ReaxFF Reactive Molecular Dynamics Study on Methanation Reaction from Syngas

Abstract

The side reactions The side reactions in the syngas methanation process can lead to carbon deposition and deactivation of Ni-based catalysts. The existing ReaxFF reaction force field parameters are not suitable for the present study system; thus, new force field parameters of Ni-C/H/O need to be developed for the syngas methanation process. The DFT method was used to calculate the adsorption energies and transition state energy barriers for elementary reactions, which were used as the training set of the force field. The transition state was searched by DFT and reaction force field methods, respectively, to narrow the gap between the two energy barriers under similar structures. The comparison of the results of DFT and ReaxFF indicates that the developed force field suits the system. Based on the developed force field, ReaxFF was used to study the transformation process of CH x (x = 0−3) species on the Ni surface. The results show that at high temperatures and low H coverage, CH x species are easily dissociated and eventually become C species on the Ni(111) surface. Increasing H coverage can significantly increase the hydrogenation of CH x species to methane and inhibit the dissociation of CH x species. The methanation activity on the Ni(211) surface is higher, but the carbon deposition phenomenon is more serious. The reaction rate equations of each species were given, and the kinetic parameters of the elementary reactions were solved. Finally, the best reaction conditions with a higher yield of CH 4 and less carbon deposition were found.

Quantifying reaction rates in methane oxidation: atomistic simulations at high temperature

“…This approach enabled us to simulate and analyze the behavior of methane and oxygen molecules under hightemperature conditions, crucial for understanding the detailed dynamics of the chemical reactions involved during methane oxidation. The specific ReaxFF version of CHO 2016 description is selected in present study due to following considerations: The ReaxFF CHO 2016 force field has the advanced capabilities in accurately modeling the combustion chemistry of smaller hydrocarbons like methane, addressing limitations observed in earlier versions and the observations are welldocumented in studies such as [24,26,27]. The parameters of the chosen force field were specifically enhanced to provide a more balanced reactivity of O 2 , enabling more accurate simulations of methane's oxidation dynamics at elevated temperatures.…”

Reactive Force Field Development for Propane Dehydrogenation on Platinum Surfaces

“…The ReaxFF developed by van Duin in 2001, − uses the so-called bond order (BO) formalism, which is a general relation between bond length and bond order, and further bond order and bond energy, leading to proper bond dissociation/formation energies. The ReaxFF approach has demonstrated significant potential in diverse fields, including investigations of catalyzed reactions, − conformational dynamics of biomolecules, oxidation of metal surfaces, and other applications. ,, Accurate reactive ReaxFF calculations require the assessment of the transferability of existing force-field parameters and, in many cases, the development of specific force-field parameters for the target catalytic process. In the development process, one must generate either computational or experimental reference data for training and validation sets.…”