Palladium catalysts protected by embedding in polymer films proved suitable as a means to markedly prolong the life-time of the catalyst in hydrodechlorination and hydrogenation reactions for substrates from the water phase. The present work examines and summarizes optimization strategies for synthesis of embedded Pd catalysts. The polymer and the type of Pd catalyst were varied and several synthesis strategies were compared.

Poly(dimethylsiloxane) (PDMS) was confirmed to best maintaining long-term stability and offering easy surface coating with highly permeable but resistant membrane layers. The generation of catalytically active Pd species in situ within the polymer (in situ synthesis) allows higher catalyst activities due to suppression of Pd agglomeration which was omnipresent when embedding unsupported nanoparticles (ex situ synthesis). Highest Pd activities were achieved with supported porous catalysts, such as Pd on γ-Al₂O₃. The loss in catalyst activity due to embedding compared to freely water-suspended catalysts is less pronounced for nano-sized and supported nano-sized Pd than for micro-sized Pd. Polymer embedded Pd/Al₂O₃ better maintains its catalytic activity than unsupported Pd nanoparticles and Pd black. The loss of activity due to PDMS embedding is a factor of 3, 190 and 1000 respectively. Higher catalyst dispersion and Pd loadings (up to 4 wt%) were obtained with condensation-vulcanizing PDMS instead of addition-vulcanizing PDMS, where the Pd load was limited due to lower Pd precursor solubility. Tailoring of the catalyst behaviour using in situ synthesized Pd-PDMS was successful by making a selection in the PDMS type, Pd loading, temperature of nanoparticle generation and type of Pd precursor.