Low Temperature Combustion of C5 Cyclic Molecules

Probing reaction mechanisms during low-temperature combustion of cyclopentane, which is a representative naphthene species, is necessary for building a broader understanding of the effect of functional groups present in C₅ cyclic biofuels, such as cyclopentanol and cyclopentanone. At temperatures below 1000 K, competing reactions of naphthenes include ring-opening of initial radicals (Ṙ) and oxidation of Ṙ via reaction with O₂ that yields either conjugate alkenes, coincident with HOȮ, or peroxy radicals (ROȮ) that can isomerize into hydroperoxyl-substituted radicals (Q̇OOH). Subsequently, Q̇OOH radicals can either undergo unimolecular decomposition or second O₂-addition. The balance of the two types of reactions affects rates of chain-branching and depends on temperature, pressure, and oxygen concentration. 

Quantitative, isomer-resolved measurements of partially oxidized intermediates from cyclopentyl oxidation at 1 atm in a jet-stirred reactor (JSR) are analyzed in order to assess the effect of temperature and oxygen concentration on the balance of reactions that Q̇OOH radicals undergo. Subsequent comparison of species profiles produced from such competing reactions were also compared with predictions using detailed chemical kinetics mechanisms in order to provide critical constraints for understanding cyclopentane combustion. 

In addition to JSR experiments, time-resolved experiments were conducted to probe intermediates of Ṙ + O₂ reactions in the oxidation of cyclopentanol using a high-pressure flow reactor paired with multiplexed photoionization mass spectroscopy at the Advanced Light Source (ALS) synchrotron.