Iranian Journal of Chemistry and Chemical Engineering
Year:2013 | Volume:32 | Issue:3 (67)|Papers Count:14

In this paper the influence of two different sizes of silica particles (micro-silica and nano-silica) was studied on mechanical properties of sulfur and sulfur composite. To improve the structural properties, sulfur was plasticized using dicyclopentadiene (DCPD) and methyl styrene (MSt). Plasticized sulfur composite was prepared by melt blending of plasticized sulfur and silica particles. The increment in compressive and flexural strengths revealed that the micro-particles enhance mechanical properties of sulfur while nano-particles improved mechanical properties of plasticized sulfur. Viscosity measurements indicated that mechanical properties of nano composites containing matrix with low viscosity (sulfur plasticized with methyl styrene) are improved with increasing mixer speed but increasing the mixer speed had negative effect on composites containing matrix with higher viscosity (sulfur plasticized with dicyclopentadiene).

In this research, zeolite-TiO2 nanocomposite was prepared for degradation of dibenzothiophene as a typical aromatic organosulfur compound of transportation fuels. The synthesized TiO2 was immobilized on the surface of clinoptilolite by Solid State Dispersion (SSD) method. The nanocomposite was then characterized by XRD, FTIR, TEM and SEM techniques. Photodegradation of dibenzothiophene in n-hexane solution by the prepared photocatalyst was then studied under different experimental conditions. The reaction products were identified by GC and GC-MS techniques. The removal of degradation products from the solution was examined by b- zeolite. The results showed that under optimized conditions, the photocatalyst was able to degrade %88 of dibenzothiophene and that the degradation products were adsorbed by b-zeolite so that the remaining solution was deeply desulfurized. It was also concluded that the kinetics of the reaction was first order.

Ferulic acid (4-hydroxy-3-methoxycinnamic acid), an effective component of medical plant, is a phenolic acid with low toxicity that can be absorbed and easily metabolized in the human body. The solubility of Ferulic Acid (FA) is very low in aqueous solutions which can cause problem in preparation of pharmaceutical products, but it can easily be dissolved in oil/water interface of nano-emulsions. In the present work, a kind of ferulic acid nano-emulsion was prepared using the spontaneous emulsification method which occurs when an organic phase and an aqueous phase are mixed. A chemometrics approach has been used to optimize the size of FA nanoemulsions. The experiments were performed according to a Box-behenken experimental design, one of the most suitable experimental design for modeling studies. The effect of three experimental parameters on droplet size was studied using multivariate analysis. The factors studied and the related levels were the concentration of lecithin (0.7-2 % w/w, in aqueous phase), the concentration of tween-80 (2-8 % w/w, in aqueous phase) and sounication time (10-45 minutes). In all the experiments, the water phase was added to the organic phase including lecithin, tween-80 and FA in ethanol solvent. Then experimental droplet sizes were fitted to the polynomial model. Good descriptive and predictive ability of the model was verified as high values of the statistics R2 (0.996) and F (112.5) were obtained for the linear relationship between predicted and experimental values of the dependent variable.

Calcium carbonate nano-particles were synthesized by a reverse micro-emulsion method at room temperature with Tween® 80 and Span® 80 as co-surfactants. The nano-particles synthesized were surface modified by stearic acid. An important operating variable in the Span 80-Tween 80/toluene/water reverse micro-emulsion system, the w-value (water/surfactant molar ratio) was investigated. The material was characterized by SEM, TEM, X-Ray Diffraction (XRD), FT-IR, UV-VIS and TGA/DTA techniques. The size of the nano-particles was determined by TEM as well as XRD data for various concentrations of surfactants. The results showed that the size of the nano-particles was influenced by the concentration of the surfactants in the micro-emulsion system. The XRD analysis at room temperature showed single phase formation of calcite. FT-IR confirmed the formation of calcite with characteristic absorption bands observed at 712, 881 and 1460 cm-1, corresponding to v4, v2, and v3 modes of CO3-2 absorption bands of calcite. The results of the UV-VIS spectrophotometric analysis indicated that the calcite (CaCO3) is an indirect gap material [(5.60 eV (30 wt. % surfactant), 5.40 eV (36 wt. % surfactant) and 5.36 eV (42 wt. % surfactant)] at room temperature.

