Sharif Digital Repository

Highly active unsupported MoO3 and (Co) MoO3 catalysts were synthesized utilizing the solution combustion method where the Ammonium molybdate powder and an organic additive were used as precursors. Different organic materials including Ethylene Diamin Tetra-acetic acid (EDTA), Polyethylene Glycol 200 (PEG 200), Sorbitol and Urea were used as additive in order to investigate the effect of additive structure on morphology and particle size of products. Also various reaction parameters such as the additive/Mo molar ratio, concentration of metal ion in solution, pH of the reaction and temperature of the synthesis media were changed to study effects on product morphology and size. Outcomes were... 

Natural gas (NG) has emerged as an alternative energy source in transportation sector as it provides clean combustion and hence lowers exhaust pollution. NG can be stored as an adsorbed phase in porous materials and is referred to ANG. The use of adsorbent materials for storing NG, at relatively low pressure (3.5–4 MPa), is a possibility for making ANG technology competitive with CNG. Among all adsorbents, carbon nanostructures with pore diameter (0.8-1.4 nm) has shown the highest adsorption capacity of natural gas. In the present study, cellulose has been used as the carbonaceous precursor and Activated Carbon (AC) has been prepared using hydrothermal carbonization of cellulose followed by... 

Monolithic nanocatalysts for naphta hydrodesulfurization process have been prepared and evaluated. Commercial cordierite monolith was used as a ceramic substrate. Initially, the monoliths were pretreated with nitric acid solution in order to increase specific surface area. After that, carbon nanotubes were grown through catalytic decomposition of methane over prepared monoliths. Finally, the CNT-coated monoliths were oxidized with ozone and an aqueous solution of H2O2. For the preparation of HDS Co-Mo nanocatalysts, the metal content of aqueous solution including cobalt nitrate, ammonium heptamolybdate were then impregnated onto the prepared supports. Next, samples of prepared supports and... 

One of the most important world issues is environmental constraints regarding the pollutants released by transportation fuels and refinery products, sulfur reduction being one of the most significant objectives. Deep hydrodesulfurization processes result in great sulfur reduction in refinery streams. However, such harsh process conditions increase undesired side reactions and facilitate coke formation as well as affecting the surfaces. More effective alternatives for hard process conditions are highly active and selective hydrodesulfurization catalysts, which enable the process to be performed at milder pressure and reaction conditions. Catalyst bases play a very important role in hydrogen... 

In this research convective heat transfer coefficient enhancement of nanofluids prepared from high surface area graphene has been investigated in laminar flow in the developing region. The nanofluid has been prepared from nanoporous graphene with high surface area and with concentration of 0.025 to 0.1 %wt. Deionized water has been used as the base fluid and a type of Ter-Polymer has been utilized as the surfactant. The results indicate that thermal conductivity of nanofluid with concentration of 0.1 %wt remains quite constant, with only %3.8 enhancement, while convective heat transfer coefficient improves significantly, with 34% enhancement. The behavior of this enhancement related to the... 

In the current work, jatropha oil was studied in the hetrogenious solid catalytic transesterfication reaction. For this perpous, KOH/CNT catalyst which was prepared by dry impregnation method was used. SEM, XRD and TGA were applied for the catalyst characterization. The results showed that for the KOH/CNT catalyst, by increasing the loading of KOH, the activity of the catalyst increased and the most active catalyst was prepared by 20% loading of KOH. The optimum conditions for transesterfication reaction in the percense of this catalyst were: 4.7% catalyst weigth and the 24.5 molar ratio of methanol to oil and also the reaction time of 2 houres which the rate of reaction at this time is... 

In this research, molybdenum and tungsten catalysts modified with cobalt and nickel on a carbon support have been synthesized and investigated in the oxidation desulfurization process. A model fuel was used to evaluate the synthesized catalysts. This model fuel was n-decane. dibenzothiophene was also used as a sulfur model. The synthesized catalysts were subjected to various analyzes such as XRD, FTIR, Raman, BET-BJH, NH3-TPD, TEM and ICP-OES for structural evaluation. On the other hand, synthetic parameters such as metal loading rate, molar or weight ratio of secondary metal (cobalt and nickel) to primary metal (molybdenum and tungsten) and molar ratio of citric acid to primary metal as... 

The selective oxidation of H2S into elemental sulfur is a complementary desulfurization method for reducing H2S emissions from gas streams. Several studies have been conducted in recent years to develop active, selective, and stable catalysts. The purpose of this research is to develop a catalyst with high activity and selectivity that is suitable for the gas output of one of the country's refineries. For this purpose, three supports of mixed metal oxide (solid solution), Ce-Al, Ce-Si, and Ce-Zr with a molar ratio of 1:2 (ceria: metal) were made by the co-precipitation method. In the following, three samples named 10V-CeAl, 10V-CeSi, and 10V-CeZr were prepared by impregnating 10% wt vanadium... 

In this study, thermal and rheological properties of nanofluids of water/carbon nanotubes, water/spherical silica nanoparticles and water/hybrid nanoparticles (hybrid of carbon nanotubes and spherical silica nanoparticles) have been investigated. To do so, carbon nanotubes have been synthesized by CCVD process and spherical silica nanoparticles and hybrid nanoparticles by wet chemical method. After synthesis of nanomaterials, nanofluids have been prepared by using SDBS as a dispersant with the concentration of 1.5 times of concentration of nanomaterials and then thermal conductivity, kinematic viscosity, dynamic viscosity and density of nanofluids have been investigated. As the results show,... 

