Sharif Digital Repository

One of the ways to address the modern traffic-related problems is to encourage people to use sustainable travel modes more regularly. Transportation planners need to find the factors that affect people’s opinions toward using these modes. In this study, we investigated these factors using a case study of a developing country by distributing an online survey among the students of four universities in Tehran. The number of complete responses received was 134 from SUT, 63 for UT, 31 from AUT, and 204 from IUST, summing up to 432 responses. A binomial logistic regression model was used to find the paramount factors affecting the selection of cycling and public transportation. Our model found... 

Treatment of aliphatic and aromatic aldehydes with chiral amines and trimethylsilyl cyanide in the absence or in the presence of Lewis acids (including lithium perchlorate) under solvent-free conditions afforded the corresponding α-aminonitriles in good yields and with a diastereoselectivity of 68 to 86%  

The Co-Ni alloy nanowires were electrodeposited into porous anodic aluminum oxide (AAO) templates. At the first, highly ordered AAO templates were synthesized by two-step anodizing of aluminum to increase pore ordering. Arrays of nanowires with diameter about 30 nm and length about 5000 nm were electrodeposited by alternating current. The composition and structure property of nanowires were investigated by EDX, SEM and TEM techniques. It was found that nanowire composition was related to ions concentration in solution and it was shown that at the optimum potential range of electrodeposition (17-19 V), a change at the potential was shown no strong effect on chemical composition of nanowires.... 

Driving behavior recognition is a notable topic in travel safety, as transportation and insurance companies could adopt effective tools to detect unsafe driving and internalize the associated costs. Different driving events and the related severity must be detected to distinguish abnormal behaviors. The global positioning system (GPS) provides useful information regarding the location of the vehicle at any time and is vastly used in various devices such as smartphones and GPS trackers. Other sensors, on the other hand, provide complementary valuable information but their implementation requires extra costs and more complex and intensive algorithms. We developed a threshold-based algorithm to... 

As the membrane technology developed at the last 30 years, the relevant processes have been significantly developed. One of which is the chlor alkali technology. The development of membrane technology and its effect on Chlor-Alkali process is capable of evaluation in to two different fields, environmental and energy consumption. Some of environmental problems of mercury and diaphragm processes because of their technological development have been eliminated the energy consumption of these processes is significantly decreased especially in membrane and diaphragm processes. Recently investigation in the field of membrane cell is more focused on cell construction, depolarized cathodes, and fluid... 

In this study adsorption of fluoride ion from high-fluorine solutions (<2000 ppm) using the natural and modified ground clinoptilolite is investigated. These low-cost adsorbents are carefully characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), thermos-gravimetry (TGA) and differential scanning calorimeter analysis (DSC). In order to enhance the fluoride removal capacity of natural zeolite, it is milled into nano-powders and modified using hexadecyltriammoniumions (HDTMA+). The kinetic, equilibrium, and thermodynamic of fluoride adsorption are measured and described by the well-known... 

We report the effect of gold nanoparticles on the sensitivity and selectivity of SnO2-based sensors for detection of CO in the presence of methane and C3H8, a model compound representing liquid petroleum gas (LPG). 1.0 wt% Au/SnO2 powder was prepared by a co-precipitation method. The powder formed was washed, dried at 150 °C, and calcined at 300 °C for 3 h. The BET surface area of SnO2 and Au/SnO2 was measured to be 210 and 110 m2/g, corresponding to 4 and 7.5 nm loose spherical particles, respectively. Responses of the Au/SnO2 and SnO2 sensors to 40-1000 ppm CO, 0.2-1.0% C3H8 and 1.0-3.0% CH4 were studied at 170-300 °C in an automated gas sensing system. In this temperature range, the... 

Dimensional analysis of the governing equations in liquid-phase, solid-acid-catalyzed alkylation was used to develop an empirical model for the catalyst lifetime in terms of important operating variables. It was found that the dimensionless catalyst lifetime in a continuous stirred tank reactor was a function of four dimensionless groups, incorporating all important kinetic and operating variables. A power-law correlation was found to be adequate in representing the available experimental data. Because the alkylation reactions are highly diffusion-limited, it was shown that only three of the four exponents in the power-law correlation were independent. As such, the fourth exponent was... 

