Sharif Digital Repository

The present study examined the sorption capacity and sorption kinetics of four-type perlite for oil spills clean up. These four types are different on their porous space, expansion ability and special surface area. The tests were done both in static and dynamic methods. Experiments showed that the perlite spread on oil spill rapidly and floated on the surface of oil spill because of its low density (80-180 kg/m3). Scanning Electron Micrograph (SEM) of a typical structure of expanded perlite showed that it of high porous space. Sorption kinetic of oil spill into porous expanded perlite was evaluated by weight increase of crude oil with sorption time. According to kinetic study sorption of oil... 

This paper presents a state of the art review of adsorption models for a new plant-based surfactant adsorption onto sandstone minerals. The adsorption data at both kinetic and equilibrium modes were obtained from batch experiments. Four adsorption kinetic models, five two-parameter, and six three-parameter equilibrium models were used for interpretation of the obtained data. Among the two and three-parameter isotherm models applied, the Jovanovic and the Khan isotherms showed the best fit, respectively. And the pseudo-second order model presented a better fit than other kinetic models. Finally, a computer-based modeling approach was developed and used for predicting the kinetics of... 

The radical chlorination of polyethylene was carried out in perchloroethylene solvent using chlorine gas and ultraviolet photoradiation to investigate a reaction kinetics model. The recurrent structure of chloromethylene (-CHCl-) and methylene (-CH 2 -) groups and the percentage of substituted chlorine were determined using hydrogen-nuclear magnetic resonance (H-NMR) (500 MHz) spectra. A kinetics model has been proposed for this reaction in which the conversion of methylene (-CH 2 -) units to chloromethylene (-CHCl-) units was considered to be the main reaction step. The simplified version of the obtained kinetics model indicates that the reaction is first order with respect to the chlorine... 

This paper presents a state of the art review of adsorption models for a new plant-based surfactant adsorption onto sandstone minerals. The adsorption data at both kinetic and equilibrium modes were obtained from batch experiments. Four adsorption kinetic models, five two-parameter, and six three-parameter equilibrium models were used for interpretation of the obtained data. Among the two and three-parameter isotherm models applied, the Jovanovic and the Khan isotherms showed the best fit, respectively. And the pseudo-second order model presented a better fit than other kinetic models. Finally, a computer-based modeling approach was developed and used for predicting the kinetics of... 

Biodiesel is considered an alternative replacement for petroleum diesel, and enzymatic reaction is one method for biodiesel production. Understanding the kinetics of this reaction is important to achieve higher production rates. The kinetics of transesterification of castor oil using Novozym 435 was investigated in this study. The genetic algorithm was employed for estimation of kinetic parameters including Vmax, KmTG, and KmA in the Ping Pong kinetic model at different temperatures. In most enzymatic reactions that follow the Ping Pong mechanism, inhibition by alcohol has been taken into consideration. Here, we examined a competitive inhibition mechanism and found no inhibition effect at... 

Al-Si3N4 couples were heat-treated at 850-1150°C for 250 hours. The thickness of the interacted area was measured by scanning electron microscopy (SEM) and scanning/transmission electron microscopy (TEM/STEM). The interaction rate increases exponentially with inverse temperature, with an activation energy of 194.23 kJ/mol and diffusion pre-coefficient of 5 × 10−9 m2/s, indicating that the interaction is diffusion-dependent. As the results showed, the interfacial area is comprised of Al alloy channels, Si precipitates, and AlN grains. Al-Si transfer through the solid solution (Si3-xAlxN4-y) at the interface of Al alloy and β-Si3N4 grains controls the kinetic of the interaction. When... 

The effectiveness and reducibility of the methane combustion kinetic mechanisms were examined for the TPOX process in a porous medium. To this end, TPOX was successfully simulated using ANSYS CHEMKIN-Pro through a reactor network model composed of perfectly stirred and honeycomb-monolith reactors. The efficacy of six chemical kinetic mechanisms was compared for the equivalence ratios (ERs) ranging from 2.4 to 2.6 with a constant thermal load of 1540 kW/m2. This comparison revealed that Konnov was the most successful mechanism in the prediction of the H2 and CO mole fractions. This mechanism along with the GRI-3.0 and USC-Mech 2.0 mechanisms were then reduced by the direct relation graph with... 

