Iranian Journal of Chemistry and Chemical Engineering
Year:2011 | Volume:30 | Issue:2 (58)|Papers Count:17

This mini review article, intends to provide the essential information about microemulsion technique as a reliable approach toward the synthesis of zeolitic nano crystallites.The strategy discussed here provides a unique, effective, and potentially general methodology to the preparation of uniform and high purity nano crystallites of template-free zeolitic materials including LTA, faujasite type and other zeolitic-like materials (i.e. zeotype materials). Microemulsion is a reliable approach for controlled synthesis of uniform nano sized zeolitic particulates. On the other hand, the microwave assisted microemulsion technique has the advantages of short reaction time, producing smaller and more uniform particles with a narrower size distribution and high purity, in comparing to the conventional heating approaches.

LTA Zeolite nanoparticles was successfully synthesized from clear solution under controlled conditions using hydrothermal method using tetramethyl ammonium hydroxide as a structural directing agent. The as-synthesized LTA zeolite particles were characterized by powder X-ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), Fourier Transform InfraRed (FT-IR) spectroscopy, Energy Dispersive X-ray (EDX) analysis and surface area measuring technique of Brunauer, Emmett and Teller (BET). XRD patterns and FT-IR spectra were ascertained the formation of pure crystalline phase of 4A (i.e. LTA) zeolite.SEM micrograph was shown particles size in the range of 60 -170 nm with uniform morphology.The Si /Al ratio of the as-synthesized zeolite nanoparticles was 1.66 with a BET surface area of 421 m2/g.

Amino acids have been extensively used in several processes of the pharmaceutical and food industries. Treatments for the recovery and reuse of the wastewaters generated from these processes are few and little known. This work aims at studying the influence of different variables on the sorption of L-cysteine, contained in aqueous solutions, on clinoptilolite mineral. L-Cysteine (Cys) was sorbed by Clinoptilolie (Clino) from aqueous solutions of variable concentrations, temperatures and pHs. The powder X-Ray Diffraction (XRD), InfraRed (IR) spectroscopy and thermal analysis (TG, DTG and DSC) techniques were applied for characterization of materials. The results indicated that the sorption process depends strongly on pH, temperature and concentration of amino acid. Cysteine is specifically sorbed on clinoptilolite surface sites, probably through its NH3+moiety. The pH dependence suggests that these sites may be silanolate groups (ºSi-O-).The experimental data of sorption isotherms obtained and analyzed with Langmuir model showed that this model fitted the sorption data. Calculated thermodynamic parameters (DHo, DSo, and DGo) indicate that the sorption processes were exothermic.

A new category of hybrid organic-inorganic zirconium phosphonate, Zr [(O3PCH2) 2NC6H4CO2H].2H2O was synthesized and the applicability of the prepared sorbent as an ion-exchanger for removal of Ni2+, Cu2+and Zn2+ from aqueous solutions was evaluated.The characterization of the synthesis product was done using TG-DTG, SEM, XRD, FT-IR techniques.Study of the sorption isotherms and its kinetic parameters was performed by atomic absorption spectroscopy and potentiometric techniques respectively. The adsorbent showed very high sorption rate and good adsorption capacity. Based on the high sorption rates, a typical ion exchange chromatography separation was performed using a column packed with the synthesized ion-exchanger and the results are discussed.

Nano-CuFe2O4 catalysts with different Cu/Fe molar ratios (CunFemO(n+1.5m)) were prepared by hydrothermal method. The thermal decomposition performance of CunFemO(n+1.5m) on CuSO4 were determined with TG-DSC method to evaluate its catalytic activity and the roasted product was characterized by XRD. The results showed that CunFemO(n+1.5m) had superior catalytic properties and efficiency to CuSO4 crystals in 1: 1 Cu/Fe molar ratios and 4% CunFemO(n+1.5m) (in mass) contained. Under these conditions, the high and low temperature decomposition peaks of CuSO4 were overlapped. The temperature and heat of decomposition were decreased by 29.5oC and 112.1 J/g, respectively. The results were also confirmed by roasting experiments of CuSO4·5H2O in muffle furnace in the presence of CunFemO(n+1.5m) as catalyst at the same temperature.

