Iranian Journal of Chemistry and Chemical Engineering
Volume:36 Issue: 6, Novr-Dec 2017

Plasticized sulfur/montmorillonite nanocomposites were prepared by the melt-blending method and the dispersion of montmorillonite (MMT) and the mechanical properties of the nanocomposites were studied. Natural sodium montmorillonite (NaMMT) and organically modified montmorillonite (OMMT) were used as filler. Scanning electron microscope (SEM), X-Ray powder Diffraction (XRD) and Transmission Electron Microscopy (TEM) indicated that OMMT is dispersed effectively in the plasticized sulfur matrix.The effect of varying amounts of natural sodium montmorillonite (NaMMT) and organically modified montmorillonite (OMMT) on the mechanical properties of the prepared nanocomposites were studied. The compressive, tensile, and flexural strengths of the plasticized sulfur nanocomposites containing OMMT compared to that containing NaMMT were, in general, greatly improved. Best MMT dispersion observed at 1.6 wt. %.

A novel method for the preparation of α-zirconium phosphate (ZrP) nanoparticles as an eco-friendly and recyclable heterogeneous catalyst was studied. Polyethylene glycol (PEG) was used as the organic matrix which produced a better dispersion of ZrP nanoparticles. The catalyst was characterized by several physicochemical techniques such as ICP-OES, XRD, TPD-NH3, pyridine-FTIR, BET, FTIR, TGA, SEM, and TEM. The acidic property of ZrP was studied in the synthesis of 2-amino-3-cyanopyridines. When the hexagonal ZrP nanoparticles were used as the catalyst, excellent yields were obtained. The catalyst was recovered and reused at least eight times without significant loss in its catalytic activity.

Current catalysts for the alcohol oxidation in fuel cells (typically noble metals-based) are susceptible to poisoning with intermediates like CO. Hence we decided to find superseded catalysts for methanol oxidation based on incorporation of mixed oxides. In this research, a nano-size perovskite SrFeO3-δ (SrFeO3-δNPs) was synthesized by a rapid co-precipitation method assisted with ultrasonic and characterized by XRD, FT-IR, SEM and EDX techniques. A modified glassy carbon electrode with Pd nanoparticles (PdNPs) and SrFeO3-δNPs dispersed into the appropriate amount of chitosan (CH) polymer as a multifunctional catalyst was prepared and its catalytic activity toward alcohols (C1 - C3) oxidation was investigated. Based on the electrochemical studies, the PdNPs-SrFeO3-δNPs-CH nanocomposite showed considerable activity for alcohols (C1 - C3) oxidation in comparison to PdNPs-CH and SrFeO3-δNPs-CH. A direct methanol fuel cell was designed, assembled and tested with suggested PdNPs-SrFeO3-δNPs-CH nanocomposite under several different conditions. The effect of experimental parameters (temperature; methanol concentration; flow rate) as well as NaOH concentration) on the electrical performances of the fuel cell were studied and optimized.

Hexagonal mesoporous silica (SBA-15) was prepared and then functionalized by(3-mercaptopropyl)trimethoxysilane. The obtained 3-mercaptopropyl functionalized SBA-15 (SBA-Pr-SH) was then oxidized using H2O2 in methanol under an acidic condition to give sulfonic acid functionalized mesoporous silica (SBA-Pr-SO3H). The latter was characterized using different techniques (including TGA, BET, BJH, CHN, SEM, and TEM) and then used as a catalyst in organic synthesis. In the next step, SBA-Pr-SO3H catalyzed the three-component reaction of pyrazolone, salicylaldehydes, and barbituric acid in water under reflux condition. Through this procedure various pyrazolchromeno[2,3-d]pyrimidinone derivatives were obtained. The reaction conditions were completely green due to the use of water as a solvent and the presence of an environmentally benign catalyst.

A new derivative of Cyclotriphosphazene with xanthydrol as the oxygen-containing ligand was synthesized. Firstly Hexaclorocyclotriphosphazene was obtained Hexaclorocyclotriphosphazene from ammonium chloride and phosphorus pentachloride reaction and then the deprotonated xanthydrol was reacted with Hexaclorocyclotriphosphazene in the ratio of 6:1 in dry toluene as the solvent. All of the Cl atoms were substituted with hydroxyl groups of ligand to give a new product with (NP (C14H10O) 2)3 formula. This product was identified by a series of spectroscopic techniques including FTIR, 31P NMR, 13C NMR, 1H NMR and mass spectroscopy. Analyses were performed to confirm the formation of the designed product and structure.