Al86Ni10MM4 (MM: Mischmetal) amorphous ribbons were prepared by melt spinning on a child copper wheel. Non-isothermal crystallization kinetics of the amorphous alloy was studied by differential scanning calorimetry (DSC). The crystallized phases were determined by X-ray diffraction method and transmission electron microscopy. DSC traces were analyzed by Kissinger method to determine the apparent activation energy of crystallization. Changes in the activation energy (Eα) with progression of crystallization were also evaluated by differential iso-conversional method of Friedman. For the precipitation of nanometer-sized Al particles, the activation energy slightly increased with increasing the... 

A combined experimental and computational study was carried out on the gas phase pyrolysis reaction of diallylsulfoxide. Allylalcohol and Thioacrolein were detected as the major products during a unimolecular reaction. Experimental kinetic studies were carried out via a static system over the pressure of 21-55 torr and temperature of 435.2-475.1 K. Based on the experiments, the reaction is homogeneous and proceeds through a zwitterionic intermediate. Computational studies at the DFT (B3LYP) and QCISD(T) levels with 6-311++G(d,p) basis set indicated a two-step concerted pathway as the possible route. Comparison between the experimental and theoretical activation parameters for the most... 

Preparation and evaluation of chitosan-coated eggshell (CTS-ES) particles as a biosorbent for removal of Cu(II) ions from aqueous media was considered in this research. For this purpose, chitosan was coated on eggshell (ES) particles through precipitation procedure. The coated particles were characterized by Fourier transform infrared, thermogravimetric analysis, and field emission scanning electron microscopy analysis. Kinetic studies showed that coating of chitosan on ES particles improved their Cu(II) adsorption capacity. The removal of Cu(II) ions by either ES or CTS-ES particles followed the pseudo-second-order kinetics, indicating that chemical sorption is the rate-limiting step for... 

The effect of complexity level of a lumped kinetic model for heavy residue hydroconversion on estimated values of kinetic parameters was investigated in this work by imposing constraints for the parameter estimation algorithm of a complex six-lump kinetic model and deriving a simpler modified model from the complex model. Kinetic analysis was performed using available experimental data reported in the literature from a study on hydrocracking of Chinese Gudao vacuum residue in a bench-scale reactor using ammonium phosphomolybdate (APM) as a dispersed catalyst. The kinetic models also included coke formation reactions that had previously been ignored by most investigators due to the rather... 

Hydrocracking is one of the most versatile petroleum refining processes for production of valuable products including gasoline, gas oil, and jet fuel. In this paper, a five-parameter continuous lumping model was used for kinetic modeling of hydrocracking of vacuum gas oil (VGO). The model parameters were estimated from industrial data obtained from a fixed bed reactor operating at an average temperature of 400°C and residence time of 0.3 h. Product distributions were obtained in terms of the weight fraction of various boiling point cuts. The model parameters were estimated using the Nelder-Mead optimization procedure and were correlated with temperature. Comparison of experimental and... 

In this study the biodegradability of asphaltenes was investigated using four bacterial consortia isolated from oil contaminated soils and sludge. The species in consortium 1 were identified as Pseudomonas aeruginosa and Pseudomonas fluorescens. Consortium 2 contained Citrobacter amalonaticus and Enterobacter cloacae. Consortium 3 contained only one species identified as Staphylococcus hominis, and the species in consortium 4 were identified as Bacillus cereus, and Lysinibacillus fusiformis. Spectrophotometry at 281 nm wavelength was applied to quantify asphaltenes biodegradation. The biodegradation tests were performed in flasks with the initial asphaltenes concentrations of 2, 4, 10, 20,... 