One distinct concentration of copper ions was embedded into the silica matrix to xerogel form using copper source Cu (NO3)23H2O. The xerogel samples were prepared with using hydrolysis and condensation reactions of TetraEthyl Ortho-Silicate (TEOS) by the sol-gel method. In this investigation, new molar ratio of H2O/TEOS was determined to be 11.7. Also, the necessary amount of tri-hydrated copper nitrate was added to the solution in such a manner that the concentration of the copper oxide in final solution reach to 10 wt. %. The prepared samples were characterized by Thermal Gravimetric Analysis (TGA), Transmission Electron Microscopy (TEM), surface area measurement (using BET method) and Thermal Program Reduction (TPR) methods. Finally, catalytic behavior of nano-composites was studied towards carbon monoxide (CO), nitrogen monoxide (NO) oxidation and di-nitrogen oxide (N2O) decomposition reactions. The results were presented the systematic reactivity study of CO, NO oxidation and N2O decomposition on dispersed copper oxide nano-catalysts over silica supports, in order to determine the ability of these materials to convert carbon monoxide, nitrogen monoxide and di-nitrogen oxide to harmless species by different reaction paths at different temperatures.

Hydrogen can be produced for fuel cell applications by using methanol steam reforming reaction. In this article, a method was developed for regeneration of accelerated deactivated methanol-steam-reforming catalyst. Successive deactivation–regeneration cycles were studied in a 250 hours test for the first time including 6 regeneration cycles. It is shown that regeneration of the catalyst in diluted O2 results in dramatic enhancements of the methanol conversion and this catalyst could be regenerated to near fresh activity. Cokes that can deactivate the catalyst will be burned out in presence of oxygen at the regeneration step. XRD, TGA/DTG, TPR, N2O Chemisorption, TPO and SEM techniques were used for a complete catalyst characterization. Effects of temperature, water to methanol ratio, concentration of diluted oxygen, CuO/ZnO ratio and adding oxygen along with or without the main feed were also studied by a set of six experiments with duration of 100 h for each to provide a complete know-how on the developed method of regeneration.

La (OAc)3 has been used as an efficient catalytic system for the synthesis of quinoxalines. This method provides several advantages over methods that are currently employed such as a simple work-up, mild reaction conditions, good to excellent yields, and a process to recover and reuse the catalyst for five cycles with consistent activity.

SO42-/ZnO-TiO2 catalyst was prepared by sulfating ZnO-TiO2 powders with H2SO4 solution. The catalyst was characterized by XRD, IR and Hammett indicator. The catalyst showed strong acidity (H0£-16.0). The optimum conditions are found that the calcination temperature is 823K and the soaked consistency of H2SO4 is 1 mol/dm3. Then SO42-/ZnO-TiO2 was applied as the catalyst in the catalytic synthesis of dimethyl carbonate (DMC) from urea and methanol under the optimum conditions and revealed higher catalytic activity. On condition that the reaction time is 6h, the reaction temperature is 433K, the mass percent of the catalyst used in the reactants is 5wt. %, and the molar ratio of methanol to urea is 14, the yields of DMC can reach 27.9%.

The conversion of the cellulose into 5-HMF would experience three steps, cellulose to glycose, glycose to fructose and fructose to 5-HMF. Chloride ion can break down the hydrogen bond in cellucose, chromium can catalyze the isomerization of glycose to fructose, and the high temperature is helpful to cyclohydration of fructose to 5-HMF. In this paper, the sawdust has been directly degraded into 5-HMF in 1, 3-dimethyl-2-imidazolidinone (DMI) solvent containing alkali halides or ionic liquid with chromium (III) as the catalyst. The factors including the reaction temperature, reaction time, amount of catalyst and liquid-solid ratio, are investigated. The results indicate that the additive —— alkali halides plays an important role in the degradation of sawdust, for example that NaCl and KCl give rise to 28% (140oC) and 25.5% (120oC) of the final yield calculated on m(5-HMF)/m(sawdust), respectively.

