Interfacial Engineering for Oil and Gas Applications: Role of Modeling and Simulation

Jha, Kshitij C.; Singh, Vikram; Tsige, Mesfin

doi:10.1007/978-3-319-40124-9_8

Cited by 3 publications

(3 citation statements)

References 198 publications

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“…These techniques cover a wide spectrum of these steps, both in size and time scales. 33 Among them, MD simulation is a reliable tool, because of its ability to access scales and buried interfaces that are experimentally challenging to characterize, 34 especially under reaction conditions. In our previous atomistic (AA) MD simulation study, we showed that inside TiO 2 and SiC mesopores and under reaction conditions the wax (we used n-octacosane (n-C 28 ) as a representative paraffin) and water at high mole fractions (i.e., x H 2 O = 0.9655) segregate into two phases.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of the n-Octacosane–Water Mixture Confined in Graphene Mesopores: Comparison of Atomistic and Coarse-Grained Calculations and the Effect of Catalyst Nanoparticle

et al. 2021

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Fischer−Tropsch synthesis (FTS) is used extensively in the gas-to-liquids (GTL) process to produce clean, highquality low emission transportation fuels from synthesis gas. In order to gain a better understanding of the phase behavior of the produced wax−water mixtures at reaction conditions by accounting for confinement effects of either hydrophilic or hydrophobic characteristics and catalyst nanoparticles (NPs), one needs to closely examine the validity of incorporating coarse grained approaches in the context of FTS. The present study focuses on simulating by means of atomistic (AA) and coarse-grained (CG) molecular dynamics (MD; CGMD) simulations the n-octacosane (n-C 28 )−water mixture inside graphene (G) and graphene oxide (GO) mesopores under low-temperature FTS conditions (473.15 K) with the inclusion of a Co NP. Graphene derivatives were selected as they are emerging catalyst support materials in the FTS reaction and allow for direct comparisons between the AA and CG methodologies. We also evaluated the presence of long-chain alcohols such as dodecan-1-ol at 7 wt % on the n-C 28 −H 2 O mixture phase behavior. The AA simulations involved the use of the united atom TraPPE (TraPPE-UA) force field for n-C 28 and the alcohols and the TIP4P/2005 force field for water, while the MARTINI force field was used for the CG description. With regard to the mixtures inside the G pore, both AA and CG simulation methods capture the phase separation of the mixture, with water molecules occupying the center of the pore and n-C 28 forming layers at the pore walls; inside GO, both methodologies show that water separates near the surface and the model wax lies at the pore center. Both AA and CG simulations accurately capture the n-C 28 and H 2 O diffusivity as a function of the distance from the G and GO pore centers, respectively, being lower closer to the pore surface. Dodecan-1-ol is mostly located at the n-C 28 −H 2 O interface showing a higher preference toward the wax as a consequence of increased van der Waals intermolecular interactions, slightly reducing the mobility of water. The agreement between AA and CG MD simulations paved the way for novel CGMD simulations with DFT-derived parameters for Co, to study the n-C 28 −H 2 O behavior in its presence. Our results show that the Co NP does not affect phase separation of the n-C 28 −H 2 O mixture inside the pores; however, water at such high concentrations covers the Co NP surface extensively. Given the experimental difficulties in exploring the relevant mechanisms at this scale, our results showcase that CGMD using the MARTINI force field can be employed to study FTS-related processes at this level and are expected to open new pathways in the investigation of confined mixtures relevant to the FTS reaction in the presence of supported catalyst NPs.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of the n-Octacosane–Water Mixture Confined in Graphene Mesopores: Comparison of Atomistic and Coarse-Grained Calculations and the Effect of Catalyst Nanoparticle

et al. 2021

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“…Therefore, Co NPs in this size range and smaller in the presence of high water contents become thermodynamically unstable with increased mobility, resulting in hydrothermal sintering and the ultimate catalyst deactivation possibly via a mechanism of Co surface area loss ,,,, or by Co surface oxidation. ,− Molecular modeling techniques can be used to understand the fundamental mechanisms controlling such phenomena in such sizes and time scales, which may otherwise be experimentally challenging to characterize, especially under reaction conditions. In our previous Molecular Dynamics (MD) simulation study we showed that Coarse-Grained Molecular Dynamics (CGMD) simulations can be used for the study of wax–water mixtures under confinement at the mesoscale in the context of FTS .…”

