Mechanisms of Propylene Glycol and Triacetin Pyrolysis

Abstract

Propylene glycol and triacetin are chemical compounds, commonly used as food additives. Though the usage of the pure chemicals is not considered harmful when used as dietary supplements, little is known about the nature of their thermal degradation products and the impact they may have on human health. For these reasons, in this manuscript we investigate the thermal decomposition mechanisms of both neutral propylene glycol and triacetin in the gas phase by a novel simulation framework. This is based on a free energy sampling methodology followed by an accurate energy refinement. Structures, Gibbs free energy barriers, and rate constants at 800 K were computed for the different steps involved in the two pyrolytic processes. The thermal decomposition mechanisms found theoretically for propylene glycol and triacetin were validated by a qualitative experimental investigation using gas-phase chromatography-mass spectroscopy, with excellent agreement. The results provide a validation of the novel simulation framework and shed light on the potential hazard to the health that propylene glycol and triacetin may have when exposed to high temperatures.

E-Cigarettes

“…66 In its product safety materials, Dow Chemical Company states that “inhalation exposure to [propylene glycol] mists should be avoided,” 67 and the American Chemistry Council warns against its use in theater fogs because of the potential for eye and respiratory irritation. 68 When heated and vaporized, propylene glycol can form propylene oxide, an International Agency for Research on Cancer class 2B carcinogen, 69 and glycerol forms acrolein, which can cause upper respiratory tract irritation. 70,71 …”

Pyrolysis of furan and its derivatives at 1100 °C: PAH products and DFT study

“…Nevertheless, Laino et al has successfully used Py-GC-MS for the pyrolysis of propylene glycol and triacetin at 527 °C, verifying the feasibility of Py-GC-MS for liquid pyrolysis [23]. The advantages of using Py-GC-MS for product distribution when compared with tradition methods, such as MBMS and shock tube, are as follows:…”

Vape Till Your Nose Bleed

“…It can decomposes and form propylene oxide, a probable human carcinogen at high temperature. 11 Both propylene glycol and glycerol decompose to form carcinogens formaldehyde and acetaldehyde depending on the voltage of the battery used in the e-cigarette. 12,13 An e-cigarette consists of a catridgec ontining a liquid, an atomizer which is a vaporization chamber with a heating element and a battery.…”