ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Application of response surface methodology in PET recycling via glycolysis with propylene glycol using Ni/Zn/Al catalysts

Jhon Pineda-Gómez, Will Bautista-Berrio, Johana Rodríguez-Ruíz, and Edgardo Meza-Fuentes

Grupo de Estudios en Materiales y Combustibles, Universidad de Cartagena, Cartagena, Colombia

E-mail: emezaf@unicartagena.edu.co

Received: 15 October 2025  Accepted: 31 March 2026

Abstract:

This study evaluates the glycolysis of post-consumer polyethylene terephthalate (PET) using NiZnAl-derived catalysts obtained from hydrotalcite precursors, with a particular focus on the influence of operational variables and catalyst properties. A statistical approach based on response surface methodology (RSM) was applied to analyze the effects of reaction temperature, propylene glycol volume, catalyst mass, and catalyst calcination temperature on PET degradation. The results indicate that reaction temperature is the most influential variable, showing a significant positive effect on PET conversion, while propylene glycol volume and catalyst mass exhibit moderate but statistically relevant effects. In contrast, catalyst calcination temperature was not found to be statistically significant within the studied experimental domain. The fitted quadratic model suggests that the response is primarily governed by linear effects, with limited contribution from interaction and quadratic terms, indicating a system dominated by first-order trends. Experimental observations further suggest that increasing solvent volume and catalyst loading may introduce mass transfer limitations and dilution effects, reducing the efficiency of the depolymerization process. Catalysts calcined at intermediate temperatures showed higher average degradation, which may be related to differences in surface structure and accessibility of active sites, although this effect cannot be considered dominant. The predictive capability of the model was validated through scale-up experiments, where degradation values remained consistent with model predictions, demonstrating the applicability of RSM for process optimization. Overall, PET glycolysis in this system appears to be mainly controlled by thermal activation, while catalyst properties contribute to the efficiency of the reaction without acting as the primary governing factor.

Graphical abstract

PET Glycolysis with Ni–Zn–Al Catalysts: Optimization via RSM.

Keywords: PET glycolysis; Chemical recycling; Layered double hydroxides; Ni/Zn/Al catalysts; Response surface methodology

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04865-8

Chemical Papers 80 (7) 7921–7937 (2026)