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Yinhua Wan - One of the best experts on this subject based on the ideXlab platform.
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fabrication of high Silicalite 1 content filled pdms thin composite pervaporation membrane for the separation of ethanol from aqueous solutions
Journal of Membrane Science, 2017Co-Authors: Haoli Zhou, Yinhua Wan, Jinqiang Zhang, Wanqin JinAbstract:Abstract Sedimentation of Silicalite-1 occurs in the fabrication of thin Silicalite-1 filled polydimethylsiloxane (PDMS) hybrid composite membranes if the viscosity of membrane solution is low, which makes this preparation challenging. In this work, a new method that use a platinum catalytic agent to assist the pre-polymerization of PDMS polymer to increase the viscosity of the membrane solution was studied. With this method, supported Silicalite-1 filled PDMS hybrid composite membranes were fabricated and applied in the pervaporative separation of a 5 wt% dilute ethanol aqueous solution. The effect of the concentration of platinum catalytic agent on the membrane properties was first investigated using CRM, DSC and extraction experiment. Optimum of viscosity of the composite membrane solution was then conducted and a selective layer of as thin as 5 µm thickness was obtained with a flux of 5.52 kg/m 2 h in combination with a separation factor of 15.5 at 50 °C. After that the separation performances of different thick membranes, interfacial adhesion properties of hybrid membranes, comparisons with other reported results and membrane stability were investigated. Results showed homemade Silicalite-1-PDMS hybrid composite membrane offers relatively high separation performance, indicating a potential industrial application for the separation of ethanol from aqueous solutions.
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separation of acetone butanol and ethanol abe from dilute aqueous solutions by Silicalite 1 pdms hybrid pervaporation membranes
Separation and Purification Technology, 2011Co-Authors: Haoli Zhou, Xiangrong Chen, Yinhua WanAbstract:To study the effects of different factors on the separation of acetone, butanol, and ethanol (ABE) from ABE-water solutions by pervaporation with Silicalite-l/polydimethylsiloxane (PDMS) hybrid membranes, the adsorption of ABE in the Silicalite-1 in acetone-butanol-water solution and ethanol-butanol-water solution was firstly investigated and then the separation of ABE from binary aqueous solutions at different feed concentrations and temperatures was examined. Experimental results showed that butanol could be preferentially adsorbed on Silicalite-1 and the permeability of acetone through the membrane was the highest, followed by butanol and ethanol, which was not consistent with the predictions based on the experimental results of adsorption and membrane swelling measurement. This could be explained by Hansen solubility parameters for the component and polymer interactions (delta(m,c)) and for the organic solvent and water interactions (delta(w,i)). In the separation of ABE-water solution by the Silicalite-1/PDMS hybrid pervaporation membranes, acetone and ethanol could promote ABE transport through membrane and block water permeation, and the membrane performance could be significantly affected by vacuum pressure in the permeate side. (C) 2011 Elsevier B.V. All rights reserved.
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modification of Silicalite 1 by vinyltrimethoxysilane vtms and preparation of Silicalite 1 filled polydimethylsiloxane pdms hybrid pervaporation membranes
Separation and Purification Technology, 2010Co-Authors: Haoli Zhou, Xiangrong Chen, Yinhua WanAbstract:In preparation of inorganic particles filled polymer membranes, coupling agents can help to improve the compatibility between inorganic filler and polymer matrix. In this paper, surface modification of Silicalite-1 was performed by a coupling agent, vinyltrimethoxysilane (VTMS), and hybrid pervaporation membranes were prepared by incorporating the unmodified or VTMS-modified Silicalite-1 into polydimethylsiloxane (PDMS). The VTMS-modified Silicalite-1 particles and hybrid membranes were characterized by FT-IR, (29)Si CP MAS NMR, DSC, TGA, XRD and SEM. The results showed that the coupling agent VTMS was readily grafted on the surface of Silicalite-1 by hydrolysis reaction and condensation reaction, and the chemical linking between the -CH=CH(2) group on the surface-modified Silicalite-1 and -Si-H on the PDMS substantially eliminated the nonselective voids inside the membrane. When used to separate acetone, butanol, ethanol (ABE) from aqueous solution, a higher selectivity was obtained with the VTMS-modified Silicalite-1/PDMS hybrid membrane. Moreover, the surface modification of Silicalite-1 improved its dispersion in PDMS and increased the maximal loading of Silicalite-1 in membrane preparation, and thus further enhanced the separation factor of the membrane. (C) 2010 Elsevier B.V. All rights reserved.
