Sharif Digital Repository

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... 

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%  

Direct conversion of methane to methanol is a more recently developed technique by which the intermediate and expensive process of formation of synthesis gas is eliminated. On the other hand, fluidized-bed technology for heterogeneous reversible reactions posses a couple of key advantages in comparison to the commonly used fixed bed reactors. These include, pore diffusion resistances being largely eliminated due to small catalyst pellet sizes utilized. In other words, industrial fixed bed pellets are in the order of 6-12 mm diameter, whereas fluidized catalyst used may be smaller than 100 μm. In addition, equilibrium limitations induced by the reversibility of the reaction(s) are broken in... 

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... 

The construction of binary and ternary heterojunctions has gathered attention in water remediation applications. Herein, g-C3N4, MIL-101(Fe), and MIL-101(Fe)/g-C3N4 binary composite were synthesized by in-situ growth of MIL-101(Fe) crystals along with the nanosheets of g-C3N4. The materials have been characterized by XRD, FTIR, SEM, EDS, DRS, PL, and BET/BJH. The highest degradation efficiency achieved using MIL-101(Fe)/g-C3N4 nanocomposite was 99.3% while the pristine g-C3N4 degraded only 40% of the pollutants by photocatalyst dosage = 0.005 g, pH = 4.8, and irradiation time = 90 min condition. This enhanced photocatalytic performance might be attributed to improved optical properties and... 

Nano powder of natural clinoptilolite zeolite was mechanically prepared by using a planetary ball mill. Statistical experimental design was applied to optimize wet and dry milling of clinoptilolite zeolite. To determine appropriate milling conditions with respect to the final product crystallinity, particle size and distribution, different milling parameters such as dry and wet milling durations, rotational speed, balls to powder ratio and water to powder ratio (for the wet milling) were investigated. Laser beam scattering technique, scanning electron microscopy and X-ray diffraction analyses were carried out to characterize samples. Results showed that larger than 1. mm particle size of... 

Drying behavior of broad beans (Vicia faba) was studied in a pilot scaled fluidized bed dryer with inert particles assisted by dielectric heating. The effective diffusion coefficient of moisture transfer was determined by Fickian method at four different air drying temperatures of 35, 45, 55 and 65 °C. Correlations for moisture diffusivity as a function of moisture content and temperature of the drying medium were developed. The values of moisture diffusivity were obtained within the range of 1.27 × 10-9-6.48 × 10-9 m2/s and the activation energies for FBD and FBD + DE were found to be 27.71 and 17.10 kJ/mol, respectively. The shrinkage behavior of the broad beans was also investigated by... 

High silicon fly ash (HSFA) utilized as a source of silicon in synthesizing of Na-A, -X and -Y zeolites through alkali fusion followed by hydrothermal treatment at 100 °C for 12 h. Various types of zeolites with different degrees of purity were prepared by changing Si/Al ratio of the reaction mixture from 1.6 to 3.0. In addition, exact boundaries of this ratio for synthesis of each zeolite type were determined. Furthermore, the effect of NaOH amount utilized in alkaline fusion step on crystalinity of samples investigated. The synthesized zeolites were characterized using various techniques including; XRD, TGA, FTIR, SEM and BET. The ion-exchange behaviors of zeolitic samples tested with... 

The importance of the gas-to-liquid process is increasing due to growing demand for a high quality, less expensive, and cleaner fuel. Faujasite zeolites, e.g,. zeolites type X and Y, are well-known catalysts in the petrochemical industry. Faujasitic supports (mainly X zeolites) were prepared via hydrothermal synthesis with different Si/Al ratios from pure chemical materials and fly ash as a source of silicon. A high quantity of cobalt oxides was deposited on supports by varying samples Si/Al ratios during the zeolite preparation procedure. Using fly ash in synthesizing the zeolitic support resulted in a A-X zeolite material with a very high cation exchange capability and final cobalt... 

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.... 

Abstract: In this research, photocatalytic conversion of CO2 to methanol was investigated under ultraviolet (UV-A) light. For this purpose, a number of the metal–organic framework photocatalysts, including MIL-101(Fe), graphene oxide (GO), GO–iron oxide (Fe3O4), MIL-101(Fe)–GO–Fe3O4 5, 10, and 20% were synthesized and characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy (RAMAN), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy/map (EDS/map), Brunauer–Emmett–Teller (BET) surface area analysis and Barrett–Joyner–Halenda (BJH), UV–Vis diffuse reflectance spectroscopy... 

