Olefin-Assisted Electrochemical Recycling of Homogeneous Hydrosilylation Catalysts in Nonpolar Media.

Abstract

Homogeneous platinum catalysts for hydrosilylation are essential for the chemical industry and society, through the production of commodities such as functional silicones. However, the high boiling points of the products and the low concentration of the homogeneous catalysts make the implementation of traditional separation methods difficult. Catalyst loss becomes a core sustainability and techno-economic challenge. In addition, the highly active platinum-based catalysts for hydrosilylation have remarkable susceptibility to deactivation upon reaction completion. Recently, redox-mediated electrosorption has been successfully demonstrated in a number of electrically conductive media as a separation platform. However, industrial hydrosilylation systems are carried out in highly nonconductive media. Therefore, developing an electrochemical recycling system in realistic, nonconductive hydrosilylation media can be transformative for sustainable homogeneous catalysis and chemical manufacturing. Here, we overcome these challenges for hydrosilylation catalyst recycling by introducing a strongly coordinating vinyl ligand and enabling the recycling of these Pt catalysts in solvent-free, nonpolar reactant media through two distinct loops for catalyst recycling and electrosorbent regeneration. The coordinating olefin ligand maintains catalytic activity after the reaction and prevents particle aggregation, a primary mechanism for deactivation. The Pt catalyst stabilized by the coordinated ligand can be reversibly adsorbed and released by the electrosorbent, demonstrating 100% catalytic activity retention and over 90% Pt release efficiency. A techno-economic analysis supports the economic potential of the electrochemical recycling system, with cost savings of >5k USD/kg_Pt. By combining chemical design and electrochemical engineering, we demonstrate the sustainable electrochemical recycling of industrially relevant hydrosilylation catalysts in practical nonconductive media.