Sharif Digital Repository

To study the kinetics of the yttria-stabilized zirconia produced by co-precipitation method from the chemical engineering point of view, this process was studied in two parts of hydrolysis and precipitation. the hydrolysis reaction was studied by titration method, and the rate constant and fraction of formation of hydrous zirconia was determined by applying Avrami equation. The results showed that the percentage of zirconia formation until the boiling time of 12 hours was zero and after 48 hours boiling was 2.81%. moment definitions were used In order to study the kinetics of precipitation. changes in precipitated powder concentration with pH of the solution was obtained based on the... 

In this study the kinetics of extraction of various hydrocarbons from crude oil using supercritical CO2 has been studied experimentally. The effect of parameters such as temperature (35, 45, 55, 65 °C), pressure (90, 110, 130, 150 bar), initial volume of crude oil (16, 19, 22, 25 mL) were investigated. Flow rate of gas has been recorded dynamically. QUALITECH 4 and MATLAB neural network softwares have been used for designing the experiments and modeling the final results, respectively. Pressure has a direct effect on extraction yield and by increasing it, heavier fractions could be obtained. On the other hand, the effect of temperature is more complicated, by increasing the temperature, the... 

In order to obtain more insight into the enzymatic oxygen-atom-transfer (OAT) process and elucidate the relation between the structure and function of the synthetic model complexes, new molybdenum and tungsten complexes containing different chelating ligands were systematically prepared and investigated. Herein, the cis-dioxo-molybdenum(VI) complexes with new aromatic dithiolene ligands, formulated as [MoO2(2,3ppdt)2]NR4 and [MoO2(3,4ppdt)2]NR4, (2,3ppdt= pyrido-2,3-pyrazine-2,3-dithiolato, 3,4ppdt= pyrido-3,4-pyrazine-2,3-dithiol and R= Et or Bu) were prepared and investigated by elemental analysis, IR, 1H NMR and UV-Vis spectroscopic methods. An OAT reaction of [MoO2(2,3ppdt)2]2– with PPh3... 

Nanophotocatalysts containing metal oxides and oxy-acids based on the nanoporous materials such as graphene, metal-organic-frameworks and carbon nano tubes were synthesized. The photocatalytic properties of the prepared samples were evaluated by the photodegradation of different pollutants in the suspension and emulsion photocatalytic systems. This study demonstrates a new kind of photocatalytic system via utilization of the superior specific properties inherent in Pickering emulsion. We designed the new photocatalytic system using a photocatalytic active component and hydrophobic conducting nanostructures to form the stabilized Pickering emulsion (Pe-bp system). The results revealed that... 

Dwindling fossil fuel reserves with attendant rising crude oil price and the relatively rapid growth in global population have made the search for sustainable energy supply more imperative. Among the various renewable resources, biomass has attract much more attention. Glycerol as the major by-product of the biodiesel production process, can be converted to hydrogen. One of the methods for converting glycerol to hydrogen is aqueous phase reforming (APR). In the current research, glycerol aqueous phase reforming is modeled and then simulated with MATLAB software. The reactor diameter is 5 mm and its length is 20 cm and reactor operated at 250℃ and 50 bar. Glycerol conversion obtained is... 

In recent years there have been a growing number of patients who are no more capable of leading an independent life, due to strokes, accident, or a variety of diseases. Thus, vast fields of physical rehabilitation have come into the attention of goverments and researchers. High costs of rehabilitation programs and their length on one hand, and the difficulties of commuting such patients to rehabilitation centers on the other hand, has made health department of various countries to look for alternative solutions.In this thesis, a computerized system has been designed and implemented in order to assess and guide patients in their rehabilitation excercises without needing any direct contact.... 

The kinetics of side reactions in dehydrogenation of propane over a supported platinum catalyst modified by tin was investigated. Catalytic dehydrogenation over a commercial Pt-Sn/γ-Al2O3 was carried out in a laboratory-scale plug-flow reactor at 580 to 620oC under atmospheric pressure. Several kinetic models derived from different reaction mechanisms were tested using experimental data obtained over a range of reaction conditions. It was found that the kinetics of the main dehydrogenation reaction was best described in terms of a Langmuir-Hinshelwood mechanism where adsorption of propane was the rate controlling step. Simple power low rate expressions were used to express the kinetics of... 

This work examines the dissolution kinetics of Sodium meta vanadate in water medium. The effects of temperature, solid/liquid ratio, agitation speed on the leaching kinetics were investigated. the dissolution kinetics was controlled by the internal diffusion at the surface of the Sodium metavanadate particles. The activation energy for the leaching was2/13 kJ/mol. In the current project, we report the preparation of VO_2 nanorods crystals using a ethylenediaminetetracetic acid assisted and Cetyl Trimethyl Ammonium Bromide hydrothermal synthesis route. NH_4 Cl and NaVO_3 solution were used as the starting materials and vanadiumoxide crystals were obtained following growth at 180 °C for 24... 

