Direct bond fission and hydrogen migration as the trigger forces in the pyrolysis of n-pentyl nitrate at low pressure.

Nitrates are a potential class of substances as cetane improvers of diesel fuel and are critical raw materials for some military explosives. Thus, an in-depth investigation of the thermal decomposition mechanism of nitrates is important for further improving their effects. Herein, a combination of experimental and computational studies was performed for the pyrolysis of n -pentyl nitrate in the temperature range of 400‒900 K. Using synchrotron radiation vacuum ultraviolet photoionization, some intermediates and products, such as ethylene, formaldehyde, propene, ethenol, pentanal, NO 2 , and HONO, were identified according to their photoionization efficiency curves. Quantum chemical calculations at the CBS-QB3 level were conducted to elucidate the overall reaction mechanism of n -pentyl nitrate pyrolysis. Along the direct bond fission of n -pentyl nitrate, primary products, C 5 H 11 O• radical and NO 2 , and butyl radical and CH 2 ONO 2 , can further dissociate into many products, in which formaldehyde is the most dominant. In addition, two hydrogen-atom migration channels followed by decomposition are verified for the decomposition of n -pentyl nitrate according to the observation of trans -HONO, pentanal, and 1-pentene. These evidences highlight that both bond fission and hydrogen migration play comparable roles as potential driving forces in the pyrolysis of n -pentyl nitrate at low pressure. This thermal decomposition mechanism of n- pentyl nitrate provides some useful clues for developing combustion models of long chain nitrates in future. [ABSTRACT FROM AUTHOR]