Sodium acetate catalyzed the multi-component reaction of acetophenone, aromatic aldehydes, and acetoacetanilide in the water-ethanol mixture (1:1) at ambient temperature via Claisen-Schmidt condensation results in the formation of highly substituted cyclohexenones in 89–98% yields. The developed efficient catalytic approach to the substituted cyclohexenones – the promising compounds for inflammation and autoimmune diseases therapy and different biomedical applications – is beneficial from the viewpoint of diversity-oriented large-scale processes and represents facile, efficient and environmentally benign synthetic concept for multicomponent reactions strategy. This protocol offers several advantages including high yields, operational simplicity, clean reaction conditions, the minimum pollution of the environment, no need to column chromatography and simple work-up procedure.

A new aromatic diamine monomer containing ether linkage based on the phenanthrimidazole ring, ý1,1´-(4,4´- oxy bis(1,4-phenylene))bis(2-(4-aminophenyl)-1H-phenanthro[9,10-d]imidazole) was synthesized through four-ýcomponents condensation of 4,4´-diamino diphenyl ether, 4-nitrobenzaldehyde, phenanthrene-9,10-dione and ammonium ýacetate in presence of acetic acid, followed by palladium-catalyzed hydrazine monohydrate reduction. This new monomer ýwas further confirmed by FT-IR, 1H NMR, and 13C NMR spectroscopy. A series of new aromatic polyamides containing ýphenanthrimidazole ring in the main chain was prepared by direct polycondensation of the prepared diamine with four ýcommercially available aromatic and aliphatic diacids. These polymers are essentially amorphous and were soluble in polar ýaprotic solvents such as DMF, NMP, DMAc, and DMSO. Inherent viscosities of polyamides were in the range 0.42–0.53 ýdL/g indicating the formation of medium molecular weight polymers. Polyamides exhibited glass-transition temperature (Tg) in ýthe range 260-280 °C. The 10% weight loss temperature in air atmosphere measured by TGA was in the range 454-526 °C ýindicating their good thermal stabilities. The photophysical properties of diamine and polyamides were investigated by UV-Vsible and fluorescence spectroscopy.

An efficient and eco-friendly protocol for the synthesis of quinoxaline derivatives employing a condensation reaction between 1,2-diketone and 1,2-diaminobenzene derivative has been developed. The reaction of 1,2-diketone and 1,2-diaminobenzene derivative was carried out in water at room temperature using 10 mol% of task-specific dicationic ionic liquid as a catalyst. The results show that the reactions catalyzed by the dicationic ionic liquid proceeded smoothly to give the corresponding products. High yields of the products, short reaction times, mild reaction conditions and simple experimental procedure make this protocol complementary to the existing methods. Further, the catalyst can be reused for several times without obvious loss of the catalytic activity.

Several heterocyclic bioactive fluorescent 3-alkyl-3H-pyrazolo[4,3-a]acridin-11-carbonitriles were conveniently synthesized from the reaction of 1-alkyl-1H-indazoles with different aryl acetonitrile in basic methanol solution in good yields. The interactions of 3H-pyrazolo[4,3-a]acridin-11-carbonitriles with Human Serum Albumin (HSA) were studied by fluorescence spectroscopy. The binding of 3-alkyl-3H-pyrazolo[4,3-a]acridin-11-carbonitriles quenches the HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 1.28 × 103 – 1.85 × 103 M-1.A decrease in fluorescence intensity at 339 nm, when excited at 295 nm, is attributed to changes in the environment of the protein fluorophores caused by the presence of the ligand. The results show that pyrazolo[4,3-a]acridines with R=propyl, butyl, isobutyl and R'=chlorine substituents have suitable thermodynamic and binding parameters with HSA.

In this study, spectroscopic properties of the single-walled boron-nitride nanotube (SWBNNT) –a semiconductor channel in molecular diodes and molecular transistors–have been investigated under field-free and various applied electric fields by first principle methods.Our analysis shows that increasing the electric field in boron-nitride nanotube (BNNT) decreases the Highest Occupied Crystal Orbital (HOCO) /Lowest Unoccupied Crystal Orbital (LUCO) gap (HLG) significantly and the nanotube can be a conductor. The observed results suggest that the BNNTs is a useful semiconductor channel as nano-molecular diodes and nano-molecular transistors. Apart from that, the relationship between isotropic chemical shielding as an observable spectroscopic property with atomic charge and magnetizability in the presence and absence of an external electric field was studied. In order to rationalize energy changes, the relationship between the relative energy with the average electron delocalization of nitrogen and boron atoms with a variation of the external electric field is studied.

