Sharif Digital Repository

The correlations between the hardness, yield stress, and modulus of elasticity of isotactic polypropylene (iPP) were evaluated on the local and global scales. Nanoindentation and traditional macromechanical tests were incorporated for this purpose. Thus, local and global mechanical properties were measured at various temperatures and strain rates. A certain relation was found between the local and global mechanical properties. Moreover, Johnson's model (developed according to the expanding cavity model) was also evaluated at various temperatures and strain rates. The Johnson model was valid only for the yield stresses obtained by nanoindentation and compressive tests and also the elastic... 

In recent decades, great attention has been devoted to the toughening of isotactic poly(propylene) (PP) with elastomers such as ethylene-propylene rubber (EPR). The most important reasons for this interest are the moderate cost and favorable properties of PP. This article is focused on the role of EPR in the deformation and fracture mechanism of PP/EPR blends with different volume fractions of elastomer phase. Differential scanning calorimetry (DSC), tensile tests, and microscopy techniques were used in this study. The fracture mechanism of isotactic PP toughened by EPR (PP/EPR) has also been studied by three point bending (3-PB) and four point bending (4-PB) tests. Rubber particle... 

Connections have very important role in pre-cast concrete structures, especially in seismic zones, and grout connections increase strength and resistance of pre-cast concrete structures for lateral forces. High performance grout connections (HPGC) provide new opportunities to design cost-effective pre-cast concrete structures. HPGC have been proposed to decrease cost of insulation, erection and crane cost of pre-cast concrete structures and to overcome weakness of traditional pre-cast concrete structure connections .This research focuses on properties of grout materials properties which produced in Iran and the effect of propylene fiber on the performance of grout connection. In the first... 

The effect of SiO2/Al2O3 ratio on high silica content nano-sized HZSM-5 stability and selectivity in conversion of methanol to propylene (MTP) has been investigated in a continuous flow isotherm fixed-bed reactor. Highly crystalline HZSM-5 zeolite samples with SiO2/Al2O3 ratios ranging 150–200 have been prepared and characterized using XRD, ICP-AES analytical techniques, NH3-TPD, BET surface area and SEM imaging for studying their physical and chemical behavior. The reaction was conducted at 480 °C and 1bar with WHSV = 1 h−1 and a solution with 1:1 wt% of methanol and water as feed. Over thoroughly monitoring the catalyst synthesis conditions, the nanocrystal ZSM-5 zeolite samples were... 

Kinetic and morphological aspects of slurry propylene polymerization using a MgCl2-supported Ziegler-Natta catalyst synthesized from a Mg(OEt)2 precursor in the presence and absence of two different external donors are investigated. The kinetic profiles show similar trend in presence and absence of donors. The Mg(OEt)2-based catalyst show a mild activation and a long-standing activity with good replication of the catalyst particles. The results show that synthesized Mg(OEt)2-based Ziegler-Natta catalyst presents a highly stable polymerization activity and good replication due to the uniform Ti distribution all over the catalyst particles. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim  

Methanol conversion was investigated on dealuminated mordenite (DM) as well as a series of promoted DM (i.e., metal/DM) catalysts prepared by impregnation. Prepared catalysts characterized by the powder XRD, BET, and NH3-TPD techniques. Chemical analysis was performed using induced coupled plasma (ICP) method. The conversion of methanol over different metal/mordenite catalysts was compared at 460C and WHSV of 1 h-1. Several metals including Fe, La, and Ca had been used to prepare metal/DM catalysts, which displayed high selectivity toward propylene production. Ultimately, La/DM catalyst was determined to be the best material amongst those investigated for methanol conversion based upon its... 

The effects of i-butane addition to methanol in MTP reaction were investigated over an in-house prepared HZSM-5 catalyst. It was observed that, propylene yield would be enhanced when i-butane fed to the reactor along with methanol. The rising growth of the propylene yield continued to peak on till the balance in thermal condition established. Similar trends have been observed when water was added to the mixture. The effect of WHSV with fixed water composition on product distribution was also studied. The optimum point where the highest amount of propylene yielded was shown to be high depended upon the temperature and residence time  

Catalytic paraffin dehydrogenation for manufacturing olefins is considered to be one of the most significant production routes in the petrochemical industries. A reactor kinetic model for the dehydrogenation of propane to propylene in a radial-flow reactor over Pt-Sn/Al2O3 as the catalyst was investigated here. The model showed that the catalyst activity was highly time dependent. In addition, the component concentrations and the temperature varied along the reactor radius owing to the occurring endothermic reaction. Moreover, a similar trend was noticed for the propane conversion as for the propylene selectivity, with both of them decreasing over the time period studied. Furthermore, a... 

