Catalytic pyrolysis of waste composite plastics with waste FCC catalyst

Abstract

The recycling of multilayer packaging plastic films is becoming more important due to its large application. In this work, two composite plastics of PET/LDPE (Polyethylene Terephthalate/Low Density Polyethylene) and PA6/LDPE (Polyamide/Low Density Polyethylene) were catalytically pyrolysed in different heating modes with the assistance of a waste FCC (fluid catalytic cracking) catalyst. The effect of FCC catalyst on product distribution, oil compositions and heteroatom compounds (oxygen and nitrogen-containing species) in different heating modes were studied using GC-MS (Gas Chromatograph - Mass Spectrometer) and APPI FT-ICR MS (Atmospheric Pressure Photoionization Fourier Transform-Ion Cyclotron Resonance Mass Spectrometer). It was found that waste FCC catalyst can form more gas at the expense of wax and oils due to its acidity property. More alkane and aromatic can be formed in the presence of FCC catalyst. Relative to non-catalytic pyrolysis, more alkanes are formed due to the hydrogen transfer ability of the FCC catalyst. The concentration of oxygen in oil and wax can be lowered by FCC catalyst. However, the concentration of nitrogen in oil is increased due to the lower denitrification ability of FCC catalyst even though its partition into oils is decreased. The waste FCC catalyst can decrease the number of O-containing compounds in heavier parts of oils from the fast pyrolysis of PET/LDPE. The number of compounds in Ox class are increased due to the interaction between oxygen radicals from PA6 and LDPE for the catalytic pyrolysis of PA6/LDPE.