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preparation and characterization of vinyltriethoxysilane vtes modified Silicalite 1 pdms hybrid pervaporation membrane and its application in ethanol separation from dilute aqueous solution
Journal of Membrane Science, 2010Co-Authors: Yinhua WanAbstract:To improve the affinity between Silicalite-1 and polydimethylsiloxane (PDMS), the Silicalite-1 particles were modified by a silane coupling agent vinyltriethoxysilane (VTES) and incorporated into polydimethylsiloxane (PDMS) matrix for the preparation of Silicalite-1/PDMS hybrid membranes. The modified Silicalite-1 particles were examined by XRD, FT-IR and TGA, and the results showed that the silane coupling agent was bonded to the surface of Silicalite-1 particles through chemical bonds and the modification did not influence the framework of Silicalite-1 crystals. VTES could enhance the interaction of Silicalite-1 particles with PDMS through chemical bonds and hence suppressed the formation of microvoids at polymer-Silicalite-1 interface, as a result, the thermal stability of the hybrid membrane could be improved. The effect of Silicalite-1 loading on the pervaporation performances of the hybrid membranes with dilute ethanol solutions was investigated. As compared with the unmodified hybrid membranes, the VTES modified Silicalite-1/PDMS hybrid membranes effectively improved the pervaporation selectivity at different Silicalite-1 loadings. With increasing Silicalite-1 loading, membrane selectivity increased for both unmodified and VTES modified Silicalite-1/PDMS hybrid membranes, and a selectivity of 32 was obtained when VETS modified Silicalite-1 loadings was 67%. It was also found that with increasing Silicalite-1 loading, the total flux of both unmodified and VTES modified Silicalite-1/PDMS hybrid membranes decreased while the ethanol flux of both hybrid membranes increased. With increasing the feed ethanol concentration at a given temperature, the total flux, ethanol flux, and ethanol concentration in permeate increased almost proportionally, while water flux decreased and the separation factor decreased slightly. An increase in temperature increased the permeation fluxes of both ethanol and water, while the separation factor was more or less constant at a given ethanol concentration. (C) 2010 Elsevier B.V. All rights reserved.
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application of response surface methodology and central composite rotatable design in optimizing the preparation conditions of vinyltriethoxysilane modified Silicalite polydimethylsiloxane hybrid pervaporation membranes
Separation and Purification Technology, 2010Co-Authors: Yinhua WanAbstract:Response surface methodology (RSM) based on a five-level-three-variable central composite rotatable design (CCRD) was employed for optimization of preparation conditions of vinyltriethoxysilane (VTES)modified Silicalite/polydimethylsiloxane (PDMS) hybrid pervaporation membranes. The three variables considered were Silicalite loading, crosslinker/prepolymer weight ratio and polymer concentration. With a feed containing 5.0 wt% ethanol as a model solution, the main effects, quadratic effects and interactions of the three variables on the selectivity and total flux of hybrid membranes were investigated by the analysis of variance (ANOVA). The results showed that the main effect of Silicalite loading was the most significant factor that influenced the hybrid membrane's selectivity, followed by the quadratic effect of Silicalite loading, the main effect of crosslinker/prepolymer weight ratio and polymer concentration. The most significant factor that influenced the total flux was the main effect of polymer concentration. Regression equations between the preparation variables and the performance of the hybrid membranes were also established. Predicted values from the regression equations were found to be in good agreement with observed values, indicating that the regression equations could be used to predict and optimize the performance of the VTES modified Silicalite/PDMS hybrid membranes. Under the preparation conditions of 66.8% Silicalite loading, 0.098 crosslinker/prepolymer weight ratio and 23.7% polymer concentration, the maximum selectivity of 34.3 could be obtained with the feed containing 5.0 wt% ethanol at 323 K. (C) 2009 Elsevier B.V. All rights reserved.
