Loading...
Search for:
isomers
0.005 seconds
Total 22 records
Adsorption of xylene isomers on Na-BETA zeolite: Equilibrium in batch adsorber
, Article Microporous and Mesoporous Materials ; Volume 172 , 2013 , Pages 136-140 ; 13871811 (ISSN) ; Khademi, M ; Sharif University of Technology
2013
Abstract
In this article, adsorption of p-xylene, m-xylene, o-xylene, and ethylbenzene on Na-BETA type zeolite in liquid phase at 15, 25, and 35 °C has been studied and the single adsorption isotherms have been obtained and reported. The Langmuir isotherm model was used to describe the experimental adsorption isotherm data. It was found that p-xylene is more strongly adsorbed component followed by ethylbenzene, m-xylene and o-xylene. This means that this adsorbent is selective for p-xylene. Using Langmuir isotherm model, the saturation adsorption capacities of the adsorbent were obtained as follows 143 mg/g for p-xylene, 105 mg/g for ethylbenzene, 83 mg/g for m-xylene, and 68 mg/g for o-xylene at 25...
Photoluminescence emission enhancement and coordination-driven isomer-locking effects of Cr(III) on azobenzene-bearing tweezer anchored to binaphthdiaza-crown macrocycles
, Article Journal of Luminescence ; Volume 201 , 2018 , Pages 329-337 ; 00222313 (ISSN) ; Mahdavian, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In this report, the synthesis of a new bi-macrocycle tweezer linked through an azobenzene moiety, L was undertaken. The characterization of the tweezer was accomplished by employing IR, 1H and 13C NMR, UV–vis, fluorescence spectroscopy and CHN microanalysis while the UV–visible spectroscopy illustrated a trans ⇆ cis photo-isomerization for L. According to our preliminary fluorescence observations, a metal-ion chemosensing behavior was established for trans-L isomer towards Cr(III) ion among the library metal ions. The quenching of the respective trans ⇆ cis isomerization in the presence of Cr(III) ion suggested the preference of a strong interaction between Cr(III) ion with L, leading to...
Separation of Xylene Isomers
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Xylene isomers have similar boiling points and, therefore, their separation by conventional distillation is not practical. The industrial separation of these isomers is generally performed by adsorption or crystallization processes, which are very energy consuming. In this work, the various methods of the separation of these isomers have been reviewed and the equilibrium adsorption of these components in liquid phase using two commercial types of zeolite including Z-700 and Na-BETA as adsorbent at 15, 25, and 35 oC and an initial concentration range of up to 50 wt% as well as in single and binary solutions was investigated. It was found that Z-700 adsorbent has no selectivity for the binary...
Novel one-pot synthesis of (4 or 5)-aryl-2-aryloyl-(1H)-imidazoles in water and tauto-isomerization study using NMR
, Article Tetrahedron ; Volume 65, Issue 34 , 2009 , Pages 6882-6887 ; 00404020 (ISSN) ; Tondro, T ; Hashemi, M. M ; Sharif University of Technology
2009
Abstract
A simple and green route to synthesis of (4 or 5)-aryl-2-aryloyl-(1H)-imidazoles is described. Two isomers can tautomerize to each other by the heat absorption. The tauto-isomerization process was studied by NMR technique. Acidity and stability of products were studied using B3LYP method. © 2009 Elsevier Ltd. All rights reserved
Solubilities of acetaminophen in supercritical carbon dioxide with and without menthol cosolvent: Measurement and correlation
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 619-625 ; 10263098 (ISSN) ; Ghotbi, C ; Dorkoosh, F ; Striolo, A ; Sharif University of Technology
2012
Abstract
The solubility of acetaminophen in SuperCritical-Carbon Dioxide (SC- CO 2) with and without menthol as a cosolvent was measured at various temperatures (313, 328 and 343) K, and within pressures ranging from (10 to 25) MPa. It should be stated that the cosolvent, menthol, has chiral isomers with different melting points. Therefore, the effects of both menthol (I) with a lower melting point and menthol (II) with a higher melting point, as cosolvents on the solubility of acetaminophen in SC- CO 2, were studied. The experimental data collected in this work were obtained using a static flow apparatus. The experiments were replicated at least three times and the data reported are the average of...
Equilibrium modeling of xylene adsorption on molecular sieves
, Article Fluid Phase Equilibria ; Volume 298, Issue 1 , November , 2010 , Pages 54-59 ; 03783812 (ISSN) ; Baghalha, M ; Khorasheh, F ; Behvandi, A ; Sharif University of Technology
2010
Abstract
The separation of xylene isomers is an important application in separation processes that is based on their adsorption properties on different adsorbents. In this work, the Price and Danner method was employed with a neural network to investigate the adsorption behavior of binary systems of p-xylene/m-xylene, p-diethyl benzene/m-xylene, and p-diethyl benzene/p-xylene and the ternary system of p-diethyl benzene/m-xylene/p-xylene at 130 and 175°C. The Redlich-Kister, Wilson, and NRTL models were used to determine the activity coefficients in the adsorbed phase. Comparison with experimental data from the literature indicated that the proposed thermodynamic model would best determine surface...