Multi-Walled Carbon Nanotubes (MWCNTs) surfaces were serially modified by the annealing treatment under Helium flow at 1000oC, the nitric acid treatment and again the annealing treatment under same conditions and their maximum adsorption capacities for benzene and toluene were measured and analyzed. The unmodified and modified MWCNTs were
characterized by Fourier Transform InfraRed (FT-IR) and Raman spectroscopy techniques and Brunauer–Emmett–Teller (BET) specific surface area measurements. The results revealed that the nitric acid treatment leads to form the functional groups and defects on the MWCNTs surfaces and increase their specific surface areas while the annealing treatments remove the functional groups and defects and therefore improve the structural integrity of the MWCNTs and enhance the p-p ­interaction between the MWCNTs and the toluene/benzene. According to the measurements of the maximum adsorption capacities, both acid and annealing treatments increased the adsorption capacity of the MWCNTs for both the benzene and toluene. It can be finally concluded that the adsorption capacity of the carbon nanotubes for the aromatic organic adsorbates such as benzene and toluene not only depends on their specific surface area but also is influenced by the structural integrity of the carbon nanotubes.

The sorption of thorium and uranium ions by functionalized SBA–15 mesoporous silica materials with Schiff base ligating groups N–propylsalicylaldimine (SBA/SA) and ethylenediaminepropylesalicylaldimine (SBA/EnSA) from aqueous solution was investigated in fixed-bed column method. The effect of pH, sample solution volume, and the column design parameters such as sample and eluent flow rates, and column bed height were studied. These investigations allowed to obtain the experimental breakthrough curves. Regardless to the adsorbent used, application of the columns with 2.5 cm bed height and sample flow rate 0.4 mL/min, resulted in the quantitative removal of 0.5 mg of Th(IV) and U(VI) ions from 200 and 250 mL aqueous solutions, adjusted at pH 4. The quantitative desorption of the loaded ions provided a preconcentration factor of 40 and 50 for Th(IV) and U(VI), respectively. Breakthrough studies showed the higher capacity of the column packed with SBA/EnSA in comparison to that packed with SBA/SA. The breakthrough curves indicated that both of the sorbents presents higher capacity towards uranium than thorium ions. The columns could be used for at least 3 sorption-desorption cycles. The investigated columns were examined for the recovery of Th(IV) and U(VI) from tap water and seawater samples.

Dyeing wastewaters are one of the most common pollutants that cause many problems for public health and environment due to dermatitis and skin rashes, cancer production, mutagenesis, etc. Thus, treatment of these wastewaters is necessary. The purpose of this study was to investigate the efficiency of montmorillonite nanoparticles as an adsorbent in adsorption process of Reactive Yellow 15 (RY15) and Reactive Yellow 42 (RY42) dyes from aqueous solutions. In this study, montmorillonite nanoparticles were used to remove RY15 and RY42 dyes. The effect of different variables such as pH, contact time, dye concentration and adsorbent dosage was studied. Finally, the effect of process temperature and thermodynamic was studied. Also, pseudo-first and second orders of kinetics were studied. The results showed that 3 is the best pH for the removal of both dyes. As contact time increases to 15 minutes, adsorption capacity increases and then reaches an approximately constant value. Adsorption capacity was also increased with increased dye concentration. By changing the adsorbent dosage from 0.2 to 0.6 g/L, adsorption capacity for RY15 and RY42 was reduced from 142and 166 to 63 and 59 mg/g, respectively. The results also showed that both dyes had the highest correlation with pseudo-second-order kinetics. The results of analyzing the process thermodynamics and temperature showed that values of DH, DS and DG are negative for both dyes.

A mathematical model considering mass and momentum transfer was developed for simulation of ethanol dewatering via pervaporation process. The process involves removal of water from a water/ethanol liquid mixture using a dense polymeric membrane. The model domain was divided into two compartments including feed and membrane. For a description of water transport in the feed solution, Maxwell-Stefan approach was used, while for mass transfer inside the membrane the molecular diffusion mechanism was assumed. The governing equations were solved numerically using finite element method. The concentration profile inside the membrane showed a linear decrease and a parabolic fully developed velocity profile was obtained on the feed side. The results also confirmed that formation of concentration layer can be easily predicted using Maxwell-Stefan approach in dewatering of organic compounds using pervaporation process.

A novel proton exchange membrane has been prepared using sulfonated poly(styrene-divinylbenzene) resin(SPSDR)–polyethylene(PE). The membrane is characterized by FT-IR, SEM and TGA/DSC. Water uptake, oxidative resistance, ionic conductivity and methanol permeability are measured to evaluate its performance in a direct methanol fuel cell. The on-set degradation temperature of the SPSDR is above 120°C. The membranes were confirmed to retain 1–5% water vapor at 80–140 °C in the air due to the hydrophily of highly sulfonated polystyrene. The ionic conductivity and permeability of the membrane to methanol was found to increase with temperature without extra humidity supply.A direct methanol fuel cell was designed and assembled with the suggested SPSDR-PE membrane. The effect of some experimental factors such as temperature, methanol concentration, and flow rate as well as NaOH concentration on the electrical performances of fuel cells was studied and optimized.

