(693d) Polymer Upcycling By Tandem End-Scission and Random Scission Catalysts: Model and Analysis of Experiments

About 3,000 Mt. of polyethylene waste has been generated since 1950. The environmental consequences have motivated new chemical and catalytic recycling strategies. This paper considers the isomerizing ethenolysis strategy that has been introduced by Guironnet and coworkers as well as Hartwig and coworkers.^1-3 We revisit a local density approximation (LDA) method for modeling this chemistry and more generally any scheme that cuts chains non-processively and at/near chain ends. We show that the LDA method leads to second order population balance equations that accurately describe molecular weight evolution when applied to realistic initial molecular weight distributions. We also model tandem catalysis with one catalyst that cleaves chains at the end and one that cleaves chains at random interior locations. We show how the predicted molecular weight distributions change upon coordinate transformation to common presentations in the literature: carbon number distribution, logarithmic weight distribution, etc. Finally, we apply the model to experimental data from isomerizing ethenolysis and use the model to extract kinetic parameters.

Reference

1. Guironnet, D.; Peters, B., Tandem Catalysts for Polyethylene Upcycling: A Simple Kinetic Model. J Phys Chem A 2020, 124, 3935-3942.

2. Conk, R. J.; Hanna, S.; Shi, J. X.; Yang, J.; Ciccia, N. R.; Qi, L.; Bloomer, B. J.; Heuvel, S.; Wills, T.; Su, J.; Bell, A. T.; Hartwig, J. F., Catalytic deconstruction of waste polyethylene with ethylene to form propylene. Science 2022, 377, 1561-1566.

3. Wang, N. M.; Strong, G.; DaSilva, V.; Gao, L.; Huacuja, R.; Konstantinov, I. A.; Rosen, M. S.; Nett, A. J.; Ewart, S.; Geyer, R.; Scott, S. L.; Guironnet, D., Chemical Recycling of Polyethylene by Tandem Catalytic Conversion to Propylene. J Am Chem Soc 2022, 144, 18526-18531.