Scientia Iranica
Volume:20 Issue: 6, 2013

A novel synthesis of 3-substituted rhodanine and thiazolidine-2,4-dione derivatives starting from aliphatic primary amines, carbon disulfide, and methyl 2-bromoacetate is described. The reaction proceeds successfully both in water and under solvent-free conditions, but 2-thioxothiazolidin-4-one (rhodanine) derivatives were obtained under solvent free-conditions, and thiazolidine-2,4-dions were formed when water was used as the solvent.

Two multiblock copolymers of polyethylene glycol (PEG), L-lactide (LLA) and e-caprolactone (CL) were synthesized and characterized. Triblock prepolymers were first synthesized using PEG with molecular weight (Mn) of 15,000 Daltons, e-caprolactone or L-lactide in the presence of Sn(Oct)2as catalyst. The triblockPCL-b-PEG-b-PCL prepolymerwith two hydroxyl functional groups was subjected to further block copolymerization with L-lactide in the presence of Sn(Oct)2as catalyst. Similarly, the triblockPLLA-b-PEG-b-PLLA prepolymerwas subjected to further block copolymerization with e-caprolactone in the presence of the same catalyst. The molecular structures of the copolymers were characterized by 1H NMR and 13C NMR analyses. Thermal behavior and thermal stability of these copolymers were evaluated by DSC and TGA thermograms, respectively. Finally,the effect of each discrete block on the thermal behavior and stability was studied in the typical pentablock copolymers.

L-Proline has been found to be an efficient organocatalyst for one-pot synthesis of quinoxaline derivatives under solvent-free conditions. The method provided advantages such as short reaction time, high yields and simple work-up.

A mild, efficient and environmentally friendly method has been developed for the green synthesis of 2,4,5-trisubstituted imidazoles via a three-component one-pot condensation of 1,2-diketones, diammonium hydrogen phosphate, (NH4)2HPO4(DAHP) and aryl aldehydes in waterunder reflux conditions. The DAHP shows remarkable activities for the synthesis of title compounds.The key advantages of this method toward conventional methods are experimental simplicity, good functional group tolerance; excellent yields, short routine, and selectivity without the need for a transition metal or base catalyst.

A simple and efficient procedure for the preparation of 3-propyldiethylenetriaminesilica (PDTAS) by reaction of 3-chloropropylsilica with diethylene-triamine is described. 3-Propyldiethylenetriaminesilicais employed as a recyclable base catalyst for the synthesis of 2-amino-4,6-diarylnicotininitrilefrom the reaction of acetophenone derivatives, aromatic aldehydes, malononitrile, and ammonium acetate under solvent-free conditions at 100 oC. The heterogeneous solid base catalyst was recycled for four runs upon the reaction of 4-chloroacetophenone, 4-chloroenzaldehyde, malononitrile, and ammonium acetate without losing its catalytic activity.

The biosorption capability of Acacia (Acacia auriculiformis A.Cunn. ex Benth.) leaf powder in batch and small scale column was investigated. The adsorption properties were analyzed with different experimental variables such as solution pH, amount of biosorbent, initial As(III) concentration and temperature. The maximum adsorption was observed at pH 6.0 while the equilibrium was attained in 5 h. Langmuir and Freundlich equilibrium adsorption isotherm models were utilized for fitting the experimental data. The maximum adsorption capacity of A. auriculiformisleaf powder was calculated to be 41.410 μg g-1. The kinetic data were well fitted by pseudo-first-order model with the correlation coefficient greater than 0.989. Surface morphology of the biosorbent was analyzed by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was employed to characterize the surface functional groups of A. auriculiformisleaf powder.The activation energy (Ea) and heat of biosorption (∆H) were calculated to be 27.549 and 43.380 kJ mol-1 respectively. The thermodynamic parameters such as Gibbs free energy (∆G), enthalpy (∆H), and entropy (∆S) revealed the spontaneous nature of the biosorption followed by physical activated process. Small scale column tests (SSCT) were also conducted to find out the breakthrough characteristics of the column packed with biosorbent.

Dimerization and 1,3-dipolar cycloaddition reactions of isoquinolinium ylidewith isoquinolinehave been investigated to prepare diaza-dibenzo compounds in good to excellent yields and in a short reaction time. These reactions occur in the presence of base catalyst such as triethylamine at room temperature.

Nano silica phosphoric acid has been found to be a suitable catalyst for the preparation of 2,4,5-tri-substituted imidazoles via three-component reactions of benzil, aldehydes and ammonium acetate under sonication condition.

