Iranian Journal of Chemistry and Chemical Engineering
Year:2011 | Volume:30 | Issue:1 (57)|Papers Count:16

Zinc oxide (ZnO) nanoparticles were synthesized by spray pyrolysis method using an aqueous solution of zinc acetate at various concentrations from 5 to 25 wt%. The decomposition of precursor solutions was carried out at 800, 1000 and 1200oC under different atomizing pressures. The crystal structure and morphology of synthesized nanoparticles were characterized by X-Ray Diffraction (XRD) spectrometry and Transmission Electron Microscopy (TEM), which indicated that ZnO nanoparticles were of hexagonal wurtzite structure. The XRD, TEM and BET analyses of prepared ZnO powders with concentrations of 5-20 wt% showed that the crystallite size diameter and specific surface area of particles were in the range of 10-25 nm and 44-56 m2/g, respectively.It was found that impurity and unreacted zinc acetate appeared in the product with increase of precursor solution concentration beyond 20wt%.

Dissolution pressure and nozzle temperature effects on particle size and distribution were investigated for RESS (Rapid Expansion of Supercritical Solution) process. Supercritical CO2 was used as solvent and Ibuprofen was applied as the model component in all runs. The resulting Ibuprofen nano-particles (about 50 nm in optimized runs) were analyzed by SEM and laser diffraction particle size analyzer systems.Results show that in low supercritical pressure ranges, depending on the solvent and solid component properties (Lower than 105 bar for Ibuprofen-CO2 system), nozzle temperature should be as low as possible (80-90oC for Ibuprofen-CO2 system).In the other hand in high supercritical pressure ranges (above 105 bar), high nozzle temperatures work better. The border line of these two areas depends on the solvent phase behavior. Rapid Expansion of Supercritical Solution into a liquid solvent (RESOLV) was also studied with and without the presence of surfactant and compared with RESS process by measuring of formed particles size, size distribution and dissolution rate. Results show that the RESS process generally creates better conditions for achieving fine and uniform organic powders (with mean particles size of 40-180 nm), in contrast to the RESOLV method (minimum particles size of 80-400 nm).

A series of x (Co, Mn) /TiO2 catalysts (x = 2–12wt.%) containing 25%Co and 75%Mn were prepared by the co-impregnation method. All prepared catalysts have been tested in Fischer-Tropsch synthesis for production of C2-C4 olefins. It was found that the catalyst containing 8wt. %(Co, Mn) /TiO2 is an optimal catalyst for production of C2-C4 olefins. The effect of operation conditions such as the H2/CO molar feed ratios, temperature, Gas Hourly Space Velocity (GHSV) and total reaction pressure on the catalytic performance of optimal catalyst was investigated. Characterizations of both precursors and catalysts were carried out using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement, Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC).

The Oxidative Coupling of Methane (OCM) over M-Na-Mn/SiO2 catalysts (M=W, Cr, Nb and V) was investigated using a continuous-flow quartz reactor at 775o C, 1 atm and 100 cm3 min-1 gas flow rates, and correlated with the observed structure and redox properties.The interaction effects of the metal-metal and metal-support on the methane conversion and C2+ yield were investigated using X-Ray Diffraction (XRD), laser Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), and Temperature Programmed Reduction with H2 (TPR). The results revealed that the improvement of C2+ selectivity (or C2+ yield) follows the order W>Cr>Nb>V, while the catalytic conversion did not change significantly. XRD data indicated that Mn is well dispersed on the SiO2 support and also show that Mn2O3 and a-cristobalite were the predominant species in the surface catalysts. TPR data show that most of the Mn is present as Mn3+ and Mn2+.FT-IR analyses combined with the Raman results show that terminal M=O and bridging M–O–M species and the metal–metal and metal–support interactions, which take place due to the presence of sodium ion, depend on the transition metal that affect the catalyst performance. Results reveal that the interaction between metal oxide and sodium is required for high selectivity and control redox mechanism in transition metal oxide in OCM reaction.