In this research, a Dispersive Liquid-Liquid MicroExtraction (DLLME) method coupled to UV-vis spectrophotometry was developed for the indirect determination of silver ion. The method is based on the catalytic effect of the silver ion on the oxidation of congo red by potassium peroxodisulphate and extraction with DLLME procedure using chloroform (extraction solvent) containing cetyltrimethyl ammonium bromide which provides counter ion and also acts as a disperser. After extraction, the phase separation is performed with a centrifugation, and the silver ion is determined in the enriched phase by UV-Vis spectrophotometry. Several factors affecting the microextraction efficiency, such as pH of the solution, extraction time, type and volume of extraction solvent were investigated. Under optimum conditions, a linear calibration graph in the range of 0.5-105.0 ng/mL of silver ion in the initial solution with r2 = 0.9987 (n=10) was obtained. Detection limit of the method was 0.2 ng/mL and the Relative Standard Deviation (RSD) for 3 and 70 ng/mL of silver ion was 3.5 and 1.7 (n=10), respectively. The enrichment factor was 54. The method was successfully applied to the determination of trace amounts of Ag(I) in radiology film and environmental matrices.

2-Dimethyl amino ethyl azide (DMAZ) has attracted much attention as a suitable liquid fuel replacement for monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH) in propellant systems because, in contrast to these fuels, it is noncarcinogen. In this research, performance, and ignition delay time of DMAZ were studied with common liquid oxidizers such as inhibited red fuming nitric acid (IRFNA), dinitrogen tetroxide (N2O4), White Fuming Nitric Acid (WFNA). Calculation results from rocket propulsion analysis (RPA) software showed that combustion of DMAZ and N2O4yielded highest Isp (352 s) compared to the other mentioned oxidizers. Moreover, DMAZ-N2O4 gave the highest density specific impulse (457.6­ s) at an optimum oxidizer-to-fuel ratio. Open cup tests were also performed to assess the ignition behavior of the DMAZ-N2O4 bipropellant and indicated that it is hypergolic (68 ms). Therefore, it seems that the DMAZ-N2O4 bipropellant is suitable for upper stage space systems.

Hydrocyclones have been used as an operational tool to separate liquids from solids in different industries for more than 50 years. Considering the importance of this issue, many experimental and numerical attempts have been made to estimate the performance of this tool regarding the resulting pressure drop and the separation efficiency (particles separation limit diameter). Most of the numerical studies for simulating the fluid flow pattern inside Hydrocyclones have been conducted using the ‘’Fluent’’ commercial software. The other alternative for this evaluation is the application of CFD
in COMSOL Multiphysics. This work is mainly focused on studying the effect of entering tangent velocity and also determining the flow pattern by CFD simulation in the powerful COMSOL Multiphysics software. Thereafter, correlations proposed by a number of authors are compared with experimental data to evaluate their performances. Among them, the correlations suggested by Barth and Koch-Lich showed acceptable accordance with reference data and thus were chosen for sensitivity analysis. Based on the results, three geometrical parameters of the hydrocyclone body have considerable effects on the separation efficiency. The findings revealed that decreasing the outlet diameter and the inlet width result in increasing the efficiency of hydrocyclone while enlarging the body diameter has negative effects on it. Furthermore, the cyclone efficiency is enhanced as the density difference between fluid and solid and the input velocity becomes larger.

This paper presents a detailed thermodynamical exergy analysis of an optimized MSF distillation plant based on the latest published thermodynamics properties of water and seawater software of the Massachusetts Institute of Technology by using design and optimized plant operation data. Exergy flow rates are evaluated throughout the plant and the exergy flow diagram is prepared in both cases. The rates of exergy destruction and their percentages are indicated on the diagram so that the locations of each exergy destruction can easily be identified. The study concludes that as a result of an optimization, making the MSFD unit once-through cooling system to recirculating type by using cooling tower system, the unit's exergy destruction pattern changes meaningfully. Besides, in the three exist thermal desalination plants up to 53 percent of feed water, i.e.; 667 m3/h and the same amount of reject water can be conserved. Though, with this modification, the unit steam consumption has been increased up to 13 ton/h, about 50 percent of design. Moreover, the detail of the study showed that the exergy destruction can be reduced more than 39% in the pumps, and 30% in blowdown and around 29% in distillate streams. For brine heater, an enhance as small as 0.37% is also achieved. In the other hand, the rate of destruction of exergy increased around 25% in the cooling process and above 5% in the evaporators.