POLYOL CONVERSION INTO FURANIC DERIVATIVES ON BIMETALLIC CATALYSTS, NATURE OF THE CATALYTIC SITES

Bimetals prepared by addition of a noble metal (Ru, Pt, Au, Pd) on Ran ey copper catalyze very selectively the cyclodehydration reaction of p olyols into furanic derivatives (e.g. sorbitol into isosorbide) wherea s the pure metals catalyze the cleavages of C-C and C-O bonds (Cu, Ru) or are inactive (Pt, Au, Pd). The influences of the reaction conditio ns on the cyclodehydration kinetics, as well as those of the preparati on conditions of these bimetals in connection with their physicochemic al properties, were studied. It appears that the cyclodehydration site s involve copper, noble metal and halogen, this last element coming fr om the precursor salt used during the modification of Raney copper. La ck of one of these two last elements: noble metal without halogen or h alogen without noble metal, does not allow the complete removal of the hydroxylated sites responsible for the degradation reactions.