Application of Granular Activated Carbon (GAC) in adsorption process has been studied for the advanced treatment of municipal and industrial wastewater. Because of entering poisonous compounds such as furfural, phenol and sulfides into the oily wastewater of Tehran refinery, biological aeration basins of wastewater treatment unit may not have the desired performance of COD reduction. In this study, GAC is examined for reduction of COD effluent from the Dissolved Air Flotation (DAF) unit to achieve to the environmental and design regulations. The equilibrium batch experiments as well as dynamic adsorption tests were performed to determine the maximum adsorption capacity and the breakthrough curves of COD, respectively. The data derived from equilibrium studies were modeled using Langmuir theory and the isotherm parameters were determined at two different temperatures of 25 and 40 C. Dynamic adsorption modeling was carried out considering the axial dispersion model in the bed of GAC with the assumption of lump kinetic mass transfer and linear driving force into the solid phase. The model results of COD breakthrough curve concentration have shown a fairly good agreement with experimental results. The sensitivity analysis of the dynamic model was carried out at different temperatures, bed lengths, feed flow rate and feed concentration to have a proper insight for appropriate design of a GAC fixed bed. It is concluded that GAC fixed bed could be an auxiliary unit for biological treatment of wastewater to overcome the problems of biological basin in oil refineries.

Fuel cells belong to an avant-garde technology family for a wide variety of applications including micro-power, transportation power, stationary power for buildings and other distributed generation applications. The first objective of this contribution is to find a suitable reduced model of a Solid Oxide Fuel Cell (SOFC). The derived reduced model is then used to design a state estimator. In the first step, the distributed model of the SOFC that is derived using the first principle balance equations is solved by the method of lines. Since this model is too complex and sluggish for real-time applications, a representation of this model with lower number of states and good accuracy is needed. Karhunen-Loève-Galerkin (KLG) procedure is used to develop such a reduced model.

In this article, the effect of operating conditions, such as temperature, Gas Hourly Space Velocity (GHSV), CH4 /O2 ratio and diluents gas (mol% N2) on ethylene production by Oxidative Coupling of Methane (OCM) in a fixed bed reactor at atmospheric pressure was studied over Mn/Na2WO4 /SiO2 catalyst. Based on the properties of neural networks, an artificial neural network was used for model development from experimental data. In order to prevent network complexity and effective data input to network, principal component analysis method was used and the numbers of output parameters were reduced from 4 to 2. A feed-forward back-propagation network was used for simulating the relations between process operating conditions and aspects of catalytic performance, which include conversion of methane, C2+ products selectivity, yield of C2+ and C2H4 /C2H6 ratio. Levenberg– Marquardt method is presented to train the network. For first output, optimum network with 4-9-1 topology and for second output, optimum network with 4-6-1 topology was prepared.

Experimental work was carried out to investigate the influence of impeller speed, granulation time, binder mass and their interactions on granule size distribution, mean size and binder content distribution in a conical high shear granulator. It was observed that the response of high shear granulation to changes in process parameters varies significantly from one operating condition to another. For all quantities of binder, the granule mean size increased with time at lower impeller speeds, while the opposite trend was observed at higher impeller velocities. For long mixing times, increasing impeller speed decreased the granule average size constantly; whereas for other durations, an increase in the mean size followed by a decrease was observed across ascending impeller speeds. It was also found out that variations of the span of granule size distribution can be utilized to indicate the dominant rate process. Coalescence which was prevailing at lower impeller speeds, was limited by attrition, breakage or shattering at higher impeller velocities. Binder-solid ratio of granules showed a continuous increase across size at lower impeller speeds and a maximum at middle size range for higher impeller velocities. Binder content distribution showed different trends with time at different operating conditions. Furthermore, increasing impeller speed limited the domain of binder content variations and made the granule binder-solid ratio to be much closer to theoretical value.

This investigation presents the effect of various parameters on foam stability and its rheological properties. The underlying idea of this experiment is generating of drilling foam with uniform bubbles. The main problem of foam using is controlling its stability during field application. The most important parameters which cause Instability in foam are gravity drainage, gas diffusion and bubble coalescence. Among these parameters gravity drainage has the highest effect on foam instability in field application. For measuring of drainage effect it is necessary to produce foam with uniform bubbles. This Experiment was performed with a specific foaming system which constructed in Research Institute of Petroleum Industry (RIPI) just for this point. This foam system consisted of an apparatus which injected nitrogen gas through a porous plate into the foam solution.In each test one parameter was variable and the effect of this variation was measured on foam properties. The main parameters which investigated in this experiment were temperature, foamer concentration, pH effect, stabilizers, and contaminants. Obtained results from testing of each parameter can be used simultaneously to improve the foam stability in elevated temperature. In this way by changing of physical and chemical properties of foam, it becomes more stable in real condition of wellbore.