The Experts below are selected from a list of 45 Experts worldwide ranked by ideXlab platform
Yu Xi-meng - One of the best experts on this subject based on the ideXlab platform.
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A new process for the synthesis of dimethyl maleate:I preparation of catalyst
The Chemical Engineer, 2020Co-Authors: Yu Xi-mengAbstract:This article studied using Solid Molecule sieves (βzeolite)as the catalyst of the esterification of methanol and maleic anhydride,which focused on the modification conditions of β zeolite and the effects of esterification conditions to both conversion of maleic anhydride and reaction selectivity.H-β,Mg-βand Fe-βwere obtained from β zeolite through activation,ion exchange and calcinations.Activated at 550℃ for 4h and exchanged by NH4Cl,MgCl2 and FeCl3,the exchange rate of Na+ in βzeolite could reach 98.5%,96.3% and 95.2% through only one time of exchange.After calcination,the specific area of the obtained H-β,Mg-β and Fe-β zeolites reaches 390、370 and 331m2·g-1 respectively,which are almost ten times of the mother zeolites.The average hole-diameters of the three products decrease from 8.66nm before the treatments to 3.01,2.84 and 6.03 nm after calcination.
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A new process for the synthesis of dimethyl maleate:II study on the conditions of esterification
The Chemical Engineer, 2020Co-Authors: Yu Xi-mengAbstract:This article studied using Solid Molecule sieves as the catalyst of the esterification of methanol and maleic anhydride.The investigation focused on the effects of esterification conditions on both conversion of maleic anhydride and reaction selectivity.Reaction temperature,reaction time,amount of the catalyst and molar ratio of the raw materials were studied.Experimental results indicate that the increase of reaction temperature benefits the production of dimethyl maleate,with the optimum range being 105 ~110℃.Similarly,increases of the ratio of methanol to maleic anhydride,reaction time and catalyst amount also help the production of the goal ester.With the amount of the catalyst being at 0.5 percent of the maleic anhydride,the ratio of methanol to maleic anhydride being 3∶1 and reacting 12h at 110℃,the yield of dimethyl maleate may be over 93%.The catalyst can be reused for three times without substantial efficiency loss.
Tatsuto Kimura - One of the best experts on this subject based on the ideXlab platform.
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MOLECULAR DYNAMICS SIMULATION OF HETEROGENEOUS NUCLEATION OF A LIQUID DROPLET ON A Solid SURFACE
Microscale Thermophysical Engineering, 2020Co-Authors: Tatsuto Kimura, Shigeo MaruyamaAbstract:Heterogeneous nucleation of a liquid droplet on a Solid surface was simulated with the molecular dynamics method. Argon vapor was represented by 5,760 Lennard-Jones Molecules and the Solid surface was represented by one layer of 4,464 harmonic Molecules with the constant temperature heat bath model using the phantom Molecules. The potential parameter between a Solid Molecule and a vapor Molecule was varied to reproduce several surface wettabilities. When the vapor-Solid system was in equilibrium at 160 K, temperature of the Solid surface was suddenly decreased to 100 K or 80 K by the phantom method. Observed nucleation rate, critical nucleus size and free energy needed for cluster formation were not much different from the prediction of the classical heterogeneous nucleation theory in case of smaller cooling rate. The discrepancy became considerable with the increase in cooling rate and with increase in surface wettability because of the spatial temperature distribution.
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A molecular dynamics simulation of a bubble nucleation on Solid surface
Transactions of the Japan Society of Mechanical Engineers. B, 1999Co-Authors: Shigeo Maruyama, Tatsuto KimuraAbstract:In order to understand the molecular level phenomena related to the phase-change heat transfer, the authors are performing molecular dynamics simulations of a liquid droplet and a vapor bubble. Since many of practical nucleation phenomena are on the Solid surface, the authors are paying special attention to the effect of a Solid surface. Here, a heterogeneous nucleation of a vapor bubble on a Solid surface was simulated by the molecular dynamics method. Liquid argon between parallel Solid surfaces was gradually expanded, until a vapor bubble was nucleated. Argon liquid was represented by 5488 Lennard-Jones Molecules and each Solid surface was represented by three layers of harmonic Molecules with the constant temperature heat bath model using the phantom Molecules out side of the three-layers. They used a quite wettable potential parameter on the top surface and changed the wettability on the bottom surface. The wettability was varied by changing the potential parameter between argon and Solid Molecule. After the equilibrium of liquid between two Solid surfaces was obtained, they slowly expanded the surfaces. According to the increase in volume, the decrease of pressure was observed. There appeared patches of liquid where the local potential was considerably high. These patches appeared andmore » disappeared randomly in space and time. Finally, at some point of the decrease of the pressure, one of the patches successfully grew to a vapor bubble on the bottom Solid surface. Observed pressure showed the minimum at this time of the nucleation. They compared the minimum pressure for various surface potential conditions. With the increase in the surface wettability, the minimum pressure approached to the spinodal line. After the stable vapor bubble was formed on the surface, the authors stopped the expansion and observed the equilibrium structure of the vapor bubble. After averaging the two-dimensional density and potential distributions, they could define the contact angle. The contact angle was well correlated to the depth of the integrated effective surface potential in excellent agreement with the case of liquid droplet in contact with the surface.« less
Shigeo Maruyama - One of the best experts on this subject based on the ideXlab platform.