Polyaniline fiber (PANI) was synthesized by chemical interfacial method and doped with para toluene sulfonic acid (PTSA) through a sequential doping-dedoping-redoping process resulting in PANI-PTSA. The doped material was utilized to fabricate Vulcan-polyaniline composite of C-PANI-PTSA. Next, through reduction, Pt particles were deposited on to this composite to produce a Pt/C-PANI-PTSA electrocatalyst. To investigate the PANI-PTSA interaction with the carbon support as well as, to consider its effect upon the catalytic activity of Pt/C-PANI-PTSA, electrocatalysts with different ratios of 10, 15, 20, 25 and 30 wt% were synthesized and their activity was compared with the Pt/C (Electrochem).... 

Samples of V2O5 catalysts supported on nanostructures of TiO2 and γ-Al2O3 were synthesized through the hydrothermal method and used for the oxidative dehydrogenation of propane (ODHP) to propylene. The TiO2 support was utilized in both commercial microstructure and synthesized nanostructure forms. Moreover, the γ-Al2O3 support was synthesized through chemical and precipitation methods. The vanadium catalyst was then deposited onto the hybrid of the TiO2 and γ-Al2O3 materials. All prepared catalysts were characterized through the BET, FESEM, FTIR, XRD and TPR techniques. Performances of the synthesized catalysts were subsequently examined in a fixed-bed reactor. The main products were... 

A series of bifunctional Cu-ZnO-ZrO2/H-Y catalysts of different compositions were prepared by coprecipitating sedimentation method and were characterized by surface area and XRD analyses. The catalytic performance in synthesis of tetrahydrofuran was evaluated and optimized in a three-phase slurry batch reactor. The experimental results showed that the appropriate ratio of Cu/ZnO in the hydrogenation catalyst was 50/45, for which the conversion of maleic anhydride (MA) and selectivity of tetrahydrofuran (THF) reached 100% and 46%, respectively, at 50 bar and 493 K after 6 h of operation. Also, according to these results, it was demonstrated that the incorporation of zirconium oxide in the... 

Molecular diffusivity is an essential parameter for modeling of mass transfer in enhanced oil recovery processes. However, experimentally determined diffusivities for light gas-heavy oil systems in the presence of porous media are relatively rare. A few correlations are available in the literature that predict diffusivity of gases into heavy oil in presence of porous media. In this work the pressure-decay method was applied to obtain effective molecular diffusion of CO 2, CH 4 and N 2-heavy oil systems in both bulk and porous media systems at different temperatures. The diffusivity of gases in heavy oil was determined by matching the numerically calculated pressures to the measured data. A... 

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... 

In this paper, copper oxide nanoparticle was synthesized, and its surface was modified using N-(2-aminoethyl)-3-(trimethoxysilyl)propylamine. The bi-amino surface functionalized nanoparticle (BASFN) was used to remove anionic dyes from single and binary systems. The scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDAX) and X-ray diffraction were used to characterize the nanoparticle. Direct Red 80 (DR80) and Direct Green 6 (DG6) were used as anionic dyes. The effect of adsorbent dosage, dye concentration and pH on dye removal was evaluated. Kinetic of dye adsorption on BASFN followed pseudo-second order. The results... 

Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. These reactors have been studied based on Computational Fluid Dynamics (CFD) that can be used in the analysis, design and scale up of these reactors. Most of the researches done in this area are limited to single phase reactors, and a few remaining two phase flow investigations have been done based on MRF (Multi Reference Frame) and Snapshot approach. However, the MRF and snapshot approaches cannot be used in rigorous simulation of unsteady state problems. In order to simulate the unsteady state behavior of the multiphase stirred tank reactors we have used sliding mesh... 

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%. © Pleiades Publishing, Inc., 2006  

Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. Gas-liquid mixing and mass transfer between these phases is an important application in reactor design. One such an example is hydrogenation reaction of aqueous NDMA (Nitroso dimethyl amine) solution in which one of the parameters having a significant effect on the reaction rate is mass transfer. This parameter in turn is a function of impeller shape and rotational speed, gas flow rate and reactor scale. Computational Fluid Dynamics (CFD) is a useful tool in the analysis, design and scale up of stirred tank reactors via investigating hydrodynamics of gas and liquid flow,...