Catalytic pyrolysis of low density polyethylene over H-β, H-Y, H-Mordenite, and H-Ferrierite zeolite catalysts: Influence of acidity and structures

Low-density polyethylene (LDPE) catalytic pyrolysis was investigated over H-β-25, H-β-150, H-β-300, H-Y-12, H-Mordenite-20, and H-Ferrierite-20 zeolite catalysts. The numbers denote the SiO ₂/Al₂O₃ molar ratios. The influence of the zeolite's acidity on the transformation of LDPE was studied by varying the SiO₂/Al₂O₃ molar ratios of the β zeolite. The influence of the zeolite structure was investigated by using the proton forms of Y, β, Mordenite, and Ferrierite zeolites. The catalysts were characterized using X-ray powder diffraction patterns, nitrogen adsorption, and FTIR spectroscopy with pyridine as the probe molecule. The large pore and least acidic H-β-300 catalyst showed the lowest activity in the catalytic pyrolysis of LDPE. The H-β-25 catalyst, with higher acidity than H-β-300, showed higher activity for LDPE pyrolysis than H-β-300, indicating the importance of strong acid sites for this reaction. The H-Ferrierite and H-Mordenite catalysts, with small pores, showed the lowest effect on LDPE pyrolysis, although the catalysts were more acidic than H-β-25 and H-β-150, indicating that not only acidity but also the structure and pore size of zeolites are important for pyrolysis of LDPE. However, the H-Y zeolite catalyst with large pores and cavities is not suitable for this reaction because of rapid deactivation due to coke formation.