Iranian Journal of Chemistry and Chemical Engineering
Year:2011 | Volume:30 | Issue:4 (60)|Papers Count:15

In the crystal structure of the title polymeric compound, [C42 H38 N6 O33 Sr5.2 (H2 O)]n, five independent metal atoms (Sr1-Sr5) have different coordination environments. The Sr1 and Sr5 atoms are nine coordinated and feature distorted tricapped trigonal-prismatic and capped square-antiprismatic geometries, respectively. The rest Sr II atoms have eight coordination numbers.These units are connected via the carboxylate O atoms of mono- and di anionic forms of pyridine- 2, 6-dicarboxylic acid, (pydcH2), and bridging water molecules that resulted in the formation of polymeric layers in 3-D. In the crystal structure, non-covalent interactions consisting of hydrogen bonds (O_H...O and C_H...O), p-p [interplanar distances of 3.413 (2); 3.601 (2)Å] and C = O … p  [O … p distances of 3.249 (3); 3.275 (3) Å] stacking interactions play an important roles in stabilizing the structure. The protonation constants of propane-1, 2-diamine (1, 2-pn) and pyridine-2, 6-dicarboxylate ion (pydc)2-, the equilibrium constants for the pydc-1, 2-pn proton transfer system and the stoichiometry and stability of this system with Sr2+ ion in aqueous solution were investigated by potentiometric pH titrations. The stoichiometry of one of the most abundant complexed species in solution was found to be the same as that of the crystalline SrII complex.

In this study, bis (salicylaldehyde)-4-methyl-1, 2-phenylenediimine (BSMP) as a Schiff base ligand of N2O2-type and its Mn and Fe complex as M-BSMP catalyst were synthesized and characterized by UV-Vis, IR spectroscopy and elemental analysis. The efficiency of Fe- and Mn-BSMP catalysts was evaluated in the oxidative decarboxylation of arylacetic acids with tetra-butylammonium periodate (n-Bu4NIO4) in the presence of imidazol with the mole ratios of M-BSMP: imdazole: n-Bu4NIO4: carboxylic acid of 1: 2: 5: 5, respectively in CH2Cl2. Using Mn-BSMP instead of Fe-BSMP makes the decarboxylation improved, leading 60-95% of corresponding carbonyl compounds as the sole products.

The synthesis of functionalized 2-oxo-2H-coumarin derivatives has been studied by a one-pot reaction of o-hydroxybenzaldehyde, ethyl 2-bromoacetate and triphenylphosphine in the presence of catalytic amount of triethyl amine in EtOAc, water or under solvent free conditions. We have found the best results obtained under solvent free condition.

A simple and efficient one-pot method for the preparation of aromatic iodides has been developed by sequential diazotization-iodination of aromatic amines employing sodium nitrite and sodium iodide in the presence of acidic ionic liquid N-methyl-2-pyrrolidonum hydrosulfate ([H-NMP] HSO4). The diazonium salts that are formed by this ionic liquid are stable at room temperature and react rapidly with sodium iodide to produce aryl iodides in moderate to good yields. The mild reaction conditions, straightforward procedure, inexpensive and green method make these transformations superior to the reported.

An account is presented on investigation of the effects of synthesis parameters, i.e., reaction sources, silica to alumina ratio, acid molar ratio and crystallization conditions on the crystallinity, morphology and particle size of SAPO-34. The synthesis conditions were designed to produce small particles with narrow size range. The prepared samples were characterized by XRD and SEM techniques in order to evaluate the crystallinity, morphology and particle size. The XRD pattern was used to evaluate the crystallinity and phase purity. The phase purity of some samples, including SAPO-18 was determined by DIFFaX analysis from XRD data. The results were shown that formation of SAPO-18 is enhanced by increasing the acid content in the primary mixture.lower Si/Al ratio in a primary mixture resulted in production of AlPO’s and SAPO-5 impurities.The type of template, silicon and aluminum source, acid concentration, agitation during crystallization, temperature and time of crystallization were found out as the significant parameters for controlling crystallinity and purity, particle size and morphology of the product.

