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A Three dimensional dynamic CFD simulation for the direct dme production in a fixed bed reactor
, Article Computer Aided Chemical Engineering ; Volume 32 , June , 2013 , Pages 247-252 ; 15707946 (ISSN) ; Kazemeini, M ; Vafajoo, L ; Fattahi, M ; Sharif University of Technology
2013
Abstract
Dimethyl ether (DME) as a clean fuel seems to be a superior candidate for high-quality diesel fuel in near future. In this study, a comprehensive three-dimensional dynamic heterogeneous model developed to simulate the flow behavior and catalytic coupling reactions for synthesis of the DME from hydrogenation of the CO and CO2, dehydration of methanol to dimethyl ether and water gas shift reaction in a fixed bed reactor. For this purpose, a CFD simulation was articulated where the standard k-ε model with 10% turbulence tolerations implemented. Then the concentration and temperature profiles along the reactor were determined. It was revealed that under conditions considered, a single phase...
Synthesis of dithiocarbamates by Markovnikov addition reaction in PEG and their application in amidoalkylation of naphthols and indoles
, Article Journal of the Brazilian Chemical Society ; Volume 26, Issue 7 , 2015 , Pages 1500-1508 ; 01035053 (ISSN) ; Dadras, A ; Ramezani, M ; Shamiri, E. V ; Hooshmand, S. E ; Hashemi, M. M ; Sharif University of Technology
Sociedade Brasileira de Quimica
2015
Abstract
Synthesis of dithiocarbamates by the one-pot three-component Markovnikov addition reaction of an amine, carbon disulfide and an alkyl vinyl ether or N-vinylpyrrolidone is reported in polyethylene glycol (PEG) under a mild and green procedure with high yields and completely regiospecific. Also, the products were used as efficient starting materials for amidoalkylation of electron-rich arenes such as naphthols and indoles
Novel and efficient method for the silylation of hydroxyl groups with hexamethyldisilazane (hmds) under solvent-free and neutral conditions
, Article Organometallics ; Volume 23, Issue 6 , 2004 , Pages 1457-1458 ; 02767333 (ISSN) ; Saidi, M. R ; Sharif University of Technology
2004
Abstract
Various alcohols and phenols were silylated to trimethylsilyl ethers with hexamethyldisilazane in the presence of solid lithium perchlorate under very mild, neutral, and solvent-free conditions in good to excellent yields
Trimethylsilyl cyanide addition to carbonyl compounds under neutral condition catalyzed by iodine
, Article Phosphorus, Sulfur and Silicon and the Related Elements ; Volume 178, Issue 10 , 2003 , Pages 2111-2115 ; 10426507 (ISSN) ; Saidi, M. R ; Sharif University of Technology
Taylor and Francis Ltd
2003
Abstract
Reaction of trimethylsilyl cyanide with aliphatic or aromatic aldehydes and ketones in the presence of a catalytic amount of elemental iodine produced the corresponding cyanohydrin trimethylsilyl ethers in very short time and high yields
A new protocol for O-methylation of phenolic compounds with trimethyl phosphite or trimethyl phosphate under solvent-free condition and microwave irradiation
, Article Phosphorus, Sulfur and Silicon and the Related Elements ; Volume 178, Issue 11 , 2003 , Pages 2343-2348 ; 10426507 (ISSN) ; Rajabi, F ; Sharif University of Technology
Taylor and Francis Ltd
2003
Abstract
A simple method for the preparation of industrially important alkyl aryl ethers is reported. Several phenolic compounds such as phenols, naphthols, and hydroxy coumarins were O-methylated with trimethyl phosphite or trimethyl phosphate under microwave irradiation and solvent-free condition in almost quantitative yields. Reaction of 2-naphthol with trimethyl phosphate gave mixture of 2-methoxynaphthalene and 1-methyl-2-methoxynaphthalene while the reaction with trimethyl phosphite gave mostly 2-methoxynaphthalene. This method is highly efficient for the methylating of phenolic compounds with very easy experimental procedure and environmental friendly conditions
Synthesis of fulvene vinyl ethers by gold catalysis
, Article Chemistry - A European Journal ; Volume 26, Issue 23 , 2020 , Pages 5280-5287 ; Schwarz, J ; Lustosa, D. M ; Pourkaveh, R ; Hoffmann, M ; Rominger, F ; Rudolph, M ; Dreuw, A ; Hashmi, A. S. K ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
Gold-catalyzed cyclization of 1,5-diynes with ketones as reagents and solvent provides diversely substituted vinyl ethers under mild conditions. The regioselectivity of such gold-catalyzed cyclizations is usually controlled by the scaffold of the diyne. Herein, we report the first solvent-controlled switching of regioselectivity from a 6-endo-dig- to 5-endo-dig-cyclization in these transformations, providing fulvene derivatives. With respect to the functional-group tolerance, aryl fluorides, chlorides, bromides, and ethers are tolerated. Furthermore, the mechanism and selectivity are put to scrutiny by experimental studies and a thermodynamic analysis of the product. Additionally,...
