A new sustainable strategy for oil, CH4 and aluminum recovery from metallised food packaging plastics waste using catalytic pyrolysis over ZSM-5 zeolite catalyst

Abstract

Paraffin wax and syngas are the major energy products synthesized by pyrolysis of metallised food packaging plastics waste (MFPW). These pyrolysis products contain a small amount of flammable compounds with negligible economic profit. Within this framework, this work aims to upgrade wax into oil and to increase the yield of flammable gases (e.g., CH4, C2H6, C3H8) in syngas generated during pyrolysis of MFPW using the catalytic pyrolysis process over ZSM-5 zeolite catalyst (10, 30, and 50 wt.%). The thermo-chemical experiments were performed in a semi-batch pyrolysis plant at 600°C. N2, O2, CO2, CO, CH4, and H2 gases generated during the entire process were observed with a digital gas analyser, while FTIR and GC measurements were employed to specify the chemical compounds of the obtained energy products (oil or wax and gases). Finally, aluminium (Al) fraction was separated from the obtained solid product of pyrolysis using leaching process. The results showed that addition of 10 and 30 wt.% of ZSM-5 to the reaction contributed to increase in wax yield from 12% to 19% without a significant effect on its structure. At 50 wt.% of ZSM-5, wax was converted into light hydrocarbon oil abundant in flammable compounds such as p-Xylene (18.2%), Benzene (14.6%), Toluene (7.3%), and o-Xylene (4.7%). Also, GC-MS results revealed that the gas obtained from 50 wt.% batch was rich in CH group (derived from CH4 compound) and Toluene (33%), p-Xylene (27%), Benzene (14.4%). Based on that the catalytic pyrolysis with 50 wt.% ZSM-5 zeolite catalyst is considered to be a promising thermo-chemical technology that can be applied at industrial scale to convert MFPW into oil (21%), gas (66%), Al (8.8%), and Al-free char particles (3.12%).