The effects of electronic properties of inner and outer surfaces of Carbon Nano Tubes (CNTs) on the deactivation of cobalt Fischer-Tropsch (FT) catalysts were studied. The comparative characterization of the fresh and used catalysts by TEM, XRD, TPR, BET and H2 chemisorption showed that cobalt re-oxidation, cobalt-support interactions and sintering are the main sources of catalyst deactivation. TEM showed that 480 h continuous FT synthesis increased the average particles size of the particles located inside the pores from 7 to 7.4 nm while the average particles size of the particles located outside of the tubes increased from 11.5 to 25 nm. XRD analysis of the used catalyst confirmed cobalt re-oxidation and interaction between cobalt and CNTs and creation of carbide phases. When the %Co conversion and H2O partial pressure in the reactor are high, the deactivation rate is not dependent on the number of the catalyst active sites and is zero order to %CO conversion. In this case the main deactivation mechanisms are cobalt re-oxidation and metal support interactions. At lower amounts of the %Co conversion and H2O partial pressure, deactivation can be simulated with power law expressions with power orders of 11.4 for the particles outside the tubes and 30.2 for the particles inside the tubes and the main deactivation mechanism is sintering. Due to the electron deficiency of the inner sides of the CNTs, the interaction between the cobalt oxides and the support is stronger leading to lower rates of sintering as compared with the particles located on the outer layers of the CNTs. Regeneration recovered the catalyst activity by 54.3% of the total activity loss.

A series of complexes of the type trans- [Co (acacen) (amine)2] ClO4, where (acacen) is the (bis (acetyleacetone) ethylenediimine) and the amines are Benzyl amine (bzlan) 1, 2-amino pyrimidine (2ampy) 2, N-methylpipirazine (nmpip) 3, 3-methyl pyridine (3mpy) 4, p-toluidine (p-toldn) 5, has been synthesized and characterized by uv-vis. and FT-IR. The kinetics of the substitution reaction of [Co (acacen) (p-toldn)2] ClO4 with N3-, Br- and NCS- ions has been investigated in an aqueous solution by using UV-vis. spectroscopy. It has been found that the reaction occurs in two steps, hydrolysis and ligation. The first order rate constants for hydrolysis and ligation reactions in 313K have been determined. The rate of reaction is almost independent of the type and the concentration of anion. So, the interchange dissociative (Id) mechanism is suggested. The reaction has been carried out in several temperatures and the activation energy for hydrolysis and ligation (for NCS- anion) reactions have been calculated about 55 and 95 kJ/mol respectively.

This paper describes laboratory scale experiments examining the impact of microwave irradiation on the Granular Activated Carbon (GAC) exposed to toluene, a common organic vapor frequently released into work environment as well as outdoor. A stream containing 300 ppm toluene was supplied and passed through the granular activated carbon. The saturated adsorbent was placed in a quartz glass reactor and treated by microwave irradiation at heating frequency of 2450 MHz at different power levels. After successive recovery cycles the adsorption capacity was evaluated through breakthrough curves and the residue analyzed by gas chromatography. We found that exposing GAC saturated with toluene under microwave irradiation at 900W for 15 minutes can remove the pollutant from the adsorbent effectively.The recovery efficiency was more than 95% after 10 cycles at high power levels.GAC surface area and porosity values were increased slightly over recovery cycles. Our experiments indicate that GAC could be reused after several cycles of treatment and recovery processes while maintaining its original adsorption capacity and physical properties.

Al2O3-SiO2 diphasic gel was synthesized by sol gel route from aluminium nitrate and silicic acid following aqueous phase colloidal interaction. The precursor gel powder was thoroughly characterized by chemical analysis, measurement of surface area and bulk density measurement. The gel powder was further characterized by thermogravimetry, XRD diffraction study of the heat treated samples and Scanning Electron Microscopic (SEM) study of the fractured surfaces of the heat treated compacts. The gel was observed to be a truly di-phasic in nature and was capable of forming nano-structured well distributed mullite phase in the microstructure of the heat treated sample. The gel powder was heated at different temperatures and the formation of Al-O-Si linkage towards the formation of mullite phase (3Al2O3, 2SiO2) was studied by Fourier Transform Infra Red (FT-IR) spectroscopy. The characteristic Al-O-Si linkage was found to develop after 600oC indicating the formation of mullite gel and at 16000oC the linkage became very strong indicating complete crystallization of mullite.

A highly efficient, simple and green solvent-free protocol for the preparation of poly-substituted quinolines via Friedlander hetero-annulation reaction between 2-aminoaryl ketones and carbonyl compounds in the presence of silica-supported P2O5 (P2O5 / SiO2) is described. In this method, the title compounds are obtained in high to excellent yields and in short reaction times.

The possibility of using water insoluble fraction from biomass pyrolysis oil as additive in synthesis of Wood-Plastic novolac has been proved by using Differential Scanning Calorimetry (DSC) and Fourier Transformed Infra Red (FT-IR) spectroscopy.Synthesis of novolac with different concentrations (10, 20 and 30 wt %) of water insoluble fraction were performed. It was found that mechanical properties were improved by using water insoluble fraction as additive. However, furthe increasing amount of water insoluble fraction, the mechanical properties of wood-plastic novolac were decreased. When the amount of water insoluble fraction in wood-plastic novolac was 10%, the flexural strength of wood-plastic novolac was 57.8 MPa, tensile strength was 29.5 MPa. The performance and thermal behavior of novolac were characterized by DSC and TG.