Haoli Zhou - One of the best experts on this subject based on the ideXlab platform.
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fabrication of high Silicalite 1 content filled pdms thin composite pervaporation membrane for the separation of ethanol from aqueous solutions
Journal of Membrane Science, 2017Co-Authors: Haoli Zhou, Yinhua Wan, Jinqiang Zhang, Wanqin JinAbstract:Abstract Sedimentation of Silicalite-1 occurs in the fabrication of thin Silicalite-1 filled polydimethylsiloxane (PDMS) hybrid composite membranes if the viscosity of membrane solution is low, which makes this preparation challenging. In this work, a new method that use a platinum catalytic agent to assist the pre-polymerization of PDMS polymer to increase the viscosity of the membrane solution was studied. With this method, supported Silicalite-1 filled PDMS hybrid composite membranes were fabricated and applied in the pervaporative separation of a 5 wt% dilute ethanol aqueous solution. The effect of the concentration of platinum catalytic agent on the membrane properties was first investigated using CRM, DSC and extraction experiment. Optimum of viscosity of the composite membrane solution was then conducted and a selective layer of as thin as 5 µm thickness was obtained with a flux of 5.52 kg/m 2 h in combination with a separation factor of 15.5 at 50 °C. After that the separation performances of different thick membranes, interfacial adhesion properties of hybrid membranes, comparisons with other reported results and membrane stability were investigated. Results showed homemade Silicalite-1-PDMS hybrid composite membrane offers relatively high separation performance, indicating a potential industrial application for the separation of ethanol from aqueous solutions.
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separation of acetone butanol and ethanol abe from dilute aqueous solutions by Silicalite 1 pdms hybrid pervaporation membranes
Separation and Purification Technology, 2011Co-Authors: Haoli Zhou, Xiangrong Chen, Yinhua WanAbstract:To study the effects of different factors on the separation of acetone, butanol, and ethanol (ABE) from ABE-water solutions by pervaporation with Silicalite-l/polydimethylsiloxane (PDMS) hybrid membranes, the adsorption of ABE in the Silicalite-1 in acetone-butanol-water solution and ethanol-butanol-water solution was firstly investigated and then the separation of ABE from binary aqueous solutions at different feed concentrations and temperatures was examined. Experimental results showed that butanol could be preferentially adsorbed on Silicalite-1 and the permeability of acetone through the membrane was the highest, followed by butanol and ethanol, which was not consistent with the predictions based on the experimental results of adsorption and membrane swelling measurement. This could be explained by Hansen solubility parameters for the component and polymer interactions (delta(m,c)) and for the organic solvent and water interactions (delta(w,i)). In the separation of ABE-water solution by the Silicalite-1/PDMS hybrid pervaporation membranes, acetone and ethanol could promote ABE transport through membrane and block water permeation, and the membrane performance could be significantly affected by vacuum pressure in the permeate side. (C) 2011 Elsevier B.V. All rights reserved.
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modification of Silicalite 1 by vinyltrimethoxysilane vtms and preparation of Silicalite 1 filled polydimethylsiloxane pdms hybrid pervaporation membranes
Separation and Purification Technology, 2010Co-Authors: Haoli Zhou, Xiangrong Chen, Yinhua WanAbstract:In preparation of inorganic particles filled polymer membranes, coupling agents can help to improve the compatibility between inorganic filler and polymer matrix. In this paper, surface modification of Silicalite-1 was performed by a coupling agent, vinyltrimethoxysilane (VTMS), and hybrid pervaporation membranes were prepared by incorporating the unmodified or VTMS-modified Silicalite-1 into polydimethylsiloxane (PDMS). The VTMS-modified Silicalite-1 particles and hybrid membranes were characterized by FT-IR, (29)Si CP MAS NMR, DSC, TGA, XRD and SEM. The results showed that the coupling agent VTMS was readily grafted on the surface of Silicalite-1 by hydrolysis reaction and condensation reaction, and the chemical linking between the -CH=CH(2) group on the surface-modified Silicalite-1 and -Si-H on the PDMS substantially eliminated the nonselective voids inside the membrane. When used to separate acetone, butanol, ethanol (ABE) from aqueous solution, a higher selectivity was obtained with the VTMS-modified Silicalite-1/PDMS hybrid membrane. Moreover, the surface modification of Silicalite-1 improved its dispersion in PDMS and increased the maximal loading of Silicalite-1 in membrane preparation, and thus further enhanced the separation factor of the membrane. (C) 2010 Elsevier B.V. All rights reserved.
