REPOS – Innovative depolymerization technology for silicones

The collaborative project known as “REPOS” (REssourcement POlymères Silicones) is a pioneering effort aimed at developing eco-designed depolymerization chemistry for silicone waste. This groundbreaking project, led by Elkem and supported by partners such as small enterprises ACTIVATION & PROCESSIUM and CNRS labs CP2M (Catalysis, Polymerization, Process and Materials), and IMP (Ingénierie des Matériaux Polymères), seeks to create a flexible, selective, and efficient unit capable of operating at low temperatures for processing silicone waste generated by Elkem and its customers.  

Two Distinct Loops for Sustainable Outcomes  

The primary objective of the REPOS project is to establish two crucial recycling loops:  

1. Monomer Production Loop: This loop focuses on producing monomer silicone materials, seamlessly integrating them back into the manufacturing process.  

2. Added-Value Product Loop: Here, the remaining oligomers from the depolymerization process are transformed to create innovative, high-value products.  

Elkem’s Commitment to Sustainability  

Elkem, as a key player in the global chemicals industry, is deeply committed to sustainability. Their strategic climate roadmap, unveiled in October 2021, revolves around three core pillars:  

1. Process Emissions Reduction: Elkem is dedicated to reducing process emissions significantly.  

2. Supporting the Green Transition: They actively contribute to the green transition through sustainable practices.  

3. Circular Economies Development: Elkem focuses on fostering circular economies, particularly by embracing an eco-design approach and adhering to the principles of Reduce, Reuse, and Recycle.  

This holistic approach empowers Elkem to innovate across their entire value chain.  

A Holistic Approach to Recycling  

Elkem Silicones adopts a comprehensive approach to recycling by strategically developing various complementary technologies, including chemical recycling, mechanical recycling, and pyrolysis.  

Partnership and Expertise  

REPOS is a three-year collaborative project that unites several stakeholders in the LPSE (Lyon Polymer Science and Engineering) consortium, and supported by BPI France and Region Auvergne Rhone Alpes, combining diverse expertise:  

• Chemistry, Catalysis, and Polymer Materials: Academic partner laboratories CP2M and IMP bring expertise in chemistry, catalysis, and polymer materials.  
• Industrial Implementation: ACTIVATION specializes in the implementation of industrial-scale solutions, including catalysis and continuous reaction technologies.  
• Optimization of Industrial Processes: PROCESSIUM plays a crucial role in the design and optimization of industrial processes.  
• Elkem Silicones: As a leading chemical and technology company, Elkem Silicones leverages its extensive knowledge of the silicone value chain, chemistries, and processes to drive innovation and sustainability.  

The REPOS Recycling Process  

The REPOS project focuses on setting up a flexible, selective, and low temperature depolymerization unit for silicone materials. Research has revealed that different chemistries can transform silicone waste into two key intermediates in the value chain: monomers and short oils.  

These “recycled” silicones can either be reintegrated into a new silicone polymerization cycle or undergo functionalization to create new formulations for high-value applications. Beyond the technical challenge, one of the project’s key objectives is to establish a value chain for silicone product recycling, encompassing Elkem’s waste and customer waste.  

Benefits of Recycling  

Recycling waste is a central tenet of the circular economy, yielding significant advantages such as reduced material consumption and a diminished environmental footprint. Initial calculations indicate a significant 75% reduction in carbon footprint for silicone produced in Europe and a 65% waste reduction at the Elkem facility’s gates.  

Challenges and Innovation  

Developing competitive, selective, and clean chemical recycling processes presents challenges at both academic and industrial levels. While existing depolymerization methods are well-documented, the REPOS project addresses the complexity of materials involved. Challenges include:  

• Designing innovative catalytic systems.  
• Depolymerising viscous products.  
• Handling cross-linked elastomer materials.  
• Processing silicone formulations with fillers that may hinder catalytic systems.  
• Achieving upcycling to create new products with higher added value.  
• Implementing continuous/intensified processes to limit waste, energy consumption, and CO2 emissions.  

Successful Progress and Next Steps  

Thanks to rigorous research and development efforts, the REPOS project has demonstrated the technical feasibility of depolymerizing silicone materials at low temperatures for various silicone waste streams. Key achievements include:  

• Submission of three patent applications for different catalytic depolymerization chemistries.  
• Publication on depolymerization chemistry enabling reversion to D4 (cyclic methyl siloxane).  
• Integration of new technologies within Elkem and the start of pilot trials for chemically recycled oils at Elkem Silicones site.  

The next phase of the project focuses on piloting and scaling up these new technologies towards industrialization, furthering Elkem’s commitment to sustainability and circular economies.