Predicting decomposition temperatures and carbonization feasibility of heterocycles with their decomposition mechanism

Abstract

Pyrolysis of heterocyclic compounds such as Meldrum’s acid derivatives was studied with two key mechanisms analysing their energy barrier diagrams by the hybrid density functional theory method M06-2X. The feasibility of these decomposition reactions was calculated specifically for Meldrum’s acid, monomethyl Meldrum’s acid, dimethyl Meldrum’s acid (DMMA), methylene Meldrum’s acid (MeMA) and (dimethylamino)methylene Meldrum’s acid (DMAMeMA), based on previous experimental analysis. Their initial decomposition products (ketene or substituted ketenes with CO2 and acetone) were found endothermic requiring activation energies (∼180–––230 kJ/mol) at the decomposition temperatures of 280, 299, 301, 503 and 414 K respectively. The transition state theory calculations show MeMA and DMAMeMA are thermally more stable than other derivatives with low values for the rate constants and high energy barriers to produce initial decomposition products, suggesting they can produce fine carbon materials during carbonization. DMMA is found the best option for obtaining heteroatoms-doped carbon material formation.