The present investigation studies the use of three natural precursors of volcanic origin (pozzolana, ignimbrite and pumice) in the synthesis of low-cost and environmentally friendly zeolites. The developed zeolites were evaluated as sustainable catalysts for the catalytic pyrolysis process in the chemical recycling of polypropylene. A zeolite was synthesized from each precursor. The hydrothermal treatment was performed with NaOH (3M) at 160 °C for 72 h and NH₄Cl (1M) was added to convert it into proton form. The synthesized zeolites were characterized by FTIR, XRD, SEM and BET. The evaluation of the catalytic ability of the obtained zeolites was carried out with polypropylene mixed with a 4, 6 and 8 wt.% catalyst in a ceramic crucible. Pyrolysis was always carried out at 450 °C and for 30 min in a tubular furnace with a continuous flow rate of 250 L·min⁻¹ of gaseous nitrogen. The gases generated were captured in the cooling system. The characterized zeolites show a resemblance to the ZSM-5 commercial zeolite, especially for the ignimbrite and pozzolan zeolites. Likewise, in pyrolysis, liquid products, gases and waxes were obtained. As the amount of catalyst was increased (from 4 to 8%), the yield of the desired liquid–gas products was also increased. The synthesized zeolites showed similar pyrolytic characteristics to ZSM-5, although they did not reach the same pyrolytic efficiency. Zeolites improved the pyrolysis products, especially at 8 wt.%, when compared to thermal pyrolysis. This study highlights the potential of the developed zeolite catalysts to efficiently convert PP into valuable light olefins, advancing sustainable polyolefin recycling technologies.

This study aims to synthesize sustainable zeolite catalysts by taking advantage of the great abundance of natural precursors, such as pozzolana, ignimbrite, and pumice, found in the southern zone of Peru. Different methodologies were selected. On the one hand, an alkaline fusion/hydrothermal reaction with NaOH processes was utilized and, on the other hand, the hydrothermal method was employed. The characteristics of these catalysts and their application in the catalytic pyrolysis of polypropylene were evaluated. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were employed to investigate the structure and properties of the obtained catalysts. Catalytic pyrolysis experiments of polypropylene were carried out at 450 °C for 30 min with a 6% w/w zeolite catalyst. It was possible to synthesize zeolites similar to commercial zeolites such as ZSM-5 and zeolite X, with a BET surface area of up to 451.3 m²/g⁻¹, offering the possibility of obtaining commercial products from natural materials. According to the results obtained in the pyrolytic process, method 1 (alkaline fusion/hydrothermal reaction with NaOH) presents the best results, with 94% in liquid and gaseous products. The zeolite synthesized with the pozzolan precursor was the most successful, followed by pumice.