Insight into the pyrolysis of benzene via a novel ultra-high temperature pyrolysis photoionization mass spectrometry

Abstract

It is extremely challenging to explore pyrolysis reactions in-situ at high temperatures over 2000 K. Here we present a new method that integrates ultra-high temperature graphite tube pyrolysis (UT-GTP) chemical reactor with photoionization time of flight mass spectrometer (PI-TOFMS) along with pyrolysis chemistry. The ultra-high temperature pyrolysis photoionization time of flight mass spectrometer (UT-Py-PI-TOFMS) allows in-situ detection and identification of pyrolysis products at a maximum temperature of 2370 K with a mass resolving power of ∼ 4000 at m/z = 28, and a sensitivity of benzene is better than 64 ppb. This methodology is employed to reveal the pyrolysis mechanism of benzene at 5 kPa and temperature range between 1000 K and 2370 K. A series of pyrolysis products, including radicals, carbyne, and polycyclic aromatic hydrocarbons (PAHs) with high molecular weight are observed. Compared with previous work, we observed some unreported products such as carbyne (C₈H₂, C₁₀H₂), naphthalyne (C₁₀H₆), phenanthryne (C₁₄H₈) in the pyrolysis of benzene by UT-Py-PI-TOFMS. A plausible pyrolysis mechanism is presented based on the experimental data obtained by UT-Py-PI-TOFMS, and the results can be used for future research on accurately simulating the formation of PAHs. Furthermore, this results provide a practical analytical method for the study of ultra-high temperature pyrolysis reactions.