducing sugars by spectrophotometry technique at different concentration of sugars, iodine and temperature has investigated first time. The absence of salt effect indicates that the reaction does not take place between ionic substances, and that at least one of the reactants must be non-ionic. This adds further confirmation to the hypothesis that the reaction takes place directly between the sugars and hypoiodous acid. The results indicate that the reaction is first order kinetics with respect to sugars and hypoiodous acid but it is zero order kinetic with respect to iodine concentration. The low value of energy of activation confirmed the presence of neutral molecules in rate determining step, and the negative value of entropy shows that the process is not spontaneous but the reverse process is spontaneous at all temperatures. Thermodynamic parameters have evaluated by studying kinetics at various temperatures. Suitable mechanism has proposed in consistency with the kinetic results. Key words: non-catalyzed, molecular reaction, reducing sugar, spectrophotometry technique, hypoiodous acid, kinetics.


Reaction between dimethyl acetylenedicarboxylate and phenols in the presence of dipotassium hydrogen phosphate in solvent-free conditions: an efficient environment-friendly method for the synthesis of aryl vinyl ethers
 
        A. Ramazani (PhD.)
  • A. Safari [PhD.]
  • N. Noshiranzadeh [PhD.]

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Abstract-A two-component condensation reaction between an electron-poor acetylenic ester and a phenol efficiently provides substituted aryl vinyl ethers in a one-pot reaction in the presence of dipotassium hydrogen phosphate in solvent-free conditions.

Keywords:
Dipotassium hydrogen phosphate

    Aryl vinyl ether
      Acetylenic ester
        Phenol
          Solvent-free conditions.


Microwave-assisted synthesis of 3-substituted coumarins using ZrOCl2.8H2O as an effective catalyst
 
        F. Matloubi Moghaddam (PhD.)
  • Z. Mirjafary [PhD.]
  • H. Saeidian [PhD.]

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Abstract An efficient route for the synthesis of 3-substituted coumarins via Knoevenagel condensation using ZrOCl2.8H2O (10 mol %) as the catalyst under microwave heating and solvent-free conditions is described. This procedure offers several advantages including low loading of catalyst, high yields, clean reaction, short reaction time and use of various substrates, which make it a useful and attractive strategy for the synthesis of 3-substituted coumarins.

Keywords:
3-Substituted coumarins

    ZrOCl2.8H2O
      Microwave heating


A Simple Access to the Synthesis of 5,6- Dihydro-4H-1,3-oxazines Under Solvent Free Condition and Microwave Irradiation
 
        M. Mamaghani (PhD.)
  • M.R. Taati [PhD.]
  • N.O. Mahmoodi [PhD.]
  • A. Loghmanifar [PhD.]

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2-Arylsubstituted 5,6-dihydro-4H-1,3-oxazines were conveniently synthesized by the condensation of 3-aminopropanol and desired carboxylic acids under solvent free and microwave conditions in short reaction times with moderate to good yields. A comparison of this method with the classical protocols using acid halides and nitrile substrates was also made.


Optimization of withering time and fermentation conditions during black tea manufacture using response surface methodology
 
        F. Vahabzadeh (PhD.)
  • L. Emdadi [PhD.]
  • B. Nasernajad [PhD.]
  • S.T. Shokrgozar [PhD.]
  • M. Mehranian [PhD.]

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ABSTRACT The central composite design (CCD) technique, a response surface methodology (RSM), was used to study the effect of the withering time and the fermentation conditions of the tea leaves on the black tea quality parameters. A three level, three variable design was adopted. The three independent variables investigated in this experiment, each at three levels, were withering time, the fermentation duration and the fermentation temperature. Responses were represented mathematically by second-order quadratic equation and assessed using polynomial multiple regression model. The highest levels of the theaflavins (TFs) formation (1.25%) was with the withering time at about 19-20 hrs while the fermentation duration was at about 25-30 min (fermentation temperature= 25C). The gradual increase in the thearubigins (TRs) as the function of the withering time and the fermentation temperature was noticeable. The increase in TR content at 11.5% was minor and related to the narrower ranges of the two parameters studied (x1 and x3). The predicted dependence of the TLC evaluation (%) (spectrophotometric measurement) on the fermentation duration (x2) and on the fermentation temperature (x3) was statistically significant. The results of this study suggest that the CCD and RSM can be efficiently used in the fermentation process in black tea manufacture.

Keywords:
Black tea fermentation, Theaflavins, Thearubins, Total liquor color, Response surface methodology, Experimental design.