The reaction of hydrogen peroxide and pheny -9-acridinecarboxylate in the presence of rhodamin B as a fluorophore leads to the emission of either bright blue light or bright red light, depending on the structure of fluorescer and reaction conditions.The light emitter responsible for the Chemi Luminescence (CL) reaction is acridone and that the blue light produced with out the fluorescers is a result of direct CL.The intensity and kinetic parameters for the CL systems were evaluated from fitting of the resulting intensity-time plots. The CL systems were investigated as concentration dependent of fluorescer, hydrogen peroxide, acridinium ester and sodium hydroxide as a catalyst.

The sorption and desorption behaviors of Eu (III) from aqueous solutions with cation exchange resins containing carboxyl groups (D155 resin) were studied in terms of varied Eu (III) concentration, adsorbent dosage, pH, contact time and temperature. Batch shaking sorption experiments were carried out to evaluate the performance of D155 resin in the removal of Eu (III) from aqueous solutions. The loading of Eu (III) ions onto D155 resin was found to increase significantly with the initial Eu (III) concentration increasing. The sorption was strongly dependent on pH of the medium with enhanced sorption as the pH changes from 4.00 to 6.40.The concentration of Eu (III) in aqueous solution was determined by UV–visible spectrophotometer. The adsorption kinetics, tested with Lagergren-first-order model and pseudo-second-order model, showed better agreement with Lagergren-first-order kinetics.The suitability of the Freundlich and Langmuir adsorption models was also investigated for europium–sorbent system.The thermodynamic parameters such as DG, which were all negative, indicated that the adsorption of Eu (III) ions onto D155 resin was spontaneous and the positive value of DH showed that the adsorption was endothermic in nature.Eu (III) ions can be eluted by using the 0.5mol/L HCl solution. The surface characteristic of Eu (III) on D155 resin before and after adsorption was shown using IR spectroscopic technique.Therefore, it has a good potential of the removal of Eu (III) from aqueous solutions.

The drying behavior of green peas is investigated in a pilot scaled Fluidized Bed Dryer (FBD) with inert particles assisted by an Infra Red (IR) heat source. The variation of shrinkage and moisture diffusivity with temperature and moisture content were investigated.The experimental drying curves were adjusted to the diffusion model of Fick’s law for spherical particles. The result was that, although the shrinkage was only a function of moisture content, the moisture diffusivity was dependent upon both temperature and moisture content. The effective diffusion coefficients were estimated at a temperature range of 35-70 and a moisture content range of 0.25- 3.8 kg moisture/kg dry solids. Some correlations were proposed for these properties.

The use of multilateral well is becoming an emerging method to improve oil recovery efficiently and to drain reservoirs more efficacious. By developing drilling technology, completing the oil wells as multilateral wells become more interesting especially from economic point of view. On the other hand, lack of any means for forecasting the performance of this type of wells causes drilling of them economically a risky job. The major objective of this work is to present a simple and effective means to estimate the performance of a multilateral well. In a simple approach to the multilateral well, one can consider it as several horizontal wells flowing into a common well string. By employing the concept of well interference and the Joshi's expression for horizontal well performance, a mathematical model for computing multilateral wells performance has been developed. Two correlations for estimating the multilateral well performance with odd and even branches have been presented by utilizing the concept of well interference in conjunction with a horizontal well performance expression. Consequently, the generated correlations along with the concept of equivalent length have been used in this work to present a general method for predicting a multilateral well performance. Also, economic analysis developed model for a multilateral well is presented in this paper.

FitzHugh-Nagumo (FHN) model is a famous Reaction-Diffusion System which first introduced for the conduction of electrical impulses along a nerve fiber. This model is also considered as an abstract model for pattern formation. Here, we have used the Cellular Automata method to simulate the pattern formation of the FHN model. It is shown that the pattern of this model is very similar to those of a kind of a rabbitfish which implies natural patterns could be based on reaction-diffusion systems. We have also considered the effects of different parameters of the FHN model on changing the initial pattern.

The Cellular Automata method has been used to simulate the pattern formation of the Schlogl model as a bistable Reaction-Diffusion System. Both microscopic and macroscopic Cellular Automata approaches have been considered and two different methods for obtaining the probabilities in the microscopic approach have been mentioned. The results show the tendency of the system towards the more stable phase in both microscopic and macroscopic cases. It is shown that the fluctuation effect plays an important rule in the microscopic approach while it is negligible in the macroscopic case.