Sharif Digital Repository

Three different spinel metal oxide catalytic systems including NiFe2O4, CuFe2O4 and CoFe2O4 were synthesized using co-precipitation technique and their catalytic activities were compared to each other in α-arylation of oxindole derivatives under the optimized reaction conditions. Both nickel ferrite and copper ferrite magnetic nanoparticles show approximately the same behavior in these reactions but cobalt ferrite ones indicate slightly different properties and were not as good as the other two catalysts. These superparamagnetic catalysts allowed that α-arylation of different types of oxindoles will occur in high yields under mild conditions and at very short times  

The current study demonstrates homogenous decorating of zinc oxide quantum dots (QDs) onto graphene oxide (GO) surface via simple chemical method. The AFM image exhibited that the prepared graphene was 0.8 nm thick and hence practically monolayer. Average size of the ZnO QDs was estimated by transmission electron microscopy around 3 nm. Instrumental and chemical analyses demonstrated formation of a strong bond between ZnO QDs and GO, through C-O-Zn and C-Zn bridges. The UV-visible spectra displayed that the introduction of graphene sheets to ZnO QDs resulted in higher absorption intensity of UV as well as widening of adsorption window toward visible light for ZnO-Graphene due to chemical... 

A convenient one-pot multi-component reaction of aromatic aldehydes, enolizable ketones or β-keto esters and acetonitrile in the presence of acetyl chloride and 10 mol% ZnO nanoparticles for the synthesis of β-acetamido ketones/esters at room temperature is described. © 2007 Elsevier B.V. All rights reserved  

Ship-in-a-bottle complex of nickel(II) containing the ligand N,N′-bis(2,4-dihydroxyacetophenone)-2,2-dimethylpropandiimine (H 2{salnptn(4-OH)2}) has been synthesized in zeolite Y. The characteristics of the encapsulated complex are identified by the methods of EDX, SEM, XRD, FT-IR and cyclic voltammetry. A catalytic effect in the electrochemical oxidation of glucose, fructose and sucrose, and a blocking effect in stevioside oxidation are demonstrated on the Ni II{salnptn(4-OH)2}-Y/CPE. The effects of some parameters, such as potential scan rate and concentration of carbohydrates are investigated. The rate constants for the catalytic reaction (k′) of carbohydrates are also obtained. The... 

Zeolite-based micromotors were developed to eliminate the biological and chemical contamination of water in a fast and efficient way. The motors consist of a silver-exchanged zeolite core and a partial catalytic coating. These porous engines showed rapid killing of Pseudomonas aeruginosa bacteria cells in a very short time, less than 7.5 minutes. The heavy metal uptake of the zeolitic motors during the first 20 minutes of contact was considerably higher than that of zeolite particles by 23% for Pb2+, 19% for Co2+, and 16% for Ni2+. Also, the maximum removal efficiency of the motors (at room temperature and for 6 hours) for Pb2+, Co2+, and Ni2+ was 93%, 87%, and 78%, respectively, higher than... 

The present study reports a simple electrochemical approach to the fabrication of a new nanocomposite containing PtPd nanoflowers (NFs) promoted with two-dimensional (2D) nanosheets (NSs) structure cuprous oxide (Cu2O) supported on reduced graphene oxide (rGO) (PtPd-NFs/Cu2O-NSs/rGO). Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, and energy dispersive X-ray spectroscopy are used for characterization of the PtPd-NPs/Cu2O-NPs/rGO. SEM images showed that vertical-standing arrays of Cu2O with an edge length up to 1 μm and thickness of about 20 nm are electrodeposited on the surface of rGO film. Also, PtPd needle-like NFs with visible and... 

VO2(picolinichydrazone) complex as a catalyst was stabilized on a SBA-15 mesoporous silica as a catalytic support by using (3-chloropropyl)triethoxysilane as a connector. SBA-15 is nanoporous and has a high ratio of surface area to volume. The immobilization of a metal–Schiff base complex to the surface area of SBA-15 can improve its catalytic effects by increasing the catalytic surface area. Unlike homogeneous catalysts, heterogeneous catalysts can be recovered and reused several times without any significant loss of catalytic activity. A vanadium–Schiff base complex-functionalized SBA-15 was synthesized by covalency connected by a pre-synthesised VO2(picolinichydrazone) complex to... 

Catalytic reduction of nitrobenzene is the leading technological step in aniline production. The hydrogen required for this stage, is dominantly produced from fossil fuels through reforming processes, which take much energy and emit large amounts of CO2. Biomass-derived glycerol steam reforming is an attractive alternative to traditional reforming to reduce the dependence on hydrocarbon resources and mitigate climate change. This research aims to analyze a mass- and heat-integrated multi-tubular membrane reactor, containing nitrobenzene hydrogenation (exothermic-side) and glycerol steam reforming (endothermic-side) for co-production of aniline and syngas. In this process, hydrogenation... 

A novel bi-functional polymeric catalyst was synthesized by immobilization of tungstate anions onto the nitrogen rich poly(ionic liquid)/magnetic nanocomposite. The resulting catalyst has two types of catalytic sites: (i) immobilized WO4 anions with bis-imidazolium ionic liquid cation for selective oxidation of alcohols and (ii) basic amine groups for Knoevenagel condensation between produced aldehyde and malononitrile. Due to the polymeric nature of the catalyst, large amounts of tungstate and basic nitrogen groups were presented on the solid surface which led to a decrease in the applied catalyst mass for catalytic reaction. High catalytic activity and excellent selectivity of catalyst in... 