Effect of Cell Concentration on Acylation of Penicillin G Enzymatic Reaction in Immobilized Cells
 
        F. Khorasheh (Professor)
  • M. BARIN [PhD.]
  • M. OTADI [PhD.]
  • A. Kheirolomoom [PhD.]

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ABSTRACT E.coli was immobilized by entrapment within calcium alginate beads using cell suspensions of different concentrations. The immobilization procedure resulted in beads with a homogeneous cell distribution referred to as Non-overlapping Cell (NC) configuration. If cells within the beads are allowed to grow, the NC configuration would transform into a Clustered Cell (CC) configuration as a result of cell growth. Enzyme activity and substrate conversion were obtained for NC and CC configurations of different cell density using penicillin G acylation by penicillin G acylase to produce 6-amino penicillanic acid. Enzyme activity and conversion were found to depend on both cell concentration and configuration. Beads with NC configuration resulted in higher enzyme activity and conversion compared with CC configurations of similar cell density.


Simulation of Continuous Thermal Sterilization Process in the Presence of Solid Particles
 
        A. Shahsavand (PhD.)
  • Y. Nozari [PhD.]

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Abstract Simulation of Continuous Thermal Sterilization (CTS) process is investigated for both laminar and turbulent flow regimes. Various heuristics are considered for reliable estimation of sterility (F-value) and quality (C-value) parameters. It is proved for laminar condition that using a mixer at the entrance of holding zone can drastically increase the sterility of food product while reducing its quality degradation. For turbulent flow regime, the effect of trajectories and thermal resistances of solid particles are investigated on the performance of the CTS process. It is clearly shown that the thermal resistances of relatively large particles have crucial effect on computed values of both sterility and quality parameters. Key words: Simulation, Thermal sterilization, Laminar, Turbulent, Lethality, Quality, Solid Particles.


An Optimal Radial Basis Function (RBF) Neural Network for Hyper-surface Reconstruction
 
        A. Shahsavand (PhD.)

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Abstract Data acquisition of chemical engineering processes is expensive and the collected data are always contaminated with inevitable measurement errors. Efficient algorithms are required to filter out the noise and capture the true underlying trend hidden in the training data sets. Regularization networks, which are the exact solution of multivariate linear regularization problem, provide appropriate facility to perform such a demanding task. These networks can be represented as a single hidden layer neural network with one neuron for each distinct exemplar. Efficient training of Regularization network requires calculation of linear synaptic weights, selection of isotropic spread ( ) and computation of optimum level of regularization ( ). The latter parameters ( and ) are highly correlated with each other. A novel method is presented in this article for development of a convenient procedure for de-correlating the above parameters and selecting the optimal values of and . The plot of versus suggests a threshold that can be regarded as the optimal isotropic spread for which the Regularization network provides appropriate model for the training data set. It is also shown that the effective degrees of freedom of a Regularization network is a function of both regularization level and isotropic spread. A readily calculable measure of the approximate degrees of freedom of a Regularization network is also introduced which may be used to de-couple and .

Keywords:
Neural Network, Regularization network, Function approximation, Optimum spread, Degrees of freedom


INVESTIGATION ON THE BIOLOGICAL LEACHING OF COPPER FROM CHALCOPYRITE CONCENTERATES USING MODERATE THERMOPHILIC BACTERIA
 
        M. Izadpanah (PhD.)
  • M. R. Sarrafi [PhD.]
  • A. Fazaelipoor [PhD.]
  • M. H. Mosalmanzadeh [PhD.]

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ABSTRACT Biological leaching is a process in which metals are dissolved from sulfide ores into aqueous solutions using bacteria as catalysts. Biological leaching is currently gaining acceptance as a viable alternative to pyrometallurgical smelting due to decreasing ore grades and legislated limits on sulfur dioxide gas emission to the environment. In this research the feasibility of copper bioleaching from chalcopyrite concentrates by three chemotropic strains was investigated. The strains, coded by MS1, MS2, and TSB, were moderate thermophilic bacteria.MS1 and MS2 were indigenous to the site of the mine but TSB had been isolated elsewhere from an acidic hot spring. The bioleaching experiments were done on two types of chalcopyrite concentrates with different compositions. The strains had similar performances. The copper recovery increased from about 15% to about 30% when they were grown on a concentrate with the total initial copper content of 30.16%. When they were grown on a concentrate with the initial copper content of 43.35%, the copper recovery increased from about 5% to about 35%. The time period for all experiments was 22 days. The effect of pH on the strains’ performances was also investigated. All the strains performed better when the pH was kept constant at1.5 compared to2.2.

Keywords:
biological leaching, moderate thermophilic bacteria, chalcopyrite