Surface interactions and radical generation in TCD decomposition: a DFT approach

Area of Science:

• Computational Chemistry
• Materials Science
• Aerospace Engineering

Background:

• Exo-tetrahydrodicyclopentadiene (exo-TCD) is a critical component in Jet Propellant-10 (JP-10), a high-density fuel for aerospace applications.
• Understanding the initial decomposition pathways of exo-TCD is vital, particularly with the addition of aluminum particles to enhance fuel performance.
• The catalytic role of the γ-Al₂O₃ surface in exo-TCD decomposition, including surface defect effects, requires detailed investigation.

Purpose of the Study:

• To investigate the initial hydrogen abstraction reactions in exo-TCD decomposition using density functional theory (DFT).
• To elucidate the role of the γ-Al₂O₃ surface, including surface defects, in facilitating exo-TCD decomposition pathways.
• To identify the most energetically favorable decomposition routes and radical formation processes.

Main Methods:

• Density functional theory (DFT) calculations employing the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional with SVP and TZVP basis sets.
• Utilized the resolution of identity (RI) method for computational efficiency and dispersion correction (D3).
• Modeled surface defects on γ-Al₂O₃ by considering the interaction with exo-TCD at five distinct active hydroxyl sites.

Main Results:

• Hydrogen abstraction from the R4 site of exo-TCD was identified as the most energetically favorable initial decomposition pathway.
• Complexes formed between exo-TCD and γ-Al₂O₃ sites were primarily van der Waals interactions, with energies between -11 to -20 kcal/mol.
• Surface defects on γ-Al₂O₃ were shown to enhance reactivity, facilitating spontaneous H transfer and lowering activation barriers for H-abstraction.

Conclusions:

• The R4 site is the primary target for hydrogen abstraction in exo-TCD decomposition.
• γ-Al₂O₃ surfaces, particularly those with defects, significantly catalyze exo-TCD decomposition pathways.
• Findings contribute to a better understanding of propulsion fuel decomposition and the development of advanced energetic materials.