Randall Q. Snurr - One of the best experts on this subject based on the ideXlab platform.
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Molecular modeling of binary liquid-phase adsorption of aromatics in Silicalite
AIChE Journal, 2004Co-Authors: Shaji Chempath, Randall Q. Snurr, John J. LowAbstract:Adsorption in the zeolite Silicalite from binary liquid mixtures of p-xylene, m-xylene, and toluene was investigated using grand canonical Monte Carlo (GCMC) simulations. The results obtained agree well with experimental excess adsorption isotherms from the literature. The agreement is very good when the zeolite is modeled using the PARA form of the Silicalite structure, but the results obtained with the native ORTHO structure are in some cases even qualitatively wrong. This supports the previous suggestion that the structure of Silicalite undergoes a transition from ORTHO to PARA upon adsorption of aromatic molecules. Molecular-level details of the energetics and siting within the zeolite provide insights into the macroscopic behavior. The simulated single-component and binary results were used to test ideal adsorbed solution theory for these systems. © 2004 American Institute of Chemical Engineers AIChE J, 50: 463–469, 2004
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adsorption of liquid phase alkane mixtures in Silicalite simulations and experiment
Langmuir, 2004Co-Authors: Shaji Chempath, Gino V. Baron, Joeri F. M. Denayer, Kurt De Meyer, Randall Q. SnurrAbstract:A combination of experimental and computational studies of adsorption from liquid-phase mixtures of linear alkanes in the zeolite Silicalite is presented here. Configurational biased grand canonical Monte Carlo simulations combined with identity-swap moves are used to equilibrate the simulations in reasonable times. Interesting trends observed in experiments have been captured quantitatively by simulations. A siting analysis of the simulation data reveals that, during adsorption from a liquid mixture, shorter alkanes prefer the zigzag channels and longer alkanes concentrate in the straight channels of Silicalite.
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prediction of adsorption of aromatic hydrocarbons in Silicalite from grand canonical monte carlo simulations with biased insertions
The Journal of Physical Chemistry, 1993Co-Authors: Randall Q. Snurr, Alexis T Bell, Doros N TheodorouAbstract:Adsorption isotherms and isosteric heats of adsorption for benzene and p-xylene in Silicalite have been calculated from molecular simulations. The simulations were performed using newly developed grand canonical ensemble Monte Carlo (GCMC) techniques in which insertion attempts are biased toward the most favorable regions of the zeolite pore space. The new techniques result in a substantial improvement in the efficiency of the simulations compared to traditional GCMC. The adsorption thermodynamics and molecular-level structure were studied for benzene and p-xylene in Silicalite with Pnma symmetry (ORTHO) and P2[sub 1]2[sub 1]2[sub 1] symmetry (PARA). The subtle differences between ORTHO and PARA Silicalite result in qualitatively different sorption behavior. An explanation of the experimentally observed step in the adsorption isotherm is presented, based on the results of the simulations and the ORTHO to PARA framework transformation that is observed experimentally. Predictions of the adsorption isotherms, isosteric heats, and siting locations of the adsorbates are in good agreement with experiment. 59 refs., 14 refs., 4 tabs.
Doros N Theodorou - One of the best experts on this subject based on the ideXlab platform.