Section: Introductionmentioning

confidence: 99%

Coarse-Grained Molecular Dynamics Simulation of Cobalt Nanoparticle in the n-Octacosane–Water Mixture: The Effect of Water Concentration and Nanoparticle Size

et al. 2022

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The Fischer–Tropsch synthesis (FTS) is central in the Gas-to-Liquids (GTL) process, which is commercially used in the production of environmentally benign transportation fuels from synthesis gas. However, several factors can impede the performance of FTS reactors and thereby increase the overall GTL cost, among which is water in excess concentrations. Water is a byproduct of the FTS process and is present in varying amounts. In order to gain a better understanding of the behavior of catalyst nanoparticles (NPs) inside the produced wax–water mixtures at reaction conditions and realistic scales and sizes, one needs to incorporate coarse-grained approaches in the context of FTS. The present study focuses on coarse-grained (CG) Molecular Dynamics (MD; CGMD) simulations of n-octacosane (n-C28)–water mixture at low-temperature FTS conditions (473.15 K) and considers various water mole fractions with the inclusion of different-sized Co NPs using the MARTINI force field. The Co NPs are suspended inside these bulk mixtures thereby resembling a slurry phase type of reactor. Water mole fractions below and above the solubility of water in n-C28 as predicted by MARTINI were used so as to better capture the phase behavior of the produced wax–water mixtures. Our results show that, for the NP sizes examined, water in small concentrations does not aggregate on the Co NP surface. For water concentrations above the calculated solubility in n-C28, water forms a cluster that fully encapsulates the NP, and for excess water, the NPs are completely immersed in the aqueous phase. This behavior bears implications in the mobility of the NPs examined, which appears to increase as a function of water concentration. Calculations of Co NPs self-diffusion coefficient show that the smaller nanoparticle moves faster, and that mobility drops as nanoparticle size increases. For high water mole fractions, that is, well-exceeding water solubility in bulk n-C28, an increasing effect in the mobility of the examined Co NPs was observed. The computational approach using the MARTINI force field and the results presented showcase that CGMD simulations can be employed to study the hydrodynamic effects on the NP mobility in FTS-related processes.

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“…Variations in the nature of confinement, such as soft (polymer and self-assembled monolayers) vs hard (zeolites and silica), and patterned (graphite and carbon nanotubes) vs random (hydrogels), lead to large changes in structure and dynamics of confined water. Changes in the organization and evolution of water aggregates and bound water have practical implications for membrane transport, − protein folding, − adhesion of biomacromolecules, − design of anti-icing surfaces, − selective organic remediation, − and oil recovery. − …”

Section: Introductionmentioning

confidence: 99%

Soft Templating of Water Aggregates Disrupts π–π Stacking in Crystalline Poly(3-hexylthiophene)

et al. 2017

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The π–π stacking robustness of the photoactive layer is key to maintaining efficiency of organic photovoltaics (OPVs). We show local disruption more than 2 Å on average in the π–π stack of crystalline poly(3-hexylthiophene) (P3HT), one of the most common materials used in OPVs, through formation of a chainlike water structure with limited growth and mostly pentameric cluster ends. In contrast, a 3D aggregated water cluster with constant growth is observed in amorphous P3HT. Dynamics of water molecules that form the largest aggregates in crystalline P3HT show the effect of limited mobility, when compared to amorphous P3HT, due to dual confinement from both alkyl side groups and thiophene backbone. We term this dual confinement soft templating and quantify its effect on nature, size, and hydrogen bond participation of water aggregates in crystalline and amorphous P3HT using all-atom molecular dynamics with in-house developed potentials that were previously shown to represent the interfacial and wetting behavior of P3HT systems in good agreement with experiments. Examination of disruption behavior presented for P3HT would allow smart molecular design of photoactive layers.

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Interfacial Engineering for Oil and Gas Applications: Role of Modeling and Simulation

Cited by 3 publications

References 198 publications

Molecular Dynamics Simulation of the n-Octacosane–Water Mixture Confined in Graphene Mesopores: Comparison of Atomistic and Coarse-Grained Calculations and the Effect of Catalyst Nanoparticle

Molecular Dynamics Simulation of the n-Octacosane–Water Mixture Confined in Graphene Mesopores: Comparison of Atomistic and Coarse-Grained Calculations and the Effect of Catalyst Nanoparticle

Coarse-Grained Molecular Dynamics Simulation of Cobalt Nanoparticle in the n-Octacosane–Water Mixture: The Effect of Water Concentration and Nanoparticle Size

Soft Templating of Water Aggregates Disrupts π–π Stacking in Crystalline Poly(3-hexylthiophene)

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