Comparison and optimization of conjugated linoleic acid production by Lactobacillus plantarum and Lactobacillus plantarum subsp. plantarum
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1272-1280 ; 10263098 (ISSN) ; Alemzadeh, I ; Vossoughi, M ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
Conjugated Linoleic Acid (CLA) was produced from castor oil using washed cells of Lactobacillus plantarum PTCC 1058 and Lactobacillus plantarum subsp. plantarum PTCC1745 as the catalyst. Under the optimal reaction conditions, the washed cells of Lactobacillus plantarum PTCC1058 produced 1661.26 mg of CLA/L reaction mixture (36% yield of production) from 4.6 mg/ml of castor oil after using 15% (w/v) cell for 121 h. The resulting CLA was a mixture of two CLA isomers, cis-9, trans-11 (or trans-9, cis-11)-octadecadienoic acid (CLA1, 44% of total CLA) and trans-10, cis-12-octadecadienoic acid (CLA2, 46% of total CLA). The total production of CLA is extracellular in all of the reactions performed...
Chromogenic detection of xylene isomers and luminogenic chemosensing of o-xylene employing a new macrocyclic cobalt complex: synthesis, and X-ray crystallographic, spectroscopic and computational studies
, Article New Journal of Chemistry ; Volume 46, Issue 43 , 2022 , Pages 20745-20754 ; 11440546 (ISSN) ; Asadi Mofarrah, L ; Jamjah, A ; Sharif University of Technology
Royal Society of Chemistry
2022
Abstract
Here, we report the synthesis and characterization of a binuclear Co(ii) complex (Co2(2py)2Cl4) with two dinaphtho-diazacrown ether macrocyclic ligands, bearing two pyridine arms as a colourimetric and fluorescent sensor for detecting different xylene isomers as well as acting as a catalyst for the oxidation of o- and m-xylene under vacuum at room temperature. Chromogenic detection occurred when Co2(2py)2Cl4 was exposed to the xylene isomers, wherein the original blue colour of the complex changed to green and green-blue in the presence of o- and m-xylene, respectively. Meanwhile, no colour change was observed in the presence of the p-xylene isomer. Fluorescence spectroscopy revealed that...
Optical Sensor Arrays Based on Nanostructured Materials for Quantitative Detection and Qualitative Discrimination of Pesticides and Structural Isomers
, Ph.D. Dissertation Sharif University of Technology ; Hormozi-Nezhad, Mohammad Reza (Supervisor)
Abstract
There is a growing interest in developing high-performance sensors monitoring organophosphate pesticides, primarily due to their broad usage and harmful effects on mammals. In the first part of this research, by introducing conditional sensor elements (CSE), a colorimetric sensor array has been proposed for the detection and discrimination of several organophosphate pesticides (OPs). citrate-capped 13 nm gold nanoparticles (AuNPs) at nine different pH/ionic strengths were employed as simple plasmonic sensing elements in the development of a colorimetric sensor array for the detection and discrimination of five organophosphate pesticides, including azinphos-methyl (AM), chlorpyrifos (CP),...
A second-order advantage achieved with the aid of gold nanoparticle catalytic activity. Determination of nitrophenol isomers in binary mixtures
, Article Analytical Methods ; Vol. 6, issue. 9 , Feb , 2014 , pp. 3056-3064 ; ISSN: 17599660 ; Abdollahi, H ; Hormozi-Nezhad, M. R ; Sharif University of Technology
Abstract
A novel, simple and rapid spectrophotometric method for the determination of nitrophenol (NP) isomer mixtures based on the catalytic activity of gold nanoparticles is described. Gold nanoparticle (∼13 nm) solution was used to catalyze the reduction of NP isomers to aminophenols with an excess amount of NaBH4. The second-order data were obtained by spectrophotometrically monitoring the reduction process of NP isomers. So, multivariate curve resolution optimized by alternative least squares (MCR-ALS) was used to analyze such data. MCR-ALS, an appropriate second-order method, can exploit the so-called 'second order advantage' (the ability to determine in the presence of uncalibrated...
