Comparison of the Synthesis Method of Zeolite Catalysts Based on Pozzolan, Pumice, and Ignimbrite Applied to the Sustainable Pyrolysis of Polymers

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.