Supercritical fluid preparation of Pt, Ru and Ni/graphene nanocomposites and their application as selective catalysts in the partial hydrogenation of limonene

Abstract

The development of new materials and methods to prepare selective hydrogenation catalysts is essential from both environmental and economic reasons due to their industrial applications. In this context, the use of reduced graphene oxide (rGO) as a metal-free catalyst and catalytic support is explored. Thanks to the penetrating and exfoliating ability of supercritical CO2 (scCO2), Pt, Ru and Ni nanoparticles were homogeneously deposited on rGO through a sustainable method. Particle size for the different metal/rGO varied from 2 to 15nm depending on the metal, methodology and metal loading (1–7% wt.). The Pt/rGO and Ru/rGO materials prepared in scCO2 were used as catalysts in the hydrogenation of limonene. The reaction was performed in CO2 at supercritical conditions. All the metal/rGO catalysts showed high activities and selectivities of ca. 90% to the partially hydrogenated form, p-menthene, that kept constant with reaction time. The Ru/rGO catalyst was reused up to 4 times with minor loss of activity and constant selectivity. The high activity and selectivity may be related to the 2D open structure of the support, which favours adsorption of reactants and desorption of intermediate products.