Posters

      Reaction Pathways for the Pyrolysis of Glycerol, Propylene Glycol and Triacetin in the Gas Phase and at Solid Surfaces

      Tuma, C.; Laino, T.; Curioni, A.; Jochnowitz, E.; Stolz, S.
      Conference date
      Sep 5, 2011
      Conference name
      CPMD 2011
      Link to more information
      Link to more information
      Topic
      Summary

      Glycerol, propylene glycol, and triacetin are commonly used as solvents, food additives, and humectants in the food and tobacco industries. Their use often involves potential exposure to high temperatures. Using metadynamics simulations we sampled the free energy spaces of these substances for gas phase low-barrier reactive events. We refined the decomposition pathways found by locating reactants, transition structures, and products on the PBE and pbe0 energy surfaces. We also performed frequency calculations to characterize the stationary points found and to derive Gibbs free energy barrier heights and rate constants for a temperature of 800 k. For the pyrolysis of glycerol we have predicted the formation of an epoxide intermediate (glycidol) as the overall rate limiting step connected to a barrier of 66.8 kcal/mol. While formaldehyde and vinyl alcohol are found as the main decomposition products, we find the formation of acrolein to be competitive at very high temperatures only. For propylene glycol we propose a novel dehydration scheme leading to the formation of propanal and only minor amounts of acetone. Similar to the case of glycerol we have predicted the formation of an epoxide intermediate (propylene oxide) as the overall rate limiting step with a barrier of 66.5 kcal/mol. For triacetin we present the first computational study related to its complex decomposition pattern. It is characterized by stepwise eliminations of acetic acid or acetic anhydride and many different intermediates. The overall rate limiting step corresponds to an initial elimination of acetic acid with a barrier of 62 kcal/mol rendering triacetin thermically slightly less stable than glycerol and propylene glycol. To study the impact of the presence of solids we have simulated the decomposition reactions at surfaces of amorphous carbon, amorphous silica and crystalline zirconia and compare to the situation in the gas phase. While silica and zirconia hardly influence the barrier height for the rate limiting steps, amorphous carbon shows a strong tendency for chemisorption reactions which results in decomposition pathways not predicted for the gas phase.

      PMIScience.com is operated by Philip Morris International for the purpose of publishing and disseminating scientific information about Philip Morris International’s efforts in support of its smoke-free product portfolio. This site is a global site for use by scientists, the public health and regulatory communities, and other stakeholders with an interest in tobacco policy. The purpose of this site is not advertising or marketing, nor is it directed at any specific market. It is not intended for use by consumers. New tobacco products sold in the United States are subject to FDA regulation; therefore the content of this site is not intended to make, and nor should it be construed as making, any product related claims in the United States without proper FDA authorization. ​
      ​
      Reduced Risk Products ("RRPs”) is the term we use to refer to products that present, are likely to present, or have the potential to present less risk of harm to smokers who switch to these products versus continuing smoking. PMI has a range of RRPs in various stages of development, scientific assessment and commercialization. All of our RRPs are smoke-free products that deliver nicotine with far lower quantities of harmful and potentially harmful constituents than found in cigarette smoke.