The Institute’s invention is a process based on selective dehydroxylation of aldaric acids derived from C6 oxidized sugars. The selective dehydroxylation is carried out in the presence of a heterogeneous carbon supported rhenium catalyst (Re/C) and a short chain primary or secondary alcohol (MeOH, EtOH, 2-PrOH,…). Under an inert (N2) atmosphere, unsaturated dimethyl ester of a C6 dicarboxylic acid is formed. If H2 is present in the gas phase, it is dissolved in MeOH and adsorbed on the catalyst surface, where it hydrogenated double bonds resulted as dimethyl adipate. Dimethyl adipate can be used directly as a monomer in the polycondensation reaction with hexamethylene to form 6,6-nylon or it can be hydrolyzed under acidic conditions to adipic acid.