(309b) Characterization of Zeolite-Based Catalysts for Catalytic Upcycling By Use of Positron Annihilation Spectroscopy

Catalysts: HZSM-5 and MESO-Y, play a pivotal role in upgrading plastics thereby transforming existing plastic materials into simpler, higher-quality value-added products. Here we present studies of various zeolites used as catalysts undergoing deactivation processes. We focus on three different experiments conducted by use of Positron Annihilation Lifetime Spectroscopy (PALS) that is excellent for examining sub-nano-meter size morphology and other techniques. First we focus on H-ZSM-5 subjected to conversion treatments involving polyurethane and polypropylene¹. The second experiment examines H-ZSM-5 zeolites with varying silica and alumina (SiO₂/Al2O₃) ratios². Finally we investigate meso-porous Y-zeolites synthetized at different sodium hydroxide (NaOH) concentrations. All of these experiments included examining the states before and after conversion.

The emphasis of this study is application of PALS, which has superb sensitivity towards sub-nanometer free volume morphology and its alterations caused by conversion process³. The PALS is compared and complemented with several other techniques: Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), thermogravimetry (TG), Nuclear Magnetic Resonance (NMR) and several other techniques. ²

1. Urban-Klaehn, J.; Jaeschke, A.; Gaffney, and all, “ Studies of Zeolite-Based Catalysts for Upcycling of Polymer Waste by Use of Positron Annihilation Spectroscopies”; 12.5^th International Workshop on Positron and Positronium Chemistry, 2021.
2. Shikhaliyev, Gaffney, A.; Urban-Klaehn, J. M.; Lauterbach, J. and all. “H-ZSM-5 Catalysts for the Catalytic Upcycling of Polypropylene Glycol. Catal. B Environ. 2023, 337, 122991. https://doi.org/10.1016/j.apcatb.2023.122991.