The FT reaction involves the conversion of syngas which is derived from natural gas or coal to different kinds of products according to the operating conditions and the type of the catalyst. In other words, it is a practical way to convert solid fuel (coal) and natural gas to various hydrocarbons (C1-C60) and oxygenates such as alkanes, alkenes etc. The main products of the reaction are naphtha and gasoline. This paper deals with developing a proper product distribution model for FT process using the appropriate kinetic model, optimizing the respective rate constants while applying them in product distribution equations. The results revealed only 8.09% deviations from the olefin experimental... 

The Nafion ionomer affects the efficiency of the platinum (Pt) catalyst by blocking the active sites thereby restricting the gas permeability of the catalyst layer; but, there is a limitation in the quantity of Nafion ionomer that needs to be added without affecting the cell performance. Sulfonation of carbon-supported catalysts as mixed electronic and protonic conductors has been reported to be an efficient way to increase the triple-phase boundaries. In order to improve the utilization and activity of cathodic catalysts in the oxygen reduction reaction (ORR), Pt nanoparticles were loaded on a mixture of Vulcan XC-72R and MWCNTs, which were functionalized in a mixture of 96% sulfuric acid... 

In this study, 15 wt. % NiO-MgO-SiO2 catalysts modified by La2O3 promoter were prepared through a co-precipitation route and employed for syngas production via propane steam reforming. Various techniques including X-Ray diffraction, BET, TPR, CO2-TPD, CO-chemisorption, TPO, and Scanning electron microscopy were utilized to characterize the final samples. The results indicated that the incorporation of La2O3 enhanced the metal-support interaction providing less reducible Ni species. In comparison with the La-free catalyst, the promoted ones possessed higher metal dispersion and smaller Ni particles. Nonetheless, excessive amounts of La covering the active sites negatively decreased the Ni... 

In this research, a series of NiO–MgO–SiO2 catalyst samples with various nickel contents (5, 10, 15 and 20 wt %) were prepared by a co-precipitation method followed by a hydrothermal treatment and employed in propane steam reforming. The analyses revealed that the enhancement of the nickel content up to 15 wt % improved the propane conversion to 98.6% at 550 °C. Nonetheless, further increase in the nickel loading reduced the catalyst activity due to the formation of larger and more poorly dispersed active sites. Besides, 15 wt % nickel loading led to the high resistance against coke deposition with no detectable carbon on the catalyst surface. In addition, it was revealed that, the decrease... 

Acetic acid is one of the most important petrochemical products. Carbonylation of methanol in homogenous phase is one of the major routes for production of acetic acid. Amongst group VIII metal catalysts used in this process iridium has displayed the best capabilities. To investigate effect of operating parameters like: temperature, pressure, methyl iodide, methyl acetate, iridium, ruthenium, and water concentrations on the carbon dioxide formation, experimental design for this system based upon central composite design (CCD) was utilized. Statistical carbon dioxide formation equation developed by this method contained individual, interactions and curvature effects of parameters on the... 

The effect of process parameters (temperature, pressure, iridium, ruthenium, methyl iodide, methyl acetate, and water concentrations) on CO2 formation and their interactions on methanol carbonylation were studied. The empirical relations for CO2 were developed. The ranking of the influence of the main effects on the CO2 formation was in the order, i.e., pressure > methyl iodide > iridium > water > temperature > methyl acetate > ruthenium. The results between the actual and predicted values were in good agreement. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference PRES (Prague, Czech... 

In this contribution, NiO-MgO-SiO2 catalysts containing 3 wt. % of CeO2, La2O3, Y2O3, and Zr2O3 were examined for propane dry reforming at 550-750 °C. The samples were synthesized by a co-precipitation route, followed by a hydrothermal treatment, and characterized by BET, XRD and TPX analyses. The results indicated that the addition of promoters enhanced the metal-support interaction and basic characteristics, while the acidic nature of the promoted catalyst was changed in a different way. The highest propane conversion of 39.6% was observed over Ce-promoter sample, while the un-promoted catalyst possessed a value of 36.8% at 700 °C. Nevertheless, La and Y-promoted catalysts possessed a...