Highly active and reusable palladium nanoparticle catalyst stabilized by polydimethylsiloxane for hydrogenation of aromatic compounds in supercritical carbon dioxide

This study describes a hydrogenation method for degrading polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in supercritical carbon dioxide catalyzed by palladium nanoparticles stabilized in polydimethylsiloxane (Pd/PDMS). The process of synthesizing metal nanoparticles embedded in PDMS polymers involves the preparation of a homogenous mixture of metal salt, silicone elastomer, and a curing agent, followed by hydrogen reduction. PCBs and PAHs can be effectively hydrogenated to saturated hydrocarbons with greater than 99% efficiency in an hour under 200 atm of CO2 containing 10 atm of H2 at 313 K using Pd/PDMS catalysts. The proposed Pd/PDMS catalysts can be reused without losing their activity and are significantly more active than commercial catalysts and a previously reported Pd nanoparticle catalyst stabilized in high-density polyethylene.

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► The detoxification of PCBs and PAHs method can be achieved through Pd/PDMS-catalyzed hydrogenation in sc-CO2 under mild conditions. And supercritical technique is eco-friendly and efficient.
► The Pd/PDMS catalyst is easy to prepare and clean, and can be reused without losing activity.
► The Pd nanoparticles show good dispersion in PDMS support. The Pd/PDMS catalyst is similar to a homogeneous catalysis environment in sc-CO2.
► Reactants can contact more active site due to the high swelling ability of PDMS polymers in sc-CO2.
► PDMS support shows good absorption and diffusion due to the strong interaction between PDMS and hydrophobic reactants.