Sharif Digital Repository

Keggin-type polyoxometalate (POM) nanoparticles based on [PW12O40]3- and [SiW12O40]4- with Ag+ and (ZrO)2+ cations were prepared under ultrasound irradiation. The results of SEM and XRD revealed the average size of particles in the range of 24–95 nm. The moles of crystallization water per mole of nanocatalysts were in the range of 3–9. EDX spectra confirmed the successful replacement of protons of H3PW12O40 and H4SiW12O40 with Ag+ and (ZrO)2+ cations. These nanoparticles were used as heterogeneous catalysts for the synthesis of a poly (amido-ester) at room temperature. All polymers were fully characterized. Although employing the nanocatalyst resulted in at least 22% improvement in the... 

Characterization and determination of a complex mixture of fatty acid methyl esters was performed for commercial fish oil using two-dimensional GC-MS data coupled with resolution techniques. Various principle component analysis methods such as significant factor analysis and fixed size moving window evolving factor analysis were used for the number of factors, zero concentration and selective regions. Then, the convoluted chromatograms were resolved into pure chromatograms and mass spectra using heuristic evolving latent projections (HELP) method. Fatty acids of C16:1ω7, C18:4ω3, C18:1ω11, C18:1ω9, C18:0, C20:2ω6, C20:1ω9, C 22:1ω11, C22:1ω9 and C24:1ω9 were resolved and identified by using... 

In this study, a novel experimental approach was used to overcome the lack of phase equilibrium information to obtain data that is more applicable to industrial situations. Liquid-liquid equilibrium (LLE) data, tie-lines, and phase boundaries were carried out for two systems of canola oil methyl esters (containing 1 wt % KOH) + glycerol + methanol and sunflower oil methyl esters (containing 1 wt % KOH) + glycerol + methanol at three different temperatures (303.15, 313.15, and 323.15 K). The quality of data was also ascertained using Othmer-Tobias correlations. The experimental LLE data was also correlated by the nonrandom two-liquid (NRTL) and the Wilson-NRF Gibbs free energy models. The... 

In this paper, LM pectin production from commercial apple pectin by using acid, alkali and ammonia methods in the presence of ethanol was studied. Also, the effect of different parameters such as, temperature, time, acid, alkali and ammonia treatment in LM pectin production were evaluated. In all the experiments, low temperature showed a better influence from a recovery, purity and low de-polymerization viewpoint. Optimum conditions in the acid method reached at pH = 2, t = 17 hrs and T = 30°C, in the alkaline method reached at pH = 11, t = 3 hrs and T = 5°C and in the ammonia method reached at 2 N ammonia and T = 5°C, were determined. © Sharif University of Technology  

A simple and efficient synthesis of diol diesters, protected chlorohydrins, chlorohydrins and β-hydroxy azides with acetyl or benzoyl, TMSN3 and TMSCl groups has been achieved by ring opening of epoxides with acetic anhydride, acetyl chloride or benzoyl chloride and TMSN3 using catalytic amount of lithium perchlorate under solvent-free conditions. All reactions proceeded in short times and afforded the corresponding products in good to excellent yields under mild reaction conditions. LiClO4 shows enhanced reactivity for the ring opening of epoxides under solvent-free conditions, therefore, reducing the reaction times dramatically and improved the yields and amount of catalyst. © 2007... 

Aryl arenesulfinates rearrange to the corresponding arenesulfinyl phenols via a thia-Fries rearrangement on catalysis by anhydrous FeCl3 in dry dichloromethane at room temperature in good to excellent yields. © 2001 Published by Elsevier Science Ltd  

Reynolds-Averaged Navier-Stokes (RANS) approach with the k-ε closure model is employed for the first time to simulate direct Solid-Phase Micro-Extraction (SPME) computationally. Simulations are performed by using COMSOL Multiphysics in order to examine methods to decrease the extraction time. Experiments are also conducted to support data obtained from the numerical framework. Di-n-Butyl Phthalate (DNBP) and etched steel wire are chosen as the analyte and the adsorbent, respectively. Stirring rate, fiber's location, stirrer magnet's size, and the method of sample rotation are examined to decrease the extraction time. In addition, the effects of adding a baffle to the vial and implementing a... 

A mild and efficient tandem process for the synthesis of new highly substituted 2-pyrones starting from commercially available 2-arylacetic acids has been developed. The synthesis is based on the Knoevenagel condensation of 1,3-cyclohexadiones with various β-formyl-esters, followed by lactonization in the presence of nano ZnO (20 mol %). Moderate to high yields and readily available cheap starting materials are the key features of the present method  

This study reports the importance of physicochemical characteristics of the core-shell structured polymer-coated Fe3O4 cluster@SiO2 nanocomposite particles for designing the biocatalysts used for transesterification of soybean oil. To demonstrate this issue, two different types of polymer molecules such as polyethylenimine (PEI) and polyacrylic acid (PAA) each with two different molecular weights are employed. The highest fatty acid methyl esters (FAMEs) synthesis yield values are achieved by the lipases immobilized onto the low- and high-molecular-weight PEI-coated particles as compared to those of the low- and high-molecular-weight PAA-coated particles (i.e., ∼64.8% and ∼73.1% versus... 

