Sharif Digital Repository

Tabas coal sample from Iran was desulfurized with combination of microwave irradiation and peroxyacetic acid washing in a batch reactor. The effect of irradiation time and power, peroxyacetic acid reaction time and temperature and particle size on reduction of sulfur was investigated. For microwaved/acid washed samples, depending on desulfurization conditions, the reduction in pyritic, organic and total sulfur ranged from 26 to 91, 2.6 to 38.4 and 17 to 65%, respectively. Microwave irradiation had positive effect on desulfurization with peroxyacetic acid. For <300 μm size fraction, after irradiation, the reduction enhanced from 49.9 to 86.6% in pyritic sulfur, 23.8 to 35% in organic sulfur... 

The purpose of this study was to develop a computational model to simulate the dynamics of intraocular gas behavior in pneumatic retinopexy (PR) procedure. The presented model predicted intraocular gas volume at any time and determined the tolerance angle within which a patient can maneuver and still gas completely covers the tear(s). Computational fluid dynamics calculations were conducted to describe PR procedure. The geometrical model was constructed based on the rabbit and human eye dimensions. SF6 in the form of pure and diluted with air was considered as the injected gas. The presented results indicated that the composition of the injected gas affected the gas absorption rate and gas... 

Production and oscillation of sonoluminescence bubbles by laser pulse in the presence of acoustic field in water and different concentrations of sulfuric acid are investigated. In the presence of acoustic field, the laser causes variable speed of sound, surface tension and density; and the host liquid acts as a compressible one and strongly affects the bubble's dynamics equations. The effect of various concentrations of sulfuric acid as a host liquid on the oscillation of bubble radius, bubble wall velocity and bubble interior temperature is studied. Furthermore, the effect of applied frequency on LI-SCBL in the presence of the acoustic field is investigated and an optimum sound wave... 

Lithium-Sulfur (Li-S) batteries are considered as one of the promising candidates for next-generation Li batteries in near future. Although, these batteries are suffering from certain drawbacks such as rapid capacity fading during the charge and discharge process due to the dissolution of polysulfides. In this paper, Sulfur/metal oxide (TiO2 and SiO2) yolk-shell structures have been successfully synthesized and utilized to overcome this problem and improve the electrochemical performance of sulfur cahtode material. Prepared materials have been characterized using Scanning Electron Microscopy(SEM), Transmission Electron Microscopy(TEM) and X-ray diffraction (XRD) techniques. The results show... 

The oxidative desulfurization of a real refinery feedstock (i.e., non-hydrotreated kerosene with total sulfur mass content of 0.16%) with a mixture of hydrogen peroxide and acetic acid was studied. The influences of various operating parameters including reaction temperature (T), acid to sulfur molar ratio (nacid/nS), and oxidant to sulfur molar ratio (nO/nS) on the sulfur removal of kerosene were investigated. The results revealed that an increase in the reaction temperature (T) and nacid/nS enhances the sulfur removal. Moreover, there is an optimum nO/nS related to the reaction temperature and the best sulfur removal could be obtained at nO/nS8 and 23 for the reaction temperatures of 25... 

In this study, a combination of energy and exergy analysis is applied for the industrial sulfur recovery unit (SRU) in commercial simulation software. The data of energy and exergy are obtained from the simulator and Excel (for physical and chemical exergy), respectively. In doing so, five intensified SRU configurations namely: (1) hot gas bypass (2) acid gas bypass (3) inlet stream preheating (4) acid gas enrichment and (5) oxygen (air) enrichment are compared in terms of energy production, reaction furnace temperature, sulfur recovery and pollutant emission into environment. Then, irreversibility in these five arrangements is compared and all the proposed methods show higher useful exergy... 

At room temperature, alcohols and phenols are efficiently protected with hexamethyldisilazane (HMDS) in the presence of silica sulfuric acid in good to excellent yields. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. Copyright © Taylor and Francis Group, LLC  

Microbiological analyses of soil chronically exposed to petroleum complex compounds of some oil springs in south of Iran resulted in isolation and purification of a new native thermophilic strain which is capable to desulfurize petroleum sulfur compounds by 4-S mechanism. Dibenzothiophene (DBT) was selected as a complex sulfiir compound model and many experiments were done to identify the metabolic pathway. The results of these experiments show that DBT is ultimately converted to 2-hydroxybiphenyl (2-HBP) and sulfite. This is a special metabolic pathway in that there is no effect on the carbon skeleton of organic compounds and would be ideal for desulfurization to upgrade the petroleum... 