Heteroatom Influence on the Basicity of Amines
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Alireza (Supervisor)
Abstract
Present work focuses on the influence of Heteroatom(s) on the bacisity of specific group of amines through the intramolecular hydrogen bonding. This group includes Aza-Crown Ethers specifically. We used Spartan and Gaussian packages to gain optimized structures for all compounds in order to explore the influence of the intramolecular hydrogen bonding on the bacisity of amines. All the gas phase optimizations and energy calculations were performed at the DFT/B3LYP/6-311++G(d,p) level of theory. The Hf/6-31+G(d,p) level was used for all single point calculations in the solution phase. As commonly used solvents in organic and biological reactions, the solution phase calculations were carried...
Synthesis of highly porous nanocrystalline alumina as a robust catalyst for dehydration of methanol to dimethyl ether
, Article Journal of Porous Materials ; Volume 20, Issue 1 , 2013 , Pages 151-157 ; 13802224 (ISSN) ; Kazemeini, M ; Aghaziarati, M ; Alamolhoda, S ; Sharif University of Technology
2013
Abstract
Highly porous nanocrystalline alumina was synthesized using two different precipitation processes and precipitating agents, which were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and porosimetry analyses. Different precipitating agents yielded nanocrystalline alumina catalysts with different morphologies and textural properties. Batch precipitation using sodium bicarbonate at constant pH resulted in a highly porous nanocrystalline γ-alumina catalyst, having surface area of 351.47 m2 g-1, total pore volume of 1.68 cm3 g -1 and mean pore diameter of 19.17 nm. The mean crystallite size was also determined to be 3.8 nm, based on the XRD results. Catalytic...
Immobilized palladium nanoparticles on MNPs@A-N-AEB as an efficient catalyst for C-O bond formation in water as a green Solvent
, Article Applied Organometallic Chemistry ; Volume 32, Issue 9 , 2018 ; 02682605 (ISSN) ; Eslami, M ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Palladium nanoparticles immobilized on the magnetic nanoparticles@2-amino-N-(2-aminoethyl) benzamide (MNPs@A-N-AEB.Pd0) have been presented as an efficient, and reusable magnetically heterogeneous catalyst for the C-O coupling reaction, namely Ullmann condensation reactions in an aqueous medium. This heterogeneous catalyst shows superior reactivity for the C-O arylation of different aryl halide (chloride, bromide, and iodide) with phenol derivatives to afford the desired products in good to excellent yields within short reaction time. Moreover, the catalyst can be easily recovered and reused for seven runs without loss of catalytic activity. The catalyst was characterized by several...
Designing a diethyl ether pilot plant
, Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) ; Haddadi, A. M ; Kazemini, M ; Sharif University of Technology
2006
Abstract
One of the ways of giving a considerable handle on the account of developing this processes using simulating software. In this work the primary simulation in Aspen plus software done for comparison of various equations of state. Hence, for preparation of one reliable and exact model, the primary prepared model studied for different kinds of Equations of state, activity coefficient and calculation methods of Equilibrium constant in existing simulator software bed. Designing Dimethyl Ether pilot plant on the basis of reactor simulation is achieved by using the compatibility between simulation data and empirical data relevant to the industrial unit. The constants of the kinetic model were...