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  

4-Aminoperoxybenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of ketones to esters. Copyright © Taylor & Francis Group, LLC  

The synthesis of amoxicillin with immobilized penicillin G acylase (PGA) in aqueous medium was investigated. The parameters studied were: time course of amoxicillin production, concentration of substrates: hydroxyphenylglycine methyl ester (HPGM) and 6-aminopeicillanic acid (6-APA) and the. effect of enzyme (PGA) content and pH, under variable and constant conditions and temperature variations. In the study of two substrate concentration on amoxicillin production, impressive results were obtained for a 1/3 ratio of 6-amino penicillanic acid (6-APA) and hydroxyl-phenylglycine methyl ester (HPGM). The. synthesis of amoxicillin was preferable at constant pH rather than a variable one. Other... 

The lipase-immobilized polyethyleneimine (PEI)- and polyacrylic acid (PAA)–coated magnetic silica nanocomposite particles (L-PEI-MS and L-PAA-MS, respectively) were prepared and applied at various transesterification reaction conditions. The reactions were carried out with soybean, sunflower, canola, and palm oils along with methanol or ethanol in the solvent-free and n-hexane systems. The highest fatty acid methyl ester (FAME) and fatty acid ethyl ester (FAEE) synthesis yields were obtained from the transesterification of palm oil, i.e., almost 7.7–10.2% higher than other oils. At the constant reaction conditions, the application of ethanol leads to higher (6.0–8.7%) reaction yields in... 

In this research, direct conversion of wet algal biomass into biodiesel using supercritical methanol was studied. In this process, microalgal lipids simultaneously was extracted and converted to biodiesel under high pressure and temperature conditions without using any catalyst. Several experiments have been performed to optimize the methanol amount and it has been revealed that the best performance was achieved by using methanol/wet biomass ratio of 8:1. The effect of using various co-solvents in increasing the efficiency of the supercritical process was investigated. It has been shown that hexane was the most effective co-solvent and its optimal ratio respect to wet biomass was 6:1. The... 

A novel, magnetic nanocarrier was successfully synthesized through a facile and economical producer in which Fe3O4 magnetic nanoparticles were coated by starch-g-poly (methyl methacrylate-co-PEG-acrylamide). The surface of nanocarrier was then modified by hydrazine to preparation of a pH-responsive carrier. The resulted nanocarrier was applied for delivery of doxorubicin (DOX) as an effective anti-cancer drug. DOX was reacted with hydrazine linkage on the surface of nanocarrier to form hydrazone bond. Due to the presence of numerous hydrazine groups on the surface of magnetic nanocarrier large amounts of DOX was loaded onto the carrier (327 mg g−1). © 2016 The Korean Society of Industrial... 

The present paper relates to an improved method for making surfactant esters, especially sorbitan monostearate and tristearate. Sorbitan esters of fatty acid, stéarate are derived from a reaction between sorbitan and fatty acid. Method of sorbitan ester production needs addition of catalyst. Sorbitan stéarate production was studied using chemical catalyst. Two steps process leading sorbitan production under atmospheric and vacuum pressure with acid catalyst resulted dehydrated product at optimal residence time of 195 min at 180°C for atmospheric conditions and optimalresidence time of 150 min at the same temperature respectively. Sorbitan stearate production was studied by utilizing sorbitan... 

LiClO4 is used as catalyst for direct Mannich-type reaction of aryl aldehydes, aryl amines, and diethyl malonic ester under solvent-free conditions. This three-component reaction afforded the corresponding β-amino esters in good yields with simple and environmentally benign procedure. Copyright © Taylor & Francis Group, LLC  

At room temperature, ZrOCl2·8H2O on montmorillonite K10 efficiently catalyzes conjugate addition of amines to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, nitriles and amides under solvent-free conditions. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. © 2005 Elsevier Ltd. All rights reserved  

Bactrocera dorsalis and B. correcta (Diptera: Tephritidae) are economically important pests of fruits and have caused serious damage to fruits for the last several years worldwide. In China, B. correcta is second economic pest of fruits after B. dorsalis. Considering the importance of Integrated Pest Management (IPM) programs, Information regarding host preference and fitness of both Bactrocera species are necessary for better management strategies. Therefore, the current study explains the response of both Bactrocera species on banana, guava, and mango fruits. The cultivar of banana, guava, and mango fruits used first time in this study. Therefore, the volatile/aromatic components of...