Catalytic pyrolysis of polyethylene: A comparison between pillared and restructured clays

• Clay based catalysts have been compared with H-ZSM5 in polyethylene cracking.
• The clay based catalysts gave higher yields of liquid products in the C15–C20 range.
• By selecting the appropriate catalyst, the choice between producing aliphatics and aromatics can be made.

In this work, three restructured smectite clays, namely a saponite, a montmorillonite, and a beidellite, as well as their Al- and Fe/Al-pillared derivatives, have been tested for their performance in the catalytic cracking of a medium-density polyethylene. All reduce the cracking process temperature to 300 °C, as compared with >650 °C for uncatalysed pyrolysis. Although generally less active than a selected H-ZSM5 (Si/Al = 235) zeolite, they are instead superior to this catalyst as regards liquid hydrocarbon formation.Different products categories can be obtained by different catalysts: in particular a choice between aliphatics and aromatics products can be made by utilising the appropriate catalysts.