Iranian Journal of Chemistry and Chemical Engineering
Year:2017 | Volume:36 | Issue:2|Papers Count:16

The reactions of propenyl magnesium halides with ethylene were studied using ab initio calculations. The structure of the transition state and the ground state were evaluated and obtained the structural properties, theoretical thermodynamic and kinetic data i.e. rate constants of the reactions. The methods used for calculations are RHF, B3LYP and MP2 with 6-31G* basis set. The comparison of the thermodynamic and kinetic data of the reactions showed that the chemical affinity of reactants increases by increasing the bond length of Mg-X in three methods. Also the results showed reactions would accelerate as increasing size of the halogen, by lowering or rasing the HOMO or LUMO energies and decreasing the HOMO-LUMO energy gap.

In this work, a polyimide (PI) containing triazole units was synthesized using 3, 5-diamino-1, 2, 4-triazole and pyromellitic dianhydride in N-methyl-2-pyrrolidinone. This polymer was used as support of manganese (III) tetrakis (4-methoxylphenyl) porphyrin acetate to attain a heterogeneous catalyst; namely Mn (T4-OMePP) OAc@PI. The synthesized PI and Mn (T4-OMePP) OAc@PI were characterized by different spectroscopic and analytical techniques. The resulted catalyst was applied for epoxidation of alkenes and dehydrogenation of Hantzsch 1, 4-dihydropyridines (1, 4-DHP) by peroxynitric acid (PNA; HOONO2) as a convenient new oxygen source. In association with HOONO2, Mn (T4-OMePP) OAc@PI was stable and proved to be an efficient, reusable and selective catalyst for epoxidation of alkenes (36-96% yield) and dehydrogenation of Hantzsch 1, 4-DHP’s (94-100% yield).

Recently, the fate of endocrine disruptors in environmentally relevant samples has attracted considerable attention. Semiconductor photocatalysis may offer an appealing methodology to treat such contaminants. In this respect, the simultaneous degradation of synthetic hormones employing UV irradiation and TiO2 as the photocatalyst was investigated. Our interest was focused on designing a photocatalytic reactor and finding a way to immobilize a powder photocatalyst by water-glass. The nanofiber powder photocatalyst NnF Ceram TiO2 was chosen as powder photocatalysts based on TiO2. The material was characterized by N2 adsorption/desorption, XRD, UV-Vis spectrometry and TEM. The reaction kinetics of hormone decomposition corresponds to a first-order reaction rate. It was shown that progesterone and all types of estradiols were decomposed most effortlessly in the presence of NnF Ceram TiO2 photocatalysts. On the other hand, the lowest conversion was reached for estrone and estriol. The photocatalysts based on TiO2 immobilized by water-glass seems to be promising for photocatalytic water purification.

The present work aimed to evaluate capability of a new molecular structure to stabilize polyethylene against thermal oxidation. Hence, effects of 3, 3-bis (4-hydroxy-2-methyl-5-propan-2-ylphenyl) -2-benzofuran-1-one (thymolphthalein) on thermo-oxidative stability of high density polyethylene (HDPE) in both solid and melt states were investigated and compared with those of SONGNOX 1010, a commercially used phenolic antioxidant for the polymer. Oven ageing experiments at 90oC followed by Fourier Transform Infrared (FT-IR) spectroscopy showed that thymolphthalein at concentrations of 0.1-1.0 wt% improves thermo-oxidative stability of the polymer strongly in the solid state so that its stabilization efficiency is comparable to that of SONGNOX 1010. Furthermore, measurements of Oxidation Onset Temperature (OOT) and Oxidative Induction Time (OIT) of the polymer samples revealed that thymolphthalein modifies thermo-oxidative stability of the polymer in the melt state remarkably. So that, an increase in OOT value of the polymer as large as 36oC was obtained by addition of 0.1 wt% of thymolphthalein. It was also confirmed that thymolphthalein does not interfere with the stabilization action of the phenolic antioxidant in the polymer neither in melt nor in solid state. Finally, a mechanism for the stabilization action of thymolphthalein in the polymer was proposed.

Composite nanofibers composed of organic polymer and inorganic nanomaterials have huge potential to be used in different industrial applications. However, the main concern on the use of composite nanofibers is the distribution properties of nanomaterials in the polymeric matrix. The effect of the capillary tip charge on the additive distribution in the electrospun nanofiber has been previously studied and can be found in the literature. In this study, focus is placed on the investigation of TiO2 nanoparticles (TiO2 NPs) distribution in the polysulfone (PSF) nanofiber. X-ray Photoelectron Spectroscopy (XPS) was conducted to measure the percentage of TiO2 on the surface of the prepared PSF/TiO2 composite nanofiber. The results showed that there was no TiO2 NPs on the surface of the nanofiber for up to 10 nm in depth. TiO2 nanoparticles were mainly found in the center of the nanofiber due to the accumulation of the hydrophobic PSF at the surface of the composite nanofiber. The findings of this work can provide better interpretation of the impact of the interfacial tension on the distribution of the inorganic nanomaterials in the electrospun nanofiber.

