Development of a catalyst Co-pyrolysis process for producing pyrolysis oil and wax from cooking oil contaminated polypropylene plastic

Abstract

The increase in food packaging waste, especially waste contaminated by cooking oil, has drawn increasing attention because of the difficulty in recycling this material. Waste-to-energy approaches are generally applied for using oily food packaging waste as solid fuel. Nevertheless, oily food packaging waste has the potential to be used as feedstock for higher-value products such as pyrolysis oil and wax. This study investigated the effects of catalysts and operating conditions of fast pyrolysis on the yield and properties of pyrolysis oil and wax produced from polypropylene plastic with palm oil as the representative oily food packaging waste. The presence of palm oil promoted wax formation but significantly increased the kinematic viscosity and acid value of pyrolysis oil. On the other hand, increasing the kaolin catalyst loading, pyrolysis temperature and heating rate reduced wax formation but did not improve the kinematic viscosity or acid value of the pyrolysis oil. The addition of activated carbon derived from rice husk as a cocatalyst effectively reduced the acid value of the pyrolysis oil and enhanced wax formation. The pyrolysis wax had a viscosity index greater than 400 and a pour point of 26 °C. The FTIR and GC-MS analyses revealed that the pyrolysis wax primarily consisted of saturated long-chain fatty acids and alcohols. Catalyst reusability testing demonstrated that there was no significant reduction in pyrolysis oil or wax yield across three consecutive cycles. Techno-economic evaluation indicated that co-producing pyrolysis oil and wax from cooking oil-contaminated PP plastic waste yielded more favorable outcomes than producing pyrolysis oil alone. A net profit of approximately 0.086 USD per kilogram of feedstock was achieved under the evaluated conditions.