Nano silica and molybdenum supported Re, Rh, Ru or Ir nanoparticles for selective solvent-free glycerol conversion to cyclic acetals with propanone and butanone under mild conditions

We described the preparation of a series of new catalysts, i.e., nano-silica supported Re, Ru, Ir, Rh NPs as well as various combinations of the above-mentioned metals as potential catalysts of glycerol acetalization with acetone or butanone for the first time. In fact, it was discovered that nano-SiO2 supported Re in particular is a highly efficient selective catalyst of glycerol acetalization for five-membered cyclic acetals. While Re supported on nano-SiO2 prefers five-membered cycles its replacement to Mo destroys this selectivity and both five- and six-membered products can be observed. Under optimal conditions, the TON that was observed significantly outperforms those that have been reported in the literature for other catalytic systems. (C) 2016 Elsevier B.V. All rights reserved.