Epoxy-Polysulfide copolymers without or with low amounts of epoxy in their structure have poor mechanical properties in oxidative curing system. To strengthen the mechanical properties of polysulfide elastomer inclusion of epoxy resin (Epon 828) as hard segment was studied. FT-IR spectroscopy and rheometry were used to verify the formation of epoxy-polysulfide copolymer. Results obtained from DMTA showed that in different epoxy/polysulfide ratio, the epoxy-polysulfide copolymer had different glass transition temperature (Tg). Gel time and curing behaviors in various ratios of epoxy-polysulfide were investigated using Rheometer and Differential Scanning Calorimeter (DSC). With increasing polysulfide weight percent in epoxy -polysulfide copolymer gel time increased but the enthalpy of cure reaction decreased and the temperature corresponding to exothermic peak was shifted to the higher temperature.Results obtained from DMTA and SEM showed that phase separation of epoxy resin from the copolymer matrix took place.

Operability analysis as one of the most important bridges between process design and process control helps the process designer to investigate the control issues quite early in the design stage. Recently, Vinson and Georgakis suggested a steady state geometrical operability index as a quantitative measure for assessment of process operability. In this paper, DME fixed-bed reactor is heterogeneously modeled based on mass and energy conservation law at steady state condition. To verify the accuracy of the model, simulation results of the conventional reactor is compared with the available industrial plant data. It is observed that there is a good agreement between the simulation result and the plant data. Then, the steady state operability characteristics of DME reactor have been analyzed by using the framework of Vinson and Georgakis. This paper demonstrates the utility of the approach to industrial chemical reactors. By measuring the operability characteristics of the reactor, the input and output operability index of the process is calculated equal to 43.31% and 57.58% respectively. The results showed the low process ability for creation of desired output by available input.

This publication usesa colorimetric method based on the absorbance spectra of dye solutionsto improve on Beer’s law when calculating the dye concentrations of a three-component mixture.The performance of the new method is compared with that of Beer’s law evaluated at three wavelengths, and Beer’s law evaluated at 16 wavelengths. Colorimetric method gives the best prediction of dye concentrations: the average relative errors in its predictions of the blue, red, and yellow concentrations are 55.64%, 12.3% and 14.84% respectively for new test solutions. Its average ternary relative error is 11.68% which is comparable to 14.31% for Beer’s law at three wavelengths.

Among the 30 strains of moderately halophilic bacteria isolated from the salty effluents of textile industries around Qom city in central Iran, a Gram-negative rod shape bacterium designated as strain IP 8 showed a remarkable ability in decolorizing of azo dyes over wide ranges of pH (7-11) and temperature (25-45oC), in presence of NaCl and Na2SO4 (0.5-1.5 M) under anaerobic and aerobic conditions. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparisons indicated that this strain was a member of the genus Halomonas with the greatest similarity to Halomonas axialensis. UV-Vis analysis before and after decolorization and the colorless bacterial biomass after treatment suggested that decolorization was due to biodegradation. HPLC analysis of dye treatment confirmed that the principal biodegradation was occurred after 48h of incubation in aeration culture. The effect of metal salts on decolorization showed that AgNO3 and NaAsO4 were of higher and lower effect on decolorization, respectively.

This study deals with bioleaching of the low grade uranium ore of Saghand mine in Iran using a mixed culture of mesophilic bacteria (Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans). Experiments were carried out in shaking flask examining the effect of temperature, initial ferrous ion concentration, pulp density and particle size.Variations of pH, Eh, ferrous ion concentration, cells growth and uranium extraction were monitored. The highest rates of leaching and extraction were obtained at 35oC, 2.5% (w/v) pulp density, 4g/l ferrous ion and -106mm particle size.

In the present investigation the biosorption potential of rosa gruss an teplitz (Red Rose) Waste Biomass (RRWB) for the removal of Pb (II) and Co (II) from aqueous solutions was studied. The effect of different process parameters such as pH, biosorbent dose, biosorbent size, temperature, contact time, initial metal concentration and pretreatments on the biosorption capacity of this waste biomass was studied. The results showed that the equilibrium data for both metal ions followed the Langmuir isotherm with a biosorption capacity of 112.0 and 115.9 mg/g for Pb (II) and Co (II) respectively. The overall biosorption process was best described by pseudo-second-order kinetics. Modification of red rose waste biomass by pretreating with different reagents significantly improved its biosorption capacity. A maximum biosorption capacity of 99.72 and 51.68 mg/g was observed for Pb (II) and Co (II) by treating the biomass with methanol and polyethyleneimine+ glutraldehyde respectively. The results clearly indicated that red rose waste biomass has a potential to remove heavy metals from aqueous solutions.