Polyethylene glycol was easily grafted to silica gel and used as a solid-liquid phase transfer catalyst in the reduction of aromatic nitro compounds. This silica-grafted polyethylene glycol is proved to be an efficient heterogeneous catalyst in the reduction of nitroarenes to the corresponding aromatic amines with zinc powder in water. The reduction reactions proceeded efficiently with excellent chemo selectivity without affecting other sensitive functional groups.

In this work, reactive absorption of gases in aqueous electrolyte solutions has been investigated resulting in the development of a procedure in order to calculate the concentrations of ionic and molecular species in the liquid phase. Two duplicate experiments were conducted to investigate simultaneous reactive absorption of ammonia and carbon dioxide in partially carbonated ammonia solutions. The experiments were carried out employing an absorption pilot plant. The compositions of the electrolytes (ammonia and carbon dioxide groups) have been determined using principle knowledge of electrolyte solutions. The results revealed that the concentrations of ionic and molecular species in the liquid phase drastically influence the absorption rates of ammonia and carbon dioxide.

Phosphoric acid (H3 PO4) and Zinc chloride (ZnCl2) catalyzed shea nut shells, subjected to a one way activation scheme was employed to study the adsorption kinetics and mode of diffusion of industrial dye uptake. Thermodynamics data obtained in this study indicate that the sorption of dye spontaneously increases with time and decreases after equilibration was reached.The adsorption follows the pseudo second order kinetic model which gave the least %SSE (0.449-1.348), best linearity (R2=0.998-0.999) and closer agreement between the experimental and calculated q e values (q e exp., 96.985/q e cal., 100.00). Mode of transport deviate from the intraparticle diffusion model. According to this study, percent dye removal coupled with the close proximity of generated data to those reviewed in literatures, is an indication that shea nut shells could compare, to a good extent with commercial activated carbon for organic dye removal from dyestuff wastewater.

3, 4- Dihydropyrano [c] chromene derivatives were synthesized using sulfonic acid functionalized silica (SiO2 -Pr-SO3 H) as a highly efficient heterogenous solid acid catalyst via one-pot three-component condensation of aromatic aldehydes with malononitrile and 4-hydroxycoumarin in excellent yields.

New diorganotin (IV) complexes of the type Ph2 SnL2, Bu2 SnL2 and Me2 SnL2 of the ligands 2-thioacetic-5-phenyl-1, 3, 4-oxadiazole (HL1) and benzamidophenylalanine (HL2).Have been synthesized and characterized by physico-chemical techniques such as (elemental analysis, and electrolytic conductance) and spectral UV-Visible, IR and 1H, 13C and 119Sn NMR). Monomer structures for the complexes, bidentate and octahedral geometry was proposed for the prepared complexes.Preliminary in vitro tests for fungicidal activity show that all prepared compounds display good fungicidal activity to Gibberela, Cercospora arachidicola, Physolospora piricola and Fusarium oxysporum.Moreover, the Ph2 Sn (L2)2 shows a higher fungicide activity than diorganotin carboxylate.

N,N-diethylethanaminium-2-(sulfooxy) ethyl sulfate was synthesized and used as an efficient, green, and recyclable catalyst and solvent for the nitration of aromatic compounds by nitric acid at 80oC.

In this paper the density and temperature dependencies of surface tension are investigated. Using the Lennard-Jones (12, 6), as an effective pair interaction potential, a linear expression is derived for isotherms of g /r2 versus r2 for some normal and ChloroFluoroCarbons (CFCs) fluids, where g is surface tension and r=1/v is molar density. The linearity behavior of the derived equation is well fitted onto the experimental data of surface tension for monatomic, diatomic, nonpolar, polar, hydrogen-bonded and chlorofluorocarbons. In addition, the temperature dependence of surface tension for 20 different fluids is examined, in which the contributions of both terms of the average effective pair potential to theg are determined. For all liquids investigated in this work, surface tension increases with density except for water. The surface tension of water for isotherms within 280-300 K decreases with density, whereas increases within the range of 310-320 K.

