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

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 alpha-NiMoO4, beta-NiMoO4 and Ni3Mo catalysts. The results show that the reactions are faster in the presence of alpha-NiMoO4 and beta-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 alpha-NiMoO4, beta-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].

Automated summary

Biodiesel, a potential alternative to fossil-based fuels, has limitations such as high viscosity, pour point, and cloud point. This study used ReaxFF molecular dynamics to investigate the decarboxylation of methyl palmitate using different catalysts. The presence of alpha-NiMoO4 and beta-NiMoO4 accelerated the reactions and resulted in higher quantities of stable products. Ni3Mo catalyst showed an initial rapid formation of products followed by a decrease. All reactions followed first-order kinetics, and the catalysts reduced the activation energies.