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• The aromatic additive was not capable of deagglomerating the asphaltenes due to low polarity and nearly planar structure. • The two polar additives disintegrated the asphaltene dimer by exfoliating off and separating the top monomer. • Hydrogen bonding and the distribution of polar groups were key to deagglomeration. • A single additive molecule yielded temporary dimer disintegration and could not prevent the eventual re-dimerization. Recycling agent plays an increasingly important role in promoting asphalt pavement sustainability, as it allows to bump up the incorporating dosage of recycled asphalt materials. The desired characteristics of a recycling agent includes not only the softening effect but also the capability of deagglomerating the oxidized asphaltenes by effectively interacting with them. The objective of this study was to provide novel insights into the deagglomerating potential of three additives selected based on the structural and compositional discrepancies, including an aromatic extract C 12 H 16 , a bio-additive myristamide C 14 H 29 NO, and a common plasticizer tributyl citrate (TBC) C 18 H 32 O 7. Steered molecular dynamics simulation was performed to obtain the intercalation in which each additive was intercalated between the stacking asphaltene sheets, with the objective to simulate the outcome of blending and mixing. These configurations were then subjected to long-time simulations during which the structural changes and the interactions were tracked. The results indicated that the aromatic extract yielded the least impact on the asphaltene dimer configuration during intercalation and had little deagglomerating effectiveness. Owing to the higher molecular flexibility and polarity, the other two additives produced more pronounced changes in the dimer structure during intercalation. They were able to disintegrate the dimer by exfoliating off and separating an asphaltene monomer, even though the effects were only temporary before re-dimerization occurred. Different types of interactions of the additives with the asphaltenes were visualized based on quantum chemical computations and discussed with respect to their contributions to the deagglomerating behaviors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The plasticizers of DBP and TBC effectively restored the stiffness, relaxation capability, and crack resistance of the aged asphalt. • Both plasticizers lowered the glass transition temperature and broadened the transition region and linear viscoelastic relaxation spectrum. • TBC exhibited a stronger deagglomerating effect based on analytical characterizations and molecular dynamics simulations. • The higher rejuvenating effectiveness of TBC was due to its higher polarity and forming hydrogen bonds with asphalt molecules. Plasticizers are common additives used to enhance the flexibility and workability of polymer materials. Recent findings suggest a great potential for typical plasticizers being used as rejuvenators to recycle oxidized paving asphalts. This study investigated the rejuvenating effectiveness of two plasticizers via rheological evaluation and explored the underlying mechanism by analytical characterizations and molecular dynamics (MD) simulations. A conventional plasticizer dibutyl phthalate (DBP) and an environmentally friendly tributyl citrate (TBC) were selected given the discrepancies in their molecular structures. Both plasticizers were effective in restoring the rheological performance of the aged asphalt; TBC was relatively more efficient which was attributed to its higher molecular polarity and the formation of hydrogen bonds with the oxidized asphalt molecules. Analyses based on the gel permeation chromatography and differential scanning calorimetry suggested the capability of the plasticizers in dissociating the oxidized asphalt molecules and improving the molecular mobility. The improved molecular mobility was considered responsible for the reversing effect of the plasticizers, as compared to aging, in terms of widening the relaxation spectrum and broadening the glass transition region. The plasticizers' dissociating effect was confirmed and visualized in the simulations by inspecting their impacts on the spatial arrangement and distribution of the asphaltenes. [ABSTRACT FROM AUTHOR]

The effect of H 2 O 2 desorption on the direct synthesis of H 2 O 2 from H 2 and O 2 over Pd-TiO 2 (B)/anatase and Pd-anatase has been investigated. The interaction between H 2 O 2 and the support has been studied by isothermal microcalorimetry and molecular dynamics (MD) simulation. H 2 O 2 desorption from TiO 2 (B)/anatase is more facile due to the existence of TiO 2 (B). The accelerated H 2 O 2 desorption from the catalyst surface can effectively decrease the hydrogenation rate of H 2 O 2 over Pd-TiO 2 (B)/anatase, which results in a 57% increase in the selectivity of H 2 O 2 synthesis. [ABSTRACT FROM AUTHOR]

Abstract: A grand canonical Monte Carlo-simulation (GCMC) study is presented focussing on the adsorption of CO2/CH4 mixtures in different nanopore models, including pristine mesoporous carbons, carbon foams, carbon nanotubes (CNTs), and nanopore models modified with hydrophilic carboxylic groups. We also report and discuss the selectivity of the different adsorbent surfaces under a wide range of temperature and pressure. Our results show that foam structures have the highest adsorption capacity of all the pristine structures studied because of its special architecture. The selectivity markedly enhanced after modification, especially at low pressures, and modified CNTs are found to have the highest selectivity among all the models tested. The effect of temperature and pressure is evaluated and the change in the selectivity trends of modified nanopore models are in contrast to that of the pristine models. The results suggest that the separation performance in carbon nanopores is greatly affected by the nature of the architecture and the heterogeneity of the materials. These findings could be beneficial in conventional pressure swing adsorption processes and the nanoporous structures could be used as parts of mixed polymer membranes. The results of this work present some guidelines for the designing nanoporous structures in order to achieve optimal separation of CO2/CH4 mixtures. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations were performed to study the hydration of Na+ inside carbon nanotubes (CNTs) under external electric fields from 0 to 0.1V/nm. The simulation results show that the hydration of Na+ varies with the electric field intensity (E). The coordination number in the first hydration shell of Na+ increases with the increase of E. The analysis of orientation distributions for water dipole shows the Na+ hydration is strengthened when the direction of external field is aligned with the electric field generated by Na+, and is weakened when these are opposite. When E is aligned with the electric field of Na+, the strength of hydration is non-monotonic as E and reaches its maximum when E is equal to 0.01V/nm. This finding provides some guidance for the application of electric field in ion-transporting channels. [Copyright &y& Elsevier]