In-situ Mechano-catalysis for Polymer Activation and ConTrolled Conversion

Introduction

Less than 9% of plastic is recycled. Currently applied recycling technology yields degraded materials because undesired mechano-chemical bond cleavage shortens the polymer upon repeated processing. Here, I introduce a new type of catalyst to exploit this undesired effect to recover the polymer building blocks, the monomers, which enables the production of new high-quality polymer.

Focus on Polyolefins

I will focus on polyolefins (PP, PE) that make up 50% of polymer production and for which the state-of-the-art pyrolysis process has high energy costs and does not yield pure monomer. That is because at the 600 °C needed to break the strong carbon-carbon (C-C) bonds of PP and PE, unwanted reactions occur.

Challenges with Current Methods

Adding a catalyst powder, a known strategy to exert reaction control, is inefficient for polymers because they cannot reach the active sites in the catalyst pores.

Innovative Approach

I will break the C-C bonds with force instead of heat. The force is provided by the collision of balls in a ball mill, a mature grinding technology that I repurpose as a reactor to introduce my tunable direct mechano-catalyst. I will chemically treat the surface of the balls to create catalytic, e.g., acid, sites that are in efficient contact with polymer through vigorous ball movement.

Proof-of-Concept Results

In our ground-breaking proof-of-concept experiment, we were surprised to see monomer form below 60 °C from PP, and a remarkable 4x increased activity over a traditional catalyst.

Future Research Directions

To realize the full potential of this new catalytic concept, I will establish the underlying fundamental framework by:

1. Understanding the mechanism of reactions following C-C cleavage.
2. Developing a predictive model of cleavage rate as a function of temperature and force.
3. Understanding the synergistic interplay of catalytic spheres and mechano-chemical activation.

Methodology Development

To achieve this, I will develop a new methodology for in-situ spectroscopy during ball milling in combination with radical trapping and apply the tunable direct mechano-catalysts to a variety of polymers.