Catalytic pyrolysis of high-density polyethylene (HDPE) using lanthanum oxide-containing ferrierite-type zeolitic catalysts

Abstract

The present work aimed to study a technological form for catalytic degradation of a plastic that accounts for a large part of Brazilian consumption, high density polyethylene (HDPE). Ferrierite zeolite in acid form (H-FER), lanthanum oxide (La₂O₃) and H-FER containing 10 and 20% of La₂O₃ were used as catalysts. The catalysts obtained were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption. Thermal and catalytic pyrolysis assays were performed via TG/DTG. Through XRD analysis, it was possible to observe that the crystal structure of H-FER was not affected by the incorporation of La₂O₃. The morphology of the La₂O₃/H-FER materials observed via SEM was characteristic of the H-FER zeolite and the La₂O₃ phase could also be observed. For the H-FER samples with La₂O₃ incorporated, there was a gradual decrease in the specific surface area with increasing La₂O₃ content. The results obtained were promising, showing the role of catalysts in the reduction of pyrolysis temperatures (from up to 77 °C) and activation energy (from up to 128 kJ/mol), when compared with the thermal pyrolysis of HDPE. In terms of apparent activation energy reduction, it was observed that the materials had the following reduction scale: 10% La₂O₃/H-FER > H-FER > 20% La₂O₃ > La₂O₃ > pure HDPE. The results suggest that the catalysts can be used for the catalytic pyrolysis of HDPE, with emphasis on the materials 10% La₂O₃/H-FER and H-FER that were more efficient.