@inproceedings{01JA5CFVA8NT0G7F7VDNYB42Z3,
  abstract     = {{Motivation
Oxymethylene ethers (OMEs) form a high-potential family of synthetic chemicals to replace fossil-based
fuels due to their favorable ignition characteristics. These alternative liquid energy carriers can
contribute to a circular carbon economy when synthesized via carbon capture and utilization technology
using renewable electricity, so-called e-fuels. Despite the potential to significantly reduce greenhouse
gas and particulate matter emissions, and the favorable ignition characteristics, little is known about the
thermal decomposition of OMEs. Fundamental insights have been obtained for pyrolysis of smaller
OMEs, but there is only little data available for longer-chain OMEs, such as oxymethylene ether-4
(OME-4).
Methodology
The pyrolysis of OME-4 is investigated for the first time in more detail by combined experimental and
kinetic modeling work. New datasets are acquired for OME-4 from experimental units with tubular and
jet-stirred reactors coupled to dedicated on-line analysis sections. The thermal decomposition is
examined over the temperature range from 423 to 1073 K in a tubular quartz reactor at 0.34 MPa. For
the jet-stirred reactor unit, the temperature ranges from 500 K to 1000 K, at a pressure of 0.107 MPa,
and with an average residence time of 2 s. This broad temperature range enables studying both the
primary and secondary reaction chemistry. A new kinetic model based on first principles consisting of
only elementary reaction steps is developed for OME-4 pyrolysis with the automatic kinetic model
generation tool ‘Genesys’. The model includes new thermodynamic and kinetic parameters obtained
from quantum chemical calculations.
Results
Pyrolysis of OME-4 forms only a limited number of products, but there is a remarkable evolution as a
function of the reaction temperature. As soon as the decomposition starts, shorter-chain OMEs and
formaldehyde are formed. At around 775 K, the formation of dimethoxymethane (DMM), oxymethylene
ether-2 (OME-2) and oxymethylene ether-3 (OME-3) reaches a maximum. A significant amount of
CH2O is formed at low temperatures, with a maximum yield of about 38 mol%. At higher temperatures,
the major products are H2 and CO. The maximum values reach beyond 40 mol%. The formation of
species with carbon-carbon bonds is limited to ethylene and ethane. The newly developed kinetic model
can predict the experimental observations on average within the uncertainty margin without fitting model
parameters. Rate of production and sensitivity analyses are performed to obtain fundamental insight
into the important decomposition pathways. It is demonstrated that different formaldehyde elimination
reactions exist, which can decompose OME-4 into DMM, OME-2 or OME-3 and formaldehyde
molecules via elementary reaction steps. These reactions turn out to be the most dominant
decomposition pathways of OME-4 during pyrolysis. The formation of large amounts of smaller OMEs
imposes that the model is sensitive towards the decomposition chemistry of these smaller molecules.
A small fraction of OME-4 decomposes via roaming reactions forming a carbene and the associated
alcohol. These carbenes can dissociate to form radicals, which initiate the radical chemistry.
Conclusion
A combined experimental and kinetic modeling study is carried out to obtain new fundamental insights
into the pyrolysis chemistry of long-chain OMEs. At low temperatures, shorter-chain OMEs and
formaldehyde are the main reaction products, while at high temperatures, H2 and CO are the major
reaction products. A new kinetic model based on first principles is proposed to describe the experimental
observations. The model predicts the experimental observations of major compounds satisfactorily.
Rate of production analyses reveal the dominancy of several formaldehyde elimination reactions.
Radical chemistry turns out to be less significant for the decomposition of OME-4, but important for the
decomposition of smaller OMEs. The formation of radicals is caused by decomposition of carbenes
formed via roaming reactions.}},
  author       = {{De Ras, Kevin and Herbinet, Olivier and Battin-Leclerc, Frédérique and John Varghese, Robin and Eschenbacher, Andreas and Thybaut, Joris and Van Geem, Kevin}},
  booktitle    = {{CI’s 40th International Symposium - Emphasizing Energy Transition, Abstracts}},
  language     = {{eng}},
  location     = {{Milan, Italy}},
  pages        = {{1}},
  title        = {{Pyrolysis of a long-chain oxymethylene ether (OME-4) in tubular and jet-stirred reactors}},
  url          = {{https://www.combustion-institute.it/news-events/38-ci-s-40th-international-symposium.html}},
  year         = {{2024}},
}