Ab initio calculation of the dynamical properties of PPP and PPV

Sousa, Regina Lélis de; Alves, H. W. Leite

doi:10.1590/s0103-97332006000300072

Cited by 16 publications

(18 citation statements)

References 18 publications

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“…The reaction free energy, energy, and entropy calculated using eqs – are reported in Table . Results from quasi-harmonic approximation analysis ,, were compared, and both methods provide very similar estimates with errors <20%. In gas and sc-CO 2 phases, ⟨Δ U ⟩ increases as the systems depart from the minima.…”

Section: Resultsmentioning

confidence: 99%

How Collective Phenomena Impact CO₂ Reactivity and Speciation in Different Media

et al. 2020

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CO 2 has attracted considerable attention in recent years due to its role in the greenhouse effect and environmental management. While its reaction with water has been studied extensively, the same cannot be said for reactivity in the supercritical CO 2 phase, where the conjugate acid/base equilibria proceed through different mechanisms and activation barriers. In spite of the apparent simplicity of the CO 2 + H 2 O reaction, the collective effect of different environments has a drastic influence on the free energy profile. Enhanced sampling techniques and well-tailored collective variables provide a detailed picture of the enthalpic and entropic drivers underscoring the differences in the formation mechanism of carbonic acid in the gas, aqueous, and supercritical CO 2 phases.

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Section: Resultsmentioning

confidence: 99%

How Collective Phenomena Impact CO₂ Reactivity and Speciation in Different Media

et al. 2020

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“…Using the VDOS the entropic contribution for each of the finite temperature trajectories can be calculated [46,47]:…”

Section: Resultsmentioning

confidence: 99%

Finite temperature dynamics of anionic water trimers

Finn,

Baletto

2014

Preprint

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Utilising Car-Parrinello molecular dynamics simulations, the finite temperature behaviour of water trimers, (H 2 O) 3 , in both neutral and anionic frameworks, has been investigated. A significant structural change in the anionic structure has been observed at temperatures above 100 K where a chain geometry has formed and stabilised entropically. On the other hand, neutral trimers have remained in their ring structure, as predicted theoretically at low temperatures, for long time periods.

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“…Thus, we explore detailed reaction mechanisms of ethanol conversion to 1-butene over 2D-pillared MFI (2D-PMFI) zeolite using a combined theoretical and experimental approach in this study. To investigate Gibbs free energies of ethanol conversion steps near the presence of Brønsted acid sites (BAS), we employ DFT-based ab initio molecular dynamics (AIMD) simulations at experimentally relevant temperatures and quasi-harmonic approximations (QHA). , The calculated vibrational density of states (VDOS), obtained from the AIMD simulations, show a good agreement with measured in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra for adsorbed ethanol intermediate. Furthermore, the resulting thermodynamic profiles, based on quasi-harmonic approximation (QHA), reveal that the entropic contribution is essential in identifying the rate-determining step (RDS).…”

Section: Introductionmentioning

confidence: 89%

Mechanistic Understanding of Catalytic Conversion of Ethanol to 1-Butene over 2D-Pillared MFI Zeolite

et al. 2020

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Ethanol is an important C 2 platform molecule for producing value-added chemicals and distillate hydrocarbon fuels (e.g., jet and diesel). Among these, catalytic upgrading of ethanol to butenes can generate valuable commodity chemicals (e.g., 1-butene) and provide C 4 olefin intermediates that can be further upgraded to jet/diesel fuels. Twodimensional (2D) zeolites offer hierarchical mesoporous structures, leading to improved mass transport and reduced diffusion length, which can help to address the coking challenges faced by ethanol conversion to hydrocarbons over three-dimensional (3D) zeolites. In this study, we investigate the acidcatalyzed conversion of ethanol to 1-butene over the Brønsted acid sites (BAS) in 2D-pillared MFI zeolite (2D-PMFI) using ab initio molecular dynamics (AIMD) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and calorimetric measurements. A detailed thermodynamic analysis, using quasi-harmonic approximation (QHA), on the Gibbs free-energy pathway of ethanol conversion shows that the consideration of entropy is critical to accurately capture the detailed thermodynamic profiles. Employing the Blue Moon ensemble method, the formation of framework-bound butoxide from ethoxy and ethene is found to be the likely ratedetermining step (RDS), proceeding via a stepwise mechanism. The reactivity of 2D-PMFI can be further tuned by manipulating RDS through careful control of the number of BAS and operating temperatures. The calculated vibrational density of states (VDOS) validate the structural models of adsorbed ethanol by comparing with the experimental DRIFTS measurements. Overall, our study provides mechanistic insights into ethanol upgrading over the 2D-PMFI and shows the importance of evaluating entropic effects in such a confined system.

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Ab initio calculation of the dynamical properties of PPP and PPV

Cited by 16 publications

References 18 publications

How Collective Phenomena Impact CO₂ Reactivity and Speciation in Different Media

How Collective Phenomena Impact CO₂ Reactivity and Speciation in Different Media

Finite temperature dynamics of anionic water trimers

Mechanistic Understanding of Catalytic Conversion of Ethanol to 1-Butene over 2D-Pillared MFI Zeolite

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Ab initio calculation of the dynamical properties of PPP and PPV

Cited by 16 publications

References 18 publications

How Collective Phenomena Impact CO2 Reactivity and Speciation in Different Media

How Collective Phenomena Impact CO2 Reactivity and Speciation in Different Media

Finite temperature dynamics of anionic water trimers

Mechanistic Understanding of Catalytic Conversion of Ethanol to 1-Butene over 2D-Pillared MFI Zeolite

Contact Info

Product

Resources

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How Collective Phenomena Impact CO₂ Reactivity and Speciation in Different Media

How Collective Phenomena Impact CO₂ Reactivity and Speciation in Different Media