In view of environmental problems and the limited energy supply, synthesis of new liquid fuel from coal or natural gas is becoming a hot research in recent years. Dimethyl ether (DME) is one of the most promising alternates of such synthetic fuels. In this project the kinetics of direct DME synthesis from syngas (H2 and CO) over the new bifunctional catalyst has been investigated in slurry reactor system. A new mechanism and rate law expression were established. The kinetic model has been fitted the experimental data, which has been obtained by other researchers. The new bifunctional catalyst was composed of Cu/ZnO/ZrO2 and Al-modified H-Mordenite zeolite. The calculated apparent... 

Dimethyl Ether (DME) is a pure and economic fuel which can be used as a suitable alternative for diesel fuels. Two processes are traditionally used for DME synthesis: producing methanol from synthesis gas and then dehydrating it to DME (direct process), and converting methanol into DME in a catalytic dehydration reactor over a solid-acid catalyst (indirect process), in which the indirect process seems to have economical advantage. In this research, the γ-Al2O3 catalyst was synthesized through precipitation process and then characterized by powder X-ray diffraction (XRD) and porosimetry analysis. Afterwards this catalyst was utilized in methanol dehydration reaction in a slurry reactor. Next,... 

In this work, bioleaching was used to extract valuable uranium from a low grade ore. Bioleaching experiments were carried out in batch cultures using a native strain of Acidithiobacillus ferrooxidans. Experiments were conducted to investigate the effects of rotation speed, initial redox potential, initially added Fe concentration, particle size, pH, temperature, pulp density, and culture type. In the shake flask systems, over 99% of the uranium was bioleached in 48 hours at some conditions. Uninoculated flasks gave only around 25% leaching. At each study, uranium and iron concentrations, solution oxidation– reduction potential and pH were measured. The results showed that 150 rpm, d80=100 ... 

In this study, leaching of Sarcheshmeh Reverberatory Furnace Dust was investigated in the H2SO4-O3 media. Response surface methodology based on central composite face-centered design (RSM-CCF), was applied to optimize the operating parameters. The optimum conditions to obtain the main goal of maximum copper and minimum iron dissolution from dust were identified to be temperature of 30˚C, leaching time of 3hr, initial pH of 0.5, pulp density of 20% and ozone flow rate of 1g/h. The copper and iron concentrations of leaching solution were found to be 27.11 and 0.89983 g/L under the optimum conditions, respectively. The results showed that selective copper extraction from the dust could be... 

Over one million motorcycles operating in Tehran produce significant amounts of CO and unburnt hydrocarbons, thereby considered as one of the major contributors to air pollution in the city of Tehran. Oxidation catalysts, as emission control device, can reduce CO and hydrocarbon emissions from motorcycles. The efficiency of these catalysts under typical operating conditions of vehicles exhaust gas has been studied in the literature. However, due to the specific features of motorcycles exhaust gas in Tehran, such as low air to fuel ratio, different exhaust gas composition and significant amount of lubricating oil consumption, selection of a highly active, durable and cost-effective catalyst... 

Air pollution is one of the main environmental problems in Iran's metropolises, especially in the city of Tehran. Taxis have a significant contribution to pollution due to the long distances they travel during the day. Due to the fact that the operation of automotive three-way catalysts is a function of their operating conditions, and considering the different fuel composition in Iran and the specific conditions of engine performance, exhaust gas composition can be different from similar cases abroad. A commercial three-way catalyst was tested to evaluate its performance under conditions relevant to the exhaust gas of Tehran's taxis fleet. In this study, CO and C3H6 were considered as the... 

Sulfur components are one of the most important impurities in various petroleum fractions that cause many problems in refining and consumption. In this thesis, hydrodesulfurization process, which has an economical and environmental especial position in petroleum and other related industries, has been discussed. In hydrodesulfurization process, under specific operation condition, sulfur components are converted catalytically to the H2S in a fixed bed reactor. In this study dibenzothiophene, which is one of the most strength and complex sulfur components, is considered as the base component. A Langmuir-Hinshelwood kinetic equation is used to describe the reaction by using the commercial... 

The main focus of this thesis was on fluorescence sensors development based on carbon dots and deep eutectic solvents. Accordingly, an attempt was made to synthesize carbon dots and modified with deep eutectic solvents as biocompatible sensors. Eventually, development and application of these sensors in analytical systems ultimately led to satisfactory and comparable results with previous methods. In the first project, a rapid and miniaturized fluorescent probe based on the ultrasound‒assisted formation of carbon dots (CDs) in a metallic deep eutectic solvent (MDES) was developed and conveniently implemented to detect 4-MeI in commercial dark soft drinks. In-situ synthesis of CDs-chelated... 

Asphaltene are the heaviest components if some crude oil which are in thermodynamic equilibrium. Any change in the equilibrium condition including change in temperature, pressure or composition may render asphaltene to come out of solution and precipitate. Asphaltene precipitation and deposition is one of the main problems in some of the oil fields. Precipitated asphaltene may deposit in the reservoir, near wellbore, wellstring, transport pipeline and surface facilities. In porous media, the deposited asphaltene over the surface and/or across pore throat can severely reduce the effective permeability and results in decreasing of the oil production. Also, the deposited asphaltene results in...