An investigation on the optimum conditions of synthesizing a magnetite based ferrofluid as MRI contrast agent using Taguchi method
, Article Materials Science- Poland ; Volume 31, Issue 2 , 2013 , Pages 253-258 ; 01371339 (ISSN) ; Hosseini, H. R. M ; Sharif University of Technology
2013
Abstract
In this study, some stabilized magnetite based ferrofluids were synthesized using Dextran as a stabilizing agent. In order to achieve optimum experimental conditions for synthesizing ferrofluids as MRI contrast agents, the Taguchi method was used. This approach was employed to design and minimize the number of required experiments. By using the Taguchi orthogonal (L16) array, four parameters including solution temperature and alkalinity, reaction temperature and stirring rate were selected at four predetermined levels for 16 experiments. Synthesizing processes established based on this set of experimental conditions were carried out and the obtained ferrofluids were characterized using PCS,...
Kinetics of glucose isomerization to fructose by immobilized glucose isomerase (Sweetzyme IT)
, Article Industrial and Engineering Chemistry Research ; Volume 48, Issue 7 , 2009 , Pages 3271-3278 ; 08885885 (ISSN) ; Shoai Tehrany, M ; Safari, I ; Sharif University of Technology
2009
Abstract
We present the kinetic parameters and equilibrium constant of the enzymatic glucose-fructose isomerization reaction with an immobilized glucose isomerase (IGI), Sweetzyme IT, using a batch stirred-tank reactor following the procedure developed by Dehkordi et al. (AIChE J. 2008, 54, 1333). The model predictions were compared with the experimental data and fair agreements were found. The influence of temperature on the equilibrium constant and kinetic parameters of glucose to fructose isomerization reaction was investigated. In addition, the frequency factors and the activation energies were determined by using Arrhenius-like expressions. Furthermore, correlations were found for the maximum...
Study of gas separation properties of ethylene vinyl acetate (EVA) copolymer membranes prepared via phase inversion method
, Article Separation and Purification Technology ; Volume 62, Issue 3 , 22 September , 2008 , Pages 642-647 ; 13835866 (ISSN) ; Sadeghi, M ; Motamed Hashemi, M. M. Y ; Pourafshari Chenar, M ; Roosta Azad, R ; Sadeghi, M ; Sharif University of Technology
2008
Abstract
The gas separation properties of ethylene vinyl acetate (EVA) membranes containing 18 and 28 wt% of vinyl acetate (VA) were investigated in this study. The effects of membrane preparation conditions, such as thermal and thermal/wet phase inversion, and the type of solvent on the gas separation properties of EVA membranes were investigated. The permeation of pure O2, N2, CH4, and CO2 gases at different feed pressures ranging from 2 to 11 bar were examined. The results indicated that the CO2 permeability was evidently higher than those of the other gases. Furthermore, the solubility mechanism was found to be the dominant mechanism for permeation of gases through EVA membranes. Moreover, the...
Central composite design with the help of multivariate curve resolution in loadability optimization of RP-HPLC to scale-up a binary mixture
, Article Journal of Separation Science ; Volume 39, Issue 6 , 2016 , Pages 1031-1040 ; 16159306 (ISSN) ; Moazeni Pourasil, R. S ; Sheikh Olia Lavasani, M ; Karami, A ; Ghassempour, A ; Sharif University of Technology
Wiley-VCH Verlag
Abstract
Chromatographic method development for preparative targets is a time-consuming and subjective process. This can be particularly problematic because of the use of valuable samples for isolation and the large consumption of solvents in preparative scale. These processes could be improved by using statistical computations to save time, solvent and experimental efforts. Thus, contributed by ESI-MS, after applying DryLab software to gain an overview of the most effective parameters in separation of synthesized celecoxib and its co-eluted compounds, design of experiment software that relies on multivariate modeling as a chemometric approach was used to predict the optimized touching-band...
Synthesis, crystal structure and DNA interaction of a new water-soluble derivative of pyrazino[2,3-f][1,10] phenanthroline; theoretical calculations, experimental and molecular docking studies
, Article Journal of Molecular Structure ; Volume 1165 , 2018 , Pages 267-275 ; 00222860 (ISSN) ; Eslami, A ; Kia, R ; Aleeshah, R ; Sharif University of Technology
Elsevier B.V
2018
Abstract
The new water-soluble derivative of pyrazino[2,3-f][1,10] phenanthroline has been synthesized and characterized by conductivity measurement, elemental analysis, FT-IR, 1H NMR, 13C NMR spectroscopic studies, as well as single crystal x-ray crystallography. Theoretical calculations have been performed using the density functional theory (DFT) in order to confirm the structure and understand the electronic structure of the synthesized compound. The DNA binding properties of the compound were investigated by absorption spectroscopy, melting temperature and viscosity measurements. The intrinsic binding constant, Kb, was determined as 7.84 × 103 M−1 at 298 K. Thermodynamic parameters showed that...
