Molecular mechanics (MM2) calculations on siloxanes

Frierson, Manton R.; Allinger, Norman L.

doi:10.1002/poc.610020710

Cited by 8 publications

(6 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The parameters for the siloxane part of the organic chains (shown in Figure 2) are taken from the MM2 force field for siloxane compounds. 33 The parameters for the rest of the organic surface groups are taken from the TraPPE force field. The charges in the surface chains need to be adjusted to maintain electrical neutrality in the simulation cell.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Builes

Vega

2012

J. Phys. Chem. C

View full text Add to dashboard Cite

It has been demonstrated that merging the inherent sorptive behavior of amorphous silica with organic groups increases the adsorption capabilities of the solid silica. However, the underlying mechanism of the adsorption process in the functionalized materials is not fully understood, limiting the possibility of designing optimal adsorbent materials for different applications; hence, the availability of complementary methods to advance in this field is of great interest. Here we present results concerning the adsorption of CO2 in amine-functionalized silica materials, by Monte Carlo simulations, providing new insight into the capture mechanism. We propose a simulation methodology for the design of postsynthesis-functionalized silica materials in which realistic model adsorbents are generated using an energy bias selection scheme for the possible grafting sites. This methodology can be applied to different materials. In this work, we evaluate a model MCM-41 for CO2 adsorption using grand canonical Monte Carlo simulations, and compared the results with available experimental data. A new methodology is presented, which allows accounting for the chemisorbed CO2 on the adsorption isotherms. The results indicate that although chemisorption is an important part of this process at low pressures, physisorption also plays a significant role in the capture of CO2 in these materials. Functionalization increases the interactions of the CO2 molecules with the surface, whereas it decreases the available space for adsorption of CO2; the overall efficiency of the improved adsorption lies on the availability of adsorption space versus stronger interactions. In addition to the adsorption isotherms, we studied the configurations of the amine chains during the adsorption process for different degrees of functionalization as well as the effect of the concentration of grafted amines on the adsorption isotherm. The overall results show that molecular simulations serve as a guide to quantify the CO2 amount that can be easily sorbed for carbon capture applications, highlighting the importance of this approach.

show abstract

Section: ■ Computational Methodsmentioning

confidence: 99%

“…The parameters for the siloxane part of the organic chains (shown in Figure ) are taken from the MM2 force field for siloxane compounds . The parameters for the rest of the organic surface groups are taken from the TraPPE force field.…”

Section: Methodsmentioning

confidence: 99%

Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Builes

Vega

2012

J. Phys. Chem. C

View full text Add to dashboard Cite

show abstract

“…The parameters for the intermolecular interactions of the adsorbate molecules are listed in Table . The parameters for the siloxane part of the organic chain are taken from the MM2 force field for silane compounds . The parameters for the rest of the CH n organic groups are taken from the TraPPE force field.…”

Section: Methodsmentioning

confidence: 99%

Effect of Immobilized Amines on the Sorption Properties of Solid Materials: Impregnation versus Grafting

Builes

Vega

2012

Langmuir

View full text Add to dashboard Cite

The underlying mechanism of the adsorption process in functionalized materials is not yet fully understood. This incomplete understanding limits the possibility of designing optimal adsorbent materials for different applications. Hence, the availability of complementary methods to advance this field is of great interest. We present here results concerning the adsorption of CO(2) in amine-functionalized silica materials by Monte Carlo simulations, providing new insights into the capture process. Two different mechanisms of functionalization are compared: impregnation (a physical mixture of the amine and the support) and grafting (a chemical bond is formed between the amine and the support). We evaluate in this work a model of MCM-41 for N(2) and CO(2) adsorption with varying degrees of density of the functionalized chains. The results indicate that the mobility of the impregnated chains allows the creation of a network of microcavities, which enhance the low-pressure adsorption capabilities of these materials. Molecular simulations allow us to study in detail the conformational changes in the functionalized chains during the adsorption process. Materials functionalized densely by grafting undergo a change in the preferential orientation of the chains, which allows the adsorption of additional molecules close to the surface of the support. The adsorption of gas molecules close to the pore surface is usually the most energetically favorable configuration; however, for densely grafted materials the adsorption close to the surface occurs only at pressures large enough to provide energy to displace the functionalized chains.

show abstract

“…The parameters for the siloxane part of the organic chain are taken from the MM2 force field for silane compounds. 39 The parameters for the rest of the CH n organic groups are taken from the TraPPE force field. The charges in the surface chains were adjusted to maintain electrical neutrality in the simulation cell.…”

Section: Computational Sectionmentioning

confidence: 99%

Alkylsilane-Functionalized Microporous and Mesoporous Materials: Molecular Simulation and Experimental Analysis of Gas Adsorption

Builes¹,

López-Aranguren²,

Fraile³

et al. 2012

J. Phys. Chem. C

View full text Add to dashboard Cite

Solid sorbents are considered as a potentially less-energy-intensive alternative to the use of liquids for the removal and separation of liquid and gaseous fluids. The control of the surface characteristics of porous inorganic materials via the deposition of an organic layer is of great interest for tailoring the properties of the sorbent. For instance, organic functionalization of traditional solid sorbents (micro-and mesoporous silica and silicates) allows tuning their surface properties, such as hydrophilicity or hydrophobicity and surface reactivity. However, the underlying mechanism of the sorption process in highly complex organic functionalized materials is not yet fully understood. This incomplete understanding limits the possibilities of designing optimal adsorbents for different applications increasing the interest in performing complementary experimental-simulation studies. In this work, the adsorption of N 2 in alkylsilane-modified disordered mesoporous silica (silica gel 40) and crystalline aluminosilicate (zeolite Y) is analyzed by a combination of experiments and simulations. The goal of the adsorption simulation study was twofold: first, to assess the ability of using grand canonical Monte Carlo to obtain quantitative predictions of the adsorption characteristics of gases on alkylsilane postfunctionalized products and, second, to provide new insights into the adsorption mechanism. A supercritical silanization experimental method was used for the postmodification of the internal surface of the studied porous substrates. This work demonstrates that even though the models of amorphous hybrid materials require simplifications related to the cell size and silane polymerization modes, it is possible to use these models to obtain an adequate insight of what happens in the macroscopic systems. These models allow us to acquire information on the mechanisms of silane functionalization and the interactions of the support and silane chains with the adsorbed gases.

show abstract

Molecular mechanics (MM2) calculations on siloxanes

Abstract: The MM2 force field has been extended so that calculations may be carried out on siloxanes. The parameters chosen give a good fit to available experimental data.

Cited by 8 publications

References 25 publications

Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Effect of Immobilized Amines on the Sorption Properties of Solid Materials: Impregnation versus Grafting

Alkylsilane-Functionalized Microporous and Mesoporous Materials: Molecular Simulation and Experimental Analysis of Gas Adsorption

Contact Info

Product

Resources

About

Molecular mechanics (MM2) calculations on siloxanes

Abstract: The MM2 force field has been extended so that calculations may be carried out on siloxanes. The parameters chosen give a good fit to available experimental data.

Cited by 8 publications

References 25 publications

Understanding CO2 Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Understanding CO2 Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Effect of Immobilized Amines on the Sorption Properties of Solid Materials: Impregnation versus Grafting

Alkylsilane-Functionalized Microporous and Mesoporous Materials: Molecular Simulation and Experimental Analysis of Gas Adsorption

Contact Info

Product

Resources

About

Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation