Sharif Digital Repository

Mixing efficiency is an important performance indicator in many chemical reactors. In the present study, using a computational fluid dynamics model, the quality of micromixing in a double-disk-spinning reactor with the ability to rotate both disks using a fast iodide-iodate competitive reaction has been investigated. The purpose of this study was to investigate the effect of operational parameters such as the speed and direction of rotation of disks, radius and number of entry points of one feed, distance between disks, volumetric flow of feed, feed inlet nozzle diameter and acid concentration (H+) on quality of micromixing. The simulation results show that by increasing the rotation speed... 

Reaction parameters in precipitation processes have a significant impact on the product characteristics. The process of formation of yttrium-stabilized zirconia precipitates was studied by co-precipitation method to investigate the parameters affecting particle size distribution. These studies aimed to investigate the reaction parameters and determine their effect on the size of the particles, taking into account the effects caused by the interaction of the parameters. To achieve this goal, the design of the experiment based on response surface methodology was used and five parameters of zirconyl chloride concentration, molar percentage of yttrium oxide, reaction time, mass percentage of... 

Partial oxidation of methane (POX) is one of the most common processes to produce synthesis gas. In this study the kinetics of this process is examined and some reduced mechanisms are introduced to model it in this study. The experimental data from Research Institute of Petroleum Industry are used as reference experimental data. Inlets of this reactor are oxygen and methane with equivalence ratio between 2.53 and 2.9. Moreover, the experimental results of previous studies with the air as the oxidant in equivalence ration between 2.4 and 2.6 are used as basis for comparison of simulation results. During the first step, partial oxidation of methane in non-catalytic porous media is simulated by... 

The aim of this study is developing and investigating heterogeneous catalysts based on natural calcite for the transesterification of canola oil and methanol in order to produce biodiesel as a renewable and alternative fuel for fossil fuels. At first calcite was calcined at high temperature to decompose calcium carbonate to calcium oxide. Afterward, Mg-Zr/CaO catalysts were prepared with mass ratio of 2:1 Mg:Zr and different weight percent(2.5, 5,7.5 and 10 wt%) on calcite supported by impregnation method. In order to characterized synthesized catalysts used different analysis such as energy dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy... 

This project evaluates the feasibility of using waste salmon fish bones as the reusable and low cost solid catalyst support for synthesis of biodiesel from waste sunflower oil via transestrification method. Calcinated waste fish bone derived hydroxyapatite (HAP) was employed as the supporter for KOH & K2CO3 to prepare an efficient solid base catalyst for biodiesel production. The catalyst were characterized by SEM-EDS, XRD, FTIR, BET, TGA, ICP. The effects of catalyst preparation conditions (such as fish bone and KOH or K2CO3 calcination temperature, loading of KOH or K2CO3 on the support), reaction conditions (such as reaction time, methanol/oil molar ratio, reaction temperature and... 

This study aims at synthesizing and investigating of heterogeneous catalysts for biodiesel production as an alternative to fossil fuel with a transesterification reaction of sunflower oil and methanol. Three main sections of this thesis concern the synthesis of clay base catalyst, characterization analysis, and investigation of the transesterification reaction under different conditions. Talc clay base catalyst impregnated with a 40 wt.% of K2CO3 as active and stable catalysts to study the transesterification reaction of sunflower oil and methanol for biodiesel production. Synthesized catalysts have been characterized by power X-ray diffraction (XRD), scanning electron microscopy (SEM),... 

The aim of this project is to investigate and synthesize CaO-based nanocatalysts derived from chicken eggshell calcination with alkali metals and sodium-potassium compounds promoters used in the transesterification reaction of canola oil and methanol. Sections of this thesis include the synthesis of nanocatalysts, catalyst characterization tests, and investigation of reaction under optimal conditions. Two groups of catalysts containing different weight percentages of alkali metals based on CaO and 1 %wt sodium-potassium based on CaO with different weight percentages of these two elements were synthesized by wet impregnation method and used in the reaction under optimum condition. Catalyst... 

High mixing efficiency and high liquid-liquid mass transfer rate are two key features of spinning disk contactors. This work presents the experimental investigation of mixing and liquid-liquid mass transfer characteristics in a new double coaxial spinning disks contactor. The micromixing efficiency was investigated using a standard system of competitive parallel reaction known as iodide/iodate test reaction. The influences of various operating conditions such as the rotational speed of the disks, the direction of rotation, the feed radial location, the feed distribution pattern, the distance between the disks, and the feed flow rate on the mixing quality were examined carefully. The obtained... 

The purpose of this study is to study heterogeneous nanocatalysts for the production of biofuels by the method of exchange of styrene using oil and methanol as a fossil fuel alternative. Preparation of nanocatalysts, performing characteristic tests and investigating the reaction in different operating conditions in the batch reactor has already been studied. Therefore, in this study, the production of biodiesel fuel using the trans-esterification of canola oil with nanocatalysts in the micro-reactor reactor will be discussed. Previously, a heterogeneous catalyst (lithium based on calcium-lanthanum) was constructed using a co-incineration method and a wet inoculum, and as active and stable... 

The efficiency of acidizing operation is usually assessed through Build up or Drawdown test (calculation of skin). These methods are performed only after the acidizing operation, so it is impossible to evaluate the efficiency of acidizing during the real time operation. Analysis of the acidizing efficiency during the operation by using the acidizing operation data is a viable approach to this costly and challenging process. In this project, it has been tried to present a well testing method for calculating changes of skin value of a carbonate reservoirs during acidizing operation by using the real field data (surface pressure, injection rate and etc.).
The estimation of skin changes... 