Turbulence structure on the gas side of a wavy stratified flow was experimentally investigated in a near horizontal 18.7 cm (H) x 10 cm (W) x 5.5m (L) rectangular duct. By applying the Variable Interval Time Averaging (VITA) technique to the hot wire anemometer measurements frequency of occurrence of turbulent events were detected near the air-water interface. Experimental results showed that frequency of occurrence of turbulent events over the waves increased with the interfacial shear at the interface. Mass transfer coefficients were calculated making use of eddy cell model and calculated turbulent event frequencies. Predicted mass transfer coefficients show good agreement with experimental correlation. Conditional averages of turbulent events were obtained by applying VITA technique to the measured instantaneous velocities. Despite near wall region, both ejection and sweep can initiate turbulent event at the interface.

Five-zone Simulating Moving Bed (SMB) system, designed for ternary separation, is a modified form of standard four-zone SMB which is only effective in binary separation. It was reported in literature that the five-zone SMB separates the extract-II stream with a lower purity value than that of raffinate and extract-I streams. To address this issue, five zone SMB was designed, using safety margin method for the separation of a ternary amino acid mixture comprises of methionine, phenylalanine and tryptophan having linear isotherms values. The operating conditions at fixed zone-I flow rate were calculated by using triangle theory and the developed mathematical model was run for the simulation studies with Aspen Chromatography vis 12.1. (2004) simulator. The simulation results of the 2-extract five-zone SMB system were illustrated for the effect of change in zone safety factor (b2, b3 and b4) values on the separation performance (product purity and recovery) and on solutes band propagation behavior at cyclic steady state.

In this paper a new process is presented for improving efficiency of cyclone de-dusting systems. The cyclone is coupled with a specially designed cylindrical chamber which includes a rotating tube inside it with air impinging nuzzles, drilled on the peripheral surface of the tube. The nuzzles help in pushing and throwing the particles to the outer radius distances during downward flow of dust included air stream inside the chamber. In this way dust particles will become concentrated near the surface of the cylindrical chamber which is then collected from a recycling stream, taken from the higher radius zone of the chamber in the lower part and passed through a cyclone for dust removal. The exhaust dusty flow of the cyclone is also recycled to the jet-impingement chamber for further de-dusting. Experiments were conducted on the apparatus by feed stream input to the chamber in such a way that the performances of chamber alone can be investigated with respect to the three variables; feed stream, recycle stream and jet-impingement stream.

An adaptive version of growing and pruning RBF neural network has been used to predict the system output and implement Linear Model-Based Predictive Controller (LMPC) and Non-linear Model-based Predictive Controller (NMPC) strategies. A radial-basis neural network with growing and pruning capabilities is introduced to carry out on-line model identification. An Unscented Kalman Filter (UKF) algorithm with an exponential time-varying forgetting factor has been presented to enable the neural network model to track any time-varying process dynamic changes. An adaptive NMPC has been designed based on the sequential quadratic programming technique. The paper makes use of a dynamic linearization approach to extract a linear model at each sampling time instant so as to develop an adaptive LMPC. The servo and regulating performances of the proposed adaptive control schemes have been illustrated on a non-linear Continuous Stirred Tank Reactor (CSTR) as a benchmark problem. The simulation results demonstrate the capability of the proposed identification strategy to effectively identify compact, accurate and transparent model for the CSTR process. It is shown that the proposed adaptive NMPC controller presents better improvement with faster response time for both servo and regulatory control objectives in comparison with the proposed adaptive LMPC, an adaptive generalized predictive controller based on Recursive Least Squares (RLS) algorithm and well-tuned PID controllers.

Bioinformatics, through the sequencing of the full genomes for many species, is increasingly relying on efficient global alignment tools exhibiting both high sensitivity and specificity. Many computational algorithms have been applied for solving the sequence alignment problem. Dynamic programming, statistical methods, approximation and heuristic algorithms are the most common methods applied to this problem. We introduce gpALIGNER, a fast pairwise DNA-DNA global alignment algorithm. gpALIGNER uses similar score schema with DIALIGN-T to produce the final alignment. It also uses the concept of "spaced seeds" to determine locally aligned subsequences which construct semi-global alignment as the preliminaries of global alignment computation. This enables gpALIGNER to have the precision provided by the DIALIGN-T algorithm in considerably less time and space complexities. We performed benchmarking of our approach based on numerous datasets from standard benchmarking databases and real sequences of NCBI database where gpALIGNER performed three times faster than DIALIGN-T. gpALIGNER is a new alternative for having sensitivity and selectivity of DIALIGN-T but with less computational cost.