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-beta-25, H-beta-150, H-beta-300, H-Y-12, H-Mordenite-20, and H-Ferrierite-20 zeolite catalysts. The numbers denote the SiO2/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 beta zeolite. The influence of the zeolite structure was investigated by using the proton forms of Y, beta, 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-beta-300 catalyst showed the lowest activity in the catalytic pyrolysis of LDPE. The H-beta-25 catalyst, with higher acidity than H-beta-300, showed higher activity for LDPE pyrolysis than H-beta-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-beta-25 and H-beta-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.