Catalytic evaluation of dendrimer and reverse microemulsion template Pd and Pt nanoparticles for the selective oxidation of styrene using TBHP

• Colloidal Pd and Pt nanoparticles catalyze oxidation of styrene with higher selectivity to styrene oxide.
• Nanoparticles synthesized by dendrimers showed better activity compared to those synthesized by reverse microemulsions.
• Pd-based nanoparticles showed higher conversion compared to Pt-based nanoparticles.
• Potential of colloidal Pd and Pt nanoparticle systems to be highly selective towards desirable compound in the oxidation reaction.

Here, we employed colloidal Pd and Pt nanoparticles synthesized by dendrimer templates as well as reverse microemulsions in the selective oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant. We investigate their catalytic behavior and the feasibility as oxidation catalysts. High selectivity to styrene oxide, was achieved in the oxidation of styrene. The catalytic activities in terms of styrene conversion decreased in the order of dendrimer-templated Pd nanoparticles > thiol-capped Pd nanoparticles by reverse microemulsions > dendrimer-templated Pt nanoparticles > thiol-capped Pt nanoparticles by reverse microemulsions. This indicated that Pd-based catalysts were more efficient to catalyze the styrene oxidation reaction as compared to Pt-based catalysts. Furthermore, the dendrimer template synthetic method produced catalysts with higher activity as compared to those prepared by the reverse microemulsion template. The catalytic activities and selectivity profiles in various reaction conditions such as solvent type, styrene to TBHP ratio, type of catalysts, catalyst dosing, and temperature are discussed. The changes of average nanoparticle size after the reactions and the recyclability of Pd and Pt catalysts are examined. Overall results indicated that although higher catalytic activities were obtained with the use of dendrimer-templated nanoparticles, better recyclability as well as selectivity to styrene oxide was achieved with the use of thiol-capped Pd nanoparticles synthesized by reverse microemulsions.

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