A diacid monomer was synthesized by the condensation of L-tryptophan amino acid and pyromellitic dianhydride (PMDA). The diacid was utilized for the synthesis of three types of poly (amide-imide) s (PAIs) using three different kinds of diamines. The synthesized monomer and PAIs were characterized using FT-IR, 1H-NMR and 13C-NMR spectroscopies and the PAIs were also used for the fabrication of chitosan (CS) /PAI blend films. XRD patterns of the PAIs, CS and CS/PAI blend films were also studied. Thermal stability of PAIs, CS and CS/PAI samples were studied using thermogravimetric analysis (TGA). The blend samples showed a higher thermal stability compared to the CS film, especially at higher temperatures. Morphology of the CS and blend CS/PAI films was studied before and after the biodegradation by SEM. The mechanical stability studies showed that blend CS/PAI films had a proper mechanical strength and their young’s modulus increased compared to the pristine chitosan. The in vitro fungal colonization of diacid monomer, PAIs, pure CS and blend CS/PAI samples were performed using Aspergillus niger fungi. After biodegradation, the pure CS showed the highest weight loss of 21.2 wt % among the samples. The blend CS/PAI samples also showed higher weight losses compared to the pure PAIs.

In this study, two Carbon Molecular Sieves using Pistachio shell (CMS P) and Walnut shell (CMS W) were prepared by a chemical vapor deposition method and used for pressure swing adsorption and separation of CO/H2 and CO/CH4. Adsorption isotherms of gases obtained for both CMS’s. The Dubinin-Radushkevich isotherm model was used for comparing pore volume of CMS’s. The obtained isotherms for both CMS were compared with Langmuir and Freundlich isotherms. It was observed that Freundlich equation can better correlate the experimental data. Adsorption capacity of each CMS and selectivity of them for separation of CO/H2 and CO/CH4 were obtained with the aid of kinetic studies. In comparison with CMS W, CMS P showed higher adsorption capacity values for gases, but lower selectivity for separation of them. Finally by fitting experimental data to a pseudo second-order equation, adsorption capacities at equilibrium were obtained for abovementioned gases on both CMS’s.

The transport properties of various anion and cation exchange membranes were studied in different electrolyte solutions using chronopotentiometry technique to get insight about influence of the counter ion on the transport properties of the membranes. The investigated samples include heterogeneous ion exchange membranes varying in the functionality of fixed charged groups, physical properties of the polymer and the preparation procedure. Chloride and nitrate were investigated as counter-ion in their sodium salts for anion exchange membranes while sodium, calcium, potassium and magnesium were selected as counter-ion in their chloride salts to study cation exchange membranes transport properties. First the current – voltage curve of an ion exchange membrane in a given solution was recorded to obtain the limiting current, then a constant current above the limiting current was used for chronopotentiometry measurement. In all the studied membranes the potential across the membrane remained constant for a time interval called the transition time, when a constant current was applied. Then the potential increased rapidly to reach the steady state potential. The permselectivty and the transport number of a membrane were calculated using the corresponding transition time.

Three-dimensional computational fluid dynamics in house-code of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) has been developed. The conservation equations are numerically solved using finite volume technique. One of the important goal of this research is the investigation of the variation of bipolar plates width effect on the fuel cell performance compared with the conventional model, which is highlighted in the results section with more details. Additionally, in the following we investigated numerically and experimentally, the effect of posing the single prominence on the GDL layers in the middle of the gas channels. The result indicat the noticable increasing in current density at the same voltages, by comparing with base model. Also the optimum size of the prominences is obtained from experiments and simulations. To validate the numerical procedure and experimental tests, the results compared with avaiable experimental data which show good agreement.

The influence of nanofluid with different wave forms in the presence of inclined asymmetric channel on peristaltic transport of a pseudoplastic fluid is examined. The governing equations for two dimensional and two directional flows of a pseudoplastic fluid along with nanofluid are modeled and then simplified under the assumptions of long wavelength and low Reynolds number approximation. The exact solutions for temperature and nano particle volume fraction are calculated. Series solution of the stream function and pressure gradient are carried out using perturbation technique. The flow quantities have been examined for various physical parameters of interest. It was found that the magnitude value of the velocity profile decreases with an increase in Q and z and increases in sinusoidal, multisinsoidal, trapezoidal and triangular waves. It was also observed that the size of the trapping bolus decreases with the decrease in the width of the channel d and increases with an increase in z.

A new and improved protocol for the synthesis, in good to excellent yields, of acridine-1, 8 (2H, 5H) -diones is described, involving a one-pot, three component reaction of dimedone, arylglyoxals, and ammonium acetate in water under microwave irradiation.