A Continuous model was developed to describe the kinetics of hydroconversion of Marlim crude oil in a slurry-phase reactor. The model was able to accurately predict the liquid product distributions as well as coke formation. The model contained one temperature-independent and six temperature-dependent parameters.The model parameters were obtained by an optimization procedure using experimental data available in the open literature for reaction temperatures of 440-460°C, hydrogen pressure of 14.7 MPa, liquid hourly space velocity (LHSV) of 0.5 h-1, and a hydrogen to oil ratio of 100 to 1 ft3/bbl. Comparison between experimental and predicted product distributions and coke yields indicated a... 

Kinetics of crystallization in an amorphous (Fe0.5Co 0.5)77Si11B9Cu0.6Nb 2.4 (at.%) alloy was investigated using differential scanning calorimetry (DSC). Transformed fraction as a function of temperature was obtained by accurate DSC measurement and the experimental data analyzed with Vyazovkin model-free kinetic method. Reconstructed form of the experimental kinetics model, g(α), clearly showed the crystallization mechanism do not belongs to a single model but almost follows the Avrami-Erofe'ev. Magnetic coercivity and hysteresis loss values of the annealed samples at 823 K were 7.5 A m-1 and 1.2 J m-3, compared to 17.1 A m-1 and 37.1 J m-3 for as spun samples. Magnetic measurements show the... 

Oxidative coupling of methane in a bench scale fixed bed tubular reactor over Mn-Na2WO4/SiO2 catalyst has been studied. Four kinetic models have been considered for oxidative coupling of methane reactions and compared through experimental data, and the best kinetic model has been selected. For removing the heat of reaction, a molten salt bath system surrounding the reactor tube has been proposed. Effects of different factors, such as CH4/O2 ratio, are investigated through experimental and simulation studies. A good agreement has been observed between simulation and experimental data. The reactor behaviors under isothermal and adiabatic conditions have also been simulated  

Biosurfactants are microbial substances which influence interfacial tension. The kinetic study was carried out for Pseudomonas aeruginosa MR01 during biosurfactant production in a two-phase liquid-liquid batch fermentation system. The maximum rhamnolipid concentration (Pmax) and the yield of biosurfactant per 1 biomass (YP/X) in a 5-L bioreactor containing soybean oil medium were found to be approximately 20.9 g.L and 3.1 g.g-1, respectively. Previously reported kinetic models in aqueous systems, three-parameter Gompertz, 2 Luedeking-Piret and Mercier equations, demonstrated adequate goodness-of-fit (r >0.9) to kinetic data recorded for biomass growth, nitrate consumption and rhamnolipid... 

To figure out the relationship between nutrient deprivation and cell growth, simulation can be effective. In the present work, the growth of Chinese Hamster Ovary (CHO) cells was simulated based on stoichiometric and kinetics calculations. The simulation results were compared to the experimental data from a packed-bed bioreactor and a good agreement was observed. The kinetic parameters (K Glc, K Amn, K Lact and μ Max) were optimized by a genetic algorithm method using stoichiometric parameters (Y X/Glc, Y X/Amm, and Y Lac/Glc). The stoichiometric and kinetic parameters were used in the simulation to study the growth of CHO cells. The concentrations of the toxic by-products, ammonium and... 

This paper presents the first kinetic data structure (KDS) for maintenance of the Euclidean minimum spanning tree (EMST) on a set of n moving points in 2-dimensional space. We build a KDS of size O(n) in O(nlogn) preprocessing time by which their EMST is maintained efficiently during the motion. In terms of the KDS performance parameters, our KDS is responsive, local, and compact  

In this work, the effect of carbon dioxide partial pressure on the calcination kinetics of high purity zinc carbonate hydroxide has been studied. Non-isothermal analysis has been performed on samples at different CO 2 partial pressures by TGA and DTA. It has been found that the calcination behaviour of this material corresponds to the shrinking core model and the reaction mechanism is phase boundary controlled. The calcination reaction of zinc carbonate hydroxide starts at 240 °C. Increasing the carbon dioxide partial pressure can result in an increase in the reaction start temperature of up to 30°C. The activation energy for the reaction is calculated as 180 ± 5 kJ/mol at...