Catalytic recycling of silicones – CARES

In the silicone value chain, from quartz to silicon then chlorosilane intermediates to silicone materials, the carbon impact of the upstream steps (silicon and intermediates) accounts for around 75% of emissions. An appealing recycling route consists of transforming waste silicone-based materials back to chlorosilanes. The direct cleavage of Si-O bond to form back Si-Cl is however very challenging. An indirect pathway has been elegantly discovered using BCl3 as an inorganic source of chloride. Nevertheless, this low temperature (< 60°C) catalytic route has a number of drawbacks (economical viability, access to BCl3, additional recycling loop of boron, etc.).
The CARES project propose to address the much more challenging direct cleavage of Si-O bond to form back Si-Cl using all-silicon pathways (via SiCl4 and MeSiCl3 as chloride source). To face this significant reactivity challenge the use of catalysis is mandatory and the CARES project brings two academic laboratory CP2M and IRCE with complementary expertises in homogenous and heterogeneous catalysis and an industrial company Elkem covering the complete value chain from quartz to silicone materials.