ReaxFF study of the decarboxylation of methyl palmitate over binary metallic nickel-molybdenum catalysts

ABSTRACT

Biodiesel has emerged as a possible replacement for fossil-based fuels, particularly in the transportation industry. Because of its high oxygen content, it has several limitations including high viscosity, pour point and cloud point. Converting biodiesel to hydrocarbons is one method of improving the poor flow properties. In this study, Reactive Force Field (ReaxFF) molecular dynamics was used to study the decarboxylation of methyl palmitate on α-NiMoO₄, β-NiMoO₄ and Ni₃Mo catalysts. The results show that the reactions are faster in the presence of α-NiMoO₄ and β-NiMoO₄, and the number of stable products, carbon dioxide and ethene was higher than they were without the catalyst. With Ni₃Mo catalyst, there is rapid initial formation of CO₂ and C₂H₄ until a maximum is reached followed by a decrease in their quantity. The C₂H₄ was found to decompose to C₂H₂ and H₂ while CO₂ was reduced to CO. All reactions were found to follow first-order kinetics, from which the activation energies (Ea) were determined. The Ea drops from 36.89 kcal/mol for uncatalyzed reaction to 25.66, 19.34 and 11.69 kcal/mol for the α-NiMoO₄, β-NiMoO₄ and Ni₃Mo catalysed reactions, respectively. The Ni₃Mo catalysed system’s Ea was also closest to the experimentally reported value of 10.11 kcal/mol [1].

KEYWORDS:

• Decarboxylation
• ReaxFF
• Methyl Palmitate
• binary NiMo catalysts
• Green diesel

Acknowledgements

The authors acknowledge Botswana International University of Science and Technology for supporting this research under BIUST Grant number SOO213 and Royal Society Grant R21-0847011243. This work also used the computational facilities of the NICIS -CHPC (RSA).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Botswana International University of Science and Technology [grant number: SOO213]; Royal Society of Chemistry [grant number: R21-0847011243].

Notes on contributors

Maipelo Nyepetsi

Maipelo Nyepetsi: Investigation, Methodology, Data curation, Formal analysis Writing – original draft, Writing – review & editing.

Olayinka A. Oyetunji

Olayinka A Oyetunji: Supervision, Writing – review & editing.

Foster Mbaiwa

Foster Mbaiwa: Conceptualisation, Funding acquisition, Investigation, Methodology, Supervision, Writing – review & editing.