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MOLECULAR DYNAMICS SIMULATION OF HETEROGENEOUS NUCLEATION OF A LIQUID DROPLET ON A Solid SURFACE
Microscale Thermophysical Engineering, 2020Co-Authors: Tatsuto Kimura, Shigeo MaruyamaAbstract:Heterogeneous nucleation of a liquid droplet on a Solid surface was simulated with the molecular dynamics method. Argon vapor was represented by 5,760 Lennard-Jones Molecules and the Solid surface was represented by one layer of 4,464 harmonic Molecules with the constant temperature heat bath model using the phantom Molecules. The potential parameter between a Solid Molecule and a vapor Molecule was varied to reproduce several surface wettabilities. When the vapor-Solid system was in equilibrium at 160 K, temperature of the Solid surface was suddenly decreased to 100 K or 80 K by the phantom method. Observed nucleation rate, critical nucleus size and free energy needed for cluster formation were not much different from the prediction of the classical heterogeneous nucleation theory in case of smaller cooling rate. The discrepancy became considerable with the increase in cooling rate and with increase in surface wettability because of the spatial temperature distribution.
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A molecular dynamics simulation of a bubble nucleation on Solid surface
Transactions of the Japan Society of Mechanical Engineers. B, 1999Co-Authors: Shigeo Maruyama, Tatsuto KimuraAbstract:In order to understand the molecular level phenomena related to the phase-change heat transfer, the authors are performing molecular dynamics simulations of a liquid droplet and a vapor bubble. Since many of practical nucleation phenomena are on the Solid surface, the authors are paying special attention to the effect of a Solid surface. Here, a heterogeneous nucleation of a vapor bubble on a Solid surface was simulated by the molecular dynamics method. Liquid argon between parallel Solid surfaces was gradually expanded, until a vapor bubble was nucleated. Argon liquid was represented by 5488 Lennard-Jones Molecules and each Solid surface was represented by three layers of harmonic Molecules with the constant temperature heat bath model using the phantom Molecules out side of the three-layers. They used a quite wettable potential parameter on the top surface and changed the wettability on the bottom surface. The wettability was varied by changing the potential parameter between argon and Solid Molecule. After the equilibrium of liquid between two Solid surfaces was obtained, they slowly expanded the surfaces. According to the increase in volume, the decrease of pressure was observed. There appeared patches of liquid where the local potential was considerably high. These patches appeared andmore » disappeared randomly in space and time. Finally, at some point of the decrease of the pressure, one of the patches successfully grew to a vapor bubble on the bottom Solid surface. Observed pressure showed the minimum at this time of the nucleation. They compared the minimum pressure for various surface potential conditions. With the increase in the surface wettability, the minimum pressure approached to the spinodal line. After the stable vapor bubble was formed on the surface, the authors stopped the expansion and observed the equilibrium structure of the vapor bubble. After averaging the two-dimensional density and potential distributions, they could define the contact angle. The contact angle was well correlated to the depth of the integrated effective surface potential in excellent agreement with the case of liquid droplet in contact with the surface.« less
Qian Ping - One of the best experts on this subject based on the ideXlab platform.
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Approximate expression of Young’s equation and molecular dynamics simulation for its applicability
Chinese Physics B, 2019Co-Authors: Qian PingAbstract:In 1805, Thomas Young was the first to propose an equation (Young's equation) to predict the value of the equilibrium contact angle of a liquid on a Solid. On the basis of our predecessors, we further clarify that the contact angle in Young's equation refers to the super-nano contact angle. Whether the equation is applicable to nanoscale systems remains an open question. Zhu et al. [College Phys. 47 (1985)] obtained the most simple and convenient approximate formula, known as the Zhu-Qian approximate formula of Young's equation. Here, using molecular dynamics simulation, we test its applicability for nanodrops. Molecular dynamics simulations are performed on argon liquid cylinders placed on a Solid surface under a temperature of 90 K, using Lennard-Jones potentials for the interaction between liquid Molecules and between a liquid Molecule and a Solid Molecule with the variable coefficient of strength a. Eight values of a between 0.650 and 0.825 are used. By comparison of the super-nano contact angles obtained from molecular dynamics simulation and the Zhu-Qian approximate formula of Young's equation, we find that it is qualitatively applicable for nanoscale systems.
Stefano A. Mezzasalma - One of the best experts on this subject based on the ideXlab platform.
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Chaotic Dynamics in a Percolation Model for Evaporation of a Solid Body: A Description of Solid/Gas Reactions with Consumption Based on Thermodiffusive Nonlinearity at the Solid/Gas Interface
Journal of Colloid and Interface Science, 1999Co-Authors: Stefano A. MezzasalmaAbstract:A nonlinear truncated model, concerning thermodiffusive chaos in gaseous media, has been employed to represent evaporation of a Solid body on the basis of nonlinearity at the Solid/gas interface. Solid/gas consumption has been described in the cell which is characterized by the wavenumber of the interfacial convective motion. The Solid Molecule/atom evaporates according to a Boltzmann law that is ruled by temperature profiles coming from the truncated model. This allows the interpretation of the evaporative mechanism as depending on a Poincare map related to the interfacial dynamics and suggests a possible correspondence between kinetics and nonlinear cooperative regimes. Percolative properties (k-th moments, critical threshold and exponents, fractal dimension) of the evaporating Solid path have been derived for different thermal levels (i.e., reactivity), namely, for different values of the reduced Rayleigh number (r), which in the model accounts for the temperature contribution. The achieved descriptions generally agree with microstructural and theoretical observations concerning gasification of reacting Solid/fluid systems. Moreover, previously proposed kinetic data (i.e., gasification rate versus fractional conversion) of char/air reactions have been interpreted in terms of a percolation theory that involves the Solid/gas reactivity and the order of the convective mode (i.e., wavenumber). This result resembles the so-called finite amplitude cellular convection in gaseous and liquid layers working in nonlinear regimes.