A standard simulating technique test was investigated to assess the atmospheric corrosion behavior of silver coating. The rates of formation of corrosion products were measured in the simulating atmospheres of 100% humidity containing SO 2,H 2S and a complex atmosphere consist of SO 2,H 2S and NO 2 gases ,based on the mass increase method. The concentrations of corrosive gases were chosen according to real world conditions. XRD, SEM and EDS were used to examine the morphology and to determine the composition of the corrosion products under different experimental conditions. Results revealed the formation of Ag 2SO 4 and Ag 2S on the silver coating surfaces in the SO 2 and H 2S containing... 

A combination of silica sulfuric acid and potassium chlorate or oxone® and silica chloride in the presence of wet SiO2 was used as an effective oxidizing agent for the oxidation of urazoles and bis-urazoles to their corresponding triazolinediones under mild and heterogeneous conditions with moderate to excellent yields. © 2006 Elsevier B.V. All rights reserved  

Background: To meet stringent emission standards stipulated by regulatory agencies, the oil industry is required to bring down the sulfur content in fuels. As some compounds cannot be desulfurized by existing desulfurizing processes (such as hydrodesulfurization, HDS) biodesulfurization has become an interesting topic for researchers. Most of the isolated biodesulfurizing microorganisms are capable of desulfurization of refined products whose predominant sulfur species are dibenzothiophenes so biocatalyst development is still needed to desulfurize the spectrum of sulfur-bearing compounds present in whole crude. Results: The first desulfurizing bacterium active at 60 °C has been isolated,... 

Presence of sulfur components in liquid fuels should be controlled due to environmental issues and process considerations. In order to decrease the level of sulfurous compounds in crude gas-oil with 5750 ppmw sulfur, electrochemical oxidative desulfurization has been investigated over electrodes of copper and stainless steel because of their easy operation and mild process conditions. In this research, the effects of stirring rate, temperature, applied potential, sodium hydroxide addition as electrolyte media and water volume have been examined on the sulfur removal efficiency. The results show that electrical conductivity of gas-oil sharply increases with addition of electrolyte up to 613... 

Sulfur compounds are essential for many industries and organisms; however, they cause serious respiratory problems in human beings. Therefore, determination of sulfur concentration is of paramount importance. The research approach in the field of detecting contaminants has led to smaller systems that provide faster and more effective ways for diagnosis purposes. In this study, a novel portable amperometric graphene oxide–protein biosensor platform is investigated. The main characteristic of this structure is the implementation of a microfluidic configuration. With albumin metalloprotein as the biorecognition element, graphene oxide was synthesized and characterized by transmission electron... 

The effect of ambient temperature on the parameters of the single-bubble sonoluminescence in sulfuric acid (SA) diluted in water is studied. Using a hydrochemical model, three dominant instabilities of shape, Bjerknes, and diffusion are considered. The phase diagrams of the bubble in the (R 0 - P a) space are presented, and the parametric dependence of the light intensity is discussed. In contrast to water, the calculated thermal-bremsstrahlung mechanism of light emission at the fixed degassing condition of high SA concentrations shows that, with increasing the temperature of aqueous SA solutions, the light intensity increases. However, at diluted SA solutions similar to water, the light... 

An experimental study was conducted on the desulfurization of non-hydrotreated kerosene with oxidation followed by liquid-liquid extraction. Various types of solvents including acetonitrile, methanol, and ethanol have been examined in the extraction of oxidized sulfur-containing compounds of kerosene. The performance of these solvents has been carefully examined and compared. It was found that their performance follows the order: acetonitrile > methanol > ethanol. The effects of number of extraction stages and solvent to kerosene ratio on the desulfurization and recovery of kerosene have been investigated. The experimental results show that for all three solvents, solvent/kerosene ratio and... 

Metal pH50 and ΔpH50 values were determined and compared for a number of organic systems to select a synergistic system for the separation of Cd from Zn. The largest ΔpH50(Zn-Cd) value was obtained with HRJ-4277 (nonylsalicylic acid)/Cyanex 471X (triisobutyl phosphine sulphide or TIBPS) system and reached 1.53 pH units, indicating excellent separation of Cd from Zn with this system. Shellsol 2046 was chosen as the diluent of the system due to its larger ΔpH50(Zn-Cd) and excellent phase separation compared with other diluents. Distribution isotherms and subsequent McCabe-Thiele diagrams indicate that 99% Cd could be extracted in two stages at pH 3.80 and A / O ratio of 1.5 : 1. The extraction... 

An experimental study was conducted to investigate the extraction of oxidized sulfur compounds from gas oil. Solvents used for this purpose included acetone, acetonitrile, methanol and propanol. The effect of solvent concentration, solvent to gas oil ratio, temperature, time and number of stages was studied. To select the best solvent and conditions for extraction, two criteria were considered: high desulfurization and more hydrocarbon recovery. Results showed that extraction time and temperature have no significant effect. Methanol for low ability of extraction of oxidized sulfur compounds and propanol for low hydrocarbon recovery were excluded from further experiments. After the tests, the...