Heterogeneous solid catalysts comprising CaO and ZrO 2 mixed oxides with various Ca-to-Zr molar ratios were synthesized by means of coprecipitation method. These synthesized mixed oxide catalysts were used for the transesterification of waste cooking oil (WCO) as feedstock with methanol to produce biodiesel fuel (BDF) at 65 °C and 1 atm. The influences of Ca-to-Zr molar ratio, catalyst loading, methanol-to-oil molar ratio, and the reaction time on the BDF yield were carefully investigated. In addition, the stability of prepared solid catalysts was studied. These catalysts were characterized by using techniques of X-ray diffraction, X-ray florescence, X-ray photoelectron spectroscopy, surface... 

A novel efficient and cost-effective heterogeneous catalyst for the production of biodiesel from transesterification of sunflower oil was prepared through the impregnation of K2CO3 upon the Talc material. The physicochemical features of the catalyst were studied through several characterization analyses. The effect of the K2CO3 loading was investigated by comparing the catalytic activity of various prepared catalysts. Moreover, the effect of the calcination temperature upon the catalytic activity was examined. To maximize the yield of the produced biodiesel fuel, reaction variables such as the reaction time and temperature, catalyst concentration, and methanol: oil molar ratio were... 

A series of heterogeneous catalysts including different molar ratios of CaO/talc was synthesized to study the transesterification reaction of canola oil and methanol under different reaction conditions. Characterization and kinetic results revealed that the activity of this catalyst was enhanced due to the increase of CaO/talc molar ratio value leading to an improvement in the biodiesel production. Moreover, the effect of various parameters on the activity of the undertaken catalysts was studied in order to determine the optimum process conditions. Leaching measurements and the durability of the CaO/talc catalyst under several reaction cycles were evaluated and proved it to be a stable... 

In this research, a solid 1%Li/Ca-La mixed oxide catalyst was prepared using co-precipitation method followed by wet impregnation. The prepared catalyst was used in the transesterification reaction of canola oil and methanol for biodiesel synthesis. The effects of calcination and reaction temperatures were investigated on the activity of the catalyst. In addition, rate of the reaction was studied through a kinetic model for which parameters were determined. Surface properties and structure of the catalyst were characterized through the powder X-ray diffraction (XRD), thermogravimetry/derivative thermogravimetry (TG/DTG), and Fourier transform infrared spectroscopy analysis. All these... 

The catalytic activity of Pt/Ni/TiO 2 nanotubes electrode toward glucose has been studied. Fabrication of Pt/Ni nanostructures was done in a single-bath solution through electrochemical pulse method by changing the deposition potential between -0.3 and -4 V vs. SCE, respectively. The resulting modified electrode represented high conductivity due to the effective presence of metallic components and uniform surface area caused by dispersion of Pt and Ni nanostructures. The scanning electron microscopy images also confirmed that a large amount of metals colonies were well-dispersed at the edge of the TiO 2 nanotubes. In addition, the Pt/Ni TiO 2 nanotubes modified electrode exhibited an... 

A reduction in catalyst's activity with time-on-stream and the formation of side products are two of the problems associated with catalytic propane dehydrogenation (PDH). Previous studies have indicated that the presence of small amounts of oxygenated additives such as water can reduce coke formation and enhance catalyst activity. The aim of the present work was to develop an appropriate kinetic model for PDH over a commercial Pt-Sn/γ-Al 2O3 catalyst in the presence of small amounts of water. Experimental data were obtained from a previous study where catalytic PDH was carried out in a bench scale reactor system at atmospheric pressure in the temperature range of 575-620°C in the presence of... 

In this study a hot filament chemical vapour deposition (HFCVD) technique was used to prepare Fe-Cr films on Si substrate as catalysts for thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from liquid petroleum gas (LPG) at 800 °C. To characterize the catalysts or CNTs, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were used. The XPS spectra obtained at different stages of Ar+ sputtering revealed that in the depth of catalyst layers, the relative Fe-Cr concentrations are higher than the top-surface. SEM images of samples after TCVD indicate a significant CNT growing at the backside of catalyst... 

The catalyst layers are the most important part of the polymer electrolyte membrane (PEM) fuel cells, and the cell performance is highly related to its structure. The gas diffusion layers (GDLs) are also the essential components of the PEM fuel cell since the reactants should pass through these layers. Model prediction shows that electrical current in catalyst layer is non-uniform, influenced by the channel-land geometry. In addition, the compression effect of GDLs and water generation due to the electrochemical reaction may cause non-uniformity in porosity and, therefore, increases the non-uniformity in reactant concentration in GDL/catalyst layer interface. Simulation results suggest that... 

TCVD growth of multiwalled carbon nanotubes (MWCNTs) was reported by catalytic decomposition of liquefied petroleum gas (LPG) at a temperature range of 580800 °C. Laser ablation was employed as a simple and rapid technique to produce Pd nanoparticles which possess effective catalytic activities for CNT synthesis. UVvisible spectroscopy and TEM images confirmed that the Pd nanoparticles are stable for a long time and have rather spherical shape with average size of 7 nm. SEM and TEM observations and Raman spectroscopy demonstrated that the CNTs have a wavy structure, dense morphology and acceptable crystallinity. Since Pd nanoparticles are inactivated or agglomerated at extremes of the... 

In this research, the effect of applied voltage and electrolyte concentration on structure, chemical composition, optical properties, and especially photo-catalytic activity of the TiO2 layers containing micro/nano-sized pores are discussed. TiO2 layers were synthesized by micro arc oxidation (MAO) process using different electrolyte concentrations and applied voltages. Surface structure of the layers was studied by scanning electron microscope (SEM); furthermore, energy dispersive spectrophotometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques were employed to determine phase structure and chemical composition of the layers. Photo-activity of the...