In the NobleFreeCat project, three systems whose activity in selective hydrogenation has been recently described in the literature will be explored: Fe-Ni, Fe-Cu and intermetallic Fe-Al compounds.

The NobleFreeCat project aims at overcoming three bottlenecks that currently impede a rational development of Fe-Ni and Fe-Cu supported catalysts:

  • a poor control of the metal nanoparticle size and structure, due to the preparation method employed (usually co-impregnation of a support by the two metal nitrates, leading to particle size in the 3-35 nm range, with less than 5% of the metals accessible to reactants, and to mixtures of particles of different structure and composition).
  • a poor control of the association between the two metals, due to metal demixing at some stage of the catalyst preparation. Because of its lower toxicity and lower cost, Cu should be favoured upon Ni. However, the possibility to form truly bimetallic Fe-Cu nanoparticles is still questioned, due the immiscibility of the two metals expected from the phase diagram. The question of a chemical order within the nanoparticles, with one of the two metals preferentially exposed at their surface, is still open.
  • the absence of information on the evolution of the nanoparticles structure and surface during the cycle of use of the catalyst, which is an especially sensitive question since Fe oxidation state seems to greatly influence the catalyst performances.

In parallel, Fe-Al intermetallic compounds have been shown to be efficient selective hydrogenation catalysts and are especially appealing due to the abundance of the two elements. However two aspects need to be considered for these systems:

  • the decrease of the particles size, as so far, they have only been prepared as single crystals exhibiting a very low metallic surface area.
  • the extent and reversibility of their oxidation when exposed to oxygen from air, to oxidic supports and to oxygen-containing molecules.

Finally, in terms of reaction medium, a bottleneck is the development of water-free alternative media that can be used for sugar hydrogenation if catalysts fail to stand harsh hydrothermal conditions.

The ultimate objective of the NobleFreeCat project will be reached when the optimal catalytic activity in the hydrogenation of mono- and di-saccharides of Fe-containing bimetallic catalysts, ideally prepared without nickel, will be correlated to a given chemical composition and chemical order in the nanoparticles, on catalysts whose stability will have been demonstrated in the catalytic medium and along their whole cycle of use.