First-principles study of molecule adsorption on Ni-decorated monolayer MoS2
, Article Journal of Computational Electronics ; Volume 18, Issue 3 , 2019 , Pages 826-835 ; 15698025 (ISSN) ; Berahman, M ; Asgari, R ; Sharif University of Technology
Springer New York LLC
2019
Abstract
The interactions between four different gas molecules (methanol, o-xylene, p-xylene and m-xylene) and Ni-decorated monolayer MoS2 were investigated by means of density functional computations to exploit its potential application as a gas sensor. The electronic properties of the Ni-decorated monolayer MoS2 and gas molecule (adsorbent–adsorbate properties) strongly depend on the Ni-decorated monolayer MoS2 structure and the molecular configuration of the adsorbate. The adsorption properties of volatile organic compound (VOC) molecules on Ni-decorated MoS2 has been studied taking into account the parameters such as adsorption energy, energy bandgap, density of states, and Mulliken charge...
New pathways of stability for NHCs derived from azole, di-azole, n-tetrazole, and ab-tetrazole, by DFT
, Article Journal of Molecular Modeling ; Volume 26, Issue 11 , 2020 ; Kassaee, M. Z ; Ayoubi Chianeh, M ; Fattahi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2020
Abstract
We have investigated the pathways of stability for NHCs derived from azole, di-azole, n-tetrazole, and ab-tetrazole (1a, 2a, 3a, and 4a, respectively), at the M06/6-311++G** level of theory. Optimization and vibrational frequency calculations of ground states (GS) and transition states (TS) are performed to identify Gibbs free energies and nature of stationary points, respectively. Two possible pathways of stability for 1a-4a are compared and contrasted which entail dimerization through hydrogen bonding (HB) and covalent bonding (CB). The CB pathway comprises head to head (HH) and head to tail (HT) dimerizations. Plausible reaction profiles are illustrated for 1a-4a along with the mechanism...
Influence of phosphate anions on the stability of immobilized enzymes. Effect of enzyme nature, immobilization protocol and inactivation conditions
, Article Process Biochemistry ; Volume 95 , August , 2020 , Pages 288-296 ; Carballares, D ; Morellon Sterling, R ; Siar, E. H ; Kashefi, S ; Chafiaa, M ; Arana Peña, S ; Rios, N. S ; Gonçalves, L. R. B ; Fernandez Lafuente, R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
A destabilizing effect at pH 7 of sodium phosphate on several lipases immobilized via interfacial activation is shown in this work. This paper investigates if this destabilizing effect is extended to other inactivation conditions, immobilization protocols or even other immobilized enzymes (ficin, trypsin, β-galactosidase, β-glucosidase, laccase, glucose oxidase and catalase). As lipases, those from Candida antarctica (A and B), Candida rugosa and Rhizomucor miehei have been used. Results confirm the very negative effect of 100 mM sodium phosphate at pH 7.0 for the stability of all studied lipases immobilized on octyl agarose, while using glutaraldehyde-support the effect is smaller (still...
Efficient generation of self-avoiding, semiflexible rotational isomeric chain ensembles in bulk, in confined geometries, and on surfaces
, Article Computer Physics Communications ; Volume 270 , 2022 ; 00104655 (ISSN) ; Galata, A. A ; Sadeghi, M ; Kröger, A ; Kröger, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
We provide an efficient ready-to-run code gensaw that generates single or large ensembles of self-avoiding, flexible, semiflexible, rotationally isometric or helical chains in the bulk or subject to arbitrary confinement and tethering conditions, where we allow for arbitrary intramolecular bending and dihedral energy functions. The resulting configuration files are provided in various common formats and can be immediately used to do molecular simulations or statistical analysis. We work out analytic expressions for the mean squared end-to-end distance and gyration radius of the semiflexible, helical and rotational isomeric state models with a finite number of bonds and arbitrary interaction...
Separation of duty in role-based access control model through fuzzy relations
, Article 3rd Internationl Symposium on Information Assurance and Security, IAS 2007, Manchester, 20 August 2007 through 31 August 2007 ; September , 2007 , Pages 125-130 ; 0769528767 (ISBN); 9780769528762 (ISBN) ; Amini, M ; Jalili, R ; Sharif University of Technology
2007
Abstract
As a security principle, separation of duty (SoD) is widely considered in computer security. In the role-based access control(RBAC) model, separation of duty constraints enforce conflict of interest policies. There are two main types of separation of duty policies in RBAC, Static SoD (SSoD) and Dynamic SoD (DSoD). In RBAC, Statically Mutually Exclusive Role (SMER) constraints are used to enforce Static Separation of Duty policies. Dynamic Separation of duty policies, like SSoD policies, are intended to limit the permissions that are available to a user. However, DSoD policies differ from SSoD policies by the context in which these limitations are imposed. A DSoD policy limits the...