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PreprintCC BYChemRxiv

Nitrogen-Centric Optimization of Polyamide Chemical Recycling: A Reaction Network Flux Analysis with New Metrics for Nitrogen Atom Economy and Nitrogen Footprint

  • Huiting Yang1,2
  1. 1Aachener Verfahrenstechnik (AVT.PT)
  2. 2RWTH Aachen University
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Abstract

Polyamide 6 and 66 (PA6/PA66) are the only commodity plastics with structural nitrogen (12.4 wt%), yet chemical recycling frameworks treat nitrogen fate as an uncontrolled byproduct. We extend Reaction Network Flux Analysis (RNFA) to a full C-H-O-N mass balance and introduce two new metrics—Nitrogen Atom Economy (NAE) and Nitrogen Footprint (NF)—enabling the first systematic nitrogen-centric optimisation of PA6/PA66 depolymerization. Across 795 NLP solves (GAMS/BARON) spanning six products, five depolymerization route families, and five objective weight scenarios, three findings emerge. First, nitrogen-centric optimisation achieves NAE = 87–100% across all products, compared with the conventional unoptimised baseline of ∼60%. Second, carbon-only objective functions generate NF 6–62× higher than nitrogen-inclusive weighting; for caprolactam and 6-ACA, two economically identical routes differ by up to 62× in nitrogen footprint. Any objective weight w2 ≥ 0.3 on the nitrogen term recovers >90% of the achievable NF reduction. Third, for five of six products, the nitrogen-optimal configuration is simultane- ously the economic optimum—no cost penalty is incurred. These results support a seventh guiding principle for nitrogen-containing polymer upcycling: maximise nitrogen circularity, extending the six-principle framework of Jehanno et al. beyond carbon-centric assessment to address the planetary nitrogen boundary, currently transgressed by a factor of ∼2.4.

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Cite

BibTeXRIS
BibTeX
@misc{yang2026nitrogencentric,
  title = {{Nitrogen-Centric Optimization of Polyamide Chemical Recycling: A Reaction Network Flux Analysis with New Metrics for Nitrogen Atom Economy and Nitrogen Footprint}},
  author = {Huiting Yang},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008194/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008194/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Nitrogen-Centric Optimization of Polyamide Chemical Recycling: A Reaction Network Flux Analysis with New Metrics for Nitrogen Atom Economy and Nitrogen Footprint
AU  - Huiting Yang
PY  - 2026
DA  - 2026/09/02
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008194/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008194/v1
AB  - Polyamide 6 and 66 (PA6/PA66) are the only commodity plastics with structural nitrogen (12.4 wt%), yet chemical recycling frameworks treat nitrogen fate as an uncontrolled byproduct. We extend Reaction Network Flux Analysis (RNFA) to a full C-H-O-N mass balance and introduce two new metrics—Nitrogen Atom Economy (NAE) and Nitrogen Footprint (NF)—enabling the first systematic nitrogen-centric optimisation of PA6/PA66 depolymerization. Across 795 NLP solves (GAMS/BARON) spanning six products, five depolymerization route families, and five objective weight scenarios, three findings emerge. First, nitrogen-centric optimisation achieves NAE = 87–100% across all products, compared with the conventional unoptimised baseline of ∼60%. Second, carbon-only objective functions generate NF 6–62× higher than nitrogen-inclusive weighting; for caprolactam and 6-ACA, two economically identical routes differ by up to 62× in nitrogen footprint. Any objective weight w2 ≥ 0.3 on the nitrogen term recovers >90% of the achievable NF reduction. Third, for five of six products, the nitrogen-optimal configuration is simultane- ously the economic optimum—no cost penalty is incurred. These results support a seventh guiding principle for nitrogen-containing polymer upcycling: maximise nitrogen circularity, extending the six-principle framework of Jehanno et al. beyond carbon-centric assessment to address the planetary nitrogen boundary, currently transgressed by a factor of ∼2.4.
ER  -