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties of photocatalyst were characterized by X-ray diffraction, Scanning Electron Microscopy, nitrogen adsorption-desorption and Ultraviolet-visible diffuse reflectance spectroscopy. The influences of different operating variables such as the pH, the photocatalyst loading, the initial concentration of phenol, were studied to improve the efficiency of phenol degradation.

Liquid–liquid equilibrium data, both binodal and tie lines are presented for the pseudo-ternary systems: {(sulfolane + n-Alkoxyethanol) + octane + toluene} at 293.15 K. The experimental liquid–liquid equilibrium data have been correlated using the nonrandom two liquid (NRTL), UNIQUAC and UNIFAC models to predict the phase composition of the systems studied here, and the binary interaction parameters of these components have been calculated. The correlated tie lines have been compared with the experimental data. The comparisons indicate thatthecalculation based onboth NRTL and UNIQUAC models gave a good representation of theequilibrium compositionsdata for all systems studied. Also Othmer, Tobias and Hand method satisfactorily correlated tie-line data of the studied systems. The agreement between the correlated and experimental results was very good. The solvent (25% sulfolane+75% 2-ethoxyethanol) shows high capacity for toluene (a distribution coefficient around unity) and for this reason it can be used for higher recovery of aromatics at lower solvent to feed ratios and temperatures.

This research deals with the numerical simulation of two viscoelastic fluids flow in an open capillary of a reservoir. The Oldroyd-B and Leonov models have been used to describe the rheological behavior of polymer solutions. The nite volume method on a structured and collocated grid has been used for discretization the governing equations. The discrete elastic viscous stress splitting technique also has been used. The steady state, isothermal and incompressible fluids past through a two dimensional micropore have been considered. The numerical method has been validated through the comparison of numerical results by the analytical solutions of Oldroyd-B fluid flow through a planar channel.The effects of fluid characteristics and operating conditions on the oil sweeping from the dead ends are investigated. The contours of velocity, stream function and pressure are presented, and the swept depth is calculated. The presented results show that with increasing the Weissenberg number the swept depth of ooding fluid in the dead ends increases considerably. However, in the studied range, the Reynolds number does not have any signi cant e ects on the sweep efficiency. The results also show that the swept depth in the case of viscoelastic fluids is more than the Newtonian and generalized Newtonian fluids.

In this study, crosslinked and non-crosslinked carboxymethylcellulose (CMC) membranes were prepared with different concentrations of polymer. Then, the permeability of pure CO2, N2, and CH4was measured through these membranes in dry state,to investigate the influence of polymer concentration and applied feed pressure on permeability and permselectivity. The permeability of CO2through membranes was higher than the other gases. A comparison of permeabilities revealed that (the)permeability of N2, CO2(,)and CH4 increased on an average of 33, 40 and 20 percent, respectivly, by increasing the feed pressure from 6 to 10 bar. Increasing CMC concentration from 1.2 to 3.0 wt%, the permeability of N2, CO2(,)and CH4 decreased on an average of 25, 12 and 19 percent, respectivly. Also, the CO2/CH4and CO2/N2 permselectivities increased 9 and 18 percent, respectivly, with an increment in CMC concentration from 1.2 to 3 wt%. The crosslinked CMC membranes with the same polymer concentrations were also prepared to investigating(to investigate) theeffects of crosslinking reaction on permeability and permselectivity.The ATR-FTIR test was applied,and the peak at about 1108 cm-1 confirmed the presence of corsslinker groups. The comparision of gas permeation test results for crosslinked and non-crosslinked CMC membranes showed that the gas permeability decreased and its permselectivity increased due to crosslinking reaction. According to Robeson’s plots, the prepared CMC membranes would have potential for commercialization.

Modeling process is very important and valuable to predict process outcome, especially to bioprocesses which are intricate. Because of complex hydrocarbon compounds and oscillations happened in the medium of process, biodegradation of mazut has not already been investigated by mathematical models. In this study, an indigenous bacterium was isolated from oil contaminated soil to investigate biodegradation of mazut at different experimental conditions. Data resulted from mazut degradation, pH, and electrical potential in the medium were recorded. Some kinetic models reported and combinations of them were investigated to practically modeling the process. In addition, a new equation, that can predict various phenomena, was applied to functionalize changes of mazut concentration, pH, and electrical potential. Any of the kinetic models didn''t have potential for modeling behavior of mazut biodegradation at different conditions. Opposed to them, the novel equation was able to predict desirable parameter using two variables, and functionalize data by appropriate coefficients.