Cobalt and Nickel Nanocatalysts Confined inside Halloysite Nanotubes for Selective Hydrogenations

Innovative cobalt and nickel catalytic materials containing metal nanoparticles immobilized into the inner tubes of pristine halloysite, a naturally occurring nanoclay, and their application in hydrogenation reactions of a large variety of substrates from biomass and industrial wastes are described herein.The catalytic materials with a high metal loading (>24 wt.%) were prepared by a one-pot two-steps procedure in the absence of additional stabilizers, leading to metal nanoparticles essentially confined into the support lumen (constituted of aggregates of small nanoparticles) as a result of the privileged electrostatic interactions between aluminols and metal acetate salts (Ni(OAc)2, Co(OAc)2).Both catalytic materials, Ni/Hal and Co/Hal, gave different chemoselectivities towards the reduction of unsaturated functional groups (carbonyl, C=C, nitrile) under solvent-free conditions, and thus affording selectively added-value compounds depending on the nature of the metal.In particular, the squalene hydrogenation monitoring permitted to identify the partial hydrogenated products and estimate the partial turnover numbers and frequencies, achieving a cumulative TON of 110 and TOF of 151 h -1 using the most active catalytic system, i.e.Ni/Hal.