Furanics are produced in high abundance from the decomposition of biomass. The thermal and chemical instability of these species leads to the formation of humins upon condensation. The ring rearrangement of furfural via the Piancatelli mechanism to form 2-cyclopentenone/cyclopentanone is a well-established reaction known to occur in the aqueous phase, but this requires a prior condensation where humin formation readily occurs. The upgrading of furfural to cyclopentanone in a single step over supported TiO2 catalysts in the vapor phase is studied. Role of water, nature of active site and mechanism were evaluated over different catalyst. This reaction was also investigated in presence of acetic acid and water that are the most abundant oxygenated chemicals obtained from biomass. Selectivity for ring rearrangement vs. C-O cleavage over TiO2 supported Ru and Pd catalysts can be tuned by manipulating the water partial pressure. Furfural and acetic acid compete for active sites. The presence of acetic acid influences the adsorption of furfural facilitating the breaking of the ring. Finally, combining the ability to synthesize carbon nanotubes with different properties, the location of the active site and important kinetics pathways for this rearrangement reaction are discussed