A joint experimental and theoretical study of kinetic and mechanism of rearrangement of allyl p-tolyl ether
, Article Journal of Molecular Structure: THEOCHEM ; Volume 893, Issues 1–3 , January , 2009 , Pages 73–76 ; Haqgu, M. (Mohammad) ; Talebi, A ; Gholami, M. R. (Mohammad Reza) ; Sharif University of Technology
Abstract
A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15–533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol−1, ΔS# = −7.88 cal mol−1 K−1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted...
Application of ideal temperature gradient technology to optimize the chemical exchange and distillation process of boron isotopes separation by (CH3)2O-BF3 complex
, Article Chemical Engineering and Processing: Process Intensification ; Volume 76 , February , 2014 , Pages 26-32 ; ISSN: 02552701 ; Ahmadi, S. J ; Sharif University of Technology
Abstract
To exert the optimum effect, the chemical exchange process to boron isotope separation was investigated. In this enrichment method the distillation of dimethyl ether-boron trifluoride complex, which was one of the most efficient industrial methods for purification of isotope boron-10, was optimized. In chemical exchange process of boron isotopes separation two chemical reactions occur. The first one is the decomposition reaction that is an endothermic reaction. The second one is the exchange reaction that is a pyrogenic reaction. With increasing temperature, the decomposition reaction is speeded while the exchange reaction is slowed down. Affecting on both decomposition and exchange...
A three dimensional CFD simulation and optimization of direct DME synthesis in a fixed bed reactor
, Article Petroleum Science ; Vol. 11, issue. 2 , 2014 , pp. 323-330 ; ISSN: 1672-5107 ; Kazemeini, M ; Fattahi, M ; Sharif University of Technology
Abstract
In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether (DME) from syngas including CO2 in a fixed bed reactor at commercial scale under both adiabatic and isothermal conditions. For this purpose, a computational fluid dynamic (CFD) simulation was carried out through which the standard k-e{open} model with 10% turbulence tolerations was implemented. At first, an adiabatic fixed bed reactor was simulated and the obtained results were compared with those of an equivalent commercial slurry reactor. Then the concentration and temperature profiles along the reactor were...
Modeling, simulation and control of a tubular fixed-bed dimethyl ether reactor
, Article Chemical and Biochemical Engineering Quarterly ; Volume 24, Issue 4 , 2010 , Pages 415-423 ; 03529568 (ISSN) ; Shahrokhi, M ; Abedini, H ; Sharif University of Technology
2010
Abstract
This paper considers the modeling and control of a tubular fixed bed reactor with recycle stream for dimethyl ether (DME) production. For simulation purposes, a pseudo homogeneous model has been developed. By reactor simulation under steady state condition, effects of parameters such as feed rate, pressure and shell temperature are investigated. Using the steady state model, an optimizer that maximizes the reactor yield has been developed. For cooling the reactor, a steam drum that uses heat of reactions to produce steam was coupled with the reactor. Through dynamic simulation, system open loop response was obtained and two control loops were considered for controlling the reactor...
Direct production of dimethyl ether from synthesis gas utilizing a new bifunctional catalyst
, Article 19th International Congress of Chemical and Process Engineering, CHISA 2010 and 7th European Congress of Chemical Engineering, ECCE-7, 28 August 2010 through 1 September 2010, Prague ; 2010 ; Kazemeini, M ; Aghaziarati, M ; Sharif University of Technology
2010
Abstract
A series of bifunctional catalysts Cu-ZnO-ZrO 2/Al-modified H-Mordenite were prepared by co precipitating sedimentation method and were characterized. Active sites were dispersed well. The synthesis of dimethyl ether (DME) via direct CO hydrogenation was evaluated in a three-phase slurry reactor. Cu-ZnO-ZrO 2/Al-modified H-Mordenite was a suitable catalyst for the production of dimethyl ether from synthesis gas. The appropriate ratio of methanol synthesis catalyst (Cu-ZnO-ZrO 2) to methanol dehydration catalyst (Al-modified H Mordenite) was 2:1. In this condition, CO conversion and DME selectivity were ≈ 68% and 82%, respectively. This is an abstract of a paper presented at the 7th European...
