Sharif Digital Repository

Thermal oxidation of commercial ilmenite concentrate from Kahnouj titanium mines, Iran, at 500-950 C was investigated for the first time. Fractional conversion was calculated from mass change of the samples during oxidation. Maximum FeO to Fe2O3 conversion of 98.63 % occurred at 900 C after 120 min. Curve fit trials together with SEM line scan results indicated constant-size shrinking core model as the closest kinetic mechanism of the oxidation process. Below 750 C, chemical reaction with activation energy of 80.65 kJ mol-1 and between 775 and 950 C, ash diffusion with activation energy of 53.50 kJ mol-1 were the prevailing mechanisms. X-ray diffraction patterns approved presence of... 

In this research nano γ-Al 2O 3 catalyst was synthesized through precipitation process then characterized and utilized for methanol dehydration reaction in a slurry batch reactor in route to the indirect synthesis of the dimethyl ether (DME). In this venue, effects of the key parameters on methanol conversion and catalyst stability were investigated. Moreover, the internal and external mass transfer resistances were eliminated; hence the intrinsic kinetics controlled the reaction. Therefore, the optimum conditions for temperature, methanol concentration, catalyst mass and stirrer speed were determined to be 300°C, 1.18mol/l, 1.5g and 1100rpm, respectively. Next, different reaction rate... 

A new nonlinear optimization method for parameter estimation in Michaelis-Menten equation has been developed. This method is based on a special mathematical form of the Michaelis-Menten equation to finding the best fit of the linear plot of R versus S/(S + Km) where R, S, and Km are the reaction rate, concentration of substrate, and the Michaelis-Menten constant, respectively. By setting the intercept of this line to zero, the proper Km will be obtained and the slope would give the saturation rate, Vmax. As a result, a nonlinear, two-parameter optimization is simplified into finding the roots of a nonlinear equation. Generated data sets were used... 

The thorough knowledge of the asphaltene aggregation phenomena and pressure/temperature related kinetics is helpful for accurate prediction/control of the asphaltene issues in all facets of petroleum production/processing. However, characterizing the asphaltene aggregation phenomena in live oils at high pressure-high temperature conditions is not well discussed in the available literature. In this work, the asphaltene aggregation phenomena as well as the kinetics of aggregation at different levels of pressure and temperature are investigated in light and heavy live oils using high pressure microscope. The results are presented and discussed in terms of asphaltene onset pressure, aggregates... 

The oxidation behavior of three types of stainless steels, namely AISI 321, AISI 316, and AISI 409, was compared. In all stainless steels, oxide layers were formed and their masses and thicknesses increased with oxidation time. Among them, AISI 409 ferritic stainless steel demonstrated higher oxidation rate. According to the kinetical oxidation behavior of them at elevated temperatures, the oxidation mechanism was determined. Among them, the AISI 409 ferritic stainless steel showed the lowest and AISI 321 austenitic stainless steel demonstrated the highest oxidation resistance. Based on the experimental results, it was suggested that the kinetic of oxide growth in stainless steels was... 

This study deals with the large-scale production of biosurfactant from soybean oil soapstock by Pseudomonas aeruginosa MR01. The production of biosurfactant was carried out in a newly designed bioreactor equipped with recycling flow under three operational conditions. Kinetic studies were conducted at both shake flask and 5-L bioreactor scales during fermentation in a soapstock medium. Mathematical equations were developed to model the kinetic patterns at both scales. RESULT: Statistical analyses demonstrated the goodness of fit, with regression r-squared, R2, between 0.97and 0.99 for different models. Furthermore, biosurfactant concentration in the bioreactor including the recycling flow,... 

The pyrolysis of low-volatile Tabas anthracite coal was investigated by thermogravimetric technique (TGA) in the temperature range from ambient to 1100 °C under non-isothermal heating conditions (1.5, 3, and 7 °C/min heating rates). Higher heating rates showed a small retarding effect on devolatilization toward higher temperatures. Iso-conversional method was used for the kinetic study of non-isothermal Thermogravimetric data. Activation energy calculated for coal conversion of 20–80% was about 319 kJ/mol which may be a result of stable ordered structure of this type of coal. Analysis of evolved gases by Fourier transform infrared spectrometry (FTIR) in 7 °C/min heating rate was conducted... 

The synthesis of cheap and environmental friendly adsorbent from residual sugarcane bagasse was done for the removal of naphthalene from aqueous solution. The activated carbon dot was obtained by KOH chemical activation of carbon dots. The characteristics of carbon dots and activated carbon dots were determined using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e., initial pH, initial naphthalene concentration, adsorbent dosage, and contact time. The kinetic data showed better fit to the... 

12-tungstophosphoric acid, polyoxometalate with Keggin structure, and γ-Al2O3 were synthesized. Loading of 12-tungstophosphoric acid (HPW) on γ-Al2O3 was performed by the post-impregnation method. The catalysts were characterized by XRD, SEM, FTIR, BET, and DRS techniques. According to the pertinent observation, using the post-impregnation method promises the stability of polyoxometalate Keggin structure after loading on γ-Al2O3 support. The stability of 20 %HPW/Al2O3 was also confirmed by a leaching test. Textural characterization demonstrates that HPW on the γ-Al2O3 had a much larger surface area as compared with the pure HPW. The 20 %HPW/Al2O3 exhibited roughly high activity toward an... 

