Development of the ReaxFF reactive force field for mechanistic studies of catalytic selective oxidation processes on BiMoO x

Abstract

We have developed a new reactive force field, ReaxFF, for use in molecular dynamics (MD) simulations to investigate the structures and reactive dynamics of complex metal oxide catalysts. The parameters in ReaxFF are derived directly from QM and have been validated to provide reasonable accuracy for a wide variety of reactions. We report the use of ReaxFF to study the activation and conversion of propene to acrolein by various metal oxide surfaces. Using high-remperature MD-simulations on metal oxides slabs exposed to a propene gas phase we find that (1) Propene is not activated by MoO 3 but it is activated by amorphous Bi 2 O 3 to form allyl which does not get oxidized by the surface; (2) Propene is activated by Bi 2 Mo 3 O 12 to form an allylradical and the hydrogen gets abstracted by a Mo@O bond, which is bridged via an O to a Bi-site; (3) Propene is activated over V 2 O 5 to form an allyl, which is then selectively oxidized on the surface to form acrolein. The propene reations on V 2 O 5 occur at lower temperatures than on Bi 2 O 3 or Bi 2 Mo 3 O 12 . The results are all consistent with experimental observations, encouraging us that such investigations will enhance our mechanistic understanding of catalytic hydrocarbon oxidation sufficiently to suggest modifications for improving efficiency and/or selectivity.

Kinetic modelling of heterogeneous catalytic systems

“…To obtain this function, one could for instance use ab initio calculations to parametrize a reactive force-field (ReaxFF [23,24]), and there has been a significant amount of work that makes use of such methods on catalytic systems [24][25][26][27][28][29][30][31]. Yet, this approach becomes extremely demanding computationally when simulating catalytic systems for long timescales.…”

Recovery Act: Molecular Simulation of Dissolved Inorganic Carbons for Underground Brine CO2 Sequestration

“…40 CO 2 and HCO 3 -molecules are randomly distributed in the center of a pre-equilibrate box of 2000 water molecules (representing 0.91M initial concentration), described using the ReaxFF forcefield for water. The initial system was equilibrated using our standard approach [21][22][23][24][25][26][27][28][29][30], heated to the required temperatures (300 and 350K) with a Nose-Hoover thermostat and simulated at 1 and 25GPa for 10ps using a Andersen barostat. The snapshot of the system with an average pressure closest to the target was selected for a further 100ps constant volume simulation.…”

Investigative Tools: Theory, Modeling, and Simulation

“…Reactive force fields for reactive dynamics simulation of materials processes • [28]. Reactive force fields allow one to simulate structure with chemistry, enabling potential impact on drug discovery and catalysis, both of which require precise differentiation between the energy costs of various reaction pathways.…”