H2 and CO production through coking wastewater in supercritical water condition: ReaxFF reactive molecular dynamics simulation

Jiang, Dandan; Wang, Yan; Zhang, Ming; Zhang, Jinli; Li, Wei; Han, You

doi:10.1016/j.ijhydene.2017.03.164

Cited by 43 publications

(14 citation statements)

References 54 publications

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“…The source of H radicals in H 2 can be classified into three routes (shown in Figure S4): (1) both H radicals are derived from GDL molecules; (2) both H radicals are derived from H 2 O molecules; (3) one H radical comes from GDL molecules, and the other H radical comes from H 2 O. In our previous study, we have found that the main route of H 2 production during the SCWG process without a catalyst is that H radical interacted with H 2 O to form H 3 O, which then converts to H 2 and OH radicals. However, the above route for pure SCWG did not happen in SCWG with a Ni catalyst.…”

Section: Resultsmentioning

confidence: 99%

Size Effect of a Ni Nanocatalyst on Supercritical Water Gasification of Lignin by Reactive Molecular Dynamics Simulations

Han

Chen

et al. 2019

Ind. Eng. Chem. Res.

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Supercritical water gasification (SCWG) is considered as an excellent technique with great potential for lignin utilization, and the addition of a Ni catalyst is effective to achieve high gasification yields. To understand the size effect of Ni nanoparticles during the SCWG process, our simulations were performed by reactive molecular dynamics methods, and the detailed pathways of lignin decomposition and hydrogen production were obtained. The cleavage of the β-O-4′ linkages consists of three main pathways, and the size of Ni catalysts influences the cleavage pathways. During the ring-opening process, the Ni catalyst could accelerate the cleavage of C–O bonds and destroy the conjugated π bond of the aromatic ring. Moreover, the generation of H2 molecules occurs entirely on the Ni catalyst. The H radicals gradually approach each other via the transformation of adsorption sites, and the diffusion is the rate-limiting step for the H2 production, especially at the initial reaction stage. The results indicate that a smaller catalyst cluster possesses higher activity, and there are more active sites at the Ni surface to weaken C–C, C–O, C–H, and O–H bonds. Through the cyclic use, the stability of the 2.0 nm catalyst cluster is better than that of 3.0 and 4.0 nm clusters due to the lower surface oxidation degree.

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Section: Resultsmentioning

confidence: 99%

Size Effect of a Ni Nanocatalyst on Supercritical Water Gasification of Lignin by Reactive Molecular Dynamics Simulations

Han

Chen

et al. 2019

Ind. Eng. Chem. Res.

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“…However, with the continuous development of molecular force fields, molecular dynamics simulations can give dynamic information about the system, and larger simulated systems can be processed quickly and efficiently. The current force fields used in molecular dynamics simulations are mainly ReaxFF [151,[163][164][165] and COMPASS [166,167].…”

Section: Molecular Dynamicsmentioning

confidence: 99%

“…The different reaction mechanisms of SCWG, SCWO and SCPWO were also discussed through MD simulations. Selecting benzo[a]pyrene (BaP) as a model compound, Jiang et al [164] found that OH• attack was the main ring-opening reaction mechanism for the SCWG system, while oxygen molecules were dominant in the initial reaction for the SCWO system, and the ring-opening reaction mechanism was initiated by an OH• and oxygen molecules for the SCWPO system. Zhang et al [151] described the routes of the N element in the whole reactions.…”

Section: Molecular Dynamicsmentioning

confidence: 99%

“…The intermediate NOH played a key role in the transformation paths and the final products of the N element, which further made NH 3 the main product in the SCWG system and N 2 the primary product in the SCWO system. Jiang et al [164] optimized the oxygen ration to improve the number of fuel gases using MD simulations. The optimal oxygen ration for maximum H 2 production was 0.2 since adding a small amount of oxygen increased the reaction rate and promoted more H atoms and C atoms to convert into H 2 and CO fuel gases.…”

Section: Molecular Dynamicsmentioning

confidence: 99%

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Review on Mechanisms and Kinetics for Supercritical Water Oxidation Processes

Jiang

Wang

et al. 2020

Applied Sciences

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Supercritical water oxidation (SCWO) is a promising wastewater treatment technology owing to its various advantages such as rapid reactions and non-polluting products. However, problems like corrosion and salt decomposition set obstacles to its commercialization. To address these problems, researchers have been developing the optimal reactor design and strengthening measures based on sufficient understandings of the degradation kinetics. The essence of the SCWO process and the roles of oxygen and hydrogen peroxide are summarized in this work. Then, the research status and progress of empirical models, semi-empirical models, and detailed chemical kinetic models (DCKMs) are systematically reviewed. Additionally, this paper is the first to summarize the research progress of quantum chemistry and molecular dynamics simulation. The challenge and further development of kinetics models for the optimization of reactors and the directional transformation of pollutants are pointed out.

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“…In this work we focus on the ReaxFF force field [18]. ReaxFF has been used to simulate supercritical state pro-cesses such as wastewater purification and hydrogen production [19][20][21][22]. However, the validity of the force field to reproduce the basic properties of SC water has never be systematically studied.…”

Section: Introductionmentioning

confidence: 99%

Benchmark of ReaxFF force field for subcritical and supercritical water

Manzano

Zhang

Raju

et al. 2018

The Journal of Chemical Physics

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Water in the subcritical and supercritical states has remarkable properties that make it an excellent solvent for oxidation of hazardous chemicals, waste separation, and green synthesis. Molecular simulations are a valuable complement to experiments in order to understand and improve the relevant sub- and super-critical reaction mechanisms. Since water molecules under these conditions can act not only as a solvent but also as a reactant, dissociative force fields are especially interesting to investigate these processes. In this work, we evaluate the capacity of the ReaxFF force field to reproduce the microstructure, hydrogen bonding, dielectric constant, diffusion, and proton transfer of sub- and super-critical water. Our results indicate that ReaxFF is able to simulate water properties in these states in very good quantitative agreement with the existing experimental data, with the exception of the static dielectric constant that is reproduced only qualitatively.

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H2 and CO production through coking wastewater in supercritical water condition: ReaxFF reactive molecular dynamics simulation

Cited by 43 publications

References 54 publications

Size Effect of a Ni Nanocatalyst on Supercritical Water Gasification of Lignin by Reactive Molecular Dynamics Simulations

Size Effect of a Ni Nanocatalyst on Supercritical Water Gasification of Lignin by Reactive Molecular Dynamics Simulations

Review on Mechanisms and Kinetics for Supercritical Water Oxidation Processes

Benchmark of ReaxFF force field for subcritical and supercritical water

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