Due to the potential risk of sulfur compounds in fossil fuels and according to today’s regulations, sulfur content should be kept as low as possible, e.g., below 5 ppm. Mercaptans are one of the sulfur components in natural gas. Scope of this research defined as catalytic removal of ethyl mercaptan from the gas stream. For this purpose, two microreactor systems placed in series. In the first microreactor, catalytic decomposition of ethyl mercaptan has been investigated. In the first step of this survey, a microreactor with 24 microchannels with a newly designed distributor has been developed with a computational fluid dynamic technique. in comparison to the conventional triangular... 

Due production and use of large amount of chemical and emissions of pollutants in air, detection and control of these compounds are necessary. One of the common methods to detect these pollutants in the ambient is using metal oxide semiconductor sensors. However, these types of sensors suffer from low selectivity toward a certain compound in the mixture of different gas components. In this study, the object was to investigate the effect of different amount of CNTs on performance of tin oxide to improve their selectivity for detection of 50 ppm of hydrogen sulfide at low temperature. To perform the study, nanoparticles of pure tin oxide and SnO2 base hybrids containing 0.25wt%, 0.5wt%, 2.5wt%... 

Monitoring is of particular importance after impounding and during dam operation. In all large dams, by installation of the required instruments the pore pressure, soil mass pressure and displacement during construction, first impounding and operation are measured, then the performance of dam will be analyzed and evaluated. The aim of this study is to evaluate the performance of the "Gavoshan" dam, which has an important role on agriculture development and drinking water supply at west part of Country. To reach this, the values resulting from instruments have been implemented by FLAC software, using "Back Analysis" method. However, this assessment is complete when "back analysis" method is... 

When demand for a product is price sensitive, pricing and lot sizing decisions are interdependent. Similarly, when a product is highly perishable, the demand may need to be backlogged to avoid costs due to deterioration, i.e., perishability and backlogging are complementary conditions.In this thesis we stablish two economic production quantity models for deteriorating items under conditions of finite production, exponential decay and partial backordering and lost sale. Two joint pricing inventory control models are developed for the problem by employing different modeling approaches over an infinite planning horizon. In two models, customer is viewed to be impatient and the fraction of the... 

Simultaneous localization and mapping (SLAM) is the action of detecting robot pose in an unknown environment and building the environment map by use of input data that captured from robot sensors. In visual SLAM, the input data for the robot, is limited to camera sensors. Nowadays, SLAM is one of the main challenges in robotic research.For autonomous action, we need robot pose in the map of the environment. The map production in the indoor environment, there is no GPS data, is one of the research issue in robotic community, in last decade. In this thesis, a new and efficient method is proposed for SLAM at the level of objects. The maps produced by state of the art methods don’t have a... 

Oil/water separation is an important field, not only for scientific research, but also for environmental, economic, and social issues. On the one hand, oily wastewater, resulting from industries such as steel, aluminum, food, textile, leather, petrochemical and metal finishing, has become the most common pollutant all over the world. On the other hand, frequent oil spill accidents are of great concern since the discharge can lead not only to serious environmental pollution, but also a great loss of energy.
In crude oil removing water is necessary due to reducing corrosion, increasing thermal values of fuels obtained from crude oil, preventing catalists from destruction by water and... 

Breast cancer is the most common type of cancer in women and the second cause of death among them. The chance of successful treatment would be significantly increased if the disease is diagnosed at its early stages. There are numerous methods to diagnose breast cancer. One of the most important methods is positron emission mammography (PEM).The main aim of this study is to investigate the feasibility of improving PEM images by considering the time of flight corrections and the penetration depth of the rays in the crystals.In this study, a commercial PEM system, Naviscan PEM, is simulated using the GATE software. In the first phase of the study, two opposing planar detectors are used to study... 

Direct speech-to-speech translation, in which all compontents are trained jointly, is advantageous over cascaded approaches, because this method employs a simple yet effective pipeline to produce the outputs with a little inference time. Direct speech-to-speech translation models suffer from data scarcity issue, because they need parallel speech data in source and target languages. In this thesis, we present a novel direct speech-to-speech translation model to translate Persian speech to English, which is based on discrete speech units and uses a conformer-based encoder which is pretrained and a transformer-based causal decoder which uses relative position multi-head attention to do the task... 

So far, much research has been done on severe plastic deformation of aluminum alloy 2024, but there is limited information on the effect of artificial aging for this alloy in the supersaturated, post-MDF state. As one of the methods of extreme plastic deformation process, multidirectional forging process (single pass) has been performed on different alloys including aluminum alloy 2024 at ambient temperature. Alloy 2024 was subjected to solution treatment at 500°C for 1 hour and multi-directional forging process was immediately performed on it. Then, at temperatures of 100, 140, 190, 240, and 290 °C, the aging process was continued for one hour until artificial aging. In order to investigate... 

Platinum is one of the most used catalysts in refining and petrochemical industries. Also, Platinum uses in other industries like automobile catalytic convertor. As respect to importance of Platinum in these industries, growth of its consumption in recent decades and its very high price, recovery of Platinum is essential. Hence, many of various methods including hydro-metallurgy are applied. In despite of these wide spreading experimental investigations, due to low information about the reactions and the nature of reaction products, a few investigations were done on kinetics of Platinum recovery. A new method that used iodine solution to extract Platinum from spent reforming catalysts was...