The widespread and growing demands for plastic over the past several decades have led to the generation of massive amounts of plastic waste. In particular, variants of polyethylene (e.g., LDPE, HDPE) account for nearly 30% of all plastic production and over 50% of single-use packaging production, yet current recycling methods remain incapable of handling this plastic waste. To promote a plastic ‘circular economy,’ whereby all plastics are recirculated through a closed-loop cycle, pyrolysis and catalytic pyrolysis reactors have demonstrated significant potential for cracking the polymers back to their constituent monomers. Using the method of “Pulse-Heated Analysis of Solid Reactions” (PHASR), pyrolysis reactions were conducted under isothermal, reaction-controlled conditions, so the intrinsic kinetics of primary polyethylene cracking were measured directly without secondary reactions. Here, we validate the application of PHASR to low density polyethylene pyrolysis, describe LDPE intrinsic kinetics via lumped kinetic models, and make comparisons between the intrinsic kinetics and apparent kinetics reported in the literature. These fundamental kinetics provide the quantitative description required for developing catalytic control of the polyethylene unzipping process and designing industrial polyolefin pyrolysis reactors.

Promoting a plastic circular economy via polyethylene pyrolysis and catalysts: Intrinsic kinetic insights from pulse heated analysis of solid reactions (PHASR)

ACS Spring 2022

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