Over 200 million motorcycles in use worldwide account for a substantial portion of global mobile source total hydrocarbons (THC) and carbon monoxide (CO) emissions. In Tehran, capital of Iran, ultrarich inefficient combustion in gasoline-fueled motorcycles results in significantly high CO and THC emissions. Motorcycle catalysts can reduce CO and C3H6(as a representative hydrocarbon) emission factors by 60-80%. In the present work, CO and propylene oxidation over a commercial Pt-Pd-based wiremesh catalyst is studied in a flow reactor setup under simulated conditions relevant to 125 cc four-stroke gasoline carburetor motorcycles. Steady-state individual and co-oxidation tests for CO and... 

In this paper, the effects of two methods of iridium impregnation into HZSM-5 on catalyst stability, selectivity for propylene and byproducts in the conversion of methanol to propylene (MTP) were investigated in a continuous flow isotherm fixed-bed reactor. XRD, BET surface area, NH 3-TPD and ICP-AES analytical techniques were applied to define the physical and chemical characteristics of zeolites. The reaction was conducted at 480°C and 1 bar with WHSV = 1 h -1, and with an equal weight percent of methanol and water in the feed. The results revealed that iridium impregnation into HZSM-5 powder led to enhanced propylene selectivity (8%) and catalyst stability while iridium impregnation into... 

In this study, mathematical modeling of fixed-bed plasma reactor operated under isothermal condition was investigated. In this process, methane and acetylene were the inputted feed and ethane, ethylene, propylene, propane, i-butane, and n-butane were the output products. The amount of methane conversion obtained was 12.7% for the former feed, however, if pure methane was inputted this conversion rose to 13.8%. Furthermore, the plasma process enhanced the conversion as well as the selectivity toward the desired product and yield. In the present study, when methane and acetylene were fed at a molar ratio of CH4/C2H2 = 10 to the reactor, the selectivity of C2, C3, and C4 hydrocarbons was... 

A series of V2O5 catalysts supported on multiwall carbon nanotube (MWCNT), single wall carbon nanotube (SWCNT), and graphene were synthesized by hydrothermal and reflux methods for oxidative dehydrogenation of propane (ODHP) to propylene. The catalysts were characterized by techniques including the BET surface area measurements, XRD, FTIR, H2-TPR, NH3-TPD, FESEM, and UV-vis diffuse reflectance spectroscopy. The performance of the catalysts and the supports were subsequently examined in a fixed bed reactor. The main products were propylene, ethylene and CO x. The vanadium catalyst supported on graphene with C/V molar ratio of 1:1 synthesized through the hydrothermal method had the best... 

The effect of oxygenate modifiers on the performance of PtSnγAl 2O3 catalyst in dehydrogenation of propane was studied. Dehydrogenation reaction was carried out in a fixed-bed quartz reactor in the temperature range of 575620 °C. Two types of oxygenate modifiers, namely water and methanol, were added to the feed. The optimum amounts of water for reaction temperatures of 575, 600 and 620 °C were 84, 120 and 140 ppm, respectively. The optimum amounts of methanol for the same reaction temperatures were 9.9, 25 and 50 ppm, respectively. Any further addition of water or methanol beyond these optimum levels resulted in a loss in activity. The addition of water or methanol led to the formation of... 

Prediction of reaction yield as the most important characteristic process of a slurry polymerization industrial process of propylene has been carried out. Stacked neural network as an effective method for modeling of inherently complex and nonlinear systems-espe-cially a system with a limited number of experimental data points-was chosen for yield prediction. Also, effect of operational parameters on propylene polymerization yield was modeled by the use of this method. The catalyst system was Mg(OEt)2/DIBP/TiCl 4/PTES/AlEt3, where Mg(OEt)2, DIBP (diisobutyl phthalate), TiCl4, PTES (phenyl triethoxy silane), and triethyl aluminum (AlEt3) (TEAl) were employed as support, internal electron...