Sharif Digital Repository

In this article, the transesterification of waste cooking oil (WCO) to biodiesel fuel (BDF) has been studied using KOH loaded on millimetric γ-Al2O3 particles in a novel type of two-impinging-jets reactor (TIJR). The effects of various parameters such as KOH loading (wt %), catalyst loading, and methanol-to-oil molar ratio on the BDF yield were studied. The catalyst particles with a KOH loading of 25 wt % at appropriate reaction conditions (i.e., catalyst loading = 4 wt % and methanol-to-oil molar ratio = 15:1) and at 65 °C were used in the TIJR. The influences of various operating and design parameters such as jet Reynolds number value, feed flow rate, jet diameter, and the internozzle... 

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  

Modeling and simulation of fixed bed three-phase catalytic reactors are considered for wet air catalytic oxidation of phenol to perform a comparative numerical analysis between tricklebed and packed-bubble column reactors. The modeling involves material balances both for the catalyst particle as well as for different fluid phases. Catalyst deactivation is also considered in a transient reactor model to investigate the effects of various parameters including reactor temperature on catalyst deactivation. The simulation results indicated that packed-bubble columns were slightly superior in performance than trickle beds. It was also found that reaction temperature was the most effective... 

To investigate the gas–solid flow pattern of a combustor-style fluid catalytic cracking regenerator, a laboratory-scale regenerator was designed. In scaling down from an actual regenerator, large-diameter hydrodynamic effects were taken into consideration. These considerations are the novelties of the present study. Applying the Eulerian–Eulerian approach, a three-dimensional computational fluid dynamics (CFD) model of the regenerator was developed. Using this model, various aspects of the hydrodynamic behavior that are potentially effective in catalyst regeneration were investigated. The CFD simulation results show that at various sections the gas–solid flow patterns exhibit different... 

Background: Kinetic andmorphological aspects of slurry propylene polymerization using a MgCl2-supported Ziegler-Natta catalyst synthesized from a Mg(OEt)2 precursor are investigated in comparison with a ball-milled Ziegler-Natta catalyst. Results: The two types of catalyst show completely different polymerization profiles: mild activation and long-standing activity with good replication of the catalyst particles for the Mg(OEt)2-based catalyst, and rapid activation and deactivation with severe fragmentation of the catalyst particles for the ball-milled catalyst. The observed differences are discussed in relation to spatial distribution of TiCl4 on the outermost part and inside of the... 

Novel type of two-impinging-jets loop reactor (TIJLR) has been proposed and tested successfully for the solid-liquid catalytic reactions. The TIJLR was tested using the catalytic reaction of isomerization of D-glucose to D-fructose by immobilized glucose isomerase catalyst as a typical model system of solid-liquid catalytic reactions. The TIJLR is characterized by a high intensity reaction chamber, which is separated by a perforated plate from other parts of the reactor. The perforated plate was used as a filter to keep the catalyst particles within the reaction chamber. A compartment model with two adjustable parameters was considered to describe the pattern of flow within the reaction... 

The catalytic wet peroxide oxidation (CWPO) of phenol with activated carbon (AC) as the catalyst has been successfully tested in a novel type of two-impinging-jets reactor (TIJR). The TIJR is characterized by a high-intensity reaction chamber, which is separated by a perforated plate from other parts of the reactor. The perforated plate was used as a filter to keep the catalyst particles within the reaction chamber. The influences of various operating and design parameters such as jet Reynolds number, feed flow rate, internozzle distance, and the jet diameter on the performance capability of the TIJR were investigated. As a result of the impinging process, turbulence, complex trajectory of... 

A hot filament chemical vapor deposition (HFCVD) method was used to prepare Fe-Cr thin film on Si substrate. The produced layers were used as catalysts for growing carbon nanotubes (CNTs) from liquid petroleum gas (LPG) at 825 °C by thermal CVD (TCVD) method. To characterize the obtained catalysts or CNTs, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman spectroscopy were used. CNTs were grown on HFCVD derived Fe-Cr catalyst with the LPG as carbon source successfully. It was found that an annealing process on catalysts enhances the surface concentration of Cr atoms and reduces the sizes of catalyst particles. The... 

Platinum content of two commercial spent reforming catalysts were extracted in aqua-regia solutions under atmospheric pressure and at temperatures up to 100 °C. Three factors, including presence of coke, catalyst particle size, and impeller agitation speed were first tested to study the relative importance of mass-transfer resistances during Pt extraction reaction. Catalyst particle sizes < 100 μm and agitation speeds > 700 rpm eliminated the internal and external mass-transfer resistances, respectively. The effect of other factors, including HNO3-to-HCl volume ratio, liquid-to-solid mass ratio, and the reaction temperature on the extraction rate of platinum were then examined. Pt extraction...