Palladium nanoparticles in polyethylene glycols: Efficient and recyclable catalyst system for hydrogenation of olefins

Ecofriendly Palladium on Wool Nanocatalysts for Cyclohexene Hydrogenation

Use of natural wool fiber supports in the fabrication of novel composite materials incorporating metal nanoparticles, which offer the possibility of “environmentally friendly” catalytic materials, has been investigated. The catalytic hydrogenation of cyclohexene to cyclohexane by palladium nanoparticles immobilized on wool (Pd/wool) was studied using moderate pressure of pure hydrogen gas. The performance of wool-supported catalysts was explored over a palladium nanoparticle loading ranging from 1.6 to 2.6 wt %. The effect of the catalytic testing conditions, including stirring rate, amount of reactants, gas pressure, and target temperature were explored. A systematic series of catalytic-activity tests carried out at 400 psi H₂ for 5 and 24 h reaction times at 40 °C using a stirring rate 750 rpm allowed us to identify differences in performance within the series of Pd/wool nanocatalysts studied. The most catalytically active samples contained Pd nanoparticles with average sizes of ca. 5 nm located predominantly on the surface and within the topmost layer of wool fibers, making them more accessible to the reactants.

Organic transformations on metal nanoparticles: controlling activity, stability, and recyclability by support and solvent interactions

The different mechanisms by which the support and the solvent can influence the catalytic properties of a metal nanoparticle (NP) are reviewed. The use of a support not only significantly facilitates the recycling of NPs but also has many additional advantages varying from enhanced stabilization of the NP dispersion to the alteration of the electronic properties of the metal, shape selectivity effects, and even active participation in the reaction mechanism. The correct choice of solvent, on the other hand, can drastically influence properties such as the morphology of the particles and, in the case of alloys, determine the composition of the NPs. Judicious solvent selection also enhances recyclability and stability, and in some cases, the solvent plays a cocatalytic role. Despite the many beneficial effects of combining metal NPs with the correct support or solvent, many processes are not well understood. Further research should be conducted on elucidating the general mechanisms behind the support-NP or solvent-NP interactions.