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transport diffusivity of n2 and co2 in Silicalite coherent quasielastic neutron scattering measurements and molecular dynamics simulations
Journal of Physical Chemistry B, 2004Co-Authors: George K Papadopoulos, Herve Jobic, Doros N TheodorouAbstract:A direct comparison of experimental measurements (coherent quasielastic neutron scattering) and simulation (molecular dynamics) is carried out for the first time to investigate the concentration dependence of transport diffusivity of nitrogen and carbon dioxide in Silicalite-1. Theoretical elaboration of the simulation results on the basis of the quasichemical mean field approximation and a model of surface diffusion due to D. A. Reed and G. Ehrlich (Surf. Sci. 1981, 102, 588) leads to the conclusion that the corrected (Darken) diffusivity D0 can exhibit significant dependence on the loading θ of the sorbed phase, varying with the strength of interactions between the sorbate molecules. As a consequence of sorbate−sorbate interactions being considerably more attractive in CO2/Silicalite-1 than in N2/Silicalite-1, D0(θ) is a decreasing function in CO2/Silicalite-1 but displays a weak maximum in N2/Silicalite-1.
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prediction of adsorption of aromatic hydrocarbons in Silicalite from grand canonical monte carlo simulations with biased insertions
The Journal of Physical Chemistry, 1993Co-Authors: Randall Q. Snurr, Alexis T Bell, Doros N TheodorouAbstract:Adsorption isotherms and isosteric heats of adsorption for benzene and p-xylene in Silicalite have been calculated from molecular simulations. The simulations were performed using newly developed grand canonical ensemble Monte Carlo (GCMC) techniques in which insertion attempts are biased toward the most favorable regions of the zeolite pore space. The new techniques result in a substantial improvement in the efficiency of the simulations compared to traditional GCMC. The adsorption thermodynamics and molecular-level structure were studied for benzene and p-xylene in Silicalite with Pnma symmetry (ORTHO) and P2[sub 1]2[sub 1]2[sub 1] symmetry (PARA). The subtle differences between ORTHO and PARA Silicalite result in qualitatively different sorption behavior. An explanation of the experimentally observed step in the adsorption isotherm is presented, based on the results of the simulations and the ORTHO to PARA framework transformation that is observed experimentally. Predictions of the adsorption isotherms, isosteric heats, and siting locations of the adsorbates are in good agreement with experiment. 59 refs., 14 refs., 4 tabs.
Y S Lin - One of the best experts on this subject based on the ideXlab platform.
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molecular sieving mfi type zeolite membranes for pervaporation separation of xylene isomers
Journal of the American Chemical Society, 2004Co-Authors: Wenhui Yuan, Y S Lin, Weishen YangAbstract:Molecular sieving MFI-type zeolite membranes were prepared by a secondary growth method without using an organic template. Silicalite membranes with intercrystalline pores minimized or eliminated were obtained by this synthesis method which avoids the template removal step. The Silicalite membrane exhibits molecular sieving characteristics with pervaporation separation factor for p-xylene to o-xylene or m-xylene of as high as about 70, the highest ever reported for a pervaporation membrane.
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synthesis of submicron polycrystalline mfi zeolite films on porous ceramic supports
Journal of Membrane Science, 1998Co-Authors: Junhang Dong, Karsten Wegner, Y S LinAbstract:Abstract This paper reports preparation and properties of ultra-thin MFI-type zeolite (Silicalite) films on sol–gel derived mesoporous 8 mol% yttria doped zirconia (YZ) supports by the in situ synthesis method. Only non-continuous zeolite films were obtained on the as-synthesized YZ supports (calcined at 450°C). Continuous polycrystalline pure Silicalite films, with a thickness of 0.5–0.7 μm, could be grown on the YZ supports pretreated at 700°C. The difference in the oxygen vacancy defect concentrations in these two types of YZ supports is suggested to explain the different results of growing Silicalite films. Moreover, defect free 2–3 μm thick Silicalite films were also prepared on the α-alumina supports under the same synthesis conditions. The Silicalite layer on the YZ support offers a significantly lower mass transfer resistance as compared to that on the alumina support. Single gas permeation data of hydrogen, methane and ethane through these membranes were measured and compared with those of Silicalite membranes prepared by other groups. The alumina supported Silicalite membranes prepared in this work show better separation factors than the literature values. The zeolite film on the YZ support is less resistant to the stress induced in the step of template removal as compared to the zeolite film on the alumina support.
