Issue 8, 2023

Conformations of polyolefins on platinum catalysts control product distribution in plastics recycling

Abstract

The design of catalysts for the chemical recycling of plastic waste will benefit greatly from an intimate knowledge of the interfacial polymer–catalyst interactions that determine reactant and product distributions. Here, we investigate backbone chain length, side chain length, and concentration effects on the density and conformation of polyethylene surrogates at the interface with Pt(111) and relate them to experimental product distributions resulting from carbon–carbon bond cleavage. Using replica-exchange molecular dynamics simulations, we characterize the polymer conformations at the interface by the distributions of trains, loops, and tails and their first moments. We find that the preponderance of short chains, in the range of 20 carbon atoms, lies entirely on the Pt surface, whereas longer chains exhibit much broader distributions of conformational features. Remarkably, the average length of trains is independent of the chain length but can be tuned via the polymer–surface interaction. Branching profoundly impacts the conformations of long chains at the interface as the distributions of trains become less dispersed and more structured, localized around short trains, with the immediate implication of a wider carbon product distribution upon C–C bond cleavage. The degree of localization increases with the number and size of the side chains. Long chains can adsorb from the melt onto the Pt surface even in melt mixtures containing shorter polymer chains at high concentrations. We confirm experimentally key computational findings and demonstrate that blends may provide a strategy to reduce the selectivity for undesired light gases.

Graphical abstract: Conformations of polyolefins on platinum catalysts control product distribution in plastics recycling

Supplementary files

Article information

Article type
Edge Article
Submitted
25 aug 2022
Accepted
03 jan 2023
First published
03 jan 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 1966-1977

Conformations of polyolefins on platinum catalysts control product distribution in plastics recycling

M. Zare, P. A. Kots, S. Caratzoulas and D. G. Vlachos, Chem. Sci., 2023, 14, 1966 DOI: 10.1039/D2SC04772A

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