Nitrogen Fate in Polyurethane Decomposition: Pathways Uncovered by In Situ Synchrotron Vacuum Ultraviolet...

Area of Science:

• Chemical Engineering
• Materials Science
• Environmental Science

Background:

• Polyurethane (PU) pyrolysis generates hazardous nitrogen-containing compounds.
• Accurate understanding of PU decomposition pathways is limited.
• Controlling toxic emissions from PU waste is an environmental challenge.

Purpose of the Study:

• To elucidate the molecular-level pyrolysis mechanisms of polyurethane (PU).
• To identify and track the formation and fate of hazardous nitrogen-containing compounds during PU decomposition.
• To propose detailed reaction pathways for PU pyrolysis.

Main Methods:

• Utilized synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS).
• Employed gas chromatography-mass spectrometry (GC-MS).
• Applied thermogravimetric Fourier transform infrared spectroscopy-mass spectrometry (TGA-FTIR-MS).

Main Results:

• Identified approximately 45 pyrolysis species, including novel intermediates like 4-isocyanato-1-methylbenzene.
• Tracked the dynamic evolution of species over time and temperature.
• Proposed two distinct PU decomposition mechanisms involving C-O and C-N bond scission.
• Detailed the formation pathways for toxic gases like HCN, NOx, and NH3.

Conclusions:

• The study provides critical molecular-level insights into PU pyrolysis.
• Findings aid in developing accurate models for predicting toxic emissions.
• Results support the design of safer PU materials and optimized pyrolysis processes to mitigate harmful pollutants.