In order to prevent the CCR catalysts from sintering and maintaining their acidity, some chloride compounds are added to these catalysts during regeneration process. The existence of these compounds in downstreams units and equipment causes problems such as corrosion, fouling, etc. Therefor for eliminating these chloride compounds from the exit stream a chloride adsorbent is used. The common compound that is suggested for this application is activated alumina for its high surface area. When Olefin or Aromatics exist in the stream, that is common in many units, a side reaction happens and green oil is formed. In this study, different factors in green oil formation has been studied. Although... 

Core-shell structures of Ag@Pt nanoparticles (NPs) dispersed on Carbon Vulcan XC-72, Multiwalled carbon nanotube and reduced graphene oxide (rGO) support containing different Ag:Pt mass ratios and applied to the oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell (PEMFC) were synthesized by the ultrasonic and reduction treatment method. The morphology of as-prepared catalysts characterized by the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and induced coupled plasma atomic emission spectroscopy (ICP-OES). The ORR activities and stabilities of catalysts were studied through electrochemical measurements utilizing the Cyclic Voltammetry... 

Nowadays, one of the most basic human problem is how to manage energy resources for sustainable development and how to deal with problems caused by growing energy consumption. Various scenarios are being discussd that the most important of them can be considered research on finding alternative energy sources that are renewable and do not have common pollution. Thus, according to researches carried out until now, using sources such as wind, water, solar biomass, etc. have been proposed. However, due to problems in the development of each of these sources, biomass as the primary option has been introduced. because biomass has several subsidiaries, research shows microalgaes (as a subset) are... 

This study aims at synthesizing and investigating of heterogeneous catalysts for biodiesel production as an alternative to fossil fuel with the transesterification of oil and methanol. Three main sections of this thesis concern the synthesis of nano-catalysts, characterization analysis, and investigation of the transesterification reaction under different condition. Two series of heterogeneous catalysts, including different molar ratios of X%Li/Ca-La (X=0-7%) and Ca/Talc (Ca, 3Ca/1Talc, 1Ca/1Talc, 1Ca/3Talc, Talc) has been synthesized as active and stable catalysts to study the transesterification reaction of canola oil and methanol for biodiesel production. Prepared catalysts have been... 

Biodiesel has drawn the attention of many researches to itself as a replacing source for crude oil, recently. Transesterification is one of the most popular methods used for biodiesel production. Enzyme transesterification is a more simple method in comparison with acidic or basic transesterification. However, the high price and low yield of enzyme transesterification has caused many obstacles in its application. Enzyme engineering has gained much attention as a way to improve enzyme performance. In this thesis, biodiesel production by a native enzyme named Bacillus thermocatenulatus, and two engineered-enzymes is studied. First, effective parameters and variables in biodiesel production by... 

Polydimethylsiloxane (PDMS) is one of the most important organosilicon elastomers. This polymer has a wide application such as medical engineering due to the unique characteristics, variety and ease of manufacture. Nowadays, the use of nanoparticles such as carbon nanotubes for improving the properties of elastomers is highly regarded owing to the fact that the improvement of properties such as mechanical properties broadens the applications of PDMS. Diamond nanoparticles has been the focus of numerous researchers in the past decade. In fact, nanodiamond has a good mechanical abrasion and thermal properties. In addition, the investigations proved that the nanoparticle is valuable in terms of... 

In this research, experimental study and modeling of biodiesel production process from microalgae has been investigated. First, to have a biomass with suitable lipid content, a novel two-step process based on cultivation under nutrient sufficient followed by cultivation under nitrogen starvation condition has been proposed. Then the effect of using different organic and inorganic carbon sources on this process has been investigated which the results indicated that sodium acetate had a better performance compare to other carbon sources. In the following, the effect of using different light regimes on growth rate, lipid content and fatty acid composition have been investigated. Experimental... 

In recent year's acrylamide as a suspected substance for tumor growth has been studied. In some researches this topic is mentioned that acrylamide is produced by the reaction of asparagine and natural sugars. This reaction takes place only at very high temperatures during the heating process. The maximum amount of this substance is determined in fried potato products. In this study, a response surface methodology (RSM) 5-level-3-factor face centre central-composite design (FCCCD) was applied to envestigate the effects of asparaginase (300-900 U/kg of flour), baking temperature (230-280 °c) and baking time (13-16 min) on acrylamide (AA) formation in yeast-leavened wheat bread and... 

In recent year's acrylamide as a suspected substance for tumor growth has been studied. In some researches this topic is mentioned that acrylamide is produced by the reaction of asparagine and natural sugars. This reaction takes place only at very high temperatures during the heating process. The maximum amount of this substance is determined in fried potato products. The purpose of this study was determined to remove and reduce acrylamide formation during frying of potato. Acrylamide production when it was blanching and when it was dipped in the enzyme solution of asparaginase was examined. When potato pieces were placed in a commercial enzyme solution 200 lU/ml, acrylamide formation was... 

In this project, the steady laminar flow coupled with heat transfer and chemical reactions corresponding to metal organic chemical vapor deposition (MOCVD) process in an axis-symmetrical rotating disk reactor has been simulated based on computational fluid dynamics (CFD) approach to optimize the parameters affecting the thickness of layer deposition. The simulation results have been validated with the benchmark solutions obtained from the literatures for the corresponding cases study. By genetic algorithms five geometrical structures have been optimized to achieve minimal radial changes in the rate of deposition. Using the optimum values, radial variations deposition rate of 22.7% decreased...