In this work, feasibility of flow pattern and oil holdup prediction for vertical upward oil–water two–phase flow using pressure fluctuation signals was experimentally investigated. Water and diesel fuel were selected as immiscible liquids. Oil holdup was measured by Quick Closing Valve (QCV) technique, and five flow patterns were identified using high speed photography through a transparent test section with Inner Diameter (ID) of 0.0254 m. The observed flow patterns were Dispersed Oil in Water (D O/W), Dispersed Water in Oil (D W/O), Transition Flow (TF), Very Fine Dispersed Oil in Water (VFD O/W) and a new flow pattern called Dispersed Oil Slug & Water in Water (D OS& W/W). The pressure fluctuation signals were also measured by a static pressure sensor and decomposed at five levels using wavelet transform. Then, standard deviation values of decomposition levels were used as input parameters of a Probabilistic Neural Network (PNN) to train the network for predicting the flow patterns. In addition, some considered numerical values for actual flow patterns together with signal energy value of each level were used as input parameters of a MultiLayer Perceptron (MLP) network to estimate the oil holdup. The results indicated good accuracy for recognition of the flow patterns (accuracy of 100% and 95.8% for training data and testing data, respectively) and oil holdup (AAPE=9.6%, R=0.984 for training data and AAPE=8.07%, R=0.99 for testing data).

In this research, the removal of Reactive Red 198 dye (RR-198) by Cuttlefish bone powder was investigated. The adsorbent was prepared in laboratory conditions and grinded by ASTM standard sieves (60-100 mesh). The progress of process is monitored spectrophotometrically by measuring the absorbance of dye at 518 nm wavelength. In addition the effects of process parameters such as adsorbent dose, pH, initial dye concentration, and contact time have been investigated. The SEM micrographs and the XRD pattern showed that the cuttlefish bone has the clearly seen pores on its surface and a crystallized form. According to the results, by increasing adsorbent dose and retention time, dye removal efficiency was increased considerably. The adsorption isotherm for initial dye concentration (50 mg/L) was in good concordance with the Langmuir and Freundlich models. The adsorption kinetic studies revealed that the adsorption of RR198 dye was complied with pseudo-second-order kinetic.

The current method for composition measurement of an industrial distillation column includes offline method, which is slow, tedious and could lead to inaccurate results. Among advantages of using online composition designed are to overcome the long time delay introduced by laboratory sampling and provide better estimation, which is suitable for online monitoring purposes. This paper presents the use of an online dynamic neural network to simultaneously predict n-butane composition of the top and bottom products of an industrial debutanizer columns. Principal component and partial least square analysis are used to determine the important variables surrounding the column prior to implementing the neural network. It is due to the different types of data available for the plant, which requires proper screening in determining the right input variables to the dynamic model. Statistical analysis is used as a model adequacy test for the composition prediction of n-butane in the column. Simulation results demonstrated that the Artificial Neural Network (ANN) can reliably predict the online composition of n-butane of the column. It is further confirmed by the statistical analysis with low Root Mean Square Error (RMSE) value indicating better prediction.

In this research, modeling, simulation and control of a methanol-to-olefins laboratory fixed-bed reactor with electrical resistance furnace has been investigated in both steady-state and dynamic conditions. The reactor was modeled as a one-dimensional pseudo-homogeneous system. Then, the reactor was simulated at steady-state conditions and the effect of different parameters including inlet flow rate, inlet temperature and electrical resistance temperature on reactor performance was studied. Results showed that the most effective parameter is electrical resistance temperature. Thus, it was selected as manipulating variable for controlling product quality. In the next step, dynamic simulation of the process was performed and the effect of different disturbances on the dynamic behavior of the reactor was assessed. Finally, PID and Neural Network Model Predictive (NNMP) controllers were utilized for process control, and their performances were compared to each other. The response of the control system to different disturbances and set point changes showed that both PID and NNMP control systems can maintain the process at the desired conditions. PID controller had smaller rise time and no offset compared to NNMP controller while NNMP controller had smaller overshoot.

Importance of recycling and utilization of recycled fiber has recently been recognized because of concerns about environmental issues and economical aspects. In spite of several advantages offered by paper recycling such as wood savings through substitution of virgin pulp and reduction in chemical usage, recycled pulp also contains great amount of fines having high relative surface area and high amount of amorphous cellulose. These fines adsorb water to a large extent and dewatering rate is lower compared to virgin pulp. Selective hydrolysis of these excess ultra-fines through eco-friendly cellulase enzymes can be utilized for enhancing the drainage rate leading to increased paper production. The present study deals with the isolation, production, biochemical characterization of alkali stable endoglucanase enzyme from Pycnoporus sanguineus NFCCI-3628 and its potential application for the improvement of pulp drainage. The enzyme produced by the fungus was stable even in neutral to alkaline pH range 7-8. In the experiments carried out, significant improvement of ~9-14% in drainability of pulp treated with endoglucanase enzyme was achieved along with better paper properties such as tensile index & smoothness.