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Coke Characterization and Re-Activation Energy Dynamics of Spent FCC Catalyst in the Catalytic Pyrolysis of Polyolefins

Bahlouli, Hussam A; Alghamdi, Rasha; Manos, George; (2025) Coke Characterization and Re-Activation Energy Dynamics of Spent FCC Catalyst in the Catalytic Pyrolysis of Polyolefins. Catalysts , 15 (9) , Article 862. 10.3390/catal15090862. Green open access

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Abstract

Chemical recycling via catalytic pyrolysis is constrained by coke deposition and costly catalyst make-up. We investigate polypropylene (PP) and low-density polyethylene (LDPE) conversion over a spent FCC equilibrium catalyst (AXL) and, critically, quantify the re-activation energy landscape of the resulting coke. Using a semi-batch reactor (350 °C) and thermogravimetric analysis to 1100 °C combined with the Ozawa–Flynn–Wall method, we distinguish soft and hard coke under inert, oxidative, and sequential N2 to air regimes. LDPE yields mainly gas (70.7 wt%) with 5.5 wt% coke, whereas PP favors liquids (47.1 wt%) with 3.4 wt% coke. LDPE-derived coke is softer (71% of total; EA = 170 kJ mol−1 soft) than PP coke (60% soft; EA = 166 kJ mol−1), evidencing a more refractory PP residue. Oxygen lowers EA to ~155 kJ mol−1 for both polymers. We introduce a simple TGA-based “softness ratio” to guide regeneration severity and show that a refinery-waste FCC catalyst delivers selective plastic-to-fuel conversion while enabling energy-aware regeneration protocols. The framework directly supports scale-up by linking polymer structure, coke quality, and atmosphere-dependent re-activation energetics.

Type: Article
Title: Coke Characterization and Re-Activation Energy Dynamics of Spent FCC Catalyst in the Catalytic Pyrolysis of Polyolefins
Open access status: An open access version is available from UCL Discovery
DOI: 10.3390/catal15090862
Publisher version: https://doi.org/10.3390/catal15090862
Language: English
Additional information: © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Keywords: pyrolysis; heterogeneous catalysis; Zeolites; Polyolefins; recycling; coke characterization
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10213913
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