A joint experimental and theoretical study of kinetic and mechanism of rearrangement of allyl p-tolyl ether
, Article Journal of Molecular Structure: THEOCHEM ; Volume 893, Issue 1-3 , 2009 , Pages 73-76 ; 01661280 (ISSN) ; Haqgu, M ; Talebi, A ; Gholami, M. R ; Sharif University of Technology
2009
Abstract
A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15-533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol-1, ΔS# = -7.88 cal mol-1 K-1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted...
Highly diastereoselective aminoalkylation of naphthols with chiral amines mediated by lithium perchlorate solution in diethyl ether
, Article Tetrahedron Asymmetry ; Volume 14, Issue 3 , 2003 , Pages 389-392 ; 09574166 (ISSN) ; Azizi, N ; Sharif University of Technology
2003
Abstract
One-pot, three-component, Mannich reaction of naphthols with in situ prepared imines in 5 M ethereal lithium perchlorate at room temperature affords the corresponding aminoalkylated products in high yields with high diastereoselectivities. The process is exemplified by the reaction of 2-naphthol with (R)-1-phenylethylamine and an aromatic aldehyde in concentrated ethereal lithium perchlorate solution, which affords a highly diastereoselective access to the requisite 2-aminoalkylated product. © 2003 Elsevier Science Ltd. All rights reserved
Proposition of Control Structure for DME Synthesis Plant
, M.Sc. Thesis Sharif University of Technology ; Pishvaie, Mahmoud Reza (Supervisor)
Abstract
The development and use of design methods for control structures has grown significantly in recent decades. In this study, a systematic plantwide control procedure proposed by Skogestad, has been used. The main idea of suggested method is based on the self-optimizing variables. One of the advantages of this method of designing a control structure is considering the economic optimization of the process in most stages of its implementation. The indirect and direct dimethyl ether synthesis from natural gas feed have been investigated in this study. In this research, indirect and direct dimethyl ether synthesis processes are simulated with Aspen Plus V10 and degree of freedom analysis is done....
Stereoelectronic effects: A simple yet powerful tool to manipulate anion affinity
, Article Organic and Biomolecular Chemistry ; Volume 13, Issue 7 , Dec , 2015 , Pages 2170-2176 ; 14770520 (ISSN) ; Fattahi, A ; Kass, S.R ; Sharif University of Technology
Royal Society of Chemistry
2015
Abstract
Different strategies are employed in designing strong and selective anion receptors but stereoelectronic effects have been largely ignored. In this work, the stereo configuration of a non-interacting ether is found to have a large impact of more than two orders of magnitude on the binding of a rigid diol with tetrabutylammonium chloride in acetonitrile-d3. A favorable carbon-oxygen dipole and an intramolecular C-H⋯OH hydrogen bond in an equatorially substituted ether is found to be energetically more important than a stabilizing hydrogen bond in the corresponding axially oriented alcohol. IR spectroscopy is also used to probe the structures of the bound complexes and several binding motifs...
Application of artificial neural networks for estimation of the reaction rate in methanol dehydration
, Article Industrial and Engineering Chemistry Research ; Volume 49, Issue 10 , April , 2010 , Pages 4620-4626 ; 08885885 (ISSN) ; Yaripour, F ; Moradi, G ; Saber, M ; Sharif University of Technology
2010
Abstract
In this paper, the artificial neural network has been applied to estimate the reaction rate of methanol dehydration in dimethyl ether synthesis. The multilayer feed forward neural network with three inputs and one output has been trained with different algorithms and different numbers of neurons in the hidden layer. Two thirds of all training data are used for training of the network and the rest are used for testing of the generalization of the network. The accuracy of the proposed model was found to agree well with the experimental results over a wide range of experimental conditions. The results clearly depict that the neural network is a powerful tool to estimate the reaction rate and...