Drop size distribution plays a key role in the liquid extraction systems and related hydrodynamic and mass transfer parameters. In current research work, the size of drops in an extraction spray column has been measured by direct photography method, and the Sauter mean diameter has been obtained accordingly. Then, two types of models are assessed based on using dimensionless analysis and appropriate software. The interfacial tension in used chemical system is 1.8-32 dyne/cm. In first type of models, the correlation is established based on dimensionless parameters similar to approaches defined by other researchers. In second types, dimensional parameters have been used and therefore a new model is introduced for multi-drop extraction columns. The results show that the drop size diameter has the most affect on Eötvös number (Eo) in the first type of model and the correlation based on Eo number predicts drop size diameter with 8.1% error. In the second ones, four dimensional parameters (dN, Dr, s, u) have been selected as the most effective variables on drop size diameters and modelling results show prediction of drop size diameters with 5.82% error. In other cases, without using "u" as a variable, the amount of error has been decreased to 5.73% which shows better fitting.

In this research the drying of four kinds of vegetables was investigated in a vacuum dryer.The effect of temperature on drying rate of samples at various temperatures (30, 35 and 45oC) was studied. Six thin-layer drying models were fitted to drying data and suitable model was selected from them. Then effective moisture diffusivity and activation energy of samples were calculated.The Diffusion approximation model gave excellent fit for fenugreek and mint leaves and vegetative parts of leek and the page model was considered adequate to describe the thin-layer drying behavior of parsley leaves. The effective diffusivity values changed from 2.92x10 -10 to 9.81x10 -10, 1.77x10 -10 to 5.99x10 -10, 9.3x10 -11 to 1.7x10 -10 and 1.27x10 -9 to 3.4x10 -9 for fenugreek, mint and parsley leaves and vegetative parts of leek, respectively. An Arrhenius type of equation was used to evaluate the effect of temperature on the effective diffusivity and the activation energy values was found 66.36, 66.34, 32.27 and 51.16 kJ/ mol for fenugreek, mint and parsley leaves and vegetative parts of leek, respectively.

A new Fault Tolerant Controller (FTC) has been presented in this research by integrating a Fault Detection and Diagnosis (FDD) mechanism in a nonlinear model predictive controller framework. The proposed FDD utilizes a Multi-Sensor Data Fusion (MSDF) methodology to enhance its reliability and estimation accuracy. An augmented state-vector model is developed to incorporate the occurred sensor faults and then a UKF algorithm is utilized to estimate the augmented state vector including system states along with the fault terms using a centralized measurement fusion scheme. The designed FDD architecture is then merged with a conventional NMPC to form a Fault-Tolerant Control System (FTCS). A series of sensor fault senarios is conducted on a Continuous Stirred Tank Reactor (CSTR) to comparatively illustrate the superiority of the proposed FTCS in eliminating the miserable impacts of the induced sensor faults against a conventional NMPC.

Safety distance has already been a main measurement for the hazard control of chemical installations interpreted to mean providing space between the hazardous installation and different types of targets. But, the problem is how to determine the enough space. This study considers the application of quantitative risk assessment to evaluating a compressed natural gas station site and to identify nearby land use limitations. In such cases, the most important consideration is to assure that the proposed site would not be incompatible with existing land uses in the vicinity. This scope is possible by categorization of estimated levels of risk imposed by the proposed site. It means that an analysis of the consequences and likelihood of credible accident scenarios coupled with general acceptable risk criteria should be undertaken. This enables the calculated risk of the proposed site to be considered at an early stage, to allow prompt responses or in the later stages to observe limitations. It is concluded that not only adequate distance is not been provided but also the compressed natural gas station is located in the vicinity of populated areas and this is chiefly because of inadequate risk assessment studies and ambiguities in defining acceptable risk criteria.