Abstract: The magnetite (Fe3O4) nanoparticles were synthesized and supported on the reduced graphene oxide. The characterization of the catalyst was performed by FT-IR, VSM, SEM, XRD, and BET techniques. The obtained results indicated that the in situ synthesis of Fe3O4 using coprecipitation method caused the homogenous formation of magnetite nanoparticles on the surface of reduced graphene oxide (average particle size ~ 71.032 nm) with high stability and catalytic activity toward electro-Fenton removal of Reactive Red 195. The effect of various factors (current intensity, initial pollutant concentration, catalyst weight, and pH) was evaluated by response surface methodology using central... 

The chitosan/poly vinyl alcohol membrane was modified by addition of some amine group to the membrane structure utilizing polyethyleneimine (PEI) in order to increase ionic metals adsorbent properties of the membrane. The removal percentage of the modified membranes was compared with the pristine membrane and activated carbon as common adsorbents. The membranes were characterized by FTIR, SEM, swelling degree and porosity measurement. The removal percentage of the membrane containing 0.5 wt.% PEI was more than 60% higher than the activated carbon and more than 40% higher than the pristine membrane. The modified membrane showed excellent adsorption capacity of 112.13, 86.08, and 75.5 mg/g for... 

Pyrolysis is a commonly used method for the recovery of used lubricating oil (ULO), which should be kinetically improved by a catalyst, due to its high level of energy consumption. In this research, the catalytic effects of carbon nanotube (CNT) and graphene nanoplatelets on the pyrolysis of ULO were studied through thermogravimetric analysis. First, the kinetic parameters of ULO pyrolysis including activation energy were calculated to be 170.12 and 167.01 kJ mol−1 by FWO and KAS methods, respectively. Then, the catalytic effects of CNT and graphene nanoplatelets on pyrolysis kinetics were studied. While CNT had a negligible effect on the pyrolysis process, graphene nanoplatelets... 

The present study dealt with the mechanism of competitive adsorption of Sb(III) and Fe(II) ions from a copper-containing aqueous solution on Purolite S957, a commercially available cationic ion-exchange adsorbent. Experiments were conducted using aqueous copper sulfate solutions containing either single or conjoint ions, using both sedentary and batch adsorption techniques to ascertain the sensitivity of the adsorption process to variation in pH, mass of resin, contact time, and temperature as well as establishing the optimal range of variables for maximum ion removal. The data from single ion adsorption tests were fitted by non-linear regression techniques to Henry, Langmuir, Freundlich,... 

In the present work, the novel ternary Fe2O3/MoO3/AgBr photocatalyst with different dosages of AgBr was successfully synthesized via a facile method. The physicochemical properties of the resultant catalyst were characterized by using various techniques such as XRD, SEM, EDX, BET, XPS, DRS, and VSM. The photocatalytic performance of as-prepared samples was evaluated by degradation of organic dye acid blue 92 (AB92) under visible light irradiation, and in dark. The impact of different operating parameters namely calcination temperature, amount of photocatalyst, dye concentration, and pH of solution were investigated in degradation reaction. Ternary nanocomposite exhibited the best... 

In this experimental study, a kinetic model has been developed for Fischer-Tropsch synthesis reactions by using sol-gel technique and Fe/Ni/Al 2O 3 as the catalyst (40% Fe/60% Ni/40 wt.%Al 2O 3) in a differential fixed-bed micro reactor assuming no internal or external diffusion. Operating conditions of the reactor were as follows: total pressure 1-12 atm; Temperature 220-260 °C; H 2/CO feed ratio 1.5-2; gas hourly space velocity 2100-7000 cm 3(STP)/h/ g cat and conversions of 6-37% of hydrogen and 7-21% of carbon monoxide. Mass transfer limitations were investigated by changing synthesis gas velocity in reactors which differ in size. Based on the hypothesis that water inhibits the intrinsic... 

Dinuclear cis-dioxomolybdenum(VI) complex [{MoO 2(Bz 2Benzenediyldtc)} 2] coordinated by a quadradentate dithiocarbamate (Bz 2Benzenediyldtc 2- = 1,4-benzenediylbis(benzyldithiocarbamate)(2-)) has been prepared and characterized by elemental analysis, 13C NMR, IR and UV-vis spectroscopy. The kinetics of the oxygen atom transfer between [{MoO 2(Bz 2Benzenediyldtc)} 2] and PPh 3 was studied spectrophotometrically in CH 2Cl 2 medium at 520 nm and four different temperatures, 288, 293, 298 and 303 K, respectively. The reaction follows second order kinetics with the rate constant k = 0.163(2) M -1 S -1 and its increasingly strong absorption at 520 nm clearly indicate the formation of a μ-oxo... 

Abstract: The magnetite (Fe3O4) nanoparticles were synthesized and supported on the reduced graphene oxide. The characterization of the catalyst was performed by FT-IR, VSM, SEM, XRD, and BET techniques. The obtained results indicated that the in situ synthesis of Fe3O4 using coprecipitation method caused the homogenous formation of magnetite nanoparticles on the surface of reduced graphene oxide (average particle size ~ 71.032 nm) with high stability and catalytic activity toward electro-Fenton removal of Reactive Red 195. The effect of various factors (current intensity, initial pollutant concentration, catalyst weight, and pH) was evaluated by response surface methodology using central... 

A simple bio-conjugation procedure to surround a single horseradish peroxidase (HRP) enzyme molecule with dendritic polyester macromolecules (polyester-32-hydroxyl-1-carboxyl bis-MPA dendron, generation 5) was proposed. The characterization of resultant nanoparticles entitled HRP dendrozyme, was performed by transmission electron microscopy, dynamic light scattering, gel permeation chromatography and Fourier transform infrared spectroscopy. The results showed that HRP nanoparticles were spherical in shape and have an average size of 14 ± 2. nm in diameter. Furthermore, bio-conformational characterization of HRP dendrozyme was performed by means of circular dichroism and fluorescence...