Catalytic Pyrolysis of Plastics over Maghemite-Impregnated Mesocellular Foam using Induction Heating

Abstract

Pyrolysis is a key technology that converts unrecyclable end-of-life plastics into value-added products. Nevertheless, the high energy consumption during plastic pyrolysis limits the economic feasibility of a scaled-up process. Development of an energy-efficient plastic pyrolysis process is necessary to realise its full potential in the circular economy. Catalysts derived from mesocellular foam possess high acidity and mesoporosity, and exhibit high catalytic activity in chemical reactions. Application of such catalyst in plastic pyrolysis has never been reported. This work presents the catalytic pyrolysis of low- and high-density polyethylene and polypropylene over maghemite-impregnated mesocellular foam (Fe@AlMCF). Fe@AlMCF has a BET surface area of 629.8 m2/g and a strong Brønsted acidity (677 µmol/gcat). The catalyst contains pentagonal and hexagonal packed mesostructure. Induction heating resulted in a rapid increase in reactor temperature (at 65 °C /min) and complete plastics conversion within 10 min. Catalytic pyrolysis produced gas products rich in C3 compounds. The liquid products were rich in alkenes (69.7-71.3 %) and alkanes, followed by aromatics (10.4-12.8 %). These observations indicate that the highly acidic Fe@AlMCF catalysed hydrocarbon aromatization within a short reaction time. Thermal analysis of the spent catalysts revealed considerably high coke yields (5.78 - 6.03 %), as the higher acidity of the original catalyst promoted coke precursor formation. Based on the research findings, induction heating can rapidly and effectively convert plastics into hydrocarbon feedstocks, and Fe@AlMCF is a valuable catalyst for plastic pyrolysis.