Sharif Digital Repository

There are more than one million motorcycles in the city of Tehran that are responsible for significant amounts of various air pollutants emissions such as carbon monoxide and hydrocarbons. Oxidation catalysis, as the exhaust aftertreatment system of motorcycles, can reduce the emission of CO and hydrocarbon pollutants. The efficiency of these catalysts under typical operating conditions of vehicle exhaust gas has been studied in the literature. However, due to the specific features of motorcycles exhaust gas in Tehran, such as ultra-rich combustion, low air to fuel ratio (lambdas as low as 0.6-0.7), different exhaust gas composition and significant amount of lubricating oil consumption,... 

Vehicle exhaust gas catalysts play a significant role in air pollution control. In order to solve the problems of cold start and limited supply of precious metals, new studies have focused on the development of three-way catalysts for gasoline vehicles with small amounts of precious metals and increase thermal stability. Different metal ions, especially rare earth metals, due to different physical and chemical properties, show different reinforcing effects on the properties of ceria-zirconia-based materials. Previous studies have shown that the enhancing effect of these materials and the ceria-zirconia ratio on catalyst activity and stability, as well as studies on thermal stability at 1050... 

According to the reports of the Tehran Air Quality Control Company, mobile sources are responsible for the emission of 70-85% of air pollutant in this metropolis. Over the past decades, compressed natural gas (CNG) is known as a cleaner fuel and a suitable alternative to gasoline and diesel fuels in the transportation section in some countries. However, methane emissions from natural gas vehicles is a significant challenge because it is a potent greenhouse gas and plays important role in global warming. In addition, because of another pollutant emissions from these vehicles, exhaust gas treatment is a crucial issue. Using Three-Way catalysts (TWC) is the conventional method in order to... 

Diesel oxidizing catalysts (DOCs) based on precious metals of Platinum and Palladium are among the most important and most widely used catalysts in the exhaust aftertreatment system of diesel cars. DOCs are used to oxidize CO and hydrocarbons to reduce their emissions to the environment. In spite of the excellent performance of DOCs, sulfur exposure can lead to their deactivation. Sulfur is mainly in the form of SO2 at the combustion chamber exit, which can be further oxidezed to SO3 on the DOC. The deactivation impact of SO2 and SO3 on DOCs are different, with SO3 leadig to higher degrees of deactivation. In this study, a kinetic model for SO2 oxidation on a bimetallic Pt-Pd-based catalyst... 

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... 

The susceptible light-harvesting and tremendous reduction capability along with the potentiality (photo)electrochemical merits of the thiospinels like CuCo2S4 (CCS) bring forth appreciably an advancement in efficacious photocatalytic reactions. However, scant oxidation potential originated from 3p orbitals of sulfur atoms puts a damper on their performance and is even conducive to self-oxidation. In this research, the surfactant/template free of hierarchical CCS thiospinels was synthesized using solvothermal sulfidation of the affordable glycerate-based CuCo-alkoxide and successfully was embedded with Z-scheme V2O5 deposited on wrinkled g-C3N4 lamella (VO-UCN) in the interest of developing... 

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... 

One of the major environmental problems in recent years is the presence of micropollutants that cause many problems for the environment and living organisms. Diclofenac is one of the micropollutants and endocrine disruptors. Conventional treatment methods do not have the ability to effectively remove pharmaceutical pollutants and micro-pollutants, and finding a suitable approach to remove these pollutants is of great importance. In recent years, biological methods such as the use of enzymes and molds have received attention, but due to the relative removal of pollutants, these methods have been combined with membrane technology to improve the level of pollutant removal and increase the... 

The photoreduction of CO2 to produce renewable solar fuel known as artificial photosynthesis attracted a lot of attention during the last two decades due to the global warming issue caused through increasing CO2 and shortage of fossil fuels resources. In this study, in order to enhance photocatalytic process of CO2 under visible light, TiO2-graphene and TiO2-copper nanocomposite utilized. A series of Cu/TiO2 photocatalysts were prepared with various Cu (2, 5 and 8 wt%) and a series of G/TiO2 photocatalysts with different graphene (G) content (5, 20 and 40 wt.%) were prepared and tested for the reduction of CO2. XRD, BET, DRS and TEM analyses employed to characterize the catalyst while the... 

Environmental regulations with respect to the marine diesel emissions have become stricter during recent years, thereby imposing traffic limitations on Iranian ships preventing them to enter emission control areas. Nitrogen oxides (NOx), as one of most important air pollutants, have adverse impacts on public health and ecosystem, so as the ships are the primary source of NOx internationally, the after-treatment system finds more urge to be developed. In this study, a NOx reduction system using non-thermal plasma technology is studied in order to determine its application and efficiency for NOx removal from the exhaust gas